diff --git a/.github/workflows/syntax-checks.yaml b/.github/workflows/syntax-checks.yaml
index 27badf441d3..f350cbb0992 100644
--- a/.github/workflows/syntax-checks.yaml
+++ b/.github/workflows/syntax-checks.yaml
@@ -59,3 +59,23 @@ jobs:
           rustup toolchain install stable --profile minimal --no-self-update -c clippy -c rustfmt
       - name: Run `cargo fmt` on top of Rust API project
         run: cd src/libcprover-rust; cargo fmt --all -- --check
+
+  # This job takes approximately 3 minutes
+  check-pass-by-value:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          submodules: recursive
+      - name: Fetch dependencies
+        env:
+          DEBIAN_FRONTEND: noninteractive
+        run: |
+          sudo apt-get update
+          sudo apt-get install --no-install-recommends -yq \
+            cmake g++ flex bison clang-18 llvm-18-dev libclang-18-dev \
+            libclang-cpp18-dev
+      - name: Configure
+        run: cmake -S . -Bbuild -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+      - name: Check for pass-by-const-reference of cheap-to-copy types
+        run: ./scripts/run_pass_by_value_check.sh build
diff --git a/.gitignore b/.gitignore
index c7511712684..7f6cf7d0197 100644
--- a/.gitignore
+++ b/.gitignore
@@ -166,3 +166,4 @@ dist/
 
 # auto generated documentation
 doc/html/
+/scripts/check-pass-by-value
diff --git a/jbmc/src/janalyzer/janalyzer_parse_options.cpp b/jbmc/src/janalyzer/janalyzer_parse_options.cpp
index 79b712d55d1..a0f7881e07d 100644
--- a/jbmc/src/janalyzer/janalyzer_parse_options.cpp
+++ b/jbmc/src/janalyzer/janalyzer_parse_options.cpp
@@ -688,7 +688,8 @@ void janalyzer_parse_optionst::process_goto_function(
   // Java virtual functions -> explicit dispatch tables:
   remove_virtual_functions(function, *class_hierarchy);
 
-  auto function_is_stub = [&symbol_table, &model](const irep_idt &id) {
+  auto function_is_stub = [&symbol_table, &model](irep_idt id)
+  {
     return symbol_table.lookup_ref(id).value.is_nil() &&
            !model.can_produce_function(id);
   };
@@ -698,7 +699,7 @@ void janalyzer_parse_optionst::process_goto_function(
   transform_assertions_assumptions(options, function.get_goto_function().body);
 }
 
-bool janalyzer_parse_optionst::can_generate_function_body(const irep_idt &name)
+bool janalyzer_parse_optionst::can_generate_function_body(irep_idt name)
 {
   static const irep_idt initialize_id = INITIALIZE_FUNCTION;
 
@@ -706,7 +707,7 @@ bool janalyzer_parse_optionst::can_generate_function_body(const irep_idt &name)
 }
 
 bool janalyzer_parse_optionst::generate_function_body(
-  const irep_idt &function_name,
+  irep_idt function_name,
   symbol_table_baset &symbol_table,
   goto_functiont &function,
   bool body_available)
diff --git a/jbmc/src/janalyzer/janalyzer_parse_options.h b/jbmc/src/janalyzer/janalyzer_parse_options.h
index b55e99db4c5..e3defce36d9 100644
--- a/jbmc/src/janalyzer/janalyzer_parse_options.h
+++ b/jbmc/src/janalyzer/janalyzer_parse_options.h
@@ -164,10 +164,10 @@ class janalyzer_parse_optionst : public parse_options_baset
     const abstract_goto_modelt &model,
     const optionst &options);
 
-  bool can_generate_function_body(const irep_idt &name);
+  bool can_generate_function_body(irep_idt name);
 
   bool generate_function_body(
-    const irep_idt &function_name,
+    irep_idt function_name,
     symbol_table_baset &symbol_table,
     goto_functiont &function,
     bool body_available);
diff --git a/jbmc/src/java_bytecode/README.md b/jbmc/src/java_bytecode/README.md
index f7593c2a23e..04ec4b8eaee 100644
--- a/jbmc/src/java_bytecode/README.md
+++ b/jbmc/src/java_bytecode/README.md
@@ -674,10 +674,10 @@ determine which loading strategy to use.
 If [lazy_methods_mode](\ref java_bytecode_language_optionst::lazy_methods_mode) is
 \ref LAZY_METHODS_MODE_EAGER then eager loading is
 used. Under eager loading
-\ref java_bytecode_languaget::convert_single_method(const irep_idt &, symbol_table_baset &, lazy_class_to_declared_symbols_mapt &, message_handlert &)
+\ref java_bytecode_languaget::convert_single_method(irep_idt, symbol_table_baset &, lazy_class_to_declared_symbols_mapt &, message_handlert &)
 is called once for each method listed in method_bytecode (described above). This
 then calls
-\ref java_bytecode_languaget::convert_single_method(const irep_idt &, symbol_table_baset &, std::optional<ci_lazy_methods_neededt>, lazy_class_to_declared_symbols_mapt &, message_handlert &);
+\ref java_bytecode_languaget::convert_single_method(irep_idt, symbol_table_baset &, std::optional<ci_lazy_methods_neededt>, lazy_class_to_declared_symbols_mapt &, message_handlert &);
 
 without a ci_lazy_methods_neededt object, which calls
 \ref java_bytecode_convert_method, passing in the method parse tree. This in
diff --git a/jbmc/src/java_bytecode/assignments_from_json.cpp b/jbmc/src/java_bytecode/assignments_from_json.cpp
index dee711f00e6..f5b76e5e604 100644
--- a/jbmc/src/java_bytecode/assignments_from_json.cpp
+++ b/jbmc/src/java_bytecode/assignments_from_json.cpp
@@ -914,7 +914,7 @@ code_with_references_listt assign_from_json_rec(
 code_with_references_listt assign_from_json(
   const exprt &expr,
   const jsont &json,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   std::optional<ci_lazy_methods_neededt> &needed_lazy_methods,
   size_t max_user_array_length,
diff --git a/jbmc/src/java_bytecode/assignments_from_json.h b/jbmc/src/java_bytecode/assignments_from_json.h
index 328fbb5c9b4..155b20d88b0 100644
--- a/jbmc/src/java_bytecode/assignments_from_json.h
+++ b/jbmc/src/java_bytecode/assignments_from_json.h
@@ -98,7 +98,7 @@ class ci_lazy_methods_neededt;
 code_with_references_listt assign_from_json(
   const exprt &expr,
   const jsont &json,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   std::optional<ci_lazy_methods_neededt> &needed_lazy_methods,
   size_t max_user_array_length,
diff --git a/jbmc/src/java_bytecode/ci_lazy_methods.cpp b/jbmc/src/java_bytecode/ci_lazy_methods.cpp
index c565b16cda3..1977f3b1317 100644
--- a/jbmc/src/java_bytecode/ci_lazy_methods.cpp
+++ b/jbmc/src/java_bytecode/ci_lazy_methods.cpp
@@ -38,7 +38,7 @@ Author: Diffblue Ltd.
 ///   Java bytecode.
 ci_lazy_methodst::ci_lazy_methodst(
   const symbol_table_baset &symbol_table,
-  const irep_idt &main_class,
+  irep_idt main_class,
   const std::vector<irep_idt> &main_jar_classes,
   const std::vector<load_extra_methodst> &lazy_methods_extra_entry_points,
   java_class_loadert &java_class_loader,
@@ -331,7 +331,7 @@ ci_lazy_methodst::convert_and_analyze_method(
   const method_convertert &method_converter,
   std::unordered_set<irep_idt> &methods_already_populated,
   const bool class_initializer_already_seen,
-  const irep_idt &method_name,
+  irep_idt method_name,
   symbol_table_baset &symbol_table,
   std::unordered_set<irep_idt> &methods_to_convert_later,
   std::unordered_set<irep_idt> &instantiated_classes,
@@ -557,8 +557,8 @@ void ci_lazy_methodst::gather_needed_globals(
 ///   `instantiated_classes`, or irep_idt() otherwise.
 irep_idt ci_lazy_methodst::get_virtual_method_target(
   const std::unordered_set<irep_idt> &instantiated_classes,
-  const irep_idt &call_basename,
-  const irep_idt &classname,
+  irep_idt call_basename,
+  irep_idt classname,
   const symbol_table_baset &symbol_table)
 {
   // Program-wide, is this class ever instantiated?
diff --git a/jbmc/src/java_bytecode/ci_lazy_methods.h b/jbmc/src/java_bytecode/ci_lazy_methods.h
index f37e153589e..89bab35433c 100644
--- a/jbmc/src/java_bytecode/ci_lazy_methods.h
+++ b/jbmc/src/java_bytecode/ci_lazy_methods.h
@@ -50,7 +50,7 @@ class method_bytecodet
   mapt map;
 
 public:
-  bool contains_method(const irep_idt &method_id) const
+  bool contains_method(irep_idt method_id) const
   {
     return map.count(method_id) != 0;
   }
@@ -63,8 +63,8 @@ class method_bytecodet
   }
 
   void add(
-    const irep_idt &class_id,
-    const irep_idt &method_id,
+    irep_idt class_id,
+    irep_idt method_id,
     const java_bytecode_parse_treet::methodt &method)
   {
     add(class_method_and_bytecodet{class_id, method_id, method});
@@ -79,7 +79,7 @@ class method_bytecodet
     return map.end();
   }
 
-  opt_reft get(const irep_idt &method_id)
+  opt_reft get(irep_idt method_id)
   {
     const auto it = map.find(method_id);
     if(it == map.end())
@@ -88,8 +88,7 @@ class method_bytecodet
   }
 };
 
-typedef std::function<
-  bool(const irep_idt &function_id, ci_lazy_methods_neededt)>
+typedef std::function<bool(irep_idt function_id, ci_lazy_methods_neededt)>
   method_convertert;
 
 typedef std::function<std::vector<irep_idt>(const symbol_table_baset &)>
@@ -100,7 +99,7 @@ class ci_lazy_methodst
 public:
   ci_lazy_methodst(
     const symbol_table_baset &symbol_table,
-    const irep_idt &main_class,
+    irep_idt main_class,
     const std::vector<irep_idt> &main_jar_classes,
     const std::vector<load_extra_methodst> &lazy_methods_extra_entry_points,
     java_class_loadert &java_class_loader,
@@ -138,13 +137,13 @@ class ci_lazy_methodst
 
   irep_idt get_virtual_method_target(
     const std::unordered_set<irep_idt> &instantiated_classes,
-    const irep_idt &call_basename,
-    const irep_idt &classname,
+    irep_idt call_basename,
+    irep_idt classname,
     const symbol_table_baset &symbol_table);
 
   static irep_idt build_virtual_method_name(
-    const irep_idt &class_name,
-    const irep_idt &component_method_name);
+    irep_idt class_name,
+    irep_idt component_method_name);
 
   class_hierarchyt class_hierarchy;
   irep_idt main_class;
@@ -169,7 +168,7 @@ class ci_lazy_methodst
     const method_convertert &method_converter,
     std::unordered_set<irep_idt> &methods_already_populated,
     const bool class_initializer_already_seen,
-    const irep_idt &method_name,
+    irep_idt method_name,
     symbol_table_baset &symbol_table,
     std::unordered_set<irep_idt> &methods_to_convert_later,
     std::unordered_set<irep_idt> &instantiated_classes,
diff --git a/jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp b/jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp
index 11d5c7dac59..817326a9bed 100644
--- a/jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp
+++ b/jbmc/src/java_bytecode/ci_lazy_methods_needed.cpp
@@ -25,8 +25,7 @@ Author: Chris Smowton, chris.smowton@diffblue.com
 /// Notes `method_symbol_name` is referenced from some reachable function, and
 /// should therefore be elaborated.
 /// \param method_symbol_name: method name; must exist in symbol table.
-void ci_lazy_methods_neededt::add_needed_method(
-  const irep_idt &method_symbol_name)
+void ci_lazy_methods_neededt::add_needed_method(irep_idt method_symbol_name)
 {
   callable_methods.insert(method_symbol_name);
 }
@@ -39,7 +38,7 @@ void ci_lazy_methods_neededt::add_needed_method(
 /// __CPROVER_start in its initial setup, and because return values of opaque
 /// methods need to be considered in ci_lazy_methods too.
 /// \param class_id: The given class id
-void ci_lazy_methods_neededt::add_clinit_call(const irep_idt &class_id)
+void ci_lazy_methods_neededt::add_clinit_call(irep_idt class_id)
 {
   const irep_idt &clinit_wrapper = clinit_wrapper_name(class_id);
   if(symbol_table.symbols.count(clinit_wrapper))
@@ -50,7 +49,7 @@ void ci_lazy_methods_neededt::add_clinit_call(const irep_idt &class_id)
 /// ancestors then note that it is needed.
 /// \param class_id: The given class id
 void ci_lazy_methods_neededt::add_cprover_nondet_initialize_if_it_exists(
-  const irep_idt &class_id)
+  irep_idt class_id)
 {
   resolve_inherited_componentt resolve_inherited_component{symbol_table};
   std::optional<resolve_inherited_componentt::inherited_componentt>
@@ -69,8 +68,7 @@ void ci_lazy_methods_neededt::add_cprover_nondet_initialize_if_it_exists(
 /// therefore reachable.
 /// \param class_symbol_name: class name; must exist in symbol table.
 /// \return Returns true if `class_symbol_name` is new (not seen before).
-bool ci_lazy_methods_neededt::add_needed_class(
-  const irep_idt &class_symbol_name)
+bool ci_lazy_methods_neededt::add_needed_class(irep_idt class_symbol_name)
 {
   if(!instantiated_classes.insert(class_symbol_name).second)
     return false;
diff --git a/jbmc/src/java_bytecode/ci_lazy_methods_needed.h b/jbmc/src/java_bytecode/ci_lazy_methods_needed.h
index 305b248a508..ed8e726489f 100644
--- a/jbmc/src/java_bytecode/ci_lazy_methods_needed.h
+++ b/jbmc/src/java_bytecode/ci_lazy_methods_needed.h
@@ -36,9 +36,9 @@ class ci_lazy_methods_neededt
       pointer_type_selector(pointer_type_selector)
   {}
 
-  void add_needed_method(const irep_idt &);
+  void add_needed_method(irep_idt);
   // Returns true if new
-  bool add_needed_class(const irep_idt &);
+  bool add_needed_class(irep_idt);
 
   void add_all_needed_classes(const pointer_typet &pointer_type);
 
@@ -57,8 +57,8 @@ class ci_lazy_methods_neededt
 
   const select_pointer_typet &pointer_type_selector;
 
-  void add_clinit_call(const irep_idt &class_id);
-  void add_cprover_nondet_initialize_if_it_exists(const irep_idt &class_id);
+  void add_clinit_call(irep_idt class_id);
+  void add_cprover_nondet_initialize_if_it_exists(irep_idt class_id);
 
   void initialize_instantiated_classes_from_pointer(
     const pointer_typet &pointer_type,
diff --git a/jbmc/src/java_bytecode/convert_java_nondet.cpp b/jbmc/src/java_bytecode/convert_java_nondet.cpp
index 8df3b972964..89e08c4ca81 100644
--- a/jbmc/src/java_bytecode/convert_java_nondet.cpp
+++ b/jbmc/src/java_bytecode/convert_java_nondet.cpp
@@ -44,7 +44,7 @@ static goto_programt get_gen_nondet_init_instructions(
   symbol_table_baset &symbol_table,
   message_handlert &message_handler,
   const java_object_factory_parameterst &object_factory_parameters,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   code_blockt gen_nondet_init_code;
   const bool skip_classid = true;
@@ -79,13 +79,13 @@ static goto_programt get_gen_nondet_init_instructions(
 /// \return The next instruction to process with this function and a boolean
 ///   indicating whether any changes were made to the goto program.
 static std::pair<goto_programt::targett, bool> insert_nondet_init_code(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   const goto_programt::targett &target,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler,
   java_object_factory_parameterst object_factory_parameters,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const auto next_instr = std::next(target);
 
@@ -164,12 +164,12 @@ static std::pair<goto_programt::targett, bool> insert_nondet_init_code(
 ///   nondet objects.
 /// \param mode: Language mode
 void convert_nondet(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler,
   const java_object_factory_parameterst &user_object_factory_parameters,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   java_object_factory_parameterst object_factory_parameters =
     user_object_factory_parameters;
@@ -202,7 +202,7 @@ void convert_nondet(
   goto_model_functiont &function,
   message_handlert &message_handler,
   const java_object_factory_parameterst &object_factory_parameters,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   convert_nondet(
     function.get_function_id(),
diff --git a/jbmc/src/java_bytecode/convert_java_nondet.h b/jbmc/src/java_bytecode/convert_java_nondet.h
index 0dd9b971b84..2452ea6c088 100644
--- a/jbmc/src/java_bytecode/convert_java_nondet.h
+++ b/jbmc/src/java_bytecode/convert_java_nondet.h
@@ -64,6 +64,6 @@ void convert_nondet(
   goto_model_functiont &function,
   message_handlert &message_handler,
   const java_object_factory_parameterst &object_factory_parameters,
-  const irep_idt &mode);
+  irep_idt mode);
 
 #endif // CPROVER_JAVA_BYTECODE_CONVERT_NONDET_H
diff --git a/jbmc/src/java_bytecode/create_array_with_type_intrinsic.cpp b/jbmc/src/java_bytecode/create_array_with_type_intrinsic.cpp
index 4477488b6c1..3ac349de9a5 100644
--- a/jbmc/src/java_bytecode/create_array_with_type_intrinsic.cpp
+++ b/jbmc/src/java_bytecode/create_array_with_type_intrinsic.cpp
@@ -39,7 +39,7 @@ irep_idt get_create_array_with_type_name()
 /// \param message_handler: any GOTO program conversion errors are logged here
 /// \return new GOTO program body for `org.cprover.CProver.createArrayWithType`.
 codet create_array_with_type_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
diff --git a/jbmc/src/java_bytecode/create_array_with_type_intrinsic.h b/jbmc/src/java_bytecode/create_array_with_type_intrinsic.h
index 9712da07b92..5a9202c407d 100644
--- a/jbmc/src/java_bytecode/create_array_with_type_intrinsic.h
+++ b/jbmc/src/java_bytecode/create_array_with_type_intrinsic.h
@@ -20,7 +20,7 @@ class symbol_table_baset;
 irep_idt get_create_array_with_type_name();
 
 codet create_array_with_type_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler);
 
diff --git a/jbmc/src/java_bytecode/generic_parameter_specialization_map.cpp b/jbmc/src/java_bytecode/generic_parameter_specialization_map.cpp
index 5444a6f11f7..e0be2d23f2b 100644
--- a/jbmc/src/java_bytecode/generic_parameter_specialization_map.cpp
+++ b/jbmc/src/java_bytecode/generic_parameter_specialization_map.cpp
@@ -52,7 +52,7 @@ void generic_parameter_specialization_mapt::pop(std::size_t container_index)
 }
 
 std::optional<reference_typet>
-generic_parameter_specialization_mapt::pop(const irep_idt &parameter_name)
+generic_parameter_specialization_mapt::pop(irep_idt parameter_name)
 {
   const auto types_it = param_to_container.find(parameter_name);
   if(types_it == param_to_container.end())
diff --git a/jbmc/src/java_bytecode/generic_parameter_specialization_map.h b/jbmc/src/java_bytecode/generic_parameter_specialization_map.h
index 2a954e11e66..d93d025ad88 100644
--- a/jbmc/src/java_bytecode/generic_parameter_specialization_map.h
+++ b/jbmc/src/java_bytecode/generic_parameter_specialization_map.h
@@ -54,7 +54,7 @@ class generic_parameter_specialization_mapt
   /// \param parameter_name: The name of the type parameter
   /// \returns: The specialization for the given type parameter, if there was
   ///   one before the pop, or an empty std::optional if the stack was empty
-  std::optional<reference_typet> pop(const irep_idt &parameter_name);
+  std::optional<reference_typet> pop(irep_idt parameter_name);
 
   /// A wrapper for a generic_parameter_specialization_mapt and a namespacet
   /// that can be output to a stream
diff --git a/jbmc/src/java_bytecode/java_bytecode_concurrency_instrumentation.cpp b/jbmc/src/java_bytecode/java_bytecode_concurrency_instrumentation.cpp
index 0ae89521cdf..a57f6d65ef6 100644
--- a/jbmc/src/java_bytecode/java_bytecode_concurrency_instrumentation.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_concurrency_instrumentation.cpp
@@ -35,8 +35,8 @@ const std::string thread_id = CPROVER_PREFIX "_thread_id";// NOLINT(*)
 /// /return returns new or existing symbol.
 static symbolt add_or_get_symbol(
   symbol_table_baset &symbol_table,
-  const irep_idt &name,
-  const irep_idt &base_name,
+  irep_idt name,
+  irep_idt base_name,
   const typet &type,
   const exprt &value,
   const bool is_thread_local,
diff --git a/jbmc/src/java_bytecode/java_bytecode_convert_class.cpp b/jbmc/src/java_bytecode/java_bytecode_convert_class.cpp
index f600348b943..f06cf432d14 100644
--- a/jbmc/src/java_bytecode/java_bytecode_convert_class.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_convert_class.cpp
@@ -158,8 +158,7 @@ class java_bytecode_convert_classt
   /// \param class_name: class the method is declared on
   /// \param method: a `methodt` object from a java bytecode parse tree
   /// \return true if the method is an ignored method, else false
-  static bool is_ignored_method(
-    const irep_idt &class_name, const methodt &method)
+  static bool is_ignored_method(irep_idt class_name, const methodt &method)
   {
     static irep_idt org_cprover_CProver_name = "org.cprover.CProver";
     return
@@ -170,7 +169,7 @@ class java_bytecode_convert_classt
 
   bool check_field_exists(
     const fieldt &field,
-    const irep_idt &qualified_fieldname,
+    irep_idt qualified_fieldname,
     const struct_union_typet::componentst &fields) const;
 
   std::unordered_set<std::string> no_load_classes;
@@ -620,7 +619,7 @@ void java_bytecode_convert_classt::convert(
 
 bool java_bytecode_convert_classt::check_field_exists(
   const java_bytecode_parse_treet::fieldt &field,
-  const irep_idt &qualified_fieldname,
+  irep_idt qualified_fieldname,
   const struct_union_typet::componentst &fields) const
 {
   if(field.is_static)
@@ -1178,7 +1177,7 @@ void convert_java_annotations(
 /// the inner class are updated to point to the type parameters of the
 /// corresponding outer classes.
 void mark_java_implicitly_generic_class_type(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table)
 {
   const std::string qualified_class_name = "java::" + id2string(class_name);
diff --git a/jbmc/src/java_bytecode/java_bytecode_convert_class.h b/jbmc/src/java_bytecode/java_bytecode_convert_class.h
index 432dc8a7760..b29f8190e42 100644
--- a/jbmc/src/java_bytecode/java_bytecode_convert_class.h
+++ b/jbmc/src/java_bytecode/java_bytecode_convert_class.h
@@ -40,7 +40,7 @@ void convert_java_annotations(
   java_bytecode_parse_treet::annotationst &annotations);
 
 void mark_java_implicitly_generic_class_type(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table);
 
 /// Register in the \p symbol_table new symbols for the objects
diff --git a/jbmc/src/java_bytecode/java_bytecode_convert_method.cpp b/jbmc/src/java_bytecode/java_bytecode_convert_method.cpp
index a6e650389dc..35ea30c850d 100644
--- a/jbmc/src/java_bytecode/java_bytecode_convert_method.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_convert_method.cpp
@@ -61,7 +61,7 @@ Author: Daniel Kroening, kroening@kroening.com
 ///   Global symbol table.
 static void assign_parameter_names(
   java_method_typet &ftype,
-  const irep_idt &name_prefix,
+  irep_idt name_prefix,
   symbol_table_baset &symbol_table)
 {
   java_method_typet::parameterst &parameters = ftype.parameters();
@@ -92,11 +92,11 @@ static void assign_parameter_names(
 }
 
 void create_method_stub_symbol(
-  const irep_idt &identifier,
-  const irep_idt &base_name,
-  const irep_idt &pretty_name,
+  irep_idt identifier,
+  irep_idt base_name,
+  irep_idt pretty_name,
   const typet &type,
-  const irep_idt &declaring_class,
+  irep_idt declaring_class,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -116,7 +116,7 @@ void create_method_stub_symbol(
   symbol_table.add(symbol);
 }
 
-static bool is_constructor(const irep_idt &method_name)
+static bool is_constructor(irep_idt method_name)
 {
   return id2string(method_name).find("<init>") != std::string::npos;
 }
@@ -155,7 +155,7 @@ void java_bytecode_convert_methodt::push(const exprt::operandst &o)
 }
 
 // JVM program locations
-irep_idt java_bytecode_convert_methodt::label(const irep_idt &address)
+irep_idt java_bytecode_convert_methodt::label(irep_idt address)
 {
   return "pc"+id2string(address);
 }
@@ -298,7 +298,7 @@ java_method_typet member_type_lazy(
 /// \param message_handler: A message handler to collect warnings.
 void java_bytecode_convert_method_lazy(
   symbolt &class_symbol,
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   const java_bytecode_parse_treet::methodt &m,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
@@ -411,7 +411,7 @@ void java_bytecode_convert_method_lazy(
 }
 
 static irep_idt get_method_identifier(
-  const irep_idt &class_identifier,
+  irep_idt class_identifier,
   const java_bytecode_parse_treet::methodt &method)
 {
   return
@@ -421,7 +421,7 @@ static irep_idt get_method_identifier(
 
 void create_parameter_names(
   const java_bytecode_parse_treet::methodt &m,
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   java_method_typet::parameterst &parameters,
   const java_bytecode_convert_methodt::method_offsett &slots_for_parameters)
 {
@@ -694,8 +694,8 @@ static member_exprt to_member(
 /// \param new_label: The label to replace `old_label` with.
 void java_bytecode_convert_methodt::replace_goto_target(
   codet &repl,
-  const irep_idt &old_label,
-  const irep_idt &new_label)
+  irep_idt old_label,
+  irep_idt new_label)
 {
   const auto &stmt=repl.get_statement();
   if(stmt==ID_goto)
@@ -981,8 +981,7 @@ static void gather_symbol_live_ranges(
 /// \param classname: Class name
 /// \return Returns a function call to the given class' static initializer
 ///   wrapper if one is needed, or a skip instruction otherwise.
-codet java_bytecode_convert_methodt::get_clinit_call(
-  const irep_idt &classname)
+codet java_bytecode_convert_methodt::get_clinit_call(irep_idt classname)
 {
   auto findit = symbol_table.symbols.find(clinit_wrapper_name(classname));
   if(findit == symbol_table.symbols.end())
@@ -2031,7 +2030,7 @@ java_bytecode_convert_methodt::convert_instructions(const methodt &method)
 }
 
 codet java_bytecode_convert_methodt::convert_pop(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op)
 {
   // these are skips
@@ -2097,7 +2096,7 @@ code_switcht java_bytecode_convert_methodt::convert_switch(
 }
 
 codet java_bytecode_convert_methodt::convert_monitorenterexit(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op,
   const source_locationt &source_location)
 {
@@ -2167,7 +2166,7 @@ void java_bytecode_convert_methodt::convert_dup2_x2(
 }
 
 exprt::operandst &java_bytecode_convert_methodt::convert_const(
-  const irep_idt &statement,
+  irep_idt statement,
   const constant_exprt &arg0,
   exprt::operandst &results) const
 {
@@ -2230,7 +2229,7 @@ static void adjust_invoke_argument_types(
 
 void java_bytecode_convert_methodt::convert_invoke(
   source_locationt location,
-  const irep_idt &statement,
+  irep_idt statement,
   class_method_descriptor_exprt &class_method_descriptor,
   codet &c,
   exprt::operandst &results)
@@ -2568,7 +2567,7 @@ code_blockt java_bytecode_convert_methodt::convert_multianewarray(
 
 code_blockt java_bytecode_convert_methodt::convert_newarray(
   const source_locationt &location,
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt &arg0,
   const exprt::operandst &op,
   exprt::operandst &results)
@@ -2737,7 +2736,7 @@ void java_bytecode_convert_methodt::convert_getstatic(
 }
 
 exprt::operandst &java_bytecode_convert_methodt::convert_cmp2(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op,
   exprt::operandst &results) const
 {
@@ -2785,7 +2784,7 @@ exprt::operandst &java_bytecode_convert_methodt::convert_cmp(
 }
 
 exprt::operandst &java_bytecode_convert_methodt::convert_shl(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op,
   exprt::operandst &results) const
 {
@@ -2802,7 +2801,7 @@ exprt::operandst &java_bytecode_convert_methodt::convert_shl(
 }
 
 exprt::operandst &java_bytecode_convert_methodt::convert_ushr(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op,
   exprt::operandst &results) const
 {
@@ -2896,7 +2895,7 @@ code_ifthenelset java_bytecode_convert_methodt::convert_ifnonull(
 code_ifthenelset java_bytecode_convert_methodt::convert_if(
   const java_bytecode_convert_methodt::address_mapt &address_map,
   const exprt::operandst &op,
-  const irep_idt &id,
+  irep_idt id,
   const mp_integer &number,
   const source_locationt &location) const
 {
@@ -2991,7 +2990,7 @@ static exprt conditional_array_cast(const exprt &expr, char type_char)
 }
 
 exprt java_bytecode_convert_methodt::convert_aload(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op)
 {
   PRECONDITION(op.size() == 2);
@@ -3032,7 +3031,7 @@ exprt java_bytecode_convert_methodt::convert_load(
 }
 
 code_blockt java_bytecode_convert_methodt::convert_store(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt &arg0,
   const exprt::operandst &op,
   const method_offsett address,
@@ -3057,7 +3056,7 @@ code_blockt java_bytecode_convert_methodt::convert_store(
 }
 
 code_blockt java_bytecode_convert_methodt::convert_astore(
-  const irep_idt &statement,
+  irep_idt statement,
   const exprt::operandst &op,
   const source_locationt &location)
 {
@@ -3313,8 +3312,8 @@ void java_bytecode_convert_method(
 /// \param classname: class whose method is referenced
 /// \param mangled_method_name: The particular overload of a given method.
 bool java_bytecode_convert_methodt::is_method_inherited(
-  const irep_idt &classname,
-  const irep_idt &mangled_method_name) const
+  irep_idt classname,
+  irep_idt mangled_method_name) const
 {
   const auto inherited_method = get_inherited_method_implementation(
     mangled_method_name, classname, symbol_table);
@@ -3328,8 +3327,8 @@ bool java_bytecode_convert_methodt::is_method_inherited(
 /// \param component_name: component (static field) name
 /// \return identifier of the actual concrete field referred to
 irep_idt java_bytecode_convert_methodt::get_static_field(
-  const irep_idt &class_identifier,
-  const irep_idt &component_name) const
+  irep_idt class_identifier,
+  irep_idt component_name) const
 {
   const auto inherited_method = get_inherited_component(
     class_identifier, component_name, symbol_table, true);
@@ -3350,7 +3349,7 @@ void java_bytecode_convert_methodt::save_stack_entries(
   const std::string &tmp_var_prefix,
   code_blockt &block,
   const bytecode_write_typet write_type,
-  const irep_idt &identifier)
+  irep_idt identifier)
 {
   const std::function<bool(
     const std::function<tvt(const exprt &expr)>, const exprt &expr)>
diff --git a/jbmc/src/java_bytecode/java_bytecode_convert_method.h b/jbmc/src/java_bytecode/java_bytecode_convert_method.h
index 8ad5d25ad96..d63b854ff32 100644
--- a/jbmc/src/java_bytecode/java_bytecode_convert_method.h
+++ b/jbmc/src/java_bytecode/java_bytecode_convert_method.h
@@ -39,17 +39,17 @@ void java_bytecode_convert_method(
   bool assert_no_exceptions_thrown);
 
 void create_method_stub_symbol(
-  const irep_idt &identifier,
-  const irep_idt &base_name,
-  const irep_idt &pretty_name,
+  irep_idt identifier,
+  irep_idt base_name,
+  irep_idt pretty_name,
   const typet &type,
-  const irep_idt &declaring_class,
+  irep_idt declaring_class,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler);
 
 void java_bytecode_convert_method_lazy(
   symbolt &class_symbol,
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   const java_bytecode_parse_treet::methodt &,
   symbol_table_baset &symbol_table,
   message_handlert &);
@@ -69,7 +69,7 @@ typedef expanding_vectort<std::vector<java_bytecode_convert_methodt::variablet>>
 /// i.e. a positive integer
 void create_parameter_names(
   const java_bytecode_parse_treet::methodt &m,
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   java_method_typet::parameterst &parameters,
   const java_bytecode_convert_methodt::method_offsett &slots_for_parameters);
 
diff --git a/jbmc/src/java_bytecode/java_bytecode_convert_method_class.h b/jbmc/src/java_bytecode/java_bytecode_convert_method_class.h
index 2d12b5377bd..bb245e9fa7b 100644
--- a/jbmc/src/java_bytecode/java_bytecode_convert_method_class.h
+++ b/jbmc/src/java_bytecode/java_bytecode_convert_method_class.h
@@ -201,7 +201,7 @@ class java_bytecode_convert_methodt
   symbol_exprt tmp_variable(const std::string &prefix, const typet &type);
 
   // JVM program locations
-  static irep_idt label(const irep_idt &address);
+  static irep_idt label(irep_idt address);
 
   // JVM Stack
   typedef std::vector<exprt> stackt;
@@ -294,10 +294,8 @@ class java_bytecode_convert_methodt
     }
   };
 
-  static void replace_goto_target(
-    codet &repl,
-    const irep_idt &old_label,
-    const irep_idt &new_label);
+  static void
+  replace_goto_target(codet &repl, irep_idt old_label, irep_idt new_label);
 
   code_blockt &get_block_for_pcrange(
     block_tree_nodet &tree,
@@ -327,14 +325,13 @@ class java_bytecode_convert_methodt
 
   code_blockt convert_instructions(const methodt &);
 
-  codet get_clinit_call(const irep_idt &classname);
+  codet get_clinit_call(irep_idt classname);
 
-  bool is_method_inherited(
-    const irep_idt &classname,
-    const irep_idt &mangled_method_name) const;
+  bool
+  is_method_inherited(irep_idt classname, irep_idt mangled_method_name) const;
 
-  irep_idt get_static_field(
-    const irep_idt &class_identifier, const irep_idt &component_name) const;
+  irep_idt
+  get_static_field(irep_idt class_identifier, irep_idt component_name) const;
 
   enum class bytecode_write_typet
   {
@@ -348,7 +345,7 @@ class java_bytecode_convert_methodt
     const std::string &,
     code_blockt &,
     const bytecode_write_typet,
-    const irep_idt &);
+    irep_idt);
 
   void create_stack_tmp_var(
     const std::string &,
@@ -375,19 +372,18 @@ class java_bytecode_convert_methodt
     codet &result_code);
 
   code_blockt convert_astore(
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt::operandst &op,
     const source_locationt &location);
 
   code_blockt convert_store(
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt &arg0,
     const exprt::operandst &op,
     const method_offsett address,
     const source_locationt &location);
 
-  static exprt
-  convert_aload(const irep_idt &statement, const exprt::operandst &op);
+  static exprt convert_aload(irep_idt statement, const exprt::operandst &op);
 
   /// Load reference from local variable.
   /// \p index must be an unsigned byte and an index in the local variable array
@@ -416,7 +412,7 @@ class java_bytecode_convert_methodt
   code_ifthenelset convert_if(
     const java_bytecode_convert_methodt::address_mapt &address_map,
     const exprt::operandst &op,
-    const irep_idt &id,
+    irep_idt id,
     const mp_integer &number,
     const source_locationt &location) const;
 
@@ -439,12 +435,12 @@ class java_bytecode_convert_methodt
     method_offsett address);
 
   exprt::operandst &convert_shl(
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt::operandst &op,
     exprt::operandst &results) const;
 
   exprt::operandst &convert_ushr(
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt::operandst &op,
     exprt::operandst &results) const;
 
@@ -452,7 +448,7 @@ class java_bytecode_convert_methodt
   convert_cmp(const exprt::operandst &op, exprt::operandst &results) const;
 
   exprt::operandst &convert_cmp2(
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt::operandst &op,
     exprt::operandst &results) const;
 
@@ -481,7 +477,7 @@ class java_bytecode_convert_methodt
 
   code_blockt convert_newarray(
     const source_locationt &location,
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt &arg0,
     const exprt::operandst &op,
     exprt::operandst &results);
@@ -511,7 +507,7 @@ class java_bytecode_convert_methodt
     exprt::operandst &results) const;
 
   codet convert_monitorenterexit(
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt::operandst &op,
     const source_locationt &source_location);
 
@@ -519,13 +515,13 @@ class java_bytecode_convert_methodt
 
   void convert_invoke(
     source_locationt location,
-    const irep_idt &statement,
+    irep_idt statement,
     class_method_descriptor_exprt &class_method_descriptor,
     codet &c,
     exprt::operandst &results);
 
   exprt::operandst &convert_const(
-    const irep_idt &statement,
+    irep_idt statement,
     const constant_exprt &arg0,
     exprt::operandst &results) const;
 
@@ -540,7 +536,7 @@ class java_bytecode_convert_methodt
     const java_bytecode_parse_treet::instructiont::argst &args,
     const source_locationt &location);
 
-  codet convert_pop(const irep_idt &statement, const exprt::operandst &op);
+  codet convert_pop(irep_idt statement, const exprt::operandst &op);
 
   friend class java_bytecode_convert_method_unit_testt;
 };
diff --git a/jbmc/src/java_bytecode/java_bytecode_instrument.cpp b/jbmc/src/java_bytecode/java_bytecode_instrument.cpp
index a37d6688be9..cc8c67b7587 100644
--- a/jbmc/src/java_bytecode/java_bytecode_instrument.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_instrument.cpp
@@ -44,7 +44,7 @@ class java_bytecode_instrumentt
   code_ifthenelset throw_exception(
     const exprt &cond,
     const source_locationt &original_loc,
-    const irep_idt &exc_name);
+    irep_idt exc_name);
 
   codet check_array_access(
     const exprt &array_struct,
@@ -93,7 +93,7 @@ const std::vector<std::string> exception_needed_classes = {
 code_ifthenelset java_bytecode_instrumentt::throw_exception(
   const exprt &cond,
   const source_locationt &original_loc,
-  const irep_idt &exc_name)
+  irep_idt exc_name)
 {
   irep_idt exc_class_name("java::"+id2string(exc_name));
 
diff --git a/jbmc/src/java_bytecode/java_bytecode_language.cpp b/jbmc/src/java_bytecode/java_bytecode_language.cpp
index b982ff625b0..0a4f87f6ec6 100644
--- a/jbmc/src/java_bytecode/java_bytecode_language.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_language.cpp
@@ -305,9 +305,8 @@ void java_bytecode_languaget::initialize_class_loader(
   {
     string_preprocess.initialize_known_type_table();
 
-    auto get_string_base_classes = [this](const irep_idt &id) {
-      return string_preprocess.get_string_type_base_classes(id);
-    };
+    auto get_string_base_classes = [this](irep_idt id)
+    { return string_preprocess.get_string_type_base_classes(id); };
 
     java_class_loader.set_extra_class_refs_function(get_string_base_classes);
   }
@@ -511,7 +510,7 @@ static void infer_opaque_type_fields(
 /// \param symbol_table: global symbol table; a symbol may be added
 /// \return java.lang.Class typed symbol expression
 static symbol_exprt get_or_create_class_literal_symbol(
-  const irep_idt &class_id,
+  irep_idt class_id,
   symbol_table_baset &symbol_table)
 {
   struct_tag_typet java_lang_Class("java::java.lang.Class");
@@ -635,10 +634,10 @@ static void generate_constant_global_variables(
 ///   to be created later.
 static void create_stub_global_symbol(
   symbol_table_baset &symbol_table,
-  const irep_idt &symbol_id,
-  const irep_idt &symbol_basename,
+  irep_idt symbol_id,
+  irep_idt symbol_basename,
   const typet &symbol_type,
-  const irep_idt &class_id,
+  irep_idt class_id,
   bool force_nondet_init)
 {
   symbolt new_symbol{symbol_id, symbol_type, ID_java};
@@ -675,7 +674,7 @@ static void create_stub_global_symbol(
 /// \return first incomplete ancestor encountered,
 ///   including start_class_id itself.
 static irep_idt get_any_incomplete_ancestor_for_stub_static_field(
-  const irep_idt &start_class_id,
+  irep_idt start_class_id,
   const symbol_table_baset &symbol_table,
   const class_hierarchyt &class_hierarchy)
 {
@@ -1120,15 +1119,15 @@ bool java_bytecode_languaget::do_ci_lazy_method_conversion(
 
   const method_convertert method_converter =
     [this, &symbol_table_builder, &class_to_declared_symbols, &message_handler](
-      const irep_idt &function_id,
-      ci_lazy_methods_neededt lazy_methods_needed) {
-      return convert_single_method(
-        function_id,
-        symbol_table_builder,
-        std::move(lazy_methods_needed),
-        class_to_declared_symbols,
-        message_handler);
-    };
+      irep_idt function_id, ci_lazy_methods_neededt lazy_methods_needed)
+  {
+    return convert_single_method(
+      function_id,
+      symbol_table_builder,
+      std::move(lazy_methods_needed),
+      class_to_declared_symbols,
+      message_handler);
+  };
 
   ci_lazy_methodst method_gather(
     symbol_table,
@@ -1182,7 +1181,7 @@ void java_bytecode_languaget::methods_provided(
 /// \param symtab: global symbol table
 /// \param message_handler: message handler
 void java_bytecode_languaget::convert_lazy_method(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symtab,
   message_handlert &message_handler)
 {
@@ -1280,7 +1279,7 @@ static void notify_static_method_calls(
 ///   they declare.
 /// \param message_handler: message handler
 bool java_bytecode_languaget::convert_single_method(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   std::optional<ci_lazy_methods_neededt> needed_lazy_methods,
   lazy_class_to_declared_symbols_mapt &class_to_declared_symbols,
@@ -1339,7 +1338,7 @@ bool java_bytecode_languaget::convert_single_method(
 ///   they declare.
 /// \param message_handler: message handler
 bool java_bytecode_languaget::convert_single_method_code(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   std::optional<ci_lazy_methods_neededt> needed_lazy_methods,
   lazy_class_to_declared_symbols_mapt &class_to_declared_symbols,
diff --git a/jbmc/src/java_bytecode/java_bytecode_language.h b/jbmc/src/java_bytecode/java_bytecode_language.h
index 1142e1fee0c..8f864ee7473 100644
--- a/jbmc/src/java_bytecode/java_bytecode_language.h
+++ b/jbmc/src/java_bytecode/java_bytecode_language.h
@@ -329,13 +329,13 @@ class java_bytecode_languaget:public languaget
   virtual void
   methods_provided(std::unordered_set<irep_idt> &methods) const override;
   virtual void convert_lazy_method(
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler) override;
 
 protected:
   void convert_single_method(
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     lazy_class_to_declared_symbols_mapt &class_to_declared_symbols,
     message_handlert &message_handler)
@@ -348,13 +348,13 @@ class java_bytecode_languaget:public languaget
       message_handler);
   }
   bool convert_single_method(
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     std::optional<ci_lazy_methods_neededt> needed_lazy_methods,
     lazy_class_to_declared_symbols_mapt &class_to_declared_symbols,
     message_handlert &);
   bool convert_single_method_code(
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     std::optional<ci_lazy_methods_neededt> needed_lazy_methods,
     lazy_class_to_declared_symbols_mapt &class_to_declared_symbols,
diff --git a/jbmc/src/java_bytecode/java_bytecode_parse_tree.cpp b/jbmc/src/java_bytecode/java_bytecode_parse_tree.cpp
index 3aa3449e4c6..520e8332f9f 100644
--- a/jbmc/src/java_bytecode/java_bytecode_parse_tree.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_parse_tree.cpp
@@ -94,7 +94,7 @@ void java_bytecode_parse_treet::annotationt::element_value_pairt::output(
 std::optional<java_bytecode_parse_treet::annotationt>
 java_bytecode_parse_treet::find_annotation(
   const annotationst &annotations,
-  const irep_idt &annotation_type_name)
+  irep_idt annotation_type_name)
 {
   const auto annotation_it = std::find_if(
     annotations.begin(),
diff --git a/jbmc/src/java_bytecode/java_bytecode_parse_tree.h b/jbmc/src/java_bytecode/java_bytecode_parse_tree.h
index cd1544ef3c1..756049d095a 100644
--- a/jbmc/src/java_bytecode/java_bytecode_parse_tree.h
+++ b/jbmc/src/java_bytecode/java_bytecode_parse_tree.h
@@ -50,7 +50,7 @@ struct java_bytecode_parse_treet
 
   static std::optional<annotationt> find_annotation(
     const annotationst &annotations,
-    const irep_idt &annotation_type_name);
+    irep_idt annotation_type_name);
 
   struct instructiont
   {
@@ -75,7 +75,7 @@ struct java_bytecode_parse_treet
     {
     }
 
-    bool has_annotation(const irep_idt &annotation_id) const
+    bool has_annotation(irep_idt annotation_id) const
     {
       return find_annotation(annotations, annotation_id).has_value();
     }
@@ -198,7 +198,7 @@ struct java_bytecode_parse_treet
     classt() = default;
 
     /// Create a class \p name.
-    explicit classt(const irep_idt &name) : name(name)
+    explicit classt(irep_idt name) : name(name)
     {
     }
 
@@ -321,7 +321,7 @@ struct java_bytecode_parse_treet
   java_bytecode_parse_treet() = default;
 
   /// Create a blank parse tree for class \p class_name.
-  explicit java_bytecode_parse_treet(const irep_idt &class_name)
+  explicit java_bytecode_parse_treet(irep_idt class_name)
     : parsed_class(class_name)
   {
   }
@@ -335,8 +335,8 @@ class fieldref_exprt : public exprt
 public:
   fieldref_exprt(
     const typet &type,
-    const irep_idt &component_name,
-    const irep_idt &class_name)
+    irep_idt component_name,
+    irep_idt class_name)
     : exprt(ID_empty_string, type)
   {
     set(ID_class, class_name);
diff --git a/jbmc/src/java_bytecode/java_bytecode_parser.cpp b/jbmc/src/java_bytecode/java_bytecode_parser.cpp
index cc55bc738ea..dea9f122311 100644
--- a/jbmc/src/java_bytecode/java_bytecode_parser.cpp
+++ b/jbmc/src/java_bytecode/java_bytecode_parser.cpp
@@ -1817,7 +1817,7 @@ void java_bytecode_parsert::rmethod()
 
 std::optional<java_bytecode_parse_treet> java_bytecode_parse(
   std::istream &istream,
-  const irep_idt &class_name,
+  irep_idt class_name,
   message_handlert &message_handler,
   bool skip_instructions)
 {
@@ -1839,7 +1839,7 @@ std::optional<java_bytecode_parse_treet> java_bytecode_parse(
 
 std::optional<java_bytecode_parse_treet> java_bytecode_parse(
   const std::string &file,
-  const irep_idt &class_name,
+  irep_idt class_name,
   message_handlert &message_handler,
   bool skip_instructions)
 {
diff --git a/jbmc/src/java_bytecode/java_bytecode_parser.h b/jbmc/src/java_bytecode/java_bytecode_parser.h
index 9150428b686..cffc909d2f2 100644
--- a/jbmc/src/java_bytecode/java_bytecode_parser.h
+++ b/jbmc/src/java_bytecode/java_bytecode_parser.h
@@ -27,7 +27,7 @@ struct java_bytecode_parse_treet;
 /// \return parse tree, or empty std::optional on failure
 std::optional<java_bytecode_parse_treet> java_bytecode_parse(
   const std::string &file,
-  const irep_idt &class_name,
+  irep_idt class_name,
   class message_handlert &msg,
   bool skip_instructions = false);
 
@@ -40,7 +40,7 @@ std::optional<java_bytecode_parse_treet> java_bytecode_parse(
 /// \return parse tree, or empty std::optional on failure
 std::optional<java_bytecode_parse_treet> java_bytecode_parse(
   std::istream &stream,
-  const irep_idt &class_name,
+  irep_idt class_name,
   class message_handlert &msg,
   bool skip_instructions = false);
 
diff --git a/jbmc/src/java_bytecode/java_class_loader.cpp b/jbmc/src/java_bytecode/java_class_loader.cpp
index 19b0c698d31..cf92bdd3161 100644
--- a/jbmc/src/java_bytecode/java_class_loader.cpp
+++ b/jbmc/src/java_bytecode/java_class_loader.cpp
@@ -15,8 +15,9 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include "java_class_loader_limit.h"
 
-java_class_loadert::parse_tree_with_overlayst &java_class_loadert::
-operator()(const irep_idt &class_name, message_handlert &message_handler)
+java_class_loadert::parse_tree_with_overlayst &java_class_loadert::operator()(
+  irep_idt class_name,
+  message_handlert &message_handler)
 {
   messaget log(message_handler);
 
@@ -105,7 +106,7 @@ static bool is_overlay_class(const java_bytecode_parse_treet::classt &c)
 }
 
 bool java_class_loadert::can_load_class(
-  const irep_idt &class_name,
+  irep_idt class_name,
   message_handlert &message_handler)
 {
   for(const auto &cp_entry : classpath_entries)
@@ -133,7 +134,7 @@ bool java_class_loadert::can_load_class(
 java_class_loadert::parse_tree_with_overlayst &
 java_class_loadert::get_parse_tree(
   java_class_loader_limitt &class_loader_limit,
-  const irep_idt &class_name,
+  irep_idt class_name,
   message_handlert &message_handler)
 {
   parse_tree_with_overlayst &parse_trees = class_map[class_name];
diff --git a/jbmc/src/java_bytecode/java_class_loader.h b/jbmc/src/java_bytecode/java_class_loader.h
index 163cc1df220..1f5ab90af90 100644
--- a/jbmc/src/java_bytecode/java_class_loader.h
+++ b/jbmc/src/java_bytecode/java_class_loader.h
@@ -33,7 +33,7 @@ class java_class_loadert : public java_class_loader_baset
     parse_tree_with_overridest_mapt;
 
   /// A function that yields a list of extra dependencies based on a class name.
-  typedef std::function<std::vector<irep_idt>(const irep_idt &)>
+  typedef std::function<std::vector<irep_idt>(irep_idt)>
     get_extra_class_refs_functiont;
 
   java_class_loadert()
@@ -41,15 +41,15 @@ class java_class_loadert : public java_class_loader_baset
   }
 
   parse_tree_with_overlayst &
-  operator()(const irep_idt &class_name, message_handlert &);
+  operator()(irep_idt class_name, message_handlert &);
 
   /// Checks whether \p class_name is parseable from the classpath,
   /// ignoring class loading limits.
-  bool can_load_class(const irep_idt &class_name, message_handlert &);
+  bool can_load_class(irep_idt class_name, message_handlert &);
 
   parse_tree_with_overlayst &get_parse_tree(
     java_class_loader_limitt &class_loader_limit,
-    const irep_idt &class_name,
+    irep_idt class_name,
     message_handlert &);
 
   /// Set the argument of the class loader limit \ref java_class_loader_limitt
@@ -84,8 +84,7 @@ class java_class_loadert : public java_class_loader_baset
   {
     return fixed_keys_map_wrappert<parse_tree_with_overridest_mapt>(class_map);
   }
-  const java_bytecode_parse_treet &get_original_class(
-    const irep_idt &class_name)
+  const java_bytecode_parse_treet &get_original_class(irep_idt class_name)
   {
     return class_map.at(class_name).front();
   }
diff --git a/jbmc/src/java_bytecode/java_class_loader_base.cpp b/jbmc/src/java_bytecode/java_class_loader_base.cpp
index 24efaaf881c..49d41a27c80 100644
--- a/jbmc/src/java_bytecode/java_class_loader_base.cpp
+++ b/jbmc/src/java_bytecode/java_class_loader_base.cpp
@@ -92,8 +92,7 @@ std::string java_class_loader_baset::file_to_class_name(const std::string &file)
 /// file_to_class_name.
 /// \param class_name: the name of the class
 /// \return the class name converted to file name
-std::string
-java_class_loader_baset::class_name_to_jar_file(const irep_idt &class_name)
+std::string java_class_loader_baset::class_name_to_jar_file(irep_idt class_name)
 {
   std::string result = id2string(class_name);
 
@@ -111,8 +110,7 @@ java_class_loader_baset::class_name_to_jar_file(const irep_idt &class_name)
 /// Convert a class name to a file name, with OS-dependent syntax
 /// \param class_name: the name of the class
 /// \return the class name converted to file name
-std::string
-java_class_loader_baset::class_name_to_os_file(const irep_idt &class_name)
+std::string java_class_loader_baset::class_name_to_os_file(irep_idt class_name)
 {
   std::string result = id2string(class_name);
 
@@ -135,7 +133,7 @@ java_class_loader_baset::class_name_to_os_file(const irep_idt &class_name)
 
 /// attempt to load a class from a classpath_entry
 std::optional<java_bytecode_parse_treet> java_class_loader_baset::load_class(
-  const irep_idt &class_name,
+  irep_idt class_name,
   const classpath_entryt &cp_entry,
   message_handlert &message_handler)
 {
@@ -158,7 +156,7 @@ std::optional<java_bytecode_parse_treet> java_class_loader_baset::load_class(
 /// \return optional value of parse tree, empty if class cannot be loaded
 std::optional<java_bytecode_parse_treet>
 java_class_loader_baset::get_class_from_jar(
-  const irep_idt &class_name,
+  irep_idt class_name,
   const std::string &jar_file,
   message_handlert &message_handler)
 {
@@ -193,7 +191,7 @@ java_class_loader_baset::get_class_from_jar(
 /// \return optional value of parse tree, empty if class cannot be loaded
 std::optional<java_bytecode_parse_treet>
 java_class_loader_baset::get_class_from_directory(
-  const irep_idt &class_name,
+  irep_idt class_name,
   const std::string &path,
   message_handlert &message_handler)
 {
diff --git a/jbmc/src/java_bytecode/java_class_loader_base.h b/jbmc/src/java_bytecode/java_class_loader_base.h
index 7507b35a6cc..b19f4ae4fb4 100644
--- a/jbmc/src/java_bytecode/java_class_loader_base.h
+++ b/jbmc/src/java_bytecode/java_class_loader_base.h
@@ -35,8 +35,8 @@ class java_class_loader_baset
   void add_classpath_entry(const std::string &, message_handlert &);
 
   static std::string file_to_class_name(const std::string &);
-  static std::string class_name_to_os_file(const irep_idt &);
-  static std::string class_name_to_jar_file(const irep_idt &);
+  static std::string class_name_to_os_file(irep_idt);
+  static std::string class_name_to_jar_file(irep_idt);
 
   /// a cache for jar_filet, by path name
   jar_poolt jar_pool;
@@ -59,20 +59,18 @@ class java_class_loader_baset
   std::list<classpath_entryt> classpath_entries;
 
   /// attempt to load a class from a classpath_entry
-  std::optional<java_bytecode_parse_treet> load_class(
-    const irep_idt &class_name,
-    const classpath_entryt &,
-    message_handlert &);
+  std::optional<java_bytecode_parse_treet>
+  load_class(irep_idt class_name, const classpath_entryt &, message_handlert &);
 
   /// attempt to load a class from a given jar file
   std::optional<java_bytecode_parse_treet> get_class_from_jar(
-    const irep_idt &class_name,
+    irep_idt class_name,
     const std::string &jar_file,
     message_handlert &);
 
   /// attempt to load a class from a given directory
   std::optional<java_bytecode_parse_treet> get_class_from_directory(
-    const irep_idt &class_name,
+    irep_idt class_name,
     const std::string &path,
     message_handlert &);
 };
diff --git a/jbmc/src/java_bytecode/java_entry_point.cpp b/jbmc/src/java_bytecode/java_entry_point.cpp
index fa074554c8e..9f84935d451 100644
--- a/jbmc/src/java_bytecode/java_entry_point.cpp
+++ b/jbmc/src/java_bytecode/java_entry_point.cpp
@@ -547,7 +547,7 @@ static codet record_exception(
 
 main_function_resultt get_main_symbol(
   const symbol_table_baset &symbol_table,
-  const irep_idt &main_class,
+  irep_idt main_class,
   message_handlert &message_handler)
 {
   messaget message(message_handler);
@@ -601,7 +601,7 @@ main_function_resultt get_main_symbol(
 
 bool java_entry_point(
   symbol_table_baset &symbol_table,
-  const irep_idt &main_class,
+  irep_idt main_class,
   message_handlert &message_handler,
   bool assume_init_pointers_not_null,
   bool assert_uncaught_exceptions,
diff --git a/jbmc/src/java_bytecode/java_entry_point.h b/jbmc/src/java_bytecode/java_entry_point.h
index 077a0438db0..16db9748192 100644
--- a/jbmc/src/java_bytecode/java_entry_point.h
+++ b/jbmc/src/java_bytecode/java_entry_point.h
@@ -76,7 +76,7 @@ using build_argumentst =
 /// \return true if error occurred on entry point search
 bool java_entry_point(
   class symbol_table_baset &symbol_table,
-  const irep_idt &main_class,
+  irep_idt main_class,
   class message_handlert &message_handler,
   bool assume_init_pointers_not_null,
   bool assert_uncaught_exceptions,
@@ -139,7 +139,7 @@ irep_idt get_java_class_literal_initializer_signature();
 /// Figures out the entry point of the code to verify
 main_function_resultt get_main_symbol(
   const symbol_table_baset &symbol_table,
-  const irep_idt &main_class,
+  irep_idt main_class,
   message_handlert &);
 
 /// Generate a _start function for a specific function. See
diff --git a/jbmc/src/java_bytecode/java_multi_path_symex_checker.cpp b/jbmc/src/java_bytecode/java_multi_path_symex_checker.cpp
index 6bd53817086..92424fced11 100644
--- a/jbmc/src/java_bytecode/java_multi_path_symex_checker.cpp
+++ b/jbmc/src/java_bytecode/java_multi_path_symex_checker.cpp
@@ -18,7 +18,7 @@ goto_tracet java_multi_path_symex_checkert::build_full_trace() const
 }
 
 goto_tracet
-java_multi_path_symex_checkert::build_trace(const irep_idt &property_id) const
+java_multi_path_symex_checkert::build_trace(irep_idt property_id) const
 {
   goto_tracet goto_trace = multi_path_symex_checkert::build_trace(property_id);
   check_trace_assumptions(
diff --git a/jbmc/src/java_bytecode/java_multi_path_symex_checker.h b/jbmc/src/java_bytecode/java_multi_path_symex_checker.h
index 99f63aa050a..50c5bc6bc75 100644
--- a/jbmc/src/java_bytecode/java_multi_path_symex_checker.h
+++ b/jbmc/src/java_bytecode/java_multi_path_symex_checker.h
@@ -29,7 +29,7 @@ class java_multi_path_symex_checkert : public multi_path_symex_checkert
   }
 
   goto_tracet build_full_trace() const override;
-  goto_tracet build_trace(const irep_idt &property_id) const override;
+  goto_tracet build_trace(irep_idt property_id) const override;
   goto_tracet build_shortest_trace() const override;
 };
 
diff --git a/jbmc/src/java_bytecode/java_object_factory.cpp b/jbmc/src/java_bytecode/java_object_factory.cpp
index 3ea4bab11eb..d38a01773f7 100644
--- a/jbmc/src/java_bytecode/java_object_factory.cpp
+++ b/jbmc/src/java_bytecode/java_object_factory.cpp
@@ -292,7 +292,7 @@ class recursion_set_entryt
   /// entry and erase it on destruction; otherwise do nothing.
   /// \param entry: entry to add
   /// \return true if added to the set (and therefore owned by this object)
-  bool insert_entry(const irep_idt &entry)
+  bool insert_entry(irep_idt entry)
   {
     INVARIANT(erase_entry.empty(), "insert_entry should only be called once");
     INVARIANT(!entry.empty(), "entry should be a struct tag");
@@ -365,7 +365,7 @@ void initialize_nondet_string_fields(
   const std::size_t &min_nondet_string_length,
   const std::size_t &max_nondet_string_length,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   bool printable,
   allocate_objectst &allocate_objects)
diff --git a/jbmc/src/java_bytecode/java_root_class.cpp b/jbmc/src/java_bytecode/java_root_class.cpp
index 36ac2802eef..81ef886a763 100644
--- a/jbmc/src/java_bytecode/java_root_class.cpp
+++ b/jbmc/src/java_bytecode/java_root_class.cpp
@@ -41,7 +41,7 @@ void java_root_class(symbolt &class_symbol)
 void java_root_class_init(
   struct_exprt &jlo,
   const struct_typet &root_type,
-  const irep_idt &class_identifier)
+  irep_idt class_identifier)
 {
   jlo.operands().resize(root_type.components().size());
 
diff --git a/jbmc/src/java_bytecode/java_root_class.h b/jbmc/src/java_bytecode/java_root_class.h
index 086c461347e..2aa0cae9a5a 100644
--- a/jbmc/src/java_bytecode/java_root_class.h
+++ b/jbmc/src/java_bytecode/java_root_class.h
@@ -24,6 +24,6 @@ void java_root_class(
 void java_root_class_init(
   struct_exprt &jlo,
   const struct_typet &root_type,
-  const irep_idt &class_identifier);
+  irep_idt class_identifier);
 
 #endif // CPROVER_JAVA_BYTECODE_JAVA_ROOT_CLASS_H
diff --git a/jbmc/src/java_bytecode/java_single_path_symex_checker.cpp b/jbmc/src/java_bytecode/java_single_path_symex_checker.cpp
index d361ebb56cb..07a0d4a31c3 100644
--- a/jbmc/src/java_bytecode/java_single_path_symex_checker.cpp
+++ b/jbmc/src/java_bytecode/java_single_path_symex_checker.cpp
@@ -26,7 +26,7 @@ goto_tracet java_single_path_symex_checkert::build_shortest_trace() const
 }
 
 goto_tracet
-java_single_path_symex_checkert::build_trace(const irep_idt &property_id) const
+java_single_path_symex_checkert::build_trace(irep_idt property_id) const
 {
   goto_tracet goto_trace = single_path_symex_checkert::build_trace(property_id);
   check_trace_assumptions(
diff --git a/jbmc/src/java_bytecode/java_single_path_symex_checker.h b/jbmc/src/java_bytecode/java_single_path_symex_checker.h
index de0862194d1..4f04266ab18 100644
--- a/jbmc/src/java_bytecode/java_single_path_symex_checker.h
+++ b/jbmc/src/java_bytecode/java_single_path_symex_checker.h
@@ -35,7 +35,7 @@ class java_single_path_symex_checkert : public single_path_symex_checkert
 
   goto_tracet build_full_trace() const override;
   goto_tracet build_shortest_trace() const override;
-  goto_tracet build_trace(const irep_idt &property_id) const override;
+  goto_tracet build_trace(irep_idt property_id) const override;
 };
 
 #endif // CPROVER_JAVA_BYTECODE_JAVA_SINGLE_PATH_SYMEX_CHECKER_H
diff --git a/jbmc/src/java_bytecode/java_static_initializers.cpp b/jbmc/src/java_bytecode/java_static_initializers.cpp
index fad44b65958..8bd4cc2f4f2 100644
--- a/jbmc/src/java_bytecode/java_static_initializers.cpp
+++ b/jbmc/src/java_bytecode/java_static_initializers.cpp
@@ -70,12 +70,12 @@ const std::string clinit_function_suffix = ".<clinit>:()V"; // NOLINT(*)
 /// Doesn't check whether the symbol actually exists
 /// \param class_name: class symbol name
 /// \return static initializer wrapper name
-irep_idt clinit_wrapper_name(const irep_idt &class_name)
+irep_idt clinit_wrapper_name(irep_idt class_name)
 {
   return id2string(class_name) + clinit_wrapper_suffix;
 }
 
-irep_idt user_specified_clinit_name(const irep_idt &class_name)
+irep_idt user_specified_clinit_name(irep_idt class_name)
 {
   return id2string(class_name) + user_specified_clinit_suffix;
 }
@@ -83,7 +83,7 @@ irep_idt user_specified_clinit_name(const irep_idt &class_name)
 /// Check if function_id is a clinit wrapper
 /// \param function_id: some function identifier
 /// \return true if the passed identifier is a clinit wrapper
-bool is_clinit_wrapper_function(const irep_idt &function_id)
+bool is_clinit_wrapper_function(irep_idt function_id)
 {
   return has_suffix(id2string(function_id), clinit_wrapper_suffix);
 }
@@ -91,7 +91,7 @@ bool is_clinit_wrapper_function(const irep_idt &function_id)
 /// Check if function_id is a clinit
 /// \param function_id: some function identifier
 /// \return true if the passed identifier is a clinit
-bool is_clinit_function(const irep_idt &function_id)
+bool is_clinit_function(irep_idt function_id)
 {
   return has_suffix(id2string(function_id), clinit_function_suffix);
 }
@@ -99,7 +99,7 @@ bool is_clinit_function(const irep_idt &function_id)
 /// Check if function_id is a user-specified clinit
 /// \param function_id: some function identifier
 /// \return true if the passed identifier is a clinit
-bool is_user_specified_clinit_function(const irep_idt &function_id)
+bool is_user_specified_clinit_function(irep_idt function_id)
 {
   return has_suffix(id2string(function_id), user_specified_clinit_suffix);
 }
@@ -114,7 +114,7 @@ bool is_user_specified_clinit_function(const irep_idt &function_id)
 /// /return returns new symbol.
 static symbolt add_new_variable_symbol(
   symbol_table_baset &symbol_table,
-  const irep_idt &name,
+  irep_idt name,
   const typet &type,
   const exprt &value,
   const bool is_thread_local,
@@ -137,7 +137,7 @@ static symbolt add_new_variable_symbol(
 /// given class.
 /// \param class_name: class symbol name
 /// \return static initializer wrapper-already run global name
-static irep_idt clinit_already_run_variable_name(const irep_idt &class_name)
+static irep_idt clinit_already_run_variable_name(irep_idt class_name)
 {
   return id2string(class_name) + "::clinit_already_run";
 }
@@ -146,7 +146,7 @@ static irep_idt clinit_already_run_variable_name(const irep_idt &class_name)
 /// if a static initializer actually exists.
 /// \param class_name: class symbol name
 /// \return Static initializer symbol name
-static irep_idt clinit_function_name(const irep_idt &class_name)
+static irep_idt clinit_function_name(irep_idt class_name)
 {
   return id2string(class_name) + clinit_function_suffix;
 }
@@ -155,7 +155,7 @@ static irep_idt clinit_function_name(const irep_idt &class_name)
 /// given class.
 /// \param class_name: class symbol name
 /// \return static initializer wrapper-state variable global name
-static irep_idt clinit_state_var_name(const irep_idt &class_name)
+static irep_idt clinit_state_var_name(irep_idt class_name)
 {
   return id2string(class_name) + CPROVER_PREFIX "clinit_state";
 }
@@ -164,7 +164,7 @@ static irep_idt clinit_state_var_name(const irep_idt &class_name)
 /// given class.
 /// \param class_name: class symbol name
 /// \return static initializer wrapper-state local state variable name
-static irep_idt clinit_thread_local_state_var_name(const irep_idt &class_name)
+static irep_idt clinit_thread_local_state_var_name(irep_idt class_name)
 {
   return id2string(class_name) + CPROVER_PREFIX "clinit_threadlocal_state";
 }
@@ -172,7 +172,7 @@ static irep_idt clinit_thread_local_state_var_name(const irep_idt &class_name)
 /// Get name of the static-initialization local variable for a given class.
 /// \param class_name: class symbol name
 /// \return static initializer wrapper-state local variable
-static irep_idt clinit_local_init_complete_var_name(const irep_idt &class_name)
+static irep_idt clinit_local_init_complete_var_name(irep_idt class_name)
 {
   return id2string(class_name) + CPROVER_PREFIX "clinit_wrapper::init_complete";
 }
@@ -228,7 +228,7 @@ gen_clinit_eqexpr(const exprt &expr, const clinit_statest state)
 /// \param message_handler: log
 static void clinit_wrapper_do_recursive_calls(
   symbol_table_baset &symbol_table,
-  const irep_idt &class_name,
+  irep_idt class_name,
   code_blockt &init_body,
   const bool nondet_static,
   const bool replace_clinit,
@@ -304,7 +304,7 @@ static void clinit_wrapper_do_recursive_calls(
 /// \param symbol_table: global symbol table
 /// \return true if a static initializer wrapper is needed
 static bool needs_clinit_wrapper(
-  const irep_idt &class_name,
+  irep_idt class_name,
   const symbol_table_baset &symbol_table)
 {
   if(symbol_table.has_symbol(clinit_function_name(class_name)))
@@ -326,9 +326,9 @@ static bool needs_clinit_wrapper(
 }
 
 static void create_function_symbol(
-  const irep_idt &class_name,
-  const irep_idt &function_name,
-  const irep_idt &function_base_name,
+  irep_idt class_name,
+  irep_idt function_name,
+  irep_idt function_base_name,
   const synthetic_method_typet &synthetic_method_type,
   symbol_table_baset &symbol_table,
   synthetic_methods_mapt &synthetic_methods)
@@ -354,7 +354,7 @@ static void create_function_symbol(
 
 // Create symbol for the "clinit_wrapper"
 static void create_clinit_wrapper_function_symbol(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table,
   synthetic_methods_mapt &synthetic_methods)
 {
@@ -369,7 +369,7 @@ static void create_clinit_wrapper_function_symbol(
 
 // Create symbol for the "user_specified_clinit"
 static void create_user_specified_clinit_function_symbol(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table,
   synthetic_methods_mapt &synthetic_methods)
 {
@@ -393,7 +393,7 @@ static void create_user_specified_clinit_function_symbol(
 /// \param thread_safe: if true state variables required to make the
 ///   clinit_wrapper thread safe will be created.
 static void create_clinit_wrapper_symbols(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table,
   synthetic_methods_mapt &synthetic_methods,
   const bool thread_safe)
@@ -518,7 +518,7 @@ static void create_clinit_wrapper_symbols(
 /// \param message_handler: log output
 /// \return the body of the static initializer wrapper
 code_blockt get_thread_safe_clinit_wrapper_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   const bool nondet_static,
   const bool replace_clinit,
@@ -716,7 +716,7 @@ code_blockt get_thread_safe_clinit_wrapper_body(
 /// \param message_handler: log output
 /// \return the body of the static initializer wrapper
 code_ifthenelset get_clinit_wrapper_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   const bool nondet_static,
   const bool replace_clinit,
@@ -789,7 +789,7 @@ class_to_declared_symbols(const symbol_table_baset &symbol_table)
 }
 
 code_blockt get_user_specified_clinit_body(
-  const irep_idt &class_id,
+  irep_idt class_id,
   const json_objectt &static_values_json,
   symbol_table_baset &symbol_table,
   std::optional<ci_lazy_methods_neededt> needed_lazy_methods,
@@ -1000,7 +1000,7 @@ void stub_global_initializer_factoryt::create_stub_global_initializer_symbols(
 /// \param message_handler: log output
 /// \return synthetic static initializer body.
 code_blockt stub_global_initializer_factoryt::get_stub_initializer_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   const java_object_factory_parameterst &object_factory_parameters,
   const select_pointer_typet &pointer_type_selector,
diff --git a/jbmc/src/java_bytecode/java_static_initializers.h b/jbmc/src/java_bytecode/java_static_initializers.h
index 3e2286bc3b9..dfb6b10b48b 100644
--- a/jbmc/src/java_bytecode/java_static_initializers.h
+++ b/jbmc/src/java_bytecode/java_static_initializers.h
@@ -24,12 +24,12 @@ class symbolt;
 struct java_object_factory_parameterst;
 struct object_creation_referencet;
 
-irep_idt clinit_wrapper_name(const irep_idt &class_name);
-irep_idt user_specified_clinit_name(const irep_idt &class_name);
+irep_idt clinit_wrapper_name(irep_idt class_name);
+irep_idt user_specified_clinit_name(irep_idt class_name);
 
-bool is_clinit_wrapper_function(const irep_idt &function_id);
-bool is_clinit_function(const irep_idt &function_id);
-bool is_user_specified_clinit_function(const irep_idt &function_id);
+bool is_clinit_wrapper_function(irep_idt function_id);
+bool is_clinit_function(irep_idt function_id);
+bool is_user_specified_clinit_function(irep_idt function_id);
 
 void create_static_initializer_symbols(
   symbol_table_baset &symbol_table,
@@ -38,7 +38,7 @@ void create_static_initializer_symbols(
   const bool is_user_clinit_needed);
 
 code_blockt get_thread_safe_clinit_wrapper_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   const bool nondet_static,
   const bool replace_clinit,
@@ -47,7 +47,7 @@ code_blockt get_thread_safe_clinit_wrapper_body(
   message_handlert &message_handler);
 
 code_ifthenelset get_clinit_wrapper_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   const bool nondet_static,
   const bool replace_clinit,
@@ -83,7 +83,7 @@ class_to_declared_symbols(const symbol_table_baset &symbol_table);
 ///   they declare.
 /// \return the body of the user_specified_clinit function as a code block.
 code_blockt get_user_specified_clinit_body(
-  const irep_idt &class_id,
+  irep_idt class_id,
   const json_objectt &static_values_json,
   symbol_table_baset &symbol_table,
   std::optional<ci_lazy_methods_neededt> needed_lazy_methods,
@@ -105,7 +105,7 @@ class stub_global_initializer_factoryt
     synthetic_methods_mapt &synthetic_methods);
 
   code_blockt get_stub_initializer_body(
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     const java_object_factory_parameterst &object_factory_parameters,
     const select_pointer_typet &pointer_type_selector,
diff --git a/jbmc/src/java_bytecode/java_string_library_preprocess.cpp b/jbmc/src/java_bytecode/java_string_library_preprocess.cpp
index 18106895546..da207b4e3cb 100644
--- a/jbmc/src/java_bytecode/java_string_library_preprocess.cpp
+++ b/jbmc/src/java_bytecode/java_string_library_preprocess.cpp
@@ -185,7 +185,7 @@ static typet string_length_type()
 /// \return a list of base classes, again without "java::" prefix.
 std::vector<irep_idt>
 java_string_library_preprocesst::get_string_type_base_classes(
-  const irep_idt &class_name)
+  irep_idt class_name)
 {
   if(!is_known_string_type(class_name))
     return {};
@@ -218,7 +218,7 @@ java_string_library_preprocesst::get_string_type_base_classes(
 /// \param class_name: a name for the class such as "java.lang.String"
 /// \param symbol_table: symbol table to which the class will be added
 void java_string_library_preprocesst::add_string_type(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table)
 {
   irep_idt class_symbol_name = "java::" + id2string(class_name);
@@ -280,7 +280,7 @@ void java_string_library_preprocesst::add_string_type(
 exprt::operandst java_string_library_preprocesst::process_parameters(
   const java_method_typet::parameterst &params,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &init_code)
 {
@@ -310,7 +310,7 @@ java_string_library_preprocesst::convert_exprt_to_string_exprt(
   const exprt &expr_to_process,
   const source_locationt &loc,
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &init_code)
 {
   PRECONDITION(implements_java_char_sequence_pointer(expr_to_process.type()));
@@ -337,7 +337,7 @@ java_string_library_preprocesst::convert_exprt_to_string_exprt(
 exprt::operandst java_string_library_preprocesst::process_operands(
   const exprt::operandst &operands,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &init_code)
 {
@@ -431,7 +431,7 @@ static exprt get_data(const exprt &expr, const symbol_table_baset &symbol_table)
 refined_string_exprt java_string_library_preprocesst::replace_char_array(
   const exprt &array_pointer,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &code)
 {
@@ -468,7 +468,7 @@ refined_string_exprt java_string_library_preprocesst::replace_char_array(
 symbol_exprt java_string_library_preprocesst::fresh_string(
   const typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table)
 {
   symbolt string_symbol =
@@ -486,7 +486,7 @@ symbol_exprt java_string_library_preprocesst::fresh_string(
 /// \return refined string expr with fresh content and length symbols
 refined_string_exprt java_string_library_preprocesst::decl_string_expr(
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &code)
 {
@@ -511,7 +511,7 @@ refined_string_exprt java_string_library_preprocesst::decl_string_expr(
 /// \return a new string_expr
 refined_string_exprt java_string_library_preprocesst::make_nondet_string_expr(
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &code)
 {
@@ -549,7 +549,7 @@ refined_string_exprt java_string_library_preprocesst::make_nondet_string_expr(
 exprt java_string_library_preprocesst::allocate_fresh_string(
   const typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &code)
 {
@@ -577,7 +577,7 @@ exprt java_string_library_preprocesst::allocate_fresh_string(
 /// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 static codet code_assign_function_application(
   const exprt &lhs,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const exprt::operandst &arguments,
   symbol_table_baset &symbol_table)
 {
@@ -597,7 +597,7 @@ static codet code_assign_function_application(
 /// return <function_id>(arguments)
 /// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 codet java_string_library_preprocesst::code_return_function_application(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const exprt::operandst &arguments,
   const typet &type,
   symbol_table_baset &symbol_table)
@@ -615,7 +615,7 @@ codet java_string_library_preprocesst::code_return_function_application(
 exprt make_nondet_infinite_char_array(
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code)
 {
   const array_typet array_type(
@@ -649,7 +649,7 @@ void add_pointer_to_array_association(
   const exprt &array,
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code)
 {
   PRECONDITION(array.type().id() == ID_array);
@@ -680,7 +680,7 @@ void add_array_to_length_association(
   const exprt &length,
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code)
 {
   const symbolt &return_sym = fresh_java_symbol(
@@ -710,10 +710,10 @@ void add_array_to_length_association(
 void add_character_set_constraint(
   const exprt &pointer,
   const exprt &length,
-  const irep_idt &char_range,
+  irep_idt char_range,
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code)
 {
   PRECONDITION(pointer.type().id() == ID_pointer);
@@ -748,7 +748,7 @@ void add_character_set_constraint(
 /// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 /// \return refined string expression `str`
 refined_string_exprt java_string_library_preprocesst::string_expr_of_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const exprt::operandst &arguments,
   const source_locationt &loc,
   symbol_table_baset &symbol_table,
@@ -917,7 +917,7 @@ java_string_library_preprocesst::string_literal_to_string_expr(
 code_blockt java_string_library_preprocesst::make_float_to_string_code(
   const java_method_typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -1076,7 +1076,7 @@ code_blockt java_string_library_preprocesst::make_float_to_string_code(
 ///     cprover_string = {.=cprover_string_length, .=cprover_string_array};
 ///
 code_blockt java_string_library_preprocesst::make_init_function_from_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const java_method_typet &type,
   const source_locationt &loc,
   symbol_table_baset &symbol_table,
@@ -1120,7 +1120,7 @@ code_blockt java_string_library_preprocesst::make_init_function_from_call(
 /// \return Code calling function with the given function name.
 code_blockt
 java_string_library_preprocesst::make_assign_and_return_function_from_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const java_method_typet &type,
   const source_locationt &loc,
   symbol_table_baset &symbol_table)
@@ -1145,7 +1145,7 @@ java_string_library_preprocesst::make_assign_and_return_function_from_call(
 /// \return Code assigning result of a call to the function with given function
 ///   name.
 code_blockt java_string_library_preprocesst::make_assign_function_from_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const java_method_typet &type,
   const source_locationt &loc,
   symbol_table_baset &symbol_table)
@@ -1171,7 +1171,7 @@ code_blockt java_string_library_preprocesst::make_assign_function_from_call(
 code_blockt java_string_library_preprocesst::make_class_identifier_code(
   const java_method_typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -1229,7 +1229,7 @@ code_blockt java_string_library_preprocesst::make_class_identifier_code(
 /// return function_id(args)
 /// ~~~~~~~~~~~~~~~~~~~~~~~~~~
 code_blockt java_string_library_preprocesst::make_function_from_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const java_method_typet &type,
   const source_locationt &loc,
   symbol_table_baset &symbol_table)
@@ -1259,7 +1259,7 @@ code_blockt java_string_library_preprocesst::make_function_from_call(
 /// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 code_blockt
 java_string_library_preprocesst::make_string_returning_function_from_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const java_method_typet &type,
   const source_locationt &loc,
   symbol_table_baset &symbol_table)
@@ -1306,7 +1306,7 @@ java_string_library_preprocesst::make_string_returning_function_from_call(
 code_blockt java_string_library_preprocesst::make_copy_string_code(
   const java_method_typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -1356,7 +1356,7 @@ code_blockt java_string_library_preprocesst::make_copy_string_code(
 code_blockt java_string_library_preprocesst::make_copy_constructor_code(
   const java_method_typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -1401,7 +1401,7 @@ code_blockt java_string_library_preprocesst::make_copy_constructor_code(
 code_returnt java_string_library_preprocesst::make_string_length_code(
   const java_method_typet &type,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -1420,7 +1420,7 @@ code_returnt java_string_library_preprocesst::make_string_length_code(
 }
 
 bool java_string_library_preprocesst::implements_function(
-  const irep_idt &function_id) const
+  irep_idt function_id) const
 {
   for(const id_mapt *map : id_maps)
     if(map->count(function_id) != 0)
diff --git a/jbmc/src/java_bytecode/java_string_library_preprocess.h b/jbmc/src/java_bytecode/java_string_library_preprocess.h
index 7fc1f014ff9..052b2129e4f 100644
--- a/jbmc/src/java_bytecode/java_string_library_preprocess.h
+++ b/jbmc/src/java_bytecode/java_string_library_preprocess.h
@@ -47,7 +47,7 @@ class java_string_library_preprocesst
   void initialize_known_type_table();
   void initialize_conversion_table();
 
-  bool implements_function(const irep_idt &function_id) const;
+  bool implements_function(irep_idt function_id) const;
   void get_all_function_names(std::unordered_set<irep_idt> &methods) const;
 
   codet code_for_function(
@@ -59,10 +59,8 @@ class java_string_library_preprocesst
   {
     return character_preprocess.replace_character_call(call);
   }
-  std::vector<irep_idt> get_string_type_base_classes(
-    const irep_idt &class_name);
-  void
-  add_string_type(const irep_idt &class_name, symbol_table_baset &symbol_table);
+  std::vector<irep_idt> get_string_type_base_classes(irep_idt class_name);
+  void add_string_type(irep_idt class_name, symbol_table_baset &symbol_table);
   bool is_known_string_type(irep_idt class_name);
 
   static bool implements_java_char_sequence_pointer(const typet &type)
@@ -106,7 +104,7 @@ class java_string_library_preprocesst
   typedef std::function<codet(
     const java_method_typet &,
     const source_locationt &,
-    const irep_idt &,
+    irep_idt,
     symbol_table_baset &,
     message_handlert &)>
     conversion_functiont;
@@ -154,35 +152,35 @@ class java_string_library_preprocesst
   code_blockt make_float_to_string_code(
     const java_method_typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler);
 
   code_blockt make_copy_string_code(
     const java_method_typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler);
 
   code_blockt make_copy_constructor_code(
     const java_method_typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler);
 
   code_returnt make_string_length_code(
     const java_method_typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler);
 
   code_blockt make_class_identifier_code(
     const java_method_typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler);
 
@@ -190,7 +188,7 @@ class java_string_library_preprocesst
   exprt::operandst process_parameters(
     const java_method_typet::parameterst &params,
     const source_locationt &loc,
-    const irep_idt &function_name,
+    irep_idt function_name,
     symbol_table_baset &symbol_table,
     code_blockt &init_code);
 
@@ -199,7 +197,7 @@ class java_string_library_preprocesst
     java_string_library_preprocesst &preprocess,
     const exprt &deref,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     code_blockt &init_code);
 
@@ -207,56 +205,56 @@ class java_string_library_preprocesst
     const exprt &deref,
     const source_locationt &loc,
     symbol_table_baset &symbol_table,
-    const irep_idt &function_name,
+    irep_idt function_name,
     code_blockt &init_code);
 
   exprt::operandst process_operands(
     const exprt::operandst &operands,
     const source_locationt &loc,
-    const irep_idt &function_name,
+    irep_idt function_name,
     symbol_table_baset &symbol_table,
     code_blockt &init_code);
 
   refined_string_exprt replace_char_array(
     const exprt &array_pointer,
     const source_locationt &loc,
-    const irep_idt &function_name,
+    irep_idt function_name,
     symbol_table_baset &symbol_table,
     code_blockt &code);
 
   symbol_exprt fresh_string(
     const typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table);
 
   refined_string_exprt decl_string_expr(
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     code_blockt &code);
 
   refined_string_exprt make_nondet_string_expr(
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     code_blockt &code);
 
   exprt allocate_fresh_string(
     const typet &type,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     code_blockt &code);
 
   codet code_return_function_application(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const exprt::operandst &arguments,
     const typet &type,
     symbol_table_baset &symbol_table);
 
   refined_string_exprt string_expr_of_function(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const exprt::operandst &arguments,
     const source_locationt &loc,
     symbol_table_baset &symbol_table,
@@ -289,32 +287,32 @@ class java_string_library_preprocesst
     code_blockt &code);
 
   code_blockt make_function_from_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const java_method_typet &type,
     const source_locationt &loc,
     symbol_table_baset &symbol_table);
 
   code_blockt make_init_function_from_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const java_method_typet &type,
     const source_locationt &loc,
     symbol_table_baset &symbol_table,
     bool is_constructor = true);
 
   code_blockt make_assign_and_return_function_from_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const java_method_typet &type,
     const source_locationt &loc,
     symbol_table_baset &symbol_table);
 
   code_blockt make_assign_function_from_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const java_method_typet &type,
     const source_locationt &loc,
     symbol_table_baset &symbol_table);
 
   code_blockt make_string_returning_function_from_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const java_method_typet &type,
     const source_locationt &loc,
     symbol_table_baset &symbol_table);
@@ -323,7 +321,7 @@ class java_string_library_preprocesst
 exprt make_nondet_infinite_char_array(
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code);
 
 void add_pointer_to_array_association(
@@ -331,7 +329,7 @@ void add_pointer_to_array_association(
   const exprt &array,
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code);
 
 void add_array_to_length_association(
@@ -339,16 +337,16 @@ void add_array_to_length_association(
   const exprt &length,
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code);
 
 void add_character_set_constraint(
   const exprt &pointer,
   const exprt &length,
-  const irep_idt &char_range,
+  irep_idt char_range,
   symbol_table_baset &symbol_table,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &code);
 
 #endif // CPROVER_JAVA_BYTECODE_JAVA_STRING_LIBRARY_PREPROCESS_H
diff --git a/jbmc/src/java_bytecode/java_string_literal_expr.h b/jbmc/src/java_bytecode/java_string_literal_expr.h
index 1c6be6eb987..c551735d657 100644
--- a/jbmc/src/java_bytecode/java_string_literal_expr.h
+++ b/jbmc/src/java_bytecode/java_string_literal_expr.h
@@ -17,7 +17,7 @@ Author: Diffblue Ltd.
 class java_string_literal_exprt : public exprt
 {
 public:
-  explicit java_string_literal_exprt(const irep_idt &literal)
+  explicit java_string_literal_exprt(irep_idt literal)
     : exprt(ID_java_string_literal)
   {
     set(ID_value, literal);
diff --git a/jbmc/src/java_bytecode/java_string_literals.cpp b/jbmc/src/java_bytecode/java_string_literals.cpp
index d63681580b9..b50e7f7040e 100644
--- a/jbmc/src/java_bytecode/java_string_literals.cpp
+++ b/jbmc/src/java_bytecode/java_string_literals.cpp
@@ -184,7 +184,7 @@ symbol_exprt get_or_create_string_literal_symbol(
 }
 
 symbol_exprt get_or_create_string_literal_symbol(
-  const irep_idt &string_value,
+  irep_idt string_value,
   symbol_table_baset &symbol_table,
   bool string_refinement_enabled)
 {
diff --git a/jbmc/src/java_bytecode/java_string_literals.h b/jbmc/src/java_bytecode/java_string_literals.h
index fa57306e1dd..c688e9ab180 100644
--- a/jbmc/src/java_bytecode/java_string_literals.h
+++ b/jbmc/src/java_bytecode/java_string_literals.h
@@ -31,7 +31,7 @@ symbol_exprt get_or_create_string_literal_symbol(
 /// get_or_create_string_literal_symbol(const exprt&, symbol_table_baset&, bool)
 /// except it takes an id/string parameter rather than a string literal exprt.
 symbol_exprt get_or_create_string_literal_symbol(
-  const irep_idt &string_value,
+  irep_idt string_value,
   symbol_table_baset &symbol_table,
   bool string_refinement_enabled);
 
diff --git a/jbmc/src/java_bytecode/java_types.cpp b/jbmc/src/java_bytecode/java_types.cpp
index d6f2c1b9ffe..4fa88fd0e7a 100644
--- a/jbmc/src/java_bytecode/java_types.cpp
+++ b/jbmc/src/java_bytecode/java_types.cpp
@@ -230,7 +230,7 @@ exprt get_array_element_type_field(const exprt &pointer)
 /// \param tag: Tag of a struct
 /// \return True if the given string is a Java array tag, i.e., has a prefix
 ///   of java::array[
-bool is_java_array_tag(const irep_idt& tag)
+bool is_java_array_tag(irep_idt tag)
 {
   return tag.starts_with("java::array[");
 }
diff --git a/jbmc/src/java_bytecode/java_types.h b/jbmc/src/java_bytecode/java_types.h
index b1e2c1a4306..c4f49cfb79a 100644
--- a/jbmc/src/java_bytecode/java_types.h
+++ b/jbmc/src/java_bytecode/java_types.h
@@ -200,7 +200,7 @@ class java_class_typet:public class_typet
   public:
     componentt() = default;
 
-    componentt(const irep_idt &_name, typet _type)
+    componentt(irep_idt _name, typet _type)
       : class_typet::componentt(_name, std::move(_type))
     {
     }
@@ -230,7 +230,7 @@ class java_class_typet:public class_typet
     return (componentst &)(add(ID_components).get_sub());
   }
 
-  const componentt &get_component(const irep_idt &component_name) const
+  const componentt &get_component(irep_idt component_name) const
   {
     return static_cast<const componentt &>(
       class_typet::get_component(component_name));
@@ -241,7 +241,7 @@ class java_class_typet:public class_typet
   public:
     methodt() = delete;
 
-    methodt(const irep_idt &_name, java_method_typet _type)
+    methodt(irep_idt _name, java_method_typet _type)
       : class_typet::methodt(_name, std::move(_type))
     {
     }
@@ -288,7 +288,7 @@ class java_class_typet:public class_typet
     }
 
     /// Sets the method's descriptor -- the mangled form of its type
-    void set_descriptor(const irep_idt &id)
+    void set_descriptor(irep_idt id)
     {
       set(ID_object_descriptor, id);
     }
@@ -324,7 +324,7 @@ class java_class_typet:public class_typet
     return get(ID_access);
   }
 
-  void set_access(const irep_idt &access)
+  void set_access(irep_idt access)
   {
     return set(ID_access, access);
   }
@@ -344,7 +344,7 @@ class java_class_typet:public class_typet
     return get(ID_outer_class);
   }
 
-  void set_outer_class(const irep_idt &outer_class)
+  void set_outer_class(irep_idt outer_class)
   {
     return set(ID_outer_class, outer_class);
   }
@@ -354,7 +354,7 @@ class java_class_typet:public class_typet
     return get(ID_super_class);
   }
 
-  void set_super_class(const irep_idt &super_class)
+  void set_super_class(irep_idt super_class)
   {
     return set(ID_super_class, super_class);
   }
@@ -560,7 +560,7 @@ class java_class_typet:public class_typet
 
   /// Set the name of the struct, which can be used to look up its symbol
   /// in the symbol table.
-  void set_name(const irep_idt &name)
+  void set_name(irep_idt name)
   {
     set(ID_name, name);
   }
@@ -572,7 +572,7 @@ class java_class_typet:public class_typet
   }
 
   /// Set the name of a java inner class.
-  void set_inner_name(const irep_idt &name)
+  void set_inner_name(irep_idt name)
   {
     set(ID_inner_name, name);
   }
@@ -690,7 +690,7 @@ std::vector<std::string> parse_raw_list_types(
   char opening_bracket,
   char closing_bracket);
 
-bool is_java_array_tag(const irep_idt &tag);
+bool is_java_array_tag(irep_idt tag);
 bool is_valid_java_array(const struct_typet &);
 
 bool equal_java_types(const typet &type1, const typet &type2);
@@ -704,7 +704,7 @@ class java_generic_parameter_tagt : public struct_tag_typet
   typedef struct_tag_typet type_variablet;
 
   java_generic_parameter_tagt(
-    const irep_idt &_type_var_name,
+    irep_idt _type_var_name,
     const struct_tag_typet &_bound)
     : struct_tag_typet(_bound)
   {
@@ -777,7 +777,7 @@ class java_generic_parametert : public reference_typet
   typedef struct_tag_typet type_variablet;
 
   java_generic_parametert(
-    const irep_idt &_type_var_name,
+    irep_idt _type_var_name,
     const struct_tag_typet &_bound)
     : reference_typet(java_reference_type(
         java_generic_parameter_tagt(_type_var_name, _bound)))
@@ -1158,7 +1158,7 @@ inline std::optional<typet> java_type_from_string_with_exception(
 /// \return Optional with the size if the identifier was found.
 inline const std::optional<size_t> java_generics_get_index_for_subtype(
   const std::vector<java_generic_parametert> &gen_types,
-  const irep_idt &identifier)
+  irep_idt identifier)
 {
   const auto iter = std::find_if(
     gen_types.cbegin(),
diff --git a/jbmc/src/java_bytecode/java_utils.cpp b/jbmc/src/java_bytecode/java_utils.cpp
index a851c2f27f6..db7ec40eb13 100644
--- a/jbmc/src/java_bytecode/java_utils.cpp
+++ b/jbmc/src/java_bytecode/java_utils.cpp
@@ -32,8 +32,7 @@ bool is_java_string_type(const struct_typet &struct_type)
          struct_type.has_component("data");
 }
 
-const java_boxed_type_infot *
-get_boxed_type_info_by_name(const irep_idt &type_name)
+const java_boxed_type_infot *get_boxed_type_info_by_name(irep_idt type_name)
 {
   static std::unordered_map<irep_idt, java_boxed_type_infot> type_info_by_name =
     {
@@ -106,7 +105,7 @@ get_java_primitive_type_info(const typet &maybe_primitive_type)
   return found == type_info_by_primitive_type.end() ? nullptr : &found->second;
 }
 
-bool is_primitive_wrapper_type_id(const irep_idt &id)
+bool is_primitive_wrapper_type_id(irep_idt id)
 {
   return get_boxed_type_info_by_name(id) != nullptr;
 }
@@ -160,7 +159,7 @@ const std::string java_class_to_package(const std::string &canonical_classname)
 }
 
 void generate_class_stub(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler,
   const struct_union_typet::componentst &componentst)
@@ -204,7 +203,7 @@ void merge_source_location_rec(
     merge_source_location_rec(op, source_location);
 }
 
-bool is_java_string_literal_id(const irep_idt &id)
+bool is_java_string_literal_id(irep_idt id)
 {
   return id.starts_with(JAVA_STRING_LITERAL_PREFIX);
 }
@@ -356,7 +355,7 @@ void java_add_components_to_class(
 /// \param symbol_table: symbol table
 /// \return newly created symbol
 static auxiliary_symbolt declare_function(
-  const irep_idt &function_name,
+  irep_idt function_name,
   const mathematical_function_typet &type,
   symbol_table_baset &symbol_table)
 {
@@ -382,7 +381,7 @@ static auxiliary_symbolt declare_function(
 /// \return a function application expression representing:
 ///   `function_name(arguments)`
 exprt make_function_application(
-  const irep_idt &function_name,
+  irep_idt function_name,
   const exprt::operandst &arguments,
   const typet &range,
   symbol_table_baset &symbol_table)
@@ -404,7 +403,7 @@ exprt make_function_application(
 /// Strip java:: prefix from given identifier
 /// \param to_strip: identifier from which the prefix is stripped
 /// \return the identifier without without java:: prefix
-irep_idt strip_java_namespace_prefix(const irep_idt &to_strip)
+irep_idt strip_java_namespace_prefix(irep_idt to_strip)
 {
   const std::string to_strip_str=id2string(to_strip);
   const std::string prefix="java::";
@@ -446,8 +445,8 @@ std::string pretty_print_java_type(const std::string &fqn_java_type)
 ///   resolve_inherited_componentt::inherited_componentt otherwise.
 std::optional<resolve_inherited_componentt::inherited_componentt>
 get_inherited_component(
-  const irep_idt &component_class_id,
-  const irep_idt &component_name,
+  irep_idt component_class_id,
+  irep_idt component_name,
   const symbol_table_baset &symbol_table,
   bool include_interfaces)
 {
@@ -516,7 +515,7 @@ get_inherited_component(
 /// Check if a symbol is a well-known non-null global
 /// \param symbolid: symbol id to check
 /// \return true if this static field is known never to be null
-bool is_non_null_library_global(const irep_idt &symbolid)
+bool is_non_null_library_global(irep_idt symbolid)
 {
   static const irep_idt in = "java::java.lang.System.in";
   static const irep_idt out = "java::java.lang.System.out";
@@ -556,7 +555,7 @@ symbolt &fresh_java_symbol(
   const typet &type,
   const std::string &basename_prefix,
   const source_locationt &source_location,
-  const irep_idt &function_name,
+  irep_idt function_name,
   symbol_table_baset &symbol_table)
 {
   PRECONDITION(!function_name.empty());
@@ -571,7 +570,7 @@ std::optional<irep_idt> declaring_class(const symbolt &symbol)
   return class_id.empty() ? std::optional<irep_idt>{} : class_id;
 }
 
-void set_declaring_class(symbolt &symbol, const irep_idt &declaring_class)
+void set_declaring_class(symbolt &symbol, irep_idt declaring_class)
 {
   symbol.type.set(ID_C_class, declaring_class);
 }
diff --git a/jbmc/src/java_bytecode/java_utils.h b/jbmc/src/java_bytecode/java_utils.h
index 4deb6183cde..76533886a28 100644
--- a/jbmc/src/java_bytecode/java_utils.h
+++ b/jbmc/src/java_bytecode/java_utils.h
@@ -60,19 +60,18 @@ struct java_boxed_type_infot
 
 /// If \p type_name is a Java boxed type tag, return information about it,
 /// otherwise return null
-const java_boxed_type_infot *
-get_boxed_type_info_by_name(const irep_idt &type_name);
+const java_boxed_type_infot *get_boxed_type_info_by_name(irep_idt type_name);
 
 /// Returns true iff the argument is the symbol-table identifier of a Java
 /// primitive wrapper type (for example, java::java.lang.Byte)
-bool is_primitive_wrapper_type_id(const irep_idt &id);
+bool is_primitive_wrapper_type_id(irep_idt id);
 
 /// Returns true iff the argument is the fully qualified name of a Java
 /// primitive wrapper type (for example, java.lang.Byte)
 bool is_primitive_wrapper_type_name(const std::string &type_name);
 
 void generate_class_stub(
-  const irep_idt &class_name,
+  irep_idt class_name,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler,
   const struct_union_typet::componentst &componentst);
@@ -104,7 +103,7 @@ void merge_source_location_rec(
 
 /// \param id: any string
 /// \return Returns true if 'id' identifies a string literal symbol
-bool is_java_string_literal_id(const irep_idt &id);
+bool is_java_string_literal_id(irep_idt id);
 
 /// Resolves a user-friendly method name (like packagename.Class.method)
 /// into an internal name (like java::packagename.Class.method:()V)
@@ -144,23 +143,23 @@ size_t find_closing_delimiter(
   char close_char);
 
 exprt make_function_application(
-  const irep_idt &function_name,
+  irep_idt function_name,
   const exprt::operandst &arguments,
   const typet &range,
   symbol_table_baset &symbol_table);
 
-irep_idt strip_java_namespace_prefix(const irep_idt &to_strip);
+irep_idt strip_java_namespace_prefix(irep_idt to_strip);
 
 std::string pretty_print_java_type(const std::string &fqn_java_type);
 
 std::optional<resolve_inherited_componentt::inherited_componentt>
 get_inherited_component(
-  const irep_idt &component_class_id,
-  const irep_idt &component_name,
+  irep_idt component_class_id,
+  irep_idt component_name,
   const symbol_table_baset &symbol_table,
   bool include_interfaces);
 
-bool is_non_null_library_global(const irep_idt &);
+bool is_non_null_library_global(irep_idt);
 
 extern const std::unordered_set<std::string> cprover_methods_to_ignore;
 
@@ -172,7 +171,7 @@ fresh_java_symbol(
   const typet &type,
   const std::string &basename_prefix,
   const source_locationt &source_location,
-  const irep_idt &function_name,
+  irep_idt function_name,
   symbol_table_baset &symbol_table);
 
 /// Gets the identifier of the class which declared a given \p symbol. If the
@@ -183,7 +182,7 @@ std::optional<irep_idt> declaring_class(const symbolt &symbol);
 
 /// Sets the identifier of the class which declared a given \p symbol to \p
 /// declaring_class.
-void set_declaring_class(symbolt &symbol, const irep_idt &declaring_class);
+void set_declaring_class(symbolt &symbol, irep_idt declaring_class);
 
 /// Get JVM type name of the class in which \p method_name is defined.
 /// Returns an empty optional if the class name cannot be retrieved,
diff --git a/jbmc/src/java_bytecode/lambda_synthesis.cpp b/jbmc/src/java_bytecode/lambda_synthesis.cpp
index 8fa28b18159..0bf3b97d743 100644
--- a/jbmc/src/java_bytecode/lambda_synthesis.cpp
+++ b/jbmc/src/java_bytecode/lambda_synthesis.cpp
@@ -35,7 +35,7 @@ static std::string escape_symbol_special_chars(std::string input)
 }
 
 irep_idt lambda_synthetic_class_name(
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   std::size_t instruction_address)
 {
   return "java::lambda_synthetic_class$" +
@@ -76,7 +76,7 @@ get_lambda_method_handle(
 static std::optional<java_class_typet::java_lambda_method_handlet>
 lambda_method_handle(
   const symbol_table_baset &symbol_table,
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   const java_method_typet &dynamic_method_type)
 {
   const namespacet ns{symbol_table};
@@ -132,7 +132,7 @@ typedef std::map<
 /// for example because both If1.f(int) and If2.f(int) are inherited here, only
 /// one is stored in the map, chosen arbitrarily.
 static const methods_by_name_and_descriptort
-get_interface_methods(const irep_idt &interface_id, const namespacet &ns)
+get_interface_methods(irep_idt interface_id, const namespacet &ns)
 {
   static const irep_idt jlo = "java::java.lang.Object";
   // Terminate recursion at Object; any other base of an interface must
@@ -204,7 +204,7 @@ get_interface_methods(const irep_idt &interface_id, const namespacet &ns)
 static const java_class_typet::methodt *try_get_unique_unimplemented_method(
   const symbol_table_baset &symbol_table,
   const struct_tag_typet &functional_interface_tag,
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   const int instruction_address,
   const messaget &log)
 {
@@ -248,7 +248,7 @@ static const java_class_typet::methodt *try_get_unique_unimplemented_method(
 }
 
 symbolt synthetic_class_symbol(
-  const irep_idt &synthetic_class_name,
+  irep_idt synthetic_class_name,
   const java_class_typet::java_lambda_method_handlet &lambda_method_handle,
   const struct_tag_typet &functional_interface_tag,
   const java_method_typet &dynamic_method_type)
@@ -297,7 +297,7 @@ symbolt synthetic_class_symbol(
 
 static symbolt constructor_symbol(
   synthetic_methods_mapt &synthetic_methods,
-  const irep_idt &synthetic_class_name,
+  irep_idt synthetic_class_name,
   java_method_typet constructor_type) // dynamic_method_type
 {
   irep_idt constructor_name = id2string(synthetic_class_name) + ".<init>";
@@ -337,7 +337,7 @@ static symbolt constructor_symbol(
 static symbolt implemented_method_symbol(
   synthetic_methods_mapt &synthetic_methods,
   const java_class_typet::methodt &method_to_implement,
-  const irep_idt &synthetic_class_name)
+  irep_idt synthetic_class_name)
 {
   const std::string implemented_method_name =
     id2string(synthetic_class_name) + "." +
@@ -393,7 +393,7 @@ static symbolt implemented_method_symbol(
 // invoke instruction will return null when eventually converted by
 // java_bytecode_convert_method.
 void create_invokedynamic_synthetic_classes(
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   const java_bytecode_parse_treet::methodt::instructionst &instructions,
   symbol_table_baset &symbol_table,
   synthetic_methods_mapt &synthetic_methods,
@@ -449,11 +449,11 @@ void create_invokedynamic_synthetic_classes(
 #endif
 static const symbolt &
 get_or_create_method_symbol(
-  const irep_idt &identifier,
-  const irep_idt &base_name,
-  const irep_idt &pretty_name,
+  irep_idt identifier,
+  irep_idt base_name,
+  irep_idt pretty_name,
   const typet &type,
-  const irep_idt &declaring_class,
+  irep_idt declaring_class,
   symbol_table_baset &symbol_table,
   message_handlert &log)
 {
@@ -473,7 +473,7 @@ get_or_create_method_symbol(
 }
 
 codet invokedynamic_synthetic_constructor(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -539,8 +539,8 @@ codet invokedynamic_synthetic_constructor(
 }
 
 static symbol_exprt create_and_declare_local(
-  const irep_idt &function_id,
-  const irep_idt &basename,
+  irep_idt function_id,
+  irep_idt basename,
   const typet &type,
   symbol_table_baset &symbol_table,
   code_blockt &method)
@@ -570,7 +570,7 @@ static symbol_exprt create_and_declare_local(
 /// \param result: will gain instructions instantiating the required type
 /// \return the newly instantiated symbol
 static symbol_exprt instantiate_new_object(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const symbolt &lambda_method_symbol,
   symbol_table_baset &symbol_table,
   code_blockt &result)
@@ -686,7 +686,7 @@ exprt box_or_unbox_type_if_necessary(
   const typet &required_type,
   code_blockt &code_block,
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::string &role)
 {
   const typet &original_type = expr.type();
@@ -745,7 +745,7 @@ exprt adjust_type_if_necessary(
   const typet &required_type,
   code_blockt &code_block,
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::string &role)
 {
   return typecast_exprt::conditional_cast(
@@ -771,7 +771,7 @@ exprt adjust_type_if_necessary(
 /// \param message_handler: log
 /// \return the method body for `function_id`
 codet invokedynamic_synthetic_method(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
diff --git a/jbmc/src/java_bytecode/lambda_synthesis.h b/jbmc/src/java_bytecode/lambda_synthesis.h
index df8d9d61c35..fd54e1fff18 100644
--- a/jbmc/src/java_bytecode/lambda_synthesis.h
+++ b/jbmc/src/java_bytecode/lambda_synthesis.h
@@ -21,11 +21,11 @@ class codet;
 class symbol_table_baset;
 
 irep_idt lambda_synthetic_class_name(
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   std::size_t instruction_address);
 
 void create_invokedynamic_synthetic_classes(
-  const irep_idt &method_identifier,
+  irep_idt method_identifier,
   const java_bytecode_parse_treet::methodt::instructionst &instructions,
   symbol_table_baset &symbol_table,
   synthetic_methods_mapt &synthetic_methods,
@@ -33,13 +33,13 @@ void create_invokedynamic_synthetic_classes(
 
 /// Create invokedynamic synthetic constructor
 codet invokedynamic_synthetic_constructor(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler);
 
 /// Create invokedynamic synthetic method
 codet invokedynamic_synthetic_method(
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler);
 
diff --git a/jbmc/src/java_bytecode/lazy_goto_functions_map.h b/jbmc/src/java_bytecode/lazy_goto_functions_map.h
index 4d7e2dcd641..f3dacfa9abd 100644
--- a/jbmc/src/java_bytecode/lazy_goto_functions_map.h
+++ b/jbmc/src/java_bytecode/lazy_goto_functions_map.h
@@ -51,13 +51,13 @@ class lazy_goto_functions_mapt final
   typedef std::size_t size_type;
 
   typedef std::function<void(
-    const irep_idt &name,
+    irep_idt name,
     goto_functionst::goto_functiont &function,
     journalling_symbol_tablet &function_symbols)>
     post_process_functiont;
-  typedef std::function<bool(const irep_idt &name)> can_generate_function_bodyt;
+  typedef std::function<bool(irep_idt name)> can_generate_function_bodyt;
   typedef std::function<bool(
-    const irep_idt &function_name,
+    irep_idt function_name,
     symbol_table_baset &symbol_table,
     goto_functiont &function,
     bool body_available)>
@@ -103,7 +103,7 @@ class lazy_goto_functions_mapt final
   /// Gets the body for a given function.
   /// \param name: The name of the function to search for.
   /// \return The function body corresponding to the given function.
-  const_mapped_type at(const key_type &name) const
+  const_mapped_type at(key_type name) const
   {
     return ensure_function_loaded_internal(name).second;
   }
@@ -111,7 +111,7 @@ class lazy_goto_functions_mapt final
   /// Gets the body for a given function.
   /// \param name: The name of the function to search for.
   /// \return The function body corresponding to the given function.
-  mapped_type at(const key_type &name)
+  mapped_type at(key_type name)
   {
     return ensure_function_loaded_internal(name).second;
   }
@@ -121,7 +121,7 @@ class lazy_goto_functions_mapt final
   /// \param name: function ID to query
   /// \return true if we can produce a function body, or false if we would leave
   ///   it a bodyless stub.
-  bool can_produce_function(const key_type &name) const
+  bool can_produce_function(key_type name) const
   {
     return language_files.can_convert_lazy_method(name) ||
            driver_program_can_generate_function_body(name);
@@ -130,12 +130,12 @@ class lazy_goto_functions_mapt final
   /// Remove the function named \p name from the function map, if it exists.
   /// \return Returns 0 when \p name was not present, and 1 when \p name was
   ///   removed.
-  std::size_t unload(const key_type &name) const
+  std::size_t unload(key_type name) const
   {
     return goto_functions.erase(name);
   }
 
-  void ensure_function_loaded(const key_type &name) const
+  void ensure_function_loaded(key_type name) const
   {
     ensure_function_loaded_internal(name);
   }
@@ -144,7 +144,7 @@ class lazy_goto_functions_mapt final
   // This returns a non-const reference, but if you use this method from a
   // const method then you should not return such a reference without making it
   // const first
-  reference ensure_function_loaded_internal(const key_type &name) const
+  reference ensure_function_loaded_internal(key_type name) const
   {
     symbol_table_buildert symbol_table_builder =
       symbol_table_buildert::wrap(symbol_table);
@@ -173,7 +173,7 @@ class lazy_goto_functions_mapt final
   ///   this so that our callers can insert a journalling table here if needed.
   /// \return reference to the new or existing goto_functions map entry.
   reference ensure_entry_converted(
-    const key_type &name,
+    key_type name,
     symbol_table_baset &function_symbol_table) const
   {
     // Fill in symbol table entry body if not already done
diff --git a/jbmc/src/java_bytecode/lazy_goto_model.cpp b/jbmc/src/java_bytecode/lazy_goto_model.cpp
index 0b49f17ddb2..bea48e4a84a 100644
--- a/jbmc/src/java_bytecode/lazy_goto_model.cpp
+++ b/jbmc/src/java_bytecode/lazy_goto_model.cpp
@@ -36,9 +36,10 @@ lazy_goto_modelt::lazy_goto_modelt(
       language_files,
       symbol_table,
       [this](
-        const irep_idt &function_name,
+        irep_idt function_name,
         goto_functionst::goto_functiont &function,
-        journalling_symbol_tablet &journalling_symbol_table) -> void {
+        journalling_symbol_tablet &journalling_symbol_table) -> void
+      {
         goto_model_functiont model_function(
           journalling_symbol_table,
           goto_model->goto_functions,
@@ -67,9 +68,10 @@ lazy_goto_modelt::lazy_goto_modelt(lazy_goto_modelt &&other)
       language_files,
       symbol_table,
       [this](
-        const irep_idt &function_name,
+        irep_idt function_name,
         goto_functionst::goto_functiont &function,
-        journalling_symbol_tablet &journalling_symbol_table) -> void {
+        journalling_symbol_tablet &journalling_symbol_table) -> void
+      {
         goto_model_functiont model_function(
           journalling_symbol_table,
           goto_model->goto_functions,
@@ -170,7 +172,7 @@ void lazy_goto_modelt::initialize(
   set_up_custom_entry_point(
     language_files,
     symbol_table,
-    [this](const irep_idt &id) { return goto_functions.unload(id); },
+    [this](irep_idt id) { return goto_functions.unload(id); },
     options,
     false,
     message_handler);
@@ -234,7 +236,7 @@ bool lazy_goto_modelt::finalize()
   return post_process_functions(*goto_model);
 }
 
-bool lazy_goto_modelt::can_produce_function(const irep_idt &id) const
+bool lazy_goto_modelt::can_produce_function(irep_idt id) const
 {
   return goto_functions.can_produce_function(id);
 }
diff --git a/jbmc/src/java_bytecode/lazy_goto_model.h b/jbmc/src/java_bytecode/lazy_goto_model.h
index 55cc4c0c584..7ae07425d78 100644
--- a/jbmc/src/java_bytecode/lazy_goto_model.h
+++ b/jbmc/src/java_bytecode/lazy_goto_model.h
@@ -156,20 +156,18 @@ class lazy_goto_modelt : public abstract_goto_modelt
   {
     return lazy_goto_modelt(
       [&handler,
-       &options](goto_model_functiont &fun, const abstract_goto_modelt &model) {
-        handler.process_goto_function(fun, model, options);
-      },
-      [&handler, &options](goto_modelt &goto_model) -> bool {
-        return handler.process_goto_functions(goto_model, options);
-      },
-      [&handler](const irep_idt &name) -> bool {
-        return handler.can_generate_function_body(name);
-      },
+       &options](goto_model_functiont &fun, const abstract_goto_modelt &model)
+      { handler.process_goto_function(fun, model, options); },
+      [&handler, &options](goto_modelt &goto_model) -> bool
+      { return handler.process_goto_functions(goto_model, options); },
+      [&handler](irep_idt name) -> bool
+      { return handler.can_generate_function_body(name); },
       [&handler](
-        const irep_idt &function_name,
+        irep_idt function_name,
         symbol_table_baset &symbol_table,
         goto_functiont &function,
-        bool is_first_chance) {
+        bool is_first_chance)
+      {
         return handler.generate_function_body(
           function_name, symbol_table, function, is_first_chance);
       },
@@ -217,7 +215,7 @@ class lazy_goto_modelt : public abstract_goto_modelt
     return symbol_table;
   }
 
-  bool can_produce_function(const irep_idt &id) const override;
+  bool can_produce_function(irep_idt id) const override;
 
   /// Get a GOTO function body. `id` must be a valid symbol-table symbol. Its
   /// body is produced by:
@@ -233,8 +231,7 @@ class lazy_goto_modelt : public abstract_goto_modelt
   ///    `languaget::convert_lazy_method` function. If that results in a `codet`
   ///    representation of the function stored in the symbol table, convert it
   ///    to GOTO and return it as in step (3).
-  const goto_functionst::goto_functiont &
-  get_goto_function(const irep_idt &id) override
+  const goto_functionst::goto_functiont &get_goto_function(irep_idt id) override
   {
     return goto_functions.at(id);
   }
diff --git a/jbmc/src/java_bytecode/nondet.cpp b/jbmc/src/java_bytecode/nondet.cpp
index e07ff81f441..41f6e0d1035 100644
--- a/jbmc/src/java_bytecode/nondet.cpp
+++ b/jbmc/src/java_bytecode/nondet.cpp
@@ -89,10 +89,10 @@ symbol_exprt generate_nondet_int(
 }
 
 code_blockt generate_nondet_switch(
-  const irep_idt &name_prefix,
+  irep_idt name_prefix,
   const alternate_casest &switch_cases,
   const typet &int_type,
-  const irep_idt &mode,
+  irep_idt mode,
   const source_locationt &source_location,
   symbol_table_baset &symbol_table)
 {
diff --git a/jbmc/src/java_bytecode/nondet.h b/jbmc/src/java_bytecode/nondet.h
index 3a6e4b3e100..95de8064bc1 100644
--- a/jbmc/src/java_bytecode/nondet.h
+++ b/jbmc/src/java_bytecode/nondet.h
@@ -93,10 +93,10 @@ typedef std::vector<codet> alternate_casest;
 /// \return Returns a nondet-switch choosing between switch_cases. The resulting
 ///   switch block has no default case.
 code_blockt generate_nondet_switch(
-  const irep_idt &name_prefix,
+  irep_idt name_prefix,
   const alternate_casest &switch_cases,
   const typet &int_type,
-  const irep_idt &mode,
+  irep_idt mode,
   const source_locationt &source_location,
   symbol_table_baset &symbol_table);
 
diff --git a/jbmc/src/java_bytecode/remove_exceptions.cpp b/jbmc/src/java_bytecode/remove_exceptions.cpp
index 0153aeb0d00..6327dfb2158 100644
--- a/jbmc/src/java_bytecode/remove_exceptions.cpp
+++ b/jbmc/src/java_bytecode/remove_exceptions.cpp
@@ -85,7 +85,7 @@ class remove_exceptionst
   typedef std::vector<catch_handlerst> stack_catcht;
 
 public:
-  typedef std::function<bool(const irep_idt &)> function_may_throwt;
+  typedef std::function<bool(irep_idt)> function_may_throwt;
 
   explicit remove_exceptionst(
     symbol_table_baset &_symbol_table,
@@ -109,8 +109,7 @@ class remove_exceptionst
   }
 
   void operator()(goto_functionst &goto_functions);
-  void
-  operator()(const irep_idt &function_identifier, goto_programt &goto_program);
+  void operator()(irep_idt function_identifier, goto_programt &goto_program);
 
 protected:
   symbol_table_baset &symbol_table;
@@ -142,28 +141,28 @@ class remove_exceptionst
     std::size_t &universal_catch);
 
   void add_exception_dispatch_sequence(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &goto_program,
     const goto_programt::targett &instr_it,
     const stack_catcht &stack_catch,
     const std::vector<symbol_exprt> &locals);
 
   bool instrument_throw(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &goto_program,
     const goto_programt::targett &,
     const stack_catcht &,
     const std::vector<symbol_exprt> &);
 
   instrumentation_resultt instrument_function_call(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &goto_program,
     const goto_programt::targett &,
     const stack_catcht &,
     const std::vector<symbol_exprt> &);
 
   void instrument_exceptions(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &goto_program);
 };
 
@@ -318,7 +317,7 @@ goto_programt::targett remove_exceptionst::find_universal_exception(
 /// \param stack_catch: exception handlers currently registered
 /// \param locals: local variables to kill on a function-exit edge
 void remove_exceptionst::add_exception_dispatch_sequence(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   const goto_programt::targett &instr_it,
   const remove_exceptionst::stack_catcht &stack_catch,
@@ -394,7 +393,7 @@ void remove_exceptionst::add_exception_dispatch_sequence(
 /// instruments each throw with conditional GOTOS to the corresponding
 /// exception handlers
 bool remove_exceptionst::instrument_throw(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   const goto_programt::targett &instr_it,
   const remove_exceptionst::stack_catcht &stack_catch,
@@ -425,7 +424,7 @@ bool remove_exceptionst::instrument_throw(
 /// GOTOS to the corresponding exception handlers
 remove_exceptionst::instrumentation_resultt
 remove_exceptionst::instrument_function_call(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   const goto_programt::targett &instr_it,
   const stack_catcht &stack_catch,
@@ -483,7 +482,7 @@ remove_exceptionst::instrument_function_call(
 /// handlers. Additionally, it re-computes the live-range of local variables in
 /// order to add DEAD instructions.
 void remove_exceptionst::instrument_exceptions(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program)
 {
   stack_catcht stack_catch; // stack of try-catch blocks
@@ -613,8 +612,9 @@ void remove_exceptionst::operator()(goto_functionst &goto_functions)
     instrument_exceptions(gf_entry.first, gf_entry.second.body);
 }
 
-void remove_exceptionst::
-operator()(const irep_idt &function_identifier, goto_programt &goto_program)
+void remove_exceptionst::operator()(
+  irep_idt function_identifier,
+  goto_programt &goto_program)
 {
   instrument_exceptions(function_identifier, goto_program);
 }
@@ -631,9 +631,7 @@ void remove_exceptions_using_instanceof(
   uncaught_exceptions(goto_functions, ns, exceptions_map);
 
   remove_exceptionst::function_may_throwt function_may_throw =
-    [&exceptions_map](const irep_idt &id) {
-      return !exceptions_map[id].empty();
-    };
+    [&exceptions_map](irep_idt id) { return !exceptions_map[id].empty(); };
 
   remove_exceptionst remove_exceptions(
     symbol_table, nullptr, function_may_throw, false, message_handler);
@@ -654,13 +652,13 @@ void remove_exceptions_using_instanceof(
 ///   the caller's responsibility.
 /// \param message_handler: logging output
 void remove_exceptions_using_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
-  remove_exceptionst::function_may_throwt any_function_may_throw =
-    [](const irep_idt &) { return true; };
+  remove_exceptionst::function_may_throwt any_function_may_throw = [](irep_idt)
+  { return true; };
 
   remove_exceptionst remove_exceptions(
     symbol_table, nullptr, any_function_may_throw, false, message_handler);
@@ -696,9 +694,7 @@ void remove_exceptions(
   uncaught_exceptions(goto_functions, ns, exceptions_map);
 
   remove_exceptionst::function_may_throwt function_may_throw =
-    [&exceptions_map](const irep_idt &id) {
-      return !exceptions_map[id].empty();
-    };
+    [&exceptions_map](irep_idt id) { return !exceptions_map[id].empty(); };
 
   remove_exceptionst remove_exceptions(
     symbol_table, &class_hierarchy, function_may_throw, true, message_handler);
@@ -721,14 +717,14 @@ void remove_exceptions(
 ///   Only needed if type == REMOVE_ADDED_INSTANCEOF; otherwise may be null.
 /// \param message_handler: logging output
 void remove_exceptions(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
   const class_hierarchyt &class_hierarchy,
   message_handlert &message_handler)
 {
-  remove_exceptionst::function_may_throwt any_function_may_throw =
-    [](const irep_idt &) { return true; };
+  remove_exceptionst::function_may_throwt any_function_may_throw = [](irep_idt)
+  { return true; };
 
   remove_exceptionst remove_exceptions(
     symbol_table,
diff --git a/jbmc/src/java_bytecode/remove_exceptions.h b/jbmc/src/java_bytecode/remove_exceptions.h
index bdbb2153eac..39351d596f7 100644
--- a/jbmc/src/java_bytecode/remove_exceptions.h
+++ b/jbmc/src/java_bytecode/remove_exceptions.h
@@ -30,7 +30,7 @@ class symbol_table_baset;
 /// and adds the required instrumentation (GOTOs and assignments)
 /// This introduces instanceof expressions.
 void remove_exceptions_using_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &,
   symbol_table_baset &,
   message_handlert &);
@@ -44,7 +44,7 @@ void remove_exceptions_using_instanceof(goto_modelt &, message_handlert &);
 /// and adds the required instrumentation (GOTOs and assignments)
 /// This does not introduce instanceof expressions.
 void remove_exceptions(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &,
   symbol_table_baset &,
   const class_hierarchyt &,
diff --git a/jbmc/src/java_bytecode/remove_instanceof.cpp b/jbmc/src/java_bytecode/remove_instanceof.cpp
index 1671b416cc9..a0930aa3e92 100644
--- a/jbmc/src/java_bytecode/remove_instanceof.cpp
+++ b/jbmc/src/java_bytecode/remove_instanceof.cpp
@@ -34,11 +34,11 @@ class remove_instanceoft
   }
 
   // Lower instanceof for a single function
-  bool lower_instanceof(const irep_idt &function_identifier, goto_programt &);
+  bool lower_instanceof(irep_idt function_identifier, goto_programt &);
 
   // Lower instanceof for a single instruction
   bool lower_instanceof(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &,
     goto_programt::targett);
 
@@ -49,7 +49,7 @@ class remove_instanceoft
   message_handlert &message_handler;
 
   bool lower_instanceof(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     exprt &,
     goto_programt &,
     goto_programt::targett);
@@ -66,7 +66,7 @@ class remove_instanceoft
 /// \return disjunction of the possible matched subtypes
 static exprt subtype_expr(
   const exprt &classid_field,
-  const irep_idt &target_type,
+  irep_idt target_type,
   const class_hierarchyt &class_hierarchy)
 {
   std::vector<irep_idt> children =
@@ -75,9 +75,9 @@ static exprt subtype_expr(
   // Sort alphabetically to make order of generated disjuncts
   // independent of class loading order
   std::sort(
-    children.begin(), children.end(), [](const irep_idt &a, const irep_idt &b) {
-      return a.compare(b) < 0;
-    });
+    children.begin(),
+    children.end(),
+    [](irep_idt a, irep_idt b) { return a.compare(b) < 0; });
 
   exprt::operandst or_ops;
   for(const auto &class_name : children)
@@ -99,7 +99,7 @@ static exprt subtype_expr(
 /// \param this_inst: instruction the expression is found at
 /// \return true if any instanceof instructionw was replaced
 bool remove_instanceoft::lower_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   exprt &expr,
   goto_programt &goto_program,
   goto_programt::targett this_inst)
@@ -237,7 +237,7 @@ static bool contains_instanceof(const exprt &e)
 /// \param target: instruction to check for instanceof expressions
 /// \return true if an instanceof has been replaced
 bool remove_instanceoft::lower_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   goto_programt::targett target)
 {
@@ -276,7 +276,7 @@ bool remove_instanceoft::lower_instanceof(
 /// \param goto_program: The function body to work on.
 /// \return true if one or more instanceof expressions have been replaced
 bool remove_instanceoft::lower_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program)
 {
   bool changed=false;
@@ -304,7 +304,7 @@ bool remove_instanceoft::lower_instanceof(
 /// \param class_hierarchy: class hierarchy analysis of symbol_table
 /// \param message_handler: logging output
 void remove_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt::targett target,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
@@ -324,7 +324,7 @@ void remove_instanceof(
 /// \param class_hierarchy: class hierarchy analysis of symbol_table
 /// \param message_handler: logging output
 void remove_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functionst::goto_functiont &function,
   symbol_table_baset &symbol_table,
   const class_hierarchyt &class_hierarchy,
diff --git a/jbmc/src/java_bytecode/remove_instanceof.h b/jbmc/src/java_bytecode/remove_instanceof.h
index 245d67db4fb..1cf0acd4da3 100644
--- a/jbmc/src/java_bytecode/remove_instanceof.h
+++ b/jbmc/src/java_bytecode/remove_instanceof.h
@@ -87,7 +87,7 @@ class message_handlert;
 class symbol_table_baset;
 
 void remove_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt::targett target,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
@@ -95,7 +95,7 @@ void remove_instanceof(
   message_handlert &);
 
 void remove_instanceof(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functionst::goto_functiont &function,
   symbol_table_baset &symbol_table,
   const class_hierarchyt &class_hierarchy,
diff --git a/jbmc/src/java_bytecode/remove_java_new.cpp b/jbmc/src/java_bytecode/remove_java_new.cpp
index 283be05498e..f2cc59893a8 100644
--- a/jbmc/src/java_bytecode/remove_java_new.cpp
+++ b/jbmc/src/java_bytecode/remove_java_new.cpp
@@ -36,13 +36,13 @@ class remove_java_newt
 
   // Lower java_new for a single function
   bool lower_java_new(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &,
     message_handlert &);
 
   // Lower java_new for a single instruction
   goto_programt::targett lower_java_new(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_programt &,
     goto_programt::targett,
     message_handlert &);
@@ -52,14 +52,14 @@ class remove_java_newt
   namespacet ns;
 
   goto_programt::targett lower_java_new(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     const exprt &lhs,
     const side_effect_exprt &rhs,
     goto_programt &,
     goto_programt::targett);
 
   goto_programt::targett lower_java_new_array(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     const exprt &lhs,
     const side_effect_exprt &rhs,
     goto_programt &,
@@ -80,7 +80,7 @@ class remove_java_newt
 /// Note: we have to take a copy of `lhs` and `rhs` since they would suffer
 ///   destruction when replacing the instruction.
 goto_programt::targett remove_java_newt::lower_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   const exprt &lhs,
   const side_effect_exprt &rhs,
   goto_programt &dest,
@@ -130,7 +130,7 @@ goto_programt::targett remove_java_newt::lower_java_new(
 /// Note: we have to take a copy of `lhs` and `rhs` since they would suffer
 ///   destruction when replacing the instruction.
 goto_programt::targett remove_java_newt::lower_java_new_array(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   const exprt &lhs,
   const side_effect_exprt &rhs,
   goto_programt &dest,
@@ -360,7 +360,7 @@ goto_programt::targett remove_java_newt::lower_java_new_array(
 /// \param message_handler: message handler
 /// \return true if a replacement has been made
 goto_programt::targett remove_java_newt::lower_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   goto_programt::targett target,
   message_handlert &message_handler)
@@ -406,7 +406,7 @@ goto_programt::targett remove_java_newt::lower_java_new(
 /// \param message_handler: message handler
 /// \return true if one or more java_new expressions have been replaced
 bool remove_java_newt::lower_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program,
   message_handlert &message_handler)
 {
@@ -436,7 +436,7 @@ bool remove_java_newt::lower_java_new(
 /// \param symbol_table: The symbol table to add symbols to.
 /// \param message_handler: a message handler
 void remove_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt::targett target,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
@@ -455,7 +455,7 @@ void remove_java_new(
 /// \param symbol_table: The symbol table to add symbols to.
 /// \param message_handler: a message handler
 void remove_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functionst::goto_functiont &function,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
diff --git a/jbmc/src/java_bytecode/remove_java_new.h b/jbmc/src/java_bytecode/remove_java_new.h
index 4ed497a92c0..ea0709fd8f1 100644
--- a/jbmc/src/java_bytecode/remove_java_new.h
+++ b/jbmc/src/java_bytecode/remove_java_new.h
@@ -19,14 +19,14 @@ class message_handlert;
 class symbol_table_baset;
 
 void remove_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt::targett target,
   goto_programt &goto_program,
   symbol_table_baset &symbol_table,
   message_handlert &_message_handler);
 
 void remove_java_new(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functionst::goto_functiont &function,
   symbol_table_baset &symbol_table,
   message_handlert &_message_handler);
diff --git a/jbmc/src/java_bytecode/replace_java_nondet.cpp b/jbmc/src/java_bytecode/replace_java_nondet.cpp
index 5615983aa24..81befc7e917 100644
--- a/jbmc/src/java_bytecode/replace_java_nondet.cpp
+++ b/jbmc/src/java_bytecode/replace_java_nondet.cpp
@@ -105,7 +105,7 @@ get_nondet_instruction_info(const goto_programt::const_targett &instr)
 /// \param expr: The expression which may be a symbol.
 /// \param identifier: Some identifier.
 /// \return True if the expression is a symbol with the specified identifier.
-static bool is_symbol_with_id(const exprt &expr, const irep_idt &identifier)
+static bool is_symbol_with_id(const exprt &expr, irep_idt identifier)
 {
   return expr.id() == ID_symbol &&
          to_symbol_expr(expr).identifier() == identifier;
@@ -116,7 +116,7 @@ static bool is_symbol_with_id(const exprt &expr, const irep_idt &identifier)
 /// \param identifier: Some identifier.
 /// \return True if the expression is a typecast with one operand, and the
 ///   typecast's identifier matches the specified identifier.
-static bool is_typecast_with_id(const exprt &expr, const irep_idt &identifier)
+static bool is_typecast_with_id(const exprt &expr, irep_idt identifier)
 {
   if(!(expr.id() == ID_typecast && expr.operands().size() == 1))
   {
@@ -140,7 +140,7 @@ static bool is_typecast_with_id(const exprt &expr, const irep_idt &identifier)
 ///   typecast's identifier matches the specified identifier.
 static bool is_assignment_from(
   const goto_programt::instructiont &instr,
-  const irep_idt &identifier)
+  irep_idt identifier)
 {
   // If not an assignment, return false
   if(!instr.is_assign())
@@ -160,7 +160,7 @@ static bool is_assignment_from(
 ///   typecast's identifier matches the specified identifier.
 static bool is_return_with_variable(
   const goto_programt::instructiont &instr,
-  const irep_idt &identifier)
+  irep_idt identifier)
 {
   if(!instr.is_set_return_value())
   {
diff --git a/jbmc/src/java_bytecode/select_pointer_type.cpp b/jbmc/src/java_bytecode/select_pointer_type.cpp
index c6bceb4fd72..93b0148e0ee 100644
--- a/jbmc/src/java_bytecode/select_pointer_type.cpp
+++ b/jbmc/src/java_bytecode/select_pointer_type.cpp
@@ -82,8 +82,8 @@ pointer_typet select_pointer_typet::specialize_generics(
 
 std::set<struct_tag_typet>
 select_pointer_typet::get_parameter_alternative_types(
-  const irep_idt &,
-  const irep_idt &,
+  irep_idt,
+  irep_idt,
   const namespacet &) const
 {
   return {};
diff --git a/jbmc/src/java_bytecode/select_pointer_type.h b/jbmc/src/java_bytecode/select_pointer_type.h
index b9ade58821f..fbd10bb0be3 100644
--- a/jbmc/src/java_bytecode/select_pointer_type.h
+++ b/jbmc/src/java_bytecode/select_pointer_type.h
@@ -44,8 +44,8 @@ class select_pointer_typet
   /// Derived classes can override this behaviour to provide more
   /// sophisticated alternative type identification.
   virtual std::set<struct_tag_typet> get_parameter_alternative_types(
-    const irep_idt &function_name,
-    const irep_idt &parameter_name,
+    irep_idt function_name,
+    irep_idt parameter_name,
     const namespacet &ns) const;
 
   /// Specialize generic parameters in a pointer type based on the current map
diff --git a/jbmc/src/java_bytecode/simple_method_stubbing.cpp b/jbmc/src/java_bytecode/simple_method_stubbing.cpp
index bdcc51908f8..521af93702d 100644
--- a/jbmc/src/java_bytecode/simple_method_stubbing.cpp
+++ b/jbmc/src/java_bytecode/simple_method_stubbing.cpp
@@ -41,7 +41,7 @@ class java_simple_method_stubst
     const typet &expected_type,
     const exprt &ptr,
     const source_locationt &loc,
-    const irep_idt &function_id,
+    irep_idt function_id,
     code_blockt &parent_block,
     unsigned insert_before_index,
     bool is_constructor,
@@ -49,7 +49,7 @@ class java_simple_method_stubst
 
   void create_method_stub(symbolt &symbol);
 
-  void check_method_stub(const irep_idt &);
+  void check_method_stub(irep_idt);
 
 protected:
   symbol_table_baset &symbol_table;
@@ -82,7 +82,7 @@ void java_simple_method_stubst::create_method_stub_at(
   const typet &expected_type,
   const exprt &ptr,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   code_blockt &parent_block,
   const unsigned insert_before_index,
   const bool is_constructor,
@@ -250,7 +250,7 @@ void java_simple_method_stubst::create_method_stub(symbolt &symbol)
 /// Replaces `sym` with a function stub per the function above if it is
 ///   of suitable type.
 /// \param symname: Symbol name to consider stubbing
-void java_simple_method_stubst::check_method_stub(const irep_idt &symname)
+void java_simple_method_stubst::check_method_stub(irep_idt symname)
 {
   const symbolt &sym = symbol_table.lookup_ref(symname);
   if(!sym.is_type && sym.value.id() == ID_nil &&
@@ -270,7 +270,7 @@ void java_simple_method_stubst::check_method_stub(const irep_idt &symname)
 }
 
 void java_generate_simple_method_stub(
-  const irep_idt &function_name,
+  irep_idt function_name,
   symbol_table_baset &symbol_table,
   bool assume_non_null,
   const java_object_factory_parameterst &object_factory_parameters,
diff --git a/jbmc/src/java_bytecode/simple_method_stubbing.h b/jbmc/src/java_bytecode/simple_method_stubbing.h
index 165d26835e7..5b4cb9d4b2b 100644
--- a/jbmc/src/java_bytecode/simple_method_stubbing.h
+++ b/jbmc/src/java_bytecode/simple_method_stubbing.h
@@ -19,7 +19,7 @@ struct java_object_factory_parameterst;
 class symbol_table_baset;
 
 void java_generate_simple_method_stub(
-  const irep_idt &function_name,
+  irep_idt function_name,
   symbol_table_baset &symbol_table,
   bool assume_non_null,
   const java_object_factory_parameterst &object_factory_parameters,
diff --git a/jbmc/src/jbmc/jbmc_parse_options.cpp b/jbmc/src/jbmc/jbmc_parse_options.cpp
index 7ed4105af63..033c28e8f84 100644
--- a/jbmc/src/jbmc/jbmc_parse_options.cpp
+++ b/jbmc/src/jbmc/jbmc_parse_options.cpp
@@ -697,7 +697,8 @@ void jbmc_parse_optionst::process_goto_function(
   // Java virtual functions -> explicit dispatch tables:
   remove_virtual_functions(function, *class_hierarchy);
 
-  auto function_is_stub = [&symbol_table, &model](const irep_idt &id) {
+  auto function_is_stub = [&symbol_table, &model](irep_idt id)
+  {
     return symbol_table.lookup_ref(id).value.is_nil() &&
            !model.can_produce_function(id);
   };
@@ -915,7 +916,7 @@ bool jbmc_parse_optionst::process_goto_functions(
   return false;
 }
 
-bool jbmc_parse_optionst::can_generate_function_body(const irep_idt &name)
+bool jbmc_parse_optionst::can_generate_function_body(irep_idt name)
 {
   static const irep_idt initialize_id = INITIALIZE_FUNCTION;
 
@@ -923,7 +924,7 @@ bool jbmc_parse_optionst::can_generate_function_body(const irep_idt &name)
 }
 
 bool jbmc_parse_optionst::generate_function_body(
-  const irep_idt &function_name,
+  irep_idt function_name,
   symbol_table_baset &symbol_table,
   goto_functiont &function,
   bool body_available)
diff --git a/jbmc/src/jbmc/jbmc_parse_options.h b/jbmc/src/jbmc/jbmc_parse_options.h
index 80a11dc1b52..faa68779789 100644
--- a/jbmc/src/jbmc/jbmc_parse_options.h
+++ b/jbmc/src/jbmc/jbmc_parse_options.h
@@ -111,10 +111,10 @@ class jbmc_parse_optionst : public parse_options_baset
     const optionst &);
   bool process_goto_functions(goto_modelt &goto_model, const optionst &options);
 
-  bool can_generate_function_body(const irep_idt &name);
+  bool can_generate_function_body(irep_idt name);
 
   bool generate_function_body(
-    const irep_idt &function_name,
+    irep_idt function_name,
     symbol_table_baset &symbol_table,
     goto_functiont &function,
     bool body_available);
diff --git a/jbmc/unit/java-testing-utils/load_java_class.cpp b/jbmc/unit/java-testing-utils/load_java_class.cpp
index 54617050f2c..6d7e4e157f9 100644
--- a/jbmc/unit/java-testing-utils/load_java_class.cpp
+++ b/jbmc/unit/java-testing-utils/load_java_class.cpp
@@ -99,10 +99,9 @@ goto_modelt load_goto_model_from_java_class(
   lazy_goto_modelt lazy_goto_model(
     [](goto_model_functiont &, const abstract_goto_modelt &) {},
     [](goto_modelt &) { return false; },
-    [](const irep_idt &) { return false; },
-    [](const irep_idt &, symbol_table_baset &, goto_functiont &, bool) {
-      return false;
-    },
+    [](irep_idt) { return false; },
+    [](irep_idt, symbol_table_baset &, goto_functiont &, bool)
+    { return false; },
     null_message_handler);
 
   // Configure the path loading
diff --git a/jbmc/unit/java-testing-utils/require_goto_statements.cpp b/jbmc/unit/java-testing-utils/require_goto_statements.cpp
index f95bbcff992..230e919e896 100644
--- a/jbmc/unit/java-testing-utils/require_goto_statements.cpp
+++ b/jbmc/unit/java-testing-utils/require_goto_statements.cpp
@@ -70,9 +70,9 @@ require_goto_statements::require_entry_point_statements(
 require_goto_statements::pointer_assignment_locationt
 require_goto_statements::find_struct_component_assignments(
   const std::vector<codet> &statements,
-  const irep_idt &structure_name,
+  irep_idt structure_name,
   const std::optional<irep_idt> &superclass_name,
-  const irep_idt &component_name,
+  irep_idt component_name,
   const symbol_table_baset &symbol_table)
 {
   pointer_assignment_locationt locations{};
@@ -167,7 +167,7 @@ require_goto_statements::find_struct_component_assignments(
 require_goto_statements::pointer_assignment_locationt
 require_goto_statements::find_this_component_assignment(
   const std::vector<codet> &statements,
-  const irep_idt &component_name)
+  irep_idt component_name)
 {
   pointer_assignment_locationt locations;
 
@@ -217,7 +217,7 @@ require_goto_statements::find_this_component_assignment(
 ///   vector of all other assignments
 require_goto_statements::pointer_assignment_locationt
 require_goto_statements::find_pointer_assignments(
-  const irep_idt &pointer_name,
+  irep_idt pointer_name,
   const std::vector<codet> &instructions)
 {
   INFO("Looking for symbol: " << pointer_name);
@@ -283,7 +283,7 @@ require_goto_statements::find_pointer_assignments(
 /// \throws no_decl_found_exceptiont if no declaration of the specific
 /// variable is found
 const code_declt &require_goto_statements::require_declaration_of_name(
-  const irep_idt &variable_name,
+  irep_idt variable_name,
   const std::vector<codet> &entry_point_instructions)
 {
   for(const auto &statement : entry_point_instructions)
@@ -308,7 +308,7 @@ const code_declt &require_goto_statements::require_declaration_of_name(
 /// \return The unique non-null expression assigned to the symbol
 const exprt &get_unique_non_null_expression_assigned_to_symbol(
   const std::vector<codet> &entry_point_instructions,
-  const irep_idt &symbol_identifier)
+  irep_idt symbol_identifier)
 {
   const auto &assignments = require_goto_statements::find_pointer_assignments(
                               symbol_identifier, entry_point_instructions)
@@ -327,9 +327,9 @@ const exprt &get_unique_non_null_expression_assigned_to_symbol(
 ///   pointer if no symbols are assigned to it
 const symbol_exprt *try_get_unique_symbol_assigned_to_symbol(
   const std::vector<codet> &entry_point_instructions,
-  const irep_idt &symbol_identifier)
+  irep_idt symbol_identifier)
 {
-  const auto &expr = get_unique_non_null_expression_assigned_to_symbol(
+  const auto expr = get_unique_non_null_expression_assigned_to_symbol(
     entry_point_instructions, symbol_identifier);
 
   return expr_try_dynamic_cast<symbol_exprt>(skip_typecast(expr));
@@ -349,10 +349,9 @@ const symbol_exprt *try_get_unique_symbol_assigned_to_symbol(
 /// \return The identifier of the symbol which is (possibly indirectly) assigned
 ///   to \p input_symbol_identifier and which does not have any symbol assigned
 ///   to it
-static const irep_idt &
-get_ultimate_source_symbol(
+static irep_idt get_ultimate_source_symbol(
   const std::vector<codet> &entry_point_instructions,
-  const irep_idt &input_symbol_identifier)
+  irep_idt input_symbol_identifier)
 {
   const symbol_exprt *symbol_assigned_to_input_symbol =
     try_get_unique_symbol_assigned_to_symbol(
@@ -382,10 +381,10 @@ get_ultimate_source_symbol(
 ///   which will be used for future calls to
 ///   `require_struct_component_assignment`.
 irep_idt require_goto_statements::require_struct_component_assignment(
-  const irep_idt &structure_name,
+  irep_idt structure_name,
   const std::optional<irep_idt> &superclass_name,
-  const irep_idt &component_name,
-  const irep_idt &component_type_name,
+  irep_idt component_name,
+  irep_idt component_type_name,
   const std::optional<irep_idt> &typecast_name,
   const std::vector<codet> &entry_point_instructions,
   const symbol_table_baset &symbol_table)
@@ -420,7 +419,7 @@ irep_idt require_goto_statements::require_struct_component_assignment(
   // right hand side, then we want to identify that the type
   // is the one we expect, e.g.:
   // struct java.lang.Integer *malloc_site$0;
-  const auto &component_declaration =
+  const auto component_declaration =
     require_goto_statements::require_declaration_of_name(
       symbol_identifier, entry_point_instructions);
   const typet &component_type =
@@ -444,10 +443,10 @@ irep_idt require_goto_statements::require_struct_component_assignment(
 /// \return The identifier of the variable assigned to the field
 const irep_idt &
 require_goto_statements::require_struct_array_component_assignment(
-  const irep_idt &structure_name,
+  irep_idt structure_name,
   const std::optional<irep_idt> &superclass_name,
-  const irep_idt &array_component_name,
-  const irep_idt &array_type_name,
+  irep_idt array_component_name,
+  irep_idt array_type_name,
   const std::vector<codet> &entry_point_instructions,
   const symbol_table_baset &symbol_table)
 {
@@ -515,7 +514,7 @@ require_goto_statements::require_struct_array_component_assignment(
 /// \param entry_point_statements: The statements to look through
 /// \return The identifier of the variable assigned to the input argument
 irep_idt require_goto_statements::require_entry_point_argument_assignment(
-  const irep_idt &argument_name,
+  irep_idt argument_name,
   const std::vector<codet> &entry_point_statements)
 {
   // Trace the creation of the object that is being supplied as the input
@@ -548,7 +547,7 @@ irep_idt require_goto_statements::require_entry_point_argument_assignment(
 /// \return All calls to the matching function inside the statements
 std::vector<code_function_callt> require_goto_statements::find_function_calls(
   const std::vector<codet> &statements,
-  const irep_idt &function_call_identifier)
+  irep_idt function_call_identifier)
 {
   std::vector<code_function_callt> function_calls;
   for(const codet &statement : statements)
diff --git a/jbmc/unit/java-testing-utils/require_goto_statements.h b/jbmc/unit/java-testing-utils/require_goto_statements.h
index 991286e7c2a..c58f855c156 100644
--- a/jbmc/unit/java-testing-utils/require_goto_statements.h
+++ b/jbmc/unit/java-testing-utils/require_goto_statements.h
@@ -46,14 +46,14 @@ class no_decl_found_exceptiont : public std::exception
 
 pointer_assignment_locationt find_struct_component_assignments(
   const std::vector<codet> &statements,
-  const irep_idt &structure_name,
+  irep_idt structure_name,
   const std::optional<irep_idt> &superclass_name,
-  const irep_idt &component_name,
+  irep_idt component_name,
   const symbol_table_baset &symbol_table);
 
 pointer_assignment_locationt find_this_component_assignment(
   const std::vector<codet> &statements,
-  const irep_idt &component_name);
+  irep_idt component_name);
 
 std::vector<codet> get_all_statements(const exprt &function_value);
 
@@ -61,7 +61,7 @@ const std::vector<codet>
 require_entry_point_statements(const symbol_table_baset &symbol_table);
 
 pointer_assignment_locationt find_pointer_assignments(
-  const irep_idt &pointer_name,
+  irep_idt pointer_name,
   const std::vector<codet> &instructions);
 
 pointer_assignment_locationt find_pointer_assignments(
@@ -69,33 +69,33 @@ pointer_assignment_locationt find_pointer_assignments(
   const std::vector<codet> &instructions);
 
 const code_declt &require_declaration_of_name(
-  const irep_idt &variable_name,
+  irep_idt variable_name,
   const std::vector<codet> &entry_point_instructions);
 
 irep_idt require_struct_component_assignment(
-  const irep_idt &structure_name,
+  irep_idt structure_name,
   const std::optional<irep_idt> &superclass_name,
-  const irep_idt &component_name,
-  const irep_idt &component_type_name,
+  irep_idt component_name,
+  irep_idt component_type_name,
   const std::optional<irep_idt> &typecast_name,
   const std::vector<codet> &entry_point_instructions,
   const symbol_table_baset &symbol_table);
 
 const irep_idt &require_struct_array_component_assignment(
-  const irep_idt &structure_name,
+  irep_idt structure_name,
   const std::optional<irep_idt> &superclass_name,
-  const irep_idt &array_component_name,
-  const irep_idt &array_type_name,
+  irep_idt array_component_name,
+  irep_idt array_type_name,
   const std::vector<codet> &entry_point_instructions,
   const symbol_table_baset &symbol_table);
 
 irep_idt require_entry_point_argument_assignment(
-  const irep_idt &argument_name,
+  irep_idt argument_name,
   const std::vector<codet> &entry_point_statements);
 
 std::vector<code_function_callt> find_function_calls(
   const std::vector<codet> &statements,
-  const irep_idt &function_call_identifier);
+  irep_idt function_call_identifier);
 }
 
 #endif // CPROVER_JAVA_TESTING_UTILS_REQUIRE_GOTO_STATEMENTS_H
diff --git a/jbmc/unit/java-testing-utils/require_parse_tree.cpp b/jbmc/unit/java-testing-utils/require_parse_tree.cpp
index 02331ca2ba5..91fcbe4d10d 100644
--- a/jbmc/unit/java-testing-utils/require_parse_tree.cpp
+++ b/jbmc/unit/java-testing-utils/require_parse_tree.cpp
@@ -51,7 +51,7 @@ require_parse_tree::require_lambda_entry_for_descriptor(
 /// \return The methodt structure with the corresponding name
 const require_parse_tree::methodt require_parse_tree::require_method(
   const java_bytecode_parse_treet::classt &parsed_class,
-  const irep_idt &method_name)
+  irep_idt method_name)
 {
   const auto method = std::find_if(
     parsed_class.methods.begin(),
diff --git a/jbmc/unit/java-testing-utils/require_parse_tree.h b/jbmc/unit/java-testing-utils/require_parse_tree.h
index 7496443c4eb..85fded0c700 100644
--- a/jbmc/unit/java-testing-utils/require_parse_tree.h
+++ b/jbmc/unit/java-testing-utils/require_parse_tree.h
@@ -28,12 +28,12 @@ typedef java_bytecode_parse_treet::methodt methodt;
 
 const methodt require_method(
   const java_bytecode_parse_treet::classt &parsed_class,
-  const irep_idt &method_name);
+  irep_idt method_name);
 
 struct expected_instructiont
 {
   expected_instructiont(
-    const irep_idt &instruction_mnemoic,
+    irep_idt instruction_mnemoic,
     const std::vector<exprt> &instruction_arguments)
     : instruction_mnemoic(instruction_mnemoic),
       instruction_arguments(instruction_arguments)
diff --git a/jbmc/unit/java-testing-utils/require_type.cpp b/jbmc/unit/java-testing-utils/require_type.cpp
index 4559d4348c5..407c10073a9 100644
--- a/jbmc/unit/java-testing-utils/require_type.cpp
+++ b/jbmc/unit/java-testing-utils/require_type.cpp
@@ -34,7 +34,7 @@ pointer_typet require_type::require_pointer(
 /// \return The component with the specified name
 java_class_typet::componentt require_type::require_component(
   const java_class_typet &java_class_type,
-  const irep_idt &component_name)
+  irep_idt component_name)
 {
   const auto &component = std::find_if(
     java_class_type.components().begin(),
@@ -53,7 +53,7 @@ java_class_typet::componentt require_type::require_component(
 /// \return The component with the specified name
 struct_typet::componentt require_type::require_component(
   const struct_typet &struct_type,
-  const irep_idt &component_name)
+  irep_idt component_name)
 {
   const auto &componet = std::find_if(
     struct_type.components().begin(),
@@ -119,7 +119,7 @@ require_type::require_java_method(const typet &type, const size_t num_params)
 ///   parameter name.
 code_typet::parametert require_type::require_parameter(
   const code_typet &function_type,
-  const irep_idt &param_name)
+  irep_idt param_name)
 {
   const auto param = std::find_if(
     function_type.parameters().begin(),
@@ -224,7 +224,7 @@ require_type::require_java_generic_parameter(const typet &type)
 /// \return The given type, cast to a java_generic_parametert
 java_generic_parametert require_type::require_java_generic_parameter(
   const typet &type,
-  const irep_idt &parameter)
+  irep_idt parameter)
 {
   const java_generic_parametert &generic_param =
     require_type::require_java_generic_parameter(type);
@@ -314,17 +314,16 @@ java_generic_class_typet require_type::require_java_generic_class(
   const java_generic_class_typet::generic_typest &generic_type_vars =
     java_generic_class_type.generic_types();
   REQUIRE(generic_type_vars.size() == type_variables.size());
-  REQUIRE(
-    std::equal(
-      type_variables.begin(),
-      type_variables.end(),
-      generic_type_vars.begin(),
-      [](
-        const irep_idt &type_var_name,
-        const java_generic_parametert &param) { //NOLINT
-        REQUIRE(is_java_generic_parameter(param));
-        return param.type_variable().get_identifier() == type_var_name;
-      }));
+  REQUIRE(std::equal(
+    type_variables.begin(),
+    type_variables.end(),
+    generic_type_vars.begin(),
+    [](
+      irep_idt type_var_name,
+      const java_generic_parametert &param) { //NOLINT
+      REQUIRE(is_java_generic_parameter(param));
+      return param.type_variable().get_identifier() == type_var_name;
+    }));
 
   return java_generic_class_type;
 }
@@ -459,7 +458,7 @@ require_type::require_complete_java_non_generic_class(const typet &class_type)
 /// \param identifier: The identifier the symbol type should have
 /// \return The cast version of the input type
 const struct_tag_typet &
-require_type::require_struct_tag(const typet &type, const irep_idt &identifier)
+require_type::require_struct_tag(const typet &type, irep_idt identifier)
 {
   REQUIRE(type.id() == ID_struct_tag);
   const struct_tag_typet &result = to_struct_tag_type(type);
@@ -471,7 +470,7 @@ require_type::require_struct_tag(const typet &type, const irep_idt &identifier)
 }
 
 pointer_typet
-require_type::require_pointer_to_tag(const typet &type, const irep_idt &tag)
+require_type::require_pointer_to_tag(const typet &type, irep_idt tag)
 {
   const auto pointer_type = require_type::require_pointer(type, {});
   require_type::require_struct_tag(pointer_type.base_type(), tag);
diff --git a/jbmc/unit/java-testing-utils/require_type.h b/jbmc/unit/java-testing-utils/require_type.h
index 84f3b51015e..d5764188064 100644
--- a/jbmc/unit/java-testing-utils/require_type.h
+++ b/jbmc/unit/java-testing-utils/require_type.h
@@ -28,25 +28,23 @@ require_pointer(const typet &type, const std::optional<typet> &subtype);
 [[gnu::no_dangling]]
 #endif
 const struct_tag_typet &
-require_struct_tag(const typet &type, const irep_idt &identifier = "");
+require_struct_tag(const typet &type, irep_idt identifier = "");
 
-pointer_typet require_pointer_to_tag(
-  const typet &type,
-  const irep_idt &identifier = irep_idt());
+pointer_typet
+require_pointer_to_tag(const typet &type, irep_idt identifier = irep_idt());
 
 java_class_typet::componentt require_component(
   const java_class_typet &java_class_type,
-  const irep_idt &component_name);
+  irep_idt component_name);
 
-struct_typet::componentt require_component(
-  const struct_typet &struct_type,
-  const irep_idt &component_name);
+struct_typet::componentt
+require_component(const struct_typet &struct_type, irep_idt component_name);
 
 code_typet require_code(const typet &type);
 java_method_typet require_java_method(const typet &type);
 
 code_typet::parametert
-require_parameter(const code_typet &function_type, const irep_idt &param_name);
+require_parameter(const code_typet &function_type, irep_idt param_name);
 
 code_typet require_code(const typet &type, const size_t num_params);
 java_method_typet
@@ -75,9 +73,8 @@ java_generic_typet require_java_generic_type(
 
 java_generic_parametert require_java_generic_parameter(const typet &type);
 
-java_generic_parametert require_java_generic_parameter(
-  const typet &type,
-  const irep_idt &parameter);
+java_generic_parametert
+require_java_generic_parameter(const typet &type, irep_idt parameter);
 
 const typet &require_java_non_generic_type(
   const typet &type,
diff --git a/jbmc/unit/java_bytecode/goto-programs/remove_virtual_functions_without_fallback.cpp b/jbmc/unit/java_bytecode/goto-programs/remove_virtual_functions_without_fallback.cpp
index 82721843801..2ea8d6f1410 100644
--- a/jbmc/unit/java_bytecode/goto-programs/remove_virtual_functions_without_fallback.cpp
+++ b/jbmc/unit/java_bytecode/goto-programs/remove_virtual_functions_without_fallback.cpp
@@ -19,7 +19,7 @@ Author: Diffblue Ltd.
 /// classid has value `actual_class_id`
 exprt resolve_classid_test(
   const exprt &expr,
-  const irep_idt &actual_class_id,
+  irep_idt actual_class_id,
   const namespacet &ns)
 {
   if(expr.id() == ID_or || expr.id() == ID_and)
@@ -56,8 +56,7 @@ exprt resolve_classid_test(
   return expr;
 }
 
-static bool is_call_to(
-  goto_programt::const_targett inst, const irep_idt &callee)
+static bool is_call_to(goto_programt::const_targett inst, irep_idt callee)
 {
   if(!inst->is_function_call())
     return false;
@@ -78,7 +77,7 @@ static bool is_assume_false(goto_programt::const_targett inst)
 /// way.
 static goto_programt::const_targett interpret_classid_comparison(
   const goto_programt &program,
-  const irep_idt &actual_class_id,
+  irep_idt actual_class_id,
   const namespacet &ns)
 {
   REQUIRE(!program.instructions.empty());
diff --git a/jbmc/unit/java_bytecode/goto_program_generics/generic_parameters_test.cpp b/jbmc/unit/java_bytecode/goto_program_generics/generic_parameters_test.cpp
index 849d8861d2f..ab15f0853be 100644
--- a/jbmc/unit/java_bytecode/goto_program_generics/generic_parameters_test.cpp
+++ b/jbmc/unit/java_bytecode/goto_program_generics/generic_parameters_test.cpp
@@ -312,7 +312,7 @@ SCENARIO(
 
       THEN("Object 'v' is of type Wrapper")
       {
-        const auto &tmp_object_declaration =
+        const auto tmp_object_declaration =
           require_goto_statements::require_declaration_of_name(
             tmp_object_name, entry_point_code);
 
@@ -362,7 +362,7 @@ SCENARIO(
 
       THEN("Object 'v' is of type Wrapper")
       {
-        const auto &tmp_object_declaration =
+        const auto tmp_object_declaration =
           require_goto_statements::require_declaration_of_name(
             tmp_object_name, entry_point_code);
 
@@ -412,7 +412,7 @@ SCENARIO(
 
       THEN("Object 'v' is of type Outer")
       {
-        const auto &tmp_object_declaration =
+        const auto tmp_object_declaration =
           require_goto_statements::require_declaration_of_name(
             tmp_object_name, entry_point_code);
 
@@ -477,7 +477,7 @@ SCENARIO(
 
       THEN("Object 'v' is of type A")
       {
-        const auto &tmp_object_declaration =
+        const auto tmp_object_declaration =
           require_goto_statements::require_declaration_of_name(
             tmp_object_name, entry_point_code);
 
diff --git a/jbmc/unit/java_bytecode/goto_program_generics/mutually_recursive_generics.cpp b/jbmc/unit/java_bytecode/goto_program_generics/mutually_recursive_generics.cpp
index 9d49647a013..51eebfea7b7 100644
--- a/jbmc/unit/java_bytecode/goto_program_generics/mutually_recursive_generics.cpp
+++ b/jbmc/unit/java_bytecode/goto_program_generics/mutually_recursive_generics.cpp
@@ -91,10 +91,9 @@ SCENARIO(
     const std::vector<codet> &entry_point_code =
       require_goto_statements::require_entry_point_statements(symbol_table);
 
-    const auto has_key_and_value_field = [&](
-      const irep_idt &field,
-      const irep_idt &key_type,
-      const irep_idt &val_type) {
+    const auto has_key_and_value_field =
+      [&](irep_idt field, irep_idt key_type, irep_idt val_type)
+    {
       require_goto_statements::require_struct_component_assignment(
         field, {}, "key", key_type, {}, entry_point_code, symbol_table);
       require_goto_statements::require_struct_component_assignment(
@@ -169,11 +168,9 @@ SCENARIO(
           entry_point_code,
           symbol_table);
 
-      const auto has_x_e_u_fields = [&](
-        const irep_idt &field,
-        const irep_idt &x_type,
-        const irep_idt &e_type,
-        const irep_idt &u_type) {
+      const auto has_x_e_u_fields =
+        [&](irep_idt field, irep_idt x_type, irep_idt e_type, irep_idt u_type)
+      {
         require_goto_statements::require_struct_component_assignment(
           field, {}, "x", x_type, {}, entry_point_code, symbol_table);
         require_goto_statements::require_struct_component_assignment(
diff --git a/jbmc/unit/java_bytecode/inherited_static_fields/inherited_static_fields.cpp b/jbmc/unit/java_bytecode/inherited_static_fields/inherited_static_fields.cpp
index 30f57f2b615..23d12280e67 100644
--- a/jbmc/unit/java_bytecode/inherited_static_fields/inherited_static_fields.cpp
+++ b/jbmc/unit/java_bytecode/inherited_static_fields/inherited_static_fields.cpp
@@ -19,7 +19,7 @@ Author: Diffblue Ltd.
 /// \param expr: expr to check
 /// \param id: symbol id to look for
 /// \return true if a suitable symbol_exprt is found
-static bool contains_symbol_reference(const exprt &expr, const irep_idt &id)
+static bool contains_symbol_reference(const exprt &expr, irep_idt id)
 {
   return std::any_of(
     expr.depth_begin(),
diff --git a/jbmc/unit/java_bytecode/java_bytecode_convert_method/convert_method.cpp b/jbmc/unit/java_bytecode/java_bytecode_convert_method/convert_method.cpp
index 7509b736f2a..f2d5b798b77 100644
--- a/jbmc/unit/java_bytecode/java_bytecode_convert_method/convert_method.cpp
+++ b/jbmc/unit/java_bytecode/java_bytecode_convert_method/convert_method.cpp
@@ -335,15 +335,14 @@ SCENARIO(
 class java_bytecode_convert_method_unit_testt
 {
 public:
-  static exprt
-  convert_aload(const irep_idt &statement, const exprt::operandst &op)
+  static exprt convert_aload(irep_idt statement, const exprt::operandst &op)
   {
     return java_bytecode_convert_methodt::convert_aload(statement, op);
   }
 
   static code_blockt convert_astore(
     java_bytecode_convert_methodt &converter,
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt::operandst &op,
     const source_locationt &location)
   {
@@ -383,7 +382,7 @@ class java_bytecode_convert_method_unit_testt
 
   static code_blockt convert_store(
     java_bytecode_convert_methodt &converter,
-    const irep_idt &statement,
+    irep_idt statement,
     const exprt &arg0,
     const exprt::operandst &op,
     const java_bytecode_convert_methodt::method_offsett address,
diff --git a/jbmc/unit/java_bytecode/java_bytecode_parser/parse_java_annotations.cpp b/jbmc/unit/java_bytecode/java_bytecode_parser/parse_java_annotations.cpp
index 6ea155a486d..c36812c22a6 100644
--- a/jbmc/unit/java_bytecode/java_bytecode_parser/parse_java_annotations.cpp
+++ b/jbmc/unit/java_bytecode/java_bytecode_parser/parse_java_annotations.cpp
@@ -32,8 +32,8 @@ class test_java_bytecode_languaget : public java_bytecode_languaget
     return parsed_class_names;
   }
 
-  java_class_loadert::parse_tree_with_overlayst &get_parse_trees_for_class(
-    const irep_idt &class_name)
+  java_class_loadert::parse_tree_with_overlayst &
+  get_parse_trees_for_class(irep_idt class_name)
   {
     return java_class_loader.get_class_with_overlays_map().at(class_name);
   }
diff --git a/jbmc/unit/java_bytecode/java_object_factory/struct_tag_types.cpp b/jbmc/unit/java_bytecode/java_object_factory/struct_tag_types.cpp
index 8594be44be2..e023f128219 100644
--- a/jbmc/unit/java_bytecode/java_object_factory/struct_tag_types.cpp
+++ b/jbmc/unit/java_bytecode/java_object_factory/struct_tag_types.cpp
@@ -17,7 +17,7 @@ Author: Diffblue Ltd.
 
 #include <algorithm>
 
-static bool is_decl_with_struct_tag(const codet &code, const irep_idt &id)
+static bool is_decl_with_struct_tag(const codet &code, irep_idt id)
 {
   if(code.get_statement() != ID_decl)
     return false;
@@ -72,7 +72,7 @@ static bool contains_decl_of_type(const codet &code, const typet &type)
   });
 }
 
-static bool contains_decl_with_struct_tag(const codet &code, const irep_idt &id)
+static bool contains_decl_with_struct_tag(const codet &code, irep_idt id)
 {
   return contains(code, [&id](const codet &subcode) {
     return is_decl_with_struct_tag(subcode, id);
diff --git a/jbmc/unit/java_bytecode/java_replace_nondet/replace_nondet.cpp b/jbmc/unit/java_bytecode/java_replace_nondet/replace_nondet.cpp
index 2ad12a18031..964332746e7 100644
--- a/jbmc/unit/java_bytecode/java_replace_nondet/replace_nondet.cpp
+++ b/jbmc/unit/java_bytecode/java_replace_nondet/replace_nondet.cpp
@@ -143,7 +143,7 @@ void load_and_test_method(
   // Then test both situations.
   THEN("Replace nondet should work after remove returns has been called.")
   {
-    remove_returns(model_function, [](const irep_idt &) { return false; });
+    remove_returns(model_function, [](irep_idt) { return false; });
 
     replace_java_nondet(model_function);
 
@@ -154,7 +154,7 @@ void load_and_test_method(
   {
     replace_java_nondet(model_function);
 
-    remove_returns(model_function, [](const irep_idt &) { return false; });
+    remove_returns(model_function, [](irep_idt) { return false; });
 
     validate_nondet_method_removed(goto_function.body.instructions);
   }
@@ -165,7 +165,7 @@ void load_and_test_method(
     "Replace and convert nondet should work after remove returns has been "
     "called.")
   {
-    remove_returns(model_function, [](const irep_idt &) { return false; });
+    remove_returns(model_function, [](irep_idt) { return false; });
 
     replace_java_nondet(model_function);
 
@@ -182,7 +182,7 @@ void load_and_test_method(
 
     convert_nondet(model_function, null_message_handler, params, ID_java);
 
-    remove_returns(model_function, [](const irep_idt &) { return false; });
+    remove_returns(model_function, [](irep_idt) { return false; });
 
     validate_nondets_converted(goto_function.body.instructions);
   }
diff --git a/jbmc/unit/java_bytecode/java_string_library_preprocess/convert_exprt_to_string_exprt.cpp b/jbmc/unit/java_bytecode/java_string_library_preprocess/convert_exprt_to_string_exprt.cpp
index 389564dd7a1..f339b08a737 100644
--- a/jbmc/unit/java_bytecode/java_string_library_preprocess/convert_exprt_to_string_exprt.cpp
+++ b/jbmc/unit/java_bytecode/java_string_library_preprocess/convert_exprt_to_string_exprt.cpp
@@ -24,7 +24,7 @@ refined_string_exprt convert_exprt_to_string_exprt_unit_test(
   java_string_library_preprocesst &preprocess,
   const exprt &deref,
   const source_locationt &loc,
-  const irep_idt &function_id,
+  irep_idt function_id,
   symbol_table_baset &symbol_table,
   code_blockt &init_code)
 {
diff --git a/jbmc/unit/java_bytecode/java_virtual_functions/virtual_functions.cpp b/jbmc/unit/java_bytecode/java_virtual_functions/virtual_functions.cpp
index 019b9a34509..5dd00aa3cec 100644
--- a/jbmc/unit/java_bytecode/java_virtual_functions/virtual_functions.cpp
+++ b/jbmc/unit/java_bytecode/java_virtual_functions/virtual_functions.cpp
@@ -20,8 +20,8 @@ Author: Diffblue Ltd.
 
 void check_function_call(
   const equal_exprt &eq_expr,
-  const irep_idt &class_name,
-  const irep_idt &function_name,
+  irep_idt class_name,
+  irep_idt function_name,
   const goto_programt::targetst &targets)
 {
   REQUIRE(eq_expr.op0().is_constant());
diff --git a/jbmc/unit/pointer-analysis/custom_value_set_analysis.cpp b/jbmc/unit/pointer-analysis/custom_value_set_analysis.cpp
index 92cca9f876c..136b8ddabbf 100644
--- a/jbmc/unit/pointer-analysis/custom_value_set_analysis.cpp
+++ b/jbmc/unit/pointer-analysis/custom_value_set_analysis.cpp
@@ -147,8 +147,7 @@ typedef
 #define TEST_FUNCTION_NAME TEST_PREFIX "test:()V"
 #define TEST_LOCAL_PREFIX TEST_FUNCTION_NAME "::"
 
-static std::size_t
-exprs_with_id(const std::vector<exprt> &exprs, const irep_idt &id)
+static std::size_t exprs_with_id(const std::vector<exprt> &exprs, irep_idt id)
 {
   return std::count_if(
     exprs.begin(),
diff --git a/scripts/check_pass_by_value.cpp b/scripts/check_pass_by_value.cpp
new file mode 100644
index 00000000000..6b72593caf8
--- /dev/null
+++ b/scripts/check_pass_by_value.cpp
@@ -0,0 +1,443 @@
+// Detect parameters of cheap-to-copy types passed by const reference.
+//
+// Implements C++ Core Guidelines F.16 ("for `in` parameters, pass cheaply
+// copied types by value and others by reference to const"). The set of
+// "cheap" types is configured below in CHEAP_TYPES; it currently lists
+// dstringt (= irep_idt), which is a wrapper around a single unsigned
+// table index and is strictly cheaper to copy than to take by reference.
+//
+// The matcher is `parmVarDecl()`. Real method/function parameters and
+// named parameters of function-type template arguments inside
+// *instantiated* class templates (e.g.
+// `std::function<void(const key_type &k)>` inside `sharing_mapt<K, V>`
+// when instantiated with K = irep_idt) are flagged. --fix can rewrite
+// the former in place; the latter are flagged but not auto-rewritten,
+// because changing the in-class declaration without the matching
+// out-of-class definition would not compile.
+//
+// Limitation: anonymous parameters in non-instantiated typedefs of
+// std::function (e.g. `using cb = std::function<void(const irep_idt &)>`)
+// don't produce a ParmVarDecl in Clang's AST and therefore are not
+// caught here. A complementary `FunctionProtoTypeLoc` walker would
+// close this gap; for now, regressions of that specific shape need
+// to be caught by code review or a follow-up grep sweep.
+//
+// Build:
+//   clang++-18 -o check-pass-by-value scripts/check_pass_by_value.cpp \
+//     $(llvm-config-18 --cxxflags | sed 's/-Werror//g') \
+//     -L/usr/lib/llvm-18/lib -lclang-cpp \
+//     $(llvm-config-18 --ldflags --libs --system-libs) -fno-rtti
+//
+// Usage (check):
+//   ./check-pass-by-value -p build/compile_commands.json src/foo/*.cpp
+// Usage (rewrite in-place):
+//   ./check-pass-by-value --fix -p build/compile_commands.json src/foo/*.cpp
+
+#include <set>
+#include <string>
+
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Tooling/CommonOptionsParser.h"
+#include "clang/Tooling/Refactoring.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+using namespace clang::ast_matchers;
+using namespace clang::tooling;
+
+static llvm::cl::OptionCategory Cat("check-pass-by-value");
+static llvm::cl::opt<bool> Fix(
+  "fix",
+  llvm::cl::desc("Rewrite each finding in place: replace 'const T &' "
+                 "with 'T '"),
+  llvm::cl::cat(Cat));
+static llvm::cl::opt<std::string> PathFilter(
+  "path-filter",
+  llvm::cl::desc("Only act on findings whose absolute path contains this "
+                 "substring (matches anywhere). Default: act everywhere."),
+  llvm::cl::cat(Cat));
+
+/// Types that are "cheap to copy" per C++ Core Guidelines F.16, expressed
+/// as canonical (typedef-stripped) names. To extend, add the canonical
+/// name here; for example, `goto_programt::const_targett` resolves to
+/// `std::__cxx11::list<goto_programt::instructiont>::const_iterator`.
+static const std::set<std::string> CHEAP_TYPES = {
+  // dstringt holds a single unsigned table index. irep_idt is a typedef
+  // for dstringt, so the canonical name we match against is "dstringt".
+  "dstringt",
+};
+
+/// Return true if QT is one of the configured cheap-to-copy types.
+static bool isCheapType(QualType QT)
+{
+  if(QT.isNull())
+    return false;
+  // Strip references and cv-qualifiers; we want the underlying record.
+  if(QT->isReferenceType())
+    QT = QT.getNonReferenceType();
+  QT = QT.getLocalUnqualifiedType();
+  // Resolve typedefs to the canonical record (e.g., irep_idt -> dstringt).
+  const CXXRecordDecl *RD = QT->getAsCXXRecordDecl();
+  if(!RD)
+    return false;
+  return CHEAP_TYPES.count(RD->getNameAsString()) > 0;
+}
+
+/// Reconstruct a short signature snippet for the parameter, of the form
+/// "const T &name", using the source spelling where possible (so users
+/// see "const irep_idt &" rather than "const dstringt &").
+static std::string spellingFor(
+  const ParmVarDecl *PVD,
+  const SourceManager &SM,
+  const LangOptions &LO)
+{
+  SourceRange R = PVD->getSourceRange();
+  if(R.isInvalid())
+    return PVD->getType().getAsString() + " " + PVD->getNameAsString();
+  CharSourceRange CSR = CharSourceRange::getTokenRange(R);
+  StringRef Text = Lexer::getSourceText(CSR, SM, LO);
+  // Collapse consecutive whitespace for readability of multi-line decls.
+  std::string Out;
+  Out.reserve(Text.size());
+  bool PrevSpace = false;
+  for(char c : Text)
+  {
+    if(c == '\n' || c == '\r' || c == '\t' || c == ' ')
+    {
+      if(!PrevSpace)
+        Out.push_back(' ');
+      PrevSpace = true;
+    }
+    else
+    {
+      Out.push_back(c);
+      PrevSpace = false;
+    }
+  }
+  return Out;
+}
+
+/// Walk through reference/qualified TypeLoc layers to reach the bare
+/// type spelling (e.g., the `irep_idt` or `dstringt` token).
+static TypeLoc innerTypeLoc(TypeLoc TL)
+{
+  while(true)
+  {
+    if(auto Ref = TL.getAs<ReferenceTypeLoc>())
+    {
+      TL = Ref.getPointeeLoc();
+      continue;
+    }
+    if(auto Qual = TL.getAs<QualifiedTypeLoc>())
+    {
+      TL = Qual.getUnqualifiedLoc();
+      continue;
+    }
+    break;
+  }
+  return TL;
+}
+
+class ParamCallback : public MatchFinder::MatchCallback
+{
+public:
+  std::map<std::string, Replacements> *Replace = nullptr;
+
+  void run(const MatchFinder::MatchResult &Result) override
+  {
+    const auto *PVD = Result.Nodes.getNodeAs<ParmVarDecl>("param");
+    if(!PVD)
+      return;
+
+    const auto &SM = *Result.SourceManager;
+    SourceLocation Loc = PVD->getLocation();
+    if(Loc.isInvalid())
+      return;
+
+    // Skip parameters declared in system headers (e.g., libstdc++
+    // template specialisations of std::less<irep_idt>): these are not
+    // ours to fix and would create thousands of spurious findings.
+    if(SM.isInSystemHeader(Loc))
+      return;
+
+    // We do *not* restrict to "main" files: most parameter declarations
+    // live in headers (class definitions, function declarations), so we
+    // need to follow #includes. Duplicates that arise from the same
+    // header being parsed by many TUs are removed below via the Seen
+    // set, keyed by (file, line, column).
+
+    // The parameter type must be a const lvalue reference to one of our
+    // cheap-to-copy types.
+    QualType PT = PVD->getType();
+    if(!PT->isLValueReferenceType())
+      return;
+    QualType Pointee = PT->getPointeeType();
+    if(!Pointee.isConstQualified())
+      return;
+    if(!isCheapType(Pointee))
+      return;
+
+    // Skip parameters of special member functions whose signature is
+    // dictated by the language: copy/move constructors and copy/move
+    // assignment operators must take `const T &` (or `T &&`) and
+    // returning by value would not compile.
+    const auto *FD = dyn_cast<FunctionDecl>(PVD->getDeclContext());
+
+    // Whether the parameter is one we are willing to rewrite in place.
+    // Parameter names that appear inside function-type template
+    // arguments (e.g. `std::function<void(const irep_idt &k)>`) have
+    // their enclosing FunctionDecl in DeclContext but are NOT in that
+    // FunctionDecl's getParamDecl() list. Rewriting them in isolation
+    // desynchronises an in-class declaration from its out-of-class
+    // definition, so we still flag them (so CI can catch any new
+    // ones), but we don't auto-rewrite them.
+    bool isFixable = false;
+    if(FD)
+    {
+      for(unsigned i = 0; i < FD->getNumParams(); ++i)
+      {
+        if(FD->getParamDecl(i) == PVD)
+        {
+          isFixable = true;
+          break;
+        }
+      }
+    }
+
+    if(FD)
+    {
+      if(const auto *CtorD = dyn_cast<CXXConstructorDecl>(FD))
+      {
+        if(CtorD->isCopyConstructor() || CtorD->isMoveConstructor())
+          return;
+      }
+      if(const auto *MD = dyn_cast<CXXMethodDecl>(FD))
+      {
+        if(MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator())
+          return;
+      }
+      // Skip parameters of function template *instantiations*. We still
+      // see the original template's parameters separately (and flag
+      // those when the type is spelled as e.g. `const irep_idt &`); the
+      // instantiations only pop up because Clang substituted a template
+      // parameter to one of our cheap types, which is not something the
+      // user can fix locally without changing the template signature
+      // (and thereby pessimising other instantiations).
+      if(FD->isTemplateInstantiation())
+        return;
+      // Same reasoning for member functions of class template
+      // specialisations: the source-as-written signature may use a
+      // template type parameter (e.g. `const keyT &`) that happens to
+      // have been substituted to one of our cheap types.
+      if(const auto *MD = dyn_cast<CXXMethodDecl>(FD))
+      {
+        if(isa<ClassTemplateSpecializationDecl>(MD->getParent()))
+          return;
+      }
+    }
+
+    // Skip if the parameter's source-as-written type is a (substituted)
+    // template type parameter or otherwise dependent. Only flag when
+    // the user actually wrote one of our cheap types, e.g.
+    // `const irep_idt &x` or `const dstringt &x`. We walk the type
+    // sugar chain rather than only inspecting the top-level type, so
+    // that constructs like `const value_type &` -- where `value_type`
+    // is a typedef whose substituted form is `dstringt` only because
+    // the enclosing class template was instantiated with a cheap key
+    // type -- are recognised and skipped.
+    if(const TypeSourceInfo *TSI = PVD->getTypeSourceInfo())
+    {
+      QualType AsWritten = TSI->getType().getNonReferenceType();
+      ASTContext &Ctx = *Result.Context;
+      QualType Cur = AsWritten;
+      while(!Cur.isNull())
+      {
+        const Type *T = Cur.getTypePtr();
+        if(
+          isa<SubstTemplateTypeParmType>(T) || isa<TemplateTypeParmType>(T) ||
+          isa<SubstTemplateTypeParmPackType>(T) || isa<DependentNameType>(T))
+          return;
+        QualType Next = Cur.getSingleStepDesugaredType(Ctx);
+        if(Next == Cur)
+          break;
+        Cur = Next;
+      }
+    }
+
+    PresumedLoc PL = SM.getPresumedLoc(Loc);
+    if(PL.isInvalid())
+      return;
+
+    // If --path-filter is set, drop findings whose file path doesn't
+    // contain that substring (after path normalisation).
+    if(!PathFilter.empty())
+    {
+      StringRef FN = PL.getFilename();
+      if(FN.find(PathFilter) == StringRef::npos)
+        return;
+    }
+
+    // Deduplicate: a single parameter declaration in source can match
+    // multiple times via template instantiations. Keying by absolute
+    // (file, line, column) collapses these to a single warning.
+    Key K{PL.getFilename(), PL.getLine(), PL.getColumn()};
+    if(!Seen.insert(K).second)
+      return;
+
+    std::string Spelling = spellingFor(PVD, SM, Result.Context->getLangOpts());
+
+    // Build the entire diagnostic line in a string and emit it with a
+    // single write, so that concurrent parallel runs do not interleave
+    // partial lines on stdout.
+    std::string Line;
+    {
+      llvm::raw_string_ostream OS(Line);
+      OS << PL.getFilename() << ":" << PL.getLine() << ":" << PL.getColumn()
+         << ": warning: parameter '" << PVD->getNameAsString() << "' has type '"
+         << PT.getAsString()
+         << "' which is cheap to copy; pass by value "
+            "[cprover-pass-cheap-by-value]: "
+         << Spelling << "\n";
+    }
+    llvm::outs() << Line;
+    llvm::outs().flush();
+
+    // In --fix mode, also queue an in-place replacement that rewrites
+    // the parameter's type from `const T &` to `T `. We replace the
+    // half-open character range from the start of the parameter
+    // declaration (which covers the leading `const`) up to the start
+    // of the parameter name, with `<spelled-T> `. This preserves the
+    // user's choice of spelling (`irep_idt` vs. `dstringt`) and
+    // absorbs any whitespace between `&` and the name.
+    if(Replace == nullptr)
+      return;
+    // Only auto-rewrite parameters that are real method/function
+    // parameters; see the isFixable comment above.
+    if(!isFixable)
+      return;
+    const TypeSourceInfo *TSI = PVD->getTypeSourceInfo();
+    if(!TSI)
+      return;
+    TypeLoc TL = TSI->getTypeLoc();
+    SourceLocation Begin = PVD->getBeginLoc();
+    SourceLocation End = PVD->getLocation();
+    if(Begin.isInvalid() || End.isInvalid() || Begin == End)
+      return;
+    // Only safe to rewrite if both endpoints map to the same file, in
+    // file (not macro-expansion) locations.
+    Begin = SM.getFileLoc(Begin);
+    End = SM.getFileLoc(End);
+    if(SM.getFileID(Begin) != SM.getFileID(End))
+      return;
+    // Extract the spelled inner type so we preserve `irep_idt` vs.
+    // `dstringt` exactly as the user wrote it.
+    TypeLoc Inner = innerTypeLoc(TL);
+    CharSourceRange InnerCSR =
+      CharSourceRange::getTokenRange(Inner.getSourceRange());
+    StringRef InnerText =
+      Lexer::getSourceText(InnerCSR, SM, Result.Context->getLangOpts());
+    if(InnerText.empty())
+      return;
+    std::string ReplaceText = InnerText.str();
+    ReplaceText.push_back(' ');
+    CharSourceRange Range = CharSourceRange::getCharRange(Begin, End);
+    Replacement R(SM, Range, ReplaceText);
+    std::string FilePath = std::string(R.getFilePath());
+    if(FilePath.empty())
+      return;
+    if(auto Err = (*Replace)[FilePath].add(R))
+    {
+      llvm::errs() << "warning: failed to add replacement for " << FilePath
+                   << ": " << llvm::toString(std::move(Err)) << "\n";
+    }
+  }
+
+private:
+  struct Key
+  {
+    std::string File;
+    unsigned Line;
+    unsigned Column;
+    bool operator<(const Key &O) const
+    {
+      if(File != O.File)
+        return File < O.File;
+      if(Line != O.Line)
+        return Line < O.Line;
+      return Column < O.Column;
+    }
+  };
+  std::set<Key> Seen;
+};
+
+int main(int argc, const char **argv)
+{
+  auto EP = CommonOptionsParser::create(argc, argv, Cat);
+  if(!EP)
+  {
+    llvm::errs() << EP.takeError();
+    return 1;
+  }
+
+  ParamCallback CB;
+  MatchFinder Finder;
+  Finder.addMatcher(parmVarDecl().bind("param"), &CB);
+
+  if(Fix)
+  {
+    RefactoringTool Tool(EP->getCompilations(), EP->getSourcePathList());
+    Tool.appendArgumentsAdjuster(getInsertArgumentAdjuster(
+      "-Wno-unknown-warning-option", ArgumentInsertPosition::BEGIN));
+    CB.Replace = &Tool.getReplacements();
+    int RC = Tool.run(newFrontendActionFactory(&Finder).get());
+    // Manually apply replacements rather than using runAndSave: the
+    // latter returns early when any TU has a parse error (e.g.,
+    // optional solver back-ends with missing third-party headers),
+    // and we still want fixes for the TUs that parsed cleanly.
+    unsigned Saved = 0;
+    for(auto &Entry : Tool.getReplacements())
+    {
+      const std::string &FilePath = Entry.first;
+      const Replacements &Reps = Entry.second;
+      auto Buffer = llvm::MemoryBuffer::getFile(FilePath);
+      if(!Buffer)
+      {
+        llvm::errs() << "warning: could not read " << FilePath << ": "
+                     << Buffer.getError().message() << "\n";
+        continue;
+      }
+      llvm::Expected<std::string> NewContent =
+        applyAllReplacements((*Buffer)->getBuffer(), Reps);
+      if(!NewContent)
+      {
+        llvm::errs() << "warning: failed to apply replacements for " << FilePath
+                     << ": " << llvm::toString(NewContent.takeError()) << "\n";
+        continue;
+      }
+      std::error_code EC;
+      llvm::raw_fd_ostream Out(FilePath, EC);
+      if(EC)
+      {
+        llvm::errs() << "warning: could not write " << FilePath << ": "
+                     << EC.message() << "\n";
+        continue;
+      }
+      Out << *NewContent;
+      ++Saved;
+    }
+    llvm::errs() << "Saved " << Saved << " files.\n";
+    return RC;
+  }
+  else
+  {
+    ClangTool Tool(EP->getCompilations(), EP->getSourcePathList());
+    Tool.appendArgumentsAdjuster(getInsertArgumentAdjuster(
+      "-Wno-unknown-warning-option", ArgumentInsertPosition::BEGIN));
+    return Tool.run(newFrontendActionFactory(&Finder).get());
+  }
+}
diff --git a/scripts/pass_by_value_baseline.txt b/scripts/pass_by_value_baseline.txt
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/scripts/run_diff.sh b/scripts/run_diff.sh
index 3f41b836994..8f9644b81cb 100755
--- a/scripts/run_diff.sh
+++ b/scripts/run_diff.sh
@@ -37,7 +37,7 @@ then
     echo "Ensure cpplint.py is inside the $script_folder directory then run again"
     exit 1
   else
-    cmd='${script_folder}/cpplint.py --exclude=jbmc/src/miniz/* --filter=-whitespace/operators,-readability/identifier_spacing $file 2>&1 >/dev/null'
+    cmd='${script_folder}/cpplint.py --exclude=jbmc/src/miniz/* --exclude=scripts/check_pass_by_value.cpp --filter=-whitespace/operators,-readability/identifier_spacing $file 2>&1 >/dev/null'
   fi
 else
   echo "Mode $mode not recognized"
diff --git a/scripts/run_pass_by_value_check.sh b/scripts/run_pass_by_value_check.sh
new file mode 100755
index 00000000000..50f562d71a4
--- /dev/null
+++ b/scripts/run_pass_by_value_check.sh
@@ -0,0 +1,135 @@
+#!/bin/bash
+# CI script: check for F.16 pass-by-const-reference violations on cheap
+# types (C++ Core Guidelines F.16). Uses scripts/check_pass_by_value.cpp
+# (Clang LibTooling) and diffs the output against
+# scripts/pass_by_value_baseline.txt.
+#
+# Build directory is taken from the first argument and defaults to "build".
+# A compile_commands.json must exist there.
+#
+# Exit codes:
+#   0  no new findings (existing baseline entries may have disappeared,
+#      in which case a notice is printed and the user is invited to
+#      regenerate the baseline)
+#   1  new findings appeared, or the tool failed to build/run
+#
+# Usage:
+#   scripts/run_pass_by_value_check.sh [build-dir]
+
+set -euo pipefail
+
+BUILD_DIR="${1:-build}"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+TOOL="$SCRIPT_DIR/check-pass-by-value"
+BASELINE="$SCRIPT_DIR/pass_by_value_baseline.txt"
+SOURCE="$SCRIPT_DIR/check_pass_by_value.cpp"
+
+# ---------------------------------------------------------------------------
+# Build the tool if it isn't present or is older than its source.
+# ---------------------------------------------------------------------------
+if [ ! -x "$TOOL" ] || [ "$SOURCE" -nt "$TOOL" ]; then
+  echo "Building check-pass-by-value..."
+  LLVM_VER="$(llvm-config --version 2>/dev/null | cut -d. -f1 || echo "")"
+  if [ -z "$LLVM_VER" ]; then
+    for v in 20 18 15; do
+      if command -v "llvm-config-$v" >/dev/null 2>&1; then
+        LLVM_VER="$v"
+        break
+      fi
+    done
+  fi
+  if [ -z "$LLVM_VER" ]; then
+    echo "Error: no LLVM installation found" >&2
+    exit 1
+  fi
+  # shellcheck disable=SC2046
+  clang++-"$LLVM_VER" -o "$TOOL" "$SOURCE" \
+    $(llvm-config-"$LLVM_VER" --cxxflags | sed 's/-Werror//g') \
+    -L/usr/lib/llvm-"$LLVM_VER"/lib -lclang-cpp \
+    $(llvm-config-"$LLVM_VER" --ldflags --libs --system-libs) \
+    -fno-rtti
+fi
+
+if [ ! -f "$BUILD_DIR/compile_commands.json" ]; then
+  echo "Error: $BUILD_DIR/compile_commands.json not found" >&2
+  echo "Run: cmake -S . -B$BUILD_DIR -DCMAKE_EXPORT_COMPILE_COMMANDS=ON" >&2
+  exit 1
+fi
+
+# ---------------------------------------------------------------------------
+# Run the tool over all C++ TUs in src/ and jbmc/src/, in parallel. Each
+# `xargs` worker writes to its own per-pid temp file to avoid stdout
+# interleaving across workers; we concatenate at the end.
+# ---------------------------------------------------------------------------
+TMP="$(mktemp -d)"
+trap 'rm -rf "$TMP"' EXIT
+
+export TMP TOOL BUILD_DIR
+# Per-TU parsing errors return non-zero from the tool; that propagates
+# through `xargs` and would normally trip `set -e`. Tolerate it: any TUs
+# that genuinely produced output have done so via the `>>` redirection,
+# and we error out below if the aggregate result is empty.
+set +e
+find "$REPO_ROOT/src" "$REPO_ROOT/jbmc/src" -name '*.cpp' -print0 \
+  | xargs -0 -P "$(nproc)" -n 8 sh -c '
+      "$TOOL" -p "$BUILD_DIR/compile_commands.json" "$@" \
+        2>/dev/null >> "$TMP/$$.out"
+    ' _
+set -e
+
+# Collapse to repo-relative paths so that the baseline is portable.
+CURRENT="$TMP/current.txt"
+cat "$TMP"/*.out 2>/dev/null \
+  | sed "s|$REPO_ROOT/||g" \
+  | sort -u > "$CURRENT"
+
+# ---------------------------------------------------------------------------
+# Diff against the baseline.
+#   comm -13 baseline current  -> new in current (NEW VIOLATIONS, fail)
+#   comm -23 baseline current  -> removed (notice, pass)
+# ---------------------------------------------------------------------------
+if [ ! -f "$BASELINE" ]; then
+  echo "Error: baseline file $BASELINE not found." >&2
+  echo "Generate it with:" >&2
+  echo "  $0 $BUILD_DIR --regenerate-baseline" >&2
+  exit 1
+fi
+
+if [ "${2:-}" = "--regenerate-baseline" ]; then
+  cp "$CURRENT" "$BASELINE"
+  echo "Baseline regenerated at $BASELINE ($(wc -l < "$BASELINE") entries)."
+  exit 0
+fi
+
+NEW="$TMP/new.txt"
+REMOVED="$TMP/removed.txt"
+comm -13 <(sort "$BASELINE") "$CURRENT" > "$NEW"
+comm -23 <(sort "$BASELINE") "$CURRENT" > "$REMOVED"
+
+NEW_COUNT="$(wc -l < "$NEW")"
+REMOVED_COUNT="$(wc -l < "$REMOVED")"
+TOTAL_COUNT="$(wc -l < "$CURRENT")"
+BASELINE_COUNT="$(wc -l < "$BASELINE")"
+
+echo "Pass-by-value check: $TOTAL_COUNT findings (baseline: $BASELINE_COUNT)."
+
+if [ "$REMOVED_COUNT" -gt 0 ]; then
+  echo ""
+  echo "Note: $REMOVED_COUNT baseline entries no longer present —"
+  echo "consider regenerating the baseline:"
+  echo "  $0 $BUILD_DIR --regenerate-baseline"
+fi
+
+if [ "$NEW_COUNT" -gt 0 ]; then
+  echo ""
+  echo "$NEW_COUNT NEW pass-by-value violation(s) found:" >&2
+  cat "$NEW" >&2
+  echo "" >&2
+  echo "These parameters take a cheap-to-copy type by const reference," >&2
+  echo "violating C++ Core Guidelines F.16. Pass them by value instead." >&2
+  exit 1
+fi
+
+echo "No new pass-by-value violations."
+exit 0
diff --git a/src/analyses/ai.cpp b/src/analyses/ai.cpp
index adc509d019e..5883bc61373 100644
--- a/src/analyses/ai.cpp
+++ b/src/analyses/ai.cpp
@@ -38,7 +38,7 @@ void ai_baset::output(
 
 void ai_baset::output(
   const namespacet &ns,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   std::ostream &out) const
 {
@@ -82,7 +82,7 @@ jsont ai_baset::output_json(
 
 jsont ai_baset::output_json(
   const namespacet &ns,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program) const
 {
   (void)function_id; // unused parameter
@@ -135,7 +135,7 @@ xmlt ai_baset::output_xml(
 
 xmlt ai_baset::output_xml(
   const namespacet &ns,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program) const
 {
   (void)function_id; // unused parameter
@@ -188,13 +188,13 @@ ai_baset::trace_ptrt ai_baset::entry_state(const goto_programt &goto_program)
 }
 
 void ai_baset::initialize(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_functionst::goto_functiont &goto_function)
 {
   initialize(function_id, goto_function.body);
 }
 
-void ai_baset::initialize(const irep_idt &, const goto_programt &goto_program)
+void ai_baset::initialize(irep_idt, const goto_programt &goto_program)
 {
   // Domains are created and set to bottom on access.
   // So we do not need to set them to be bottom before hand.
@@ -231,7 +231,7 @@ ai_baset::trace_ptrt ai_baset::get_next(working_sett &working_set)
 
 bool ai_baset::fixedpoint(
   trace_ptrt start_trace,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   const goto_functionst &goto_functions,
   const namespacet &ns)
@@ -268,7 +268,7 @@ void ai_baset::fixedpoint(
 }
 
 bool ai_baset::visit(
-  const irep_idt &function_id,
+  irep_idt function_id,
   trace_ptrt p,
   working_sett &working_set,
   const goto_programt &goto_program,
@@ -329,9 +329,9 @@ bool ai_baset::visit(
 }
 
 bool ai_baset::visit_edge(
-  const irep_idt &function_id,
+  irep_idt function_id,
   trace_ptrt p,
-  const irep_idt &to_function_id,
+  irep_idt to_function_id,
   locationt to_l,
   trace_ptrt caller_history,
   const namespacet &ns,
@@ -414,10 +414,10 @@ bool ai_baset::visit_edge(
 }
 
 bool ai_baset::visit_edge_function_call(
-  const irep_idt &calling_function_id,
+  irep_idt calling_function_id,
   trace_ptrt p_call,
   locationt l_return,
-  const irep_idt &,
+  irep_idt,
   working_sett &working_set,
   const goto_programt &,
   const goto_functionst &,
@@ -442,7 +442,7 @@ bool ai_baset::visit_edge_function_call(
 }
 
 bool ai_baset::visit_function_call(
-  const irep_idt &calling_function_id,
+  irep_idt calling_function_id,
   trace_ptrt p_call,
   working_sett &working_set,
   const goto_programt &caller,
@@ -521,7 +521,7 @@ bool ai_baset::visit_function_call(
 }
 
 bool ai_baset::visit_end_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   trace_ptrt p,
   working_sett &working_set,
   const goto_programt &goto_program,
@@ -540,10 +540,10 @@ bool ai_baset::visit_end_function(
 }
 
 bool ai_recursive_interproceduralt::visit_edge_function_call(
-  const irep_idt &calling_function_id,
+  irep_idt calling_function_id,
   trace_ptrt p_call,
   locationt l_return,
-  const irep_idt &callee_function_id,
+  irep_idt callee_function_id,
   working_sett &working_set,
   const goto_programt &callee,
   const goto_functionst &goto_functions,
diff --git a/src/analyses/ai.h b/src/analyses/ai.h
index 04fbcc9c127..42c09b6bca2 100644
--- a/src/analyses/ai.h
+++ b/src/analyses/ai.h
@@ -67,7 +67,7 @@ Author: Daniel Kroening, kroening@kroening.com
 /// It breaks into three categories:
 ///
 /// 1. Running an analysis, via \ref
-///    #operator()(const irep_idt&,const goto_programt&, const namespacet&),
+///    #operator()(irep_idt,const goto_programt&, const namespacet&),
 ///    \ref ai_baset#operator()(const goto_functionst&,const namespacet&)
 ///    and \ref ai_baset#operator()(const abstract_goto_modelt&)
 /// 2. Accessing the results of an analysis, by looking up the history objects
@@ -76,7 +76,7 @@ Author: Daniel Kroening, kroening@kroening.com
 ///    or the domains using
 ///    \ref ai_baset#abstract_state_before(locationt)const
 /// 3. Outputting the results of the analysis; see
-///    \ref ai_baset#output(const namespacet&, const irep_idt&,
+///    \ref ai_baset#output(const namespacet&, irep_idt,
 ///    const goto_programt&, std::ostream&)const et cetera.
 ///
 /// Where possible, uses should be agnostic of the particular configuration of
@@ -99,8 +99,8 @@ Author: Daniel Kroening, kroening@kroening.com
 ///    concurrency_aware_ait does this to compute a fixed point over threads.
 ///
 /// D. For pre-analysis initialization
-///    \ref ait#initialize(const irep_idt&, const goto_programt&),
-///    \ref ait#initialize(const irep_idt&,
+///    \ref ait#initialize(irep_idt, const goto_programt&),
+///    \ref ait#initialize(irep_idt,
 ///    const goto_functionst::goto_functiont&) and
 ///    \ref ait#initialize(const goto_functionst&),
 ///
@@ -141,7 +141,7 @@ class ai_baset
 
   /// Run abstract interpretation on a single function
   void operator()(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     const namespacet &ns)
   {
@@ -178,7 +178,7 @@ class ai_baset
 
   /// Run abstract interpretation on a single function
   void operator()(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_functionst::goto_functiont &goto_function,
     const namespacet &ns)
   {
@@ -279,7 +279,7 @@ class ai_baset
   /// \param out: The ostream to direct output to
   virtual void output(
     const namespacet &ns,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     std::ostream &out) const;
 
@@ -291,7 +291,7 @@ class ai_baset
   /// \return The JSON object
   virtual jsont output_json(
     const namespacet &ns,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program) const;
 
   /// Output the abstract states for a single function as XML
@@ -302,7 +302,7 @@ class ai_baset
   /// \return The XML object
   virtual xmlt output_xml(
     const namespacet &ns,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program) const;
 
   /// Output the abstract states for a whole program
@@ -391,11 +391,11 @@ class ai_baset
   /// Initialize all the abstract states for a single function. Override this to
   /// do custom per-domain initialization.
   virtual void
-  initialize(const irep_idt &function_id, const goto_programt &goto_program);
+  initialize(irep_idt function_id, const goto_programt &goto_program);
 
   /// Initialize all the abstract states for a single function.
   virtual void initialize(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_functionst::goto_functiont &goto_function);
 
   /// Initialize all the abstract states for a whole program. Override this to
@@ -429,7 +429,7 @@ class ai_baset
   /// \return True if we found something new
   virtual bool fixedpoint(
     trace_ptrt starting_trace,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     const goto_functionst &goto_functions,
     const namespacet &ns);
@@ -444,7 +444,7 @@ class ai_baset
   /// or applications of the abstract transformer
   /// \return True if the state was changed
   virtual bool visit(
-    const irep_idt &function_id,
+    irep_idt function_id,
     trace_ptrt p,
     working_sett &working_set,
     const goto_programt &goto_program,
@@ -456,7 +456,7 @@ class ai_baset
   // visit_function_call handles which function(s) to call,
   // while visit_edge_function_call handles a single call
   virtual bool visit_function_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     trace_ptrt p_call,
     working_sett &working_set,
     const goto_programt &goto_program,
@@ -464,7 +464,7 @@ class ai_baset
     const namespacet &ns);
 
   virtual bool visit_end_function(
-    const irep_idt &function_id,
+    irep_idt function_id,
     trace_ptrt p,
     working_sett &working_set,
     const goto_programt &goto_program,
@@ -473,19 +473,19 @@ class ai_baset
 
   // The most basic step, computing one edge / transformer application.
   bool visit_edge(
-    const irep_idt &function_id,
+    irep_idt function_id,
     trace_ptrt p,
-    const irep_idt &to_function_id,
+    irep_idt to_function_id,
     locationt to_l,
     trace_ptrt caller_history,
     const namespacet &ns,
     working_sett &working_set);
 
   virtual bool visit_edge_function_call(
-    const irep_idt &calling_function_id,
+    irep_idt calling_function_id,
     trace_ptrt p_call,
     locationt l_return,
-    const irep_idt &callee_function_id,
+    irep_idt callee_function_id,
     working_sett &working_set,
     const goto_programt &callee,
     const goto_functionst &goto_functions,
@@ -542,10 +542,10 @@ class ai_recursive_interproceduralt : public ai_baset
 protected:
   // Override the function that handles a single function call edge
   bool visit_edge_function_call(
-    const irep_idt &calling_function_id,
+    irep_idt calling_function_id,
     trace_ptrt p_call,
     locationt l_return,
-    const irep_idt &callee_function_id,
+    irep_idt callee_function_id,
     working_sett &working_set,
     const goto_programt &callee,
     const goto_functionst &goto_functions,
@@ -701,7 +701,7 @@ class concurrency_aware_ait:public ait<domainT>
     struct wl_entryt
     {
       wl_entryt(
-        const irep_idt &_function_id,
+        irep_idt _function_id,
         const goto_programt &_goto_program,
         locationt _location)
         : function_id(_function_id),
diff --git a/src/analyses/ai_domain.h b/src/analyses/ai_domain.h
index 85d6dcb1dfb..ab4f9a26f75 100644
--- a/src/analyses/ai_domain.h
+++ b/src/analyses/ai_domain.h
@@ -93,9 +93,9 @@ class ai_domain_baset
   /// The history aware version is used by the abstract interpreter
   /// for backwards compatability it calls the older signature
   virtual void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt to,
     ai_baset &ai,
     const namespacet &ns) = 0;
diff --git a/src/analyses/call_graph.cpp b/src/analyses/call_graph.cpp
index 27c13458271..a6d6e1f719d 100644
--- a/src/analyses/call_graph.cpp
+++ b/src/analyses/call_graph.cpp
@@ -51,7 +51,7 @@ call_grapht::call_grapht(
 
 static void forall_callsites(
   const goto_programt &body,
-  std::function<void(goto_programt::const_targett, const irep_idt &)> call_task)
+  std::function<void(goto_programt::const_targett, irep_idt)> call_task)
 {
   forall_goto_program_instructions(i_it, body)
   {
@@ -74,9 +74,9 @@ static void forall_callsites(
 ///   the calling instruction recorded in `callsites` map.
 call_grapht::call_grapht(
   const goto_functionst &goto_functions,
-  const irep_idt &root,
-  bool collect_callsites):
-  collect_callsites(collect_callsites)
+  irep_idt root,
+  bool collect_callsites)
+  : collect_callsites(collect_callsites)
 {
   std::stack<irep_idt, std::vector<irep_idt>> pending_stack;
   pending_stack.push(root);
@@ -97,13 +97,12 @@ call_grapht::call_grapht(
 
     forall_callsites(
       goto_program,
-      [&](goto_programt::const_targett i_it, const irep_idt &callee)
+      [&](goto_programt::const_targett i_it, irep_idt callee)
       {
         add(function, callee, i_it);
         if(edges.find(callee)==edges.end())
           pending_stack.push(callee);
-      }
-    ); // NOLINT
+      }); // NOLINT
   }
 }
 
@@ -114,31 +113,24 @@ call_grapht::call_grapht(
 ///   the calling instruction recorded in `callsites` map.
 call_grapht::call_grapht(
   const goto_modelt &goto_model,
-  const irep_idt &root,
-  bool collect_callsites):
-  call_grapht(goto_model.goto_functions, root, collect_callsites)
+  irep_idt root,
+  bool collect_callsites)
+  : call_grapht(goto_model.goto_functions, root, collect_callsites)
 {
 }
 
-void call_grapht::add(
-  const irep_idt &function,
-  const goto_programt &body)
+void call_grapht::add(irep_idt function, const goto_programt &body)
 {
   forall_callsites(
     body,
-    [&](goto_programt::const_targett i_it, const irep_idt &callee)
-    {
-      add(function, callee, i_it);
-    }
-  ); // NOLINT
+    [&](goto_programt::const_targett i_it, irep_idt callee)
+    { add(function, callee, i_it); }); // NOLINT
 }
 
 /// Add edge
 /// \param caller: caller function
 /// \param callee: callee function
-void call_grapht::add(
-  const irep_idt &caller,
-  const irep_idt &callee)
+void call_grapht::add(irep_idt caller, irep_idt callee)
 {
   edges.insert({caller, callee});
   nodes.insert(caller);
@@ -150,10 +142,7 @@ void call_grapht::add(
 /// \param callee: callee function
 /// \param callsite: call instruction responsible for this edge. Note this is
 ///   only stored if `collect_callsites` was specified during construction.
-void call_grapht::add(
-  const irep_idt &caller,
-  const irep_idt &callee,
-  locationt callsite)
+void call_grapht::add(irep_idt caller, irep_idt callee, locationt callsite)
 {
   add(caller, callee);
   if(collect_callsites)
@@ -186,7 +175,7 @@ class function_indicest
   {
   }
 
-  node_indext operator[](const irep_idt &function)
+  node_indext operator[](irep_idt function)
   {
     auto findit=function_indices.insert({function, 0});
     if(findit.second)
@@ -297,7 +286,7 @@ void call_grapht::output_xml(std::ostream &out) const
 }
 
 std::optional<std::size_t>
-call_grapht::directed_grapht::get_node_index(const irep_idt &function) const
+call_grapht::directed_grapht::get_node_index(irep_idt function) const
 {
   auto findit=nodes_by_name.find(function);
   if(findit==nodes_by_name.end())
diff --git a/src/analyses/call_graph.h b/src/analyses/call_graph.h
index 630f277f306..2def76b2f3c 100644
--- a/src/analyses/call_graph.h
+++ b/src/analyses/call_graph.h
@@ -52,7 +52,7 @@ class call_grapht
 
   static call_grapht create_from_root_function(
     const goto_modelt &model,
-    const irep_idt &root,
+    irep_idt root,
     bool collect_callsites)
   {
     return call_grapht(model, root, collect_callsites);
@@ -60,7 +60,7 @@ class call_grapht
 
   static call_grapht create_from_root_function(
     const goto_functionst &functions,
-    const irep_idt &root,
+    irep_idt root,
     bool collect_callsites)
   {
     return call_grapht(functions, root, collect_callsites);
@@ -69,13 +69,10 @@ class call_grapht
   // Constructors used to implement the above:
 
 private:
-  call_grapht(
-    const goto_modelt &model,
-    const irep_idt &root,
-    bool collect_callsites);
+  call_grapht(const goto_modelt &model, irep_idt root, bool collect_callsites);
   call_grapht(
     const goto_functionst &functions,
-    const irep_idt &root,
+    irep_idt root,
     bool collect_callsites);
 
 public:
@@ -115,8 +112,8 @@ class call_grapht
   /// Map from call-graph edges to a set of callsites that make the given call.
   callsitest callsites;
 
-  void add(const irep_idt &caller, const irep_idt &callee);
-  void add(const irep_idt &caller, const irep_idt &callee, locationt callsite);
+  void add(irep_idt caller, irep_idt callee);
+  void add(irep_idt caller, irep_idt callee, locationt callsite);
 
   call_grapht get_inverted() const;
 
@@ -147,7 +144,7 @@ class call_grapht
     /// Find the graph node by function name
     /// \param function: function to find
     /// \return none if function is not in this graph, or some index otherwise.
-    std::optional<node_indext> get_node_index(const irep_idt &function) const;
+    std::optional<node_indext> get_node_index(irep_idt function) const;
 
     /// Type of the node name -> node index map.
     typedef std::unordered_map<irep_idt, node_indext> nodes_by_namet;
@@ -163,8 +160,8 @@ class call_grapht
   directed_grapht get_directed_graph() const;
 
 protected:
-  void add(const irep_idt &function,
-           const goto_programt &body);
+  void add(irep_idt function, const goto_programt &body);
+
 private:
   bool collect_callsites;
   std::string format_callsites(const edget &edge) const;
diff --git a/src/analyses/call_graph_helpers.cpp b/src/analyses/call_graph_helpers.cpp
index 0723e3eb181..836b2b33835 100644
--- a/src/analyses/call_graph_helpers.cpp
+++ b/src/analyses/call_graph_helpers.cpp
@@ -17,7 +17,7 @@ Author: Chris Smowton, chris.smowton@diffblue.com
 /// \param forwards: if true, get callees; otherwise get callers.
 static std::set<irep_idt> get_neighbours(
   const call_grapht::directed_grapht &graph,
-  const irep_idt &function,
+  irep_idt function,
   bool forwards)
 {
   std::set<irep_idt> result;
@@ -28,14 +28,14 @@ static std::set<irep_idt> get_neighbours(
   return result;
 }
 
-std::set<irep_idt> get_callees(
-  const call_grapht::directed_grapht &graph, const irep_idt &function)
+std::set<irep_idt>
+get_callees(const call_grapht::directed_grapht &graph, irep_idt function)
 {
   return get_neighbours(graph, function, true);
 }
 
-std::set<irep_idt> get_callers(
-  const call_grapht::directed_grapht &graph, const irep_idt &function)
+std::set<irep_idt>
+get_callers(const call_grapht::directed_grapht &graph, irep_idt function)
 {
   return get_neighbours(graph, function, false);
 }
@@ -48,7 +48,7 @@ std::set<irep_idt> get_callers(
 ///   that can reach the given function.
 static std::set<irep_idt> get_connected_functions(
   const call_grapht::directed_grapht &graph,
-  const irep_idt &function,
+  irep_idt function,
   bool forwards)
 {
   std::vector<call_grapht::directed_grapht::node_indext> connected_nodes =
@@ -60,13 +60,15 @@ static std::set<irep_idt> get_connected_functions(
 }
 
 std::set<irep_idt> get_reachable_functions(
-  const call_grapht::directed_grapht &graph, const irep_idt &function)
+  const call_grapht::directed_grapht &graph,
+  irep_idt function)
 {
   return get_connected_functions(graph, function, true);
 }
 
 std::set<irep_idt> get_reaching_functions(
-  const call_grapht::directed_grapht &graph, const irep_idt &function)
+  const call_grapht::directed_grapht &graph,
+  irep_idt function)
 {
   return get_connected_functions(graph, function, false);
 }
@@ -90,7 +92,7 @@ std::set<irep_idt> get_functions_reachable_within_n_steps(
 
 std::set<irep_idt> get_functions_reachable_within_n_steps(
   const call_grapht::directed_grapht &graph,
-  const irep_idt &start_function,
+  irep_idt start_function,
   std::size_t n)
 {
   std::set<irep_idt> start_functions({start_function});
@@ -99,15 +101,15 @@ std::set<irep_idt> get_functions_reachable_within_n_steps(
 
 void disconnect_unreachable_functions(
   call_grapht::directed_grapht &graph,
-  const irep_idt &function)
+  irep_idt function)
 {
   graph.disconnect_unreachable(*(graph.get_node_index(function)));
 }
 
 std::list<irep_idt> get_shortest_function_path(
   const call_grapht::directed_grapht &graph,
-  const irep_idt &src,
-  const irep_idt &dest)
+  irep_idt src,
+  irep_idt dest)
 {
   std::list<irep_idt> result;
   std::list<std::size_t> path;
diff --git a/src/analyses/call_graph_helpers.h b/src/analyses/call_graph_helpers.h
index 202590e5543..db559a4319e 100644
--- a/src/analyses/call_graph_helpers.h
+++ b/src/analyses/call_graph_helpers.h
@@ -25,29 +25,31 @@ Author: Chris Smowton, chris.smowton@diffblue.com
 /// \param graph: call graph
 /// \param function: function to query
 /// \return set of called functions
-std::set<irep_idt> get_callees(
-  const call_grapht::directed_grapht &graph, const irep_idt &function);
+std::set<irep_idt>
+get_callees(const call_grapht::directed_grapht &graph, irep_idt function);
 
 /// Get functions that call a given function
 /// \param graph: call graph
 /// \param function: function to query
 /// \return set of caller functions
-std::set<irep_idt> get_callers(
-  const call_grapht::directed_grapht &graph, const irep_idt &function);
+std::set<irep_idt>
+get_callers(const call_grapht::directed_grapht &graph, irep_idt function);
 
 /// Get functions reachable from a given function
 /// \param graph: call graph
 /// \param function: function to query
 /// \return set of reachable functions, including `function`
 std::set<irep_idt> get_reachable_functions(
-  const call_grapht::directed_grapht &graph, const irep_idt &function);
+  const call_grapht::directed_grapht &graph,
+  irep_idt function);
 
 /// Get functions that can reach a given function
 /// \param graph: call graph
 /// \param function: function to query
 /// \return set of functions that can reach the target, including `function`
 std::set<irep_idt> get_reaching_functions(
-  const call_grapht::directed_grapht &graph, const irep_idt &function);
+  const call_grapht::directed_grapht &graph,
+  irep_idt function);
 
 /// Get either callers or callees reachable from a given
 /// list of functions within N steps
@@ -70,7 +72,7 @@ std::set<irep_idt> get_functions_reachable_within_n_steps(
 ///   including the start function
 std::set<irep_idt> get_functions_reachable_within_n_steps(
   const call_grapht::directed_grapht &graph,
-  const irep_idt &start_function,
+  irep_idt start_function,
   std::size_t n);
 
 /// Get list of functions on the shortest path between two functions
@@ -80,8 +82,8 @@ std::set<irep_idt> get_functions_reachable_within_n_steps(
 /// \return list of functions on shortest path
 std::list<irep_idt> get_shortest_function_path(
   const call_grapht::directed_grapht &graph,
-  const irep_idt &src,
-  const irep_idt &dest);
+  irep_idt src,
+  irep_idt dest);
 
 /// Disconnects all functions in the call graph that are unreachable from
 /// a given start function.
@@ -92,6 +94,6 @@ std::list<irep_idt> get_shortest_function_path(
 /// \param function: start function
 void disconnect_unreachable_functions(
   call_grapht::directed_grapht &graph,
-  const irep_idt &function);
+  irep_idt function);
 
 #endif
diff --git a/src/analyses/constant_propagator.cpp b/src/analyses/constant_propagator.cpp
index d0fb72f8f0e..2d77023f9df 100644
--- a/src/analyses/constant_propagator.cpp
+++ b/src/analyses/constant_propagator.cpp
@@ -122,9 +122,9 @@ void constant_propagator_domaint::assign_rec(
 }
 
 void constant_propagator_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
@@ -426,7 +426,7 @@ class constant_propagator_can_forward_propagatet : public can_forward_propagatet
   {
   }
 
-  bool is_constant(const irep_idt &id) const
+  bool is_constant(irep_idt id) const
   {
     return replace_const.replaces_symbol(id);
   }
@@ -451,7 +451,7 @@ bool constant_propagator_domaint::valuest::is_constant(
 }
 
 bool constant_propagator_domaint::valuest::is_constant(
-  const irep_idt &id,
+  irep_idt id,
   const namespacet &ns) const
 {
   return constant_propagator_can_forward_propagatet(replace_const, ns)
diff --git a/src/analyses/constant_propagator.h b/src/analyses/constant_propagator.h
index fd249904404..297d1548675 100644
--- a/src/analyses/constant_propagator.h
+++ b/src/analyses/constant_propagator.h
@@ -34,9 +34,9 @@ class constant_propagator_domaint:public ai_domain_baset
 {
 public:
   virtual void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai_base,
     const namespacet &ns) final override;
@@ -120,7 +120,7 @@ class constant_propagator_domaint:public ai_domain_baset
 
     bool is_constant(const exprt &expr, const namespacet &ns) const;
 
-    bool is_constant(const irep_idt &id, const namespacet &ns) const;
+    bool is_constant(irep_idt id, const namespacet &ns) const;
 
     bool is_empty() const
     {
@@ -201,7 +201,7 @@ class constant_propagator_ait:public ait<constant_propagator_domaint>
   }
 
   constant_propagator_ait(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_functionst::goto_functiont &goto_function,
     const namespacet &ns,
     should_track_valuet should_track_value = track_all_values)
diff --git a/src/analyses/custom_bitvector_analysis.cpp b/src/analyses/custom_bitvector_analysis.cpp
index 6e3a56a16e7..a89a7ac6511 100644
--- a/src/analyses/custom_bitvector_analysis.cpp
+++ b/src/analyses/custom_bitvector_analysis.cpp
@@ -22,7 +22,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <iostream>
 
 void custom_bitvector_domaint::set_bit(
-  const irep_idt &identifier,
+  irep_idt identifier,
   unsigned bit_nr,
   modet mode)
 {
@@ -118,7 +118,7 @@ void custom_bitvector_domaint::assign_lhs(
 }
 
 void custom_bitvector_domaint::assign_lhs(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const vectorst &vectors)
 {
   // we erase blank ones to avoid noise
@@ -135,7 +135,7 @@ void custom_bitvector_domaint::assign_lhs(
 }
 
 custom_bitvector_domaint::vectorst
-  custom_bitvector_domaint::get_rhs(const irep_idt &identifier) const
+custom_bitvector_domaint::get_rhs(irep_idt identifier) const
 {
   vectorst vectors;
 
@@ -269,9 +269,9 @@ void custom_bitvector_domaint::assign_struct_rec(
 }
 
 void custom_bitvector_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
diff --git a/src/analyses/custom_bitvector_analysis.h b/src/analyses/custom_bitvector_analysis.h
index 786811365dd..788dc0d8fcd 100644
--- a/src/analyses/custom_bitvector_analysis.h
+++ b/src/analyses/custom_bitvector_analysis.h
@@ -24,9 +24,9 @@ class custom_bitvector_domaint:public ai_domain_baset
 {
 public:
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
@@ -98,9 +98,9 @@ class custom_bitvector_domaint:public ai_domain_baset
     const namespacet &);
 
   void assign_lhs(const exprt &, const vectorst &);
-  void assign_lhs(const irep_idt &, const vectorst &);
+  void assign_lhs(irep_idt, const vectorst &);
   vectorst get_rhs(const exprt &) const;
-  vectorst get_rhs(const irep_idt &) const;
+  vectorst get_rhs(irep_idt) const;
 
   tvt has_values;
 
@@ -117,7 +117,7 @@ class custom_bitvector_domaint:public ai_domain_baset
   enum class modet { SET_MUST, CLEAR_MUST, SET_MAY, CLEAR_MAY };
 
   void set_bit(const exprt &, unsigned bit_nr, modet);
-  void set_bit(const irep_idt &, unsigned bit_nr, modet);
+  void set_bit(irep_idt, unsigned bit_nr, modet);
 
   static inline void set_bit(bit_vectort &dest, unsigned bit_nr)
   {
diff --git a/src/analyses/dependence_graph.cpp b/src/analyses/dependence_graph.cpp
index efb7c6ae8fc..73240ad02f0 100644
--- a/src/analyses/dependence_graph.cpp
+++ b/src/analyses/dependence_graph.cpp
@@ -50,7 +50,7 @@ bool dep_graph_domaint::merge(
 }
 
 void dep_graph_domaint::control_dependencies(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::const_targett from,
   goto_programt::const_targett to,
   dependence_grapht &dep_graph)
@@ -153,7 +153,7 @@ static bool may_be_def_use_pair(
 
 void dep_graph_domaint::data_dependencies(
   goto_programt::const_targett,
-  const irep_idt &function_to,
+  irep_idt function_to,
   goto_programt::const_targett to,
   dependence_grapht &dep_graph,
   const namespacet &ns)
@@ -215,9 +215,9 @@ void dep_graph_domaint::data_dependencies(
 }
 
 void dep_graph_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
diff --git a/src/analyses/dependence_graph.h b/src/analyses/dependence_graph.h
index c053dc2a699..573282efd20 100644
--- a/src/analyses/dependence_graph.h
+++ b/src/analyses/dependence_graph.h
@@ -79,9 +79,9 @@ class dep_graph_domaint:public ai_domain_baset
   bool merge(const dep_graph_domaint &src, trace_ptrt from, trace_ptrt to);
 
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
@@ -200,14 +200,14 @@ class dep_graph_domaint:public ai_domain_baset
     dependence_graph_test_get_data_deps(const dep_graph_domaint &);
 
   void control_dependencies(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::const_targett from,
     goto_programt::const_targett to,
     dependence_grapht &dep_graph);
 
   void data_dependencies(
     goto_programt::const_targett from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     goto_programt::const_targett to,
     dependence_grapht &dep_graph,
     const namespacet &ns);
@@ -243,7 +243,7 @@ class dependence_grapht:
     }
   }
 
-  void initialize(const irep_idt &function, const goto_programt &goto_program)
+  void initialize(irep_idt function, const goto_programt &goto_program)
   {
     ait<dep_graph_domaint>::initialize(function, goto_program);
 
diff --git a/src/analyses/dirty.cpp b/src/analyses/dirty.cpp
index 941d6b79622..a52e36d3c4e 100644
--- a/src/analyses/dirty.cpp
+++ b/src/analyses/dirty.cpp
@@ -110,7 +110,7 @@ void dirtyt::output(std::ostream &out) const
 /// \param id: function id to analyse
 /// \param function: function to analyse
 void incremental_dirtyt::populate_dirty_for_function(
-  const irep_idt &id,
+  irep_idt id,
   const goto_functionst::goto_functiont &function)
 {
   auto insert_result = dirty_processed_functions.insert(id);
diff --git a/src/analyses/dirty.h b/src/analyses/dirty.h
index 0f91890e333..326760041c8 100644
--- a/src/analyses/dirty.h
+++ b/src/analyses/dirty.h
@@ -63,7 +63,7 @@ class dirtyt
 
   void output(std::ostream &out) const;
 
-  bool operator()(const irep_idt &id) const
+  bool operator()(irep_idt id) const
   {
     die_if_uninitialized();
     return dirty.find(id) != dirty.end();
@@ -118,10 +118,10 @@ class incremental_dirtyt
 {
 public:
   void populate_dirty_for_function(
-    const irep_idt &id,
+    irep_idt id,
     const goto_functionst::goto_functiont &function);
 
-  bool operator()(const irep_idt &id) const
+  bool operator()(irep_idt id) const
   {
     return dirty(id);
   }
diff --git a/src/analyses/escape_analysis.cpp b/src/analyses/escape_analysis.cpp
index 5e85c86248c..6f14d813d18 100644
--- a/src/analyses/escape_analysis.cpp
+++ b/src/analyses/escape_analysis.cpp
@@ -165,9 +165,9 @@ void escape_domaint::get_rhs_aliases_address_of(
 }
 
 void escape_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
diff --git a/src/analyses/escape_analysis.h b/src/analyses/escape_analysis.h
index c5cb40ec9f6..a1688a0a59f 100644
--- a/src/analyses/escape_analysis.h
+++ b/src/analyses/escape_analysis.h
@@ -27,9 +27,9 @@ class escape_domaint:public ai_domain_baset
   }
 
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
diff --git a/src/analyses/flow_insensitive_analysis.cpp b/src/analyses/flow_insensitive_analysis.cpp
index 23baf81a93f..98ca065571b 100644
--- a/src/analyses/flow_insensitive_analysis.cpp
+++ b/src/analyses/flow_insensitive_analysis.cpp
@@ -47,8 +47,9 @@ void flow_insensitive_analysis_baset::operator()(
   fixedpoint(goto_functions);
 }
 
-void flow_insensitive_analysis_baset::
-operator()(const irep_idt &function_id, const goto_programt &goto_program)
+void flow_insensitive_analysis_baset::operator()(
+  irep_idt function_id,
+  const goto_programt &goto_program)
 {
   initialize(goto_program);
   goto_functionst goto_functions;
@@ -69,7 +70,7 @@ void flow_insensitive_analysis_baset::output(
 }
 
 void flow_insensitive_analysis_baset::output(
-  const irep_idt &,
+  irep_idt,
   const goto_programt &,
   std::ostream &out)
 {
@@ -94,7 +95,7 @@ flow_insensitive_analysis_baset::get_next(
 }
 
 bool flow_insensitive_analysis_baset::fixedpoint(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   const goto_functionst &goto_functions)
 {
@@ -123,7 +124,7 @@ bool flow_insensitive_analysis_baset::fixedpoint(
 }
 
 bool flow_insensitive_analysis_baset::visit(
-  const irep_idt &function_id,
+  irep_idt function_id,
   locationt l,
   working_sett &working_set,
   const goto_programt &goto_program,
@@ -188,7 +189,7 @@ bool flow_insensitive_analysis_baset::visit(
 }
 
 bool flow_insensitive_analysis_baset::do_function_call(
-  const irep_idt &calling_function,
+  irep_idt calling_function,
   locationt l_call,
   const goto_functionst &goto_functions,
   const goto_functionst::function_mapt::const_iterator f_it,
@@ -271,7 +272,7 @@ bool flow_insensitive_analysis_baset::do_function_call(
 }
 
 bool flow_insensitive_analysis_baset::do_function_call_rec(
-  const irep_idt &calling_function,
+  irep_idt calling_function,
   locationt l_call,
   const exprt &function,
   const exprt::operandst &arguments,
diff --git a/src/analyses/flow_insensitive_analysis.h b/src/analyses/flow_insensitive_analysis.h
index 15689382bd2..def3d84b93d 100644
--- a/src/analyses/flow_insensitive_analysis.h
+++ b/src/analyses/flow_insensitive_analysis.h
@@ -47,9 +47,9 @@ class flow_insensitive_abstract_domain_baset
 
   virtual bool transform(
     const namespacet &ns,
-    const irep_idt &function_from,
+    irep_idt function_from,
     locationt from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     locationt to) = 0;
 
   virtual ~flow_insensitive_abstract_domain_baset()
@@ -129,7 +129,7 @@ class flow_insensitive_analysis_baset
   virtual void update(const goto_functionst &goto_functions);
 
   virtual void
-  operator()(const irep_idt &function_id, const goto_programt &goto_program);
+  operator()(irep_idt function_id, const goto_programt &goto_program);
 
   virtual void operator()(
     const goto_functionst &goto_functions);
@@ -148,7 +148,7 @@ class flow_insensitive_analysis_baset
     std::ostream &out);
 
   virtual void output(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     std::ostream &out);
 
@@ -172,7 +172,7 @@ class flow_insensitive_analysis_baset
 
   // true = found something new
   bool fixedpoint(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     const goto_functionst &goto_functions);
 
@@ -181,7 +181,7 @@ class flow_insensitive_analysis_baset
 
   // true = found something new
   bool visit(
-    const irep_idt &function_id,
+    irep_idt function_id,
     locationt l,
     working_sett &working_set,
     const goto_programt &goto_program,
@@ -203,7 +203,7 @@ class flow_insensitive_analysis_baset
 
   // function calls
   bool do_function_call_rec(
-    const irep_idt &calling_function,
+    irep_idt calling_function,
     locationt l_call,
     const exprt &function,
     const exprt::operandst &arguments,
@@ -211,7 +211,7 @@ class flow_insensitive_analysis_baset
     const goto_functionst &goto_functions);
 
   bool do_function_call(
-    const irep_idt &calling_function,
+    irep_idt calling_function,
     locationt l_call,
     const goto_functionst &goto_functions,
     const goto_functionst::function_mapt::const_iterator f_it,
diff --git a/src/analyses/global_may_alias.cpp b/src/analyses/global_may_alias.cpp
index 812737517ec..97ed37b53f2 100644
--- a/src/analyses/global_may_alias.cpp
+++ b/src/analyses/global_may_alias.cpp
@@ -93,9 +93,9 @@ void global_may_alias_domaint::get_rhs_aliases_address_of(
 }
 
 void global_may_alias_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
diff --git a/src/analyses/global_may_alias.h b/src/analyses/global_may_alias.h
index 91935163ad6..7b948c092c5 100644
--- a/src/analyses/global_may_alias.h
+++ b/src/analyses/global_may_alias.h
@@ -27,9 +27,9 @@ class global_may_alias_domaint:public ai_domain_baset
 
   /// Abstract Interpretation domain transform function.
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
diff --git a/src/analyses/goto_rw.cpp b/src/analyses/goto_rw.cpp
index 312540e22e7..685e0e3e390 100644
--- a/src/analyses/goto_rw.cpp
+++ b/src/analyses/goto_rw.cpp
@@ -519,7 +519,7 @@ void rw_range_sett::get_objects_address_of(const exprt &object)
 
 void rw_range_sett::add(
   get_modet mode,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const range_spect &range_start,
   const range_spect &range_end)
 {
@@ -662,7 +662,7 @@ void rw_range_sett::get_objects_rec(const typet &type)
 }
 
 void rw_range_sett::get_array_objects(
-  const irep_idt &,
+  irep_idt,
   goto_programt::const_targett,
   get_modet mode,
   const exprt &pointer)
@@ -757,7 +757,7 @@ void rw_guarded_range_set_value_sett::get_objects_if(
 
 void rw_guarded_range_set_value_sett::add(
   get_modet mode,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const range_spect &range_start,
   const range_spect &range_end)
 {
@@ -776,7 +776,7 @@ void rw_guarded_range_set_value_sett::add(
 }
 
 static void goto_rw_assign(
-  const irep_idt &function,
+  irep_idt function,
   goto_programt::const_targett target,
   const exprt &lhs,
   const exprt &rhs,
@@ -788,7 +788,7 @@ static void goto_rw_assign(
 }
 
 static void goto_rw_other(
-  const irep_idt &function,
+  irep_idt function,
   goto_programt::const_targett target,
   const codet &code,
   rw_range_sett &rw_set)
@@ -843,7 +843,7 @@ static void goto_rw_other(
 }
 
 static void goto_rw(
-  const irep_idt &function,
+  irep_idt function,
   goto_programt::const_targett target,
   const exprt &lhs,
   const exprt &function_expr,
@@ -865,7 +865,7 @@ static void goto_rw(
 }
 
 void goto_rw(
-  const irep_idt &function,
+  irep_idt function,
   goto_programt::const_targett target,
   rw_range_sett &rw_set)
 {
@@ -933,7 +933,7 @@ void goto_rw(
 }
 
 void goto_rw(
-  const irep_idt &function,
+  irep_idt function,
   const goto_programt &goto_program,
   rw_range_sett &rw_set)
 {
@@ -941,9 +941,10 @@ void goto_rw(
     goto_rw(function, i_it, rw_set);
 }
 
-void goto_rw(const goto_functionst &goto_functions,
-             const irep_idt &function,
-             rw_range_sett &rw_set)
+void goto_rw(
+  const goto_functionst &goto_functions,
+  irep_idt function,
+  rw_range_sett &rw_set)
 {
   goto_functionst::function_mapt::const_iterator f_it=
     goto_functions.function_map.find(function);
diff --git a/src/analyses/goto_rw.h b/src/analyses/goto_rw.h
index 43391173885..c997d6ec0f2 100644
--- a/src/analyses/goto_rw.h
+++ b/src/analyses/goto_rw.h
@@ -27,18 +27,13 @@ class message_handlert;
 class rw_range_sett;
 
 void goto_rw(
-  const irep_idt &function,
+  irep_idt function,
   goto_programt::const_targett target,
   rw_range_sett &rw_set);
 
-void goto_rw(
-  const irep_idt &function,
-  const goto_programt &,
-  rw_range_sett &rw_set);
+void goto_rw(irep_idt function, const goto_programt &, rw_range_sett &rw_set);
 
-void goto_rw(const goto_functionst &,
-             const irep_idt &function,
-             rw_range_sett &rw_set);
+void goto_rw(const goto_functionst &, irep_idt function, rw_range_sett &rw_set);
 
 class range_domain_baset
 {
@@ -234,7 +229,7 @@ class rw_range_sett
   enum class get_modet { LHS_W, READ };
 
   virtual void get_objects_rec(
-    const irep_idt &,
+    irep_idt,
     goto_programt::const_targett,
     get_modet mode,
     const exprt &expr)
@@ -242,16 +237,14 @@ class rw_range_sett
     get_objects_rec(mode, expr);
   }
 
-  virtual void get_objects_rec(
-    const irep_idt &,
-    goto_programt::const_targett,
-    const typet &type)
+  virtual void
+  get_objects_rec(irep_idt, goto_programt::const_targett, const typet &type)
   {
     get_objects_rec(type);
   }
 
   virtual void get_array_objects(
-    const irep_idt &,
+    irep_idt,
     goto_programt::const_targett,
     get_modet,
     const exprt &);
@@ -348,7 +341,7 @@ class rw_range_sett
 
   virtual void add(
     get_modet mode,
-    const irep_idt &identifier,
+    irep_idt identifier,
     const range_spect &range_start,
     const range_spect &range_end);
 };
@@ -375,7 +368,7 @@ class rw_range_set_value_sett:public rw_range_sett
   }
 
   void get_objects_rec(
-    const irep_idt &_function,
+    irep_idt _function,
     goto_programt::const_targett _target,
     get_modet mode,
     const exprt &expr) override
@@ -387,7 +380,7 @@ class rw_range_set_value_sett:public rw_range_sett
   }
 
   void get_objects_rec(
-    const irep_idt &_function,
+    irep_idt _function,
     goto_programt::const_targett _target,
     const typet &type) override
   {
@@ -398,7 +391,7 @@ class rw_range_set_value_sett:public rw_range_sett
   }
 
   void get_array_objects(
-    const irep_idt &_function,
+    irep_idt _function,
     goto_programt::const_targett _target,
     get_modet mode,
     const exprt &pointer) override
@@ -478,7 +471,7 @@ class rw_guarded_range_set_value_sett:public rw_range_set_value_sett
   }
 
   void get_objects_rec(
-    const irep_idt &_function,
+    irep_idt _function,
     goto_programt::const_targett _target,
     get_modet mode,
     const exprt &expr) override
@@ -489,7 +482,7 @@ class rw_guarded_range_set_value_sett:public rw_range_set_value_sett
   }
 
   void get_objects_rec(
-    const irep_idt &function,
+    irep_idt function,
     goto_programt::const_targett target,
     const typet &type) override
   {
@@ -510,7 +503,7 @@ class rw_guarded_range_set_value_sett:public rw_range_set_value_sett
 
   void add(
     get_modet mode,
-    const irep_idt &identifier,
+    irep_idt identifier,
     const range_spect &range_start,
     const range_spect &range_end) override;
 };
diff --git a/src/analyses/interval_domain.cpp b/src/analyses/interval_domain.cpp
index dcc22a1ac34..18f82dfc5a6 100644
--- a/src/analyses/interval_domain.cpp
+++ b/src/analyses/interval_domain.cpp
@@ -57,9 +57,9 @@ void interval_domaint::output(
 }
 
 void interval_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
diff --git a/src/analyses/interval_domain.h b/src/analyses/interval_domain.h
index 31638097c4a..08530f2f7f7 100644
--- a/src/analyses/interval_domain.h
+++ b/src/analyses/interval_domain.h
@@ -32,9 +32,9 @@ class interval_domaint:public ai_domain_baset
   }
 
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
diff --git a/src/analyses/invariant_propagation.cpp b/src/analyses/invariant_propagation.cpp
index a8fb79e2a77..3ad7d1754df 100644
--- a/src/analyses/invariant_propagation.cpp
+++ b/src/analyses/invariant_propagation.cpp
@@ -241,7 +241,7 @@ bool invariant_propagationt::check_type(const typet &type) const
 }
 
 void invariant_propagationt::initialize(
-  const irep_idt &function,
+  irep_idt function,
   const goto_programt &goto_program)
 {
   baset::initialize(function, goto_program);
diff --git a/src/analyses/invariant_propagation.h b/src/analyses/invariant_propagation.h
index 09bf46207f4..7dbc1eea65d 100644
--- a/src/analyses/invariant_propagation.h
+++ b/src/analyses/invariant_propagation.h
@@ -29,8 +29,8 @@ class invariant_propagationt:public
     return (*this)[l].invariant_set;
   }
 
-  void initialize(const irep_idt &function, const goto_programt &goto_program)
-    override;
+  void
+  initialize(irep_idt function, const goto_programt &goto_program) override;
 
   void make_all_true();
   void make_all_false();
diff --git a/src/analyses/invariant_set_domain.cpp b/src/analyses/invariant_set_domain.cpp
index cdcb145d02a..241d0ee515a 100644
--- a/src/analyses/invariant_set_domain.cpp
+++ b/src/analyses/invariant_set_domain.cpp
@@ -15,9 +15,9 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <util/simplify_expr.h>
 
 void invariant_set_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
diff --git a/src/analyses/invariant_set_domain.h b/src/analyses/invariant_set_domain.h
index cc6f8c0aa0e..1a984d87580 100644
--- a/src/analyses/invariant_set_domain.h
+++ b/src/analyses/invariant_set_domain.h
@@ -54,9 +54,9 @@ class invariant_set_domaint:public ai_domain_baset
   }
 
   virtual void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
diff --git a/src/analyses/is_threaded.cpp b/src/analyses/is_threaded.cpp
index 631f4d19c03..b39e0d0b14f 100644
--- a/src/analyses/is_threaded.cpp
+++ b/src/analyses/is_threaded.cpp
@@ -44,9 +44,9 @@ class is_threaded_domaint:public ai_domain_baset
   }
 
   void transform(
-    const irep_idt &,
+    irep_idt,
     trace_ptrt trace_from,
-    const irep_idt &,
+    irep_idt,
     trace_ptrt,
     ai_baset &,
     const namespacet &) override
diff --git a/src/analyses/local_bitvector_analysis.cpp b/src/analyses/local_bitvector_analysis.cpp
index 20907f36f5f..2c60f758b66 100644
--- a/src/analyses/local_bitvector_analysis.cpp
+++ b/src/analyses/local_bitvector_analysis.cpp
@@ -52,7 +52,7 @@ bool local_bitvector_analysist::merge(points_tot &a, points_tot &b)
 }
 
 /// \return return 'true' iff we track the object with given identifier
-bool local_bitvector_analysist::is_tracked(const irep_idt &identifier)
+bool local_bitvector_analysist::is_tracked(irep_idt identifier)
 {
   localst::locals_sett::const_iterator it = locals.locals.find(identifier);
   return it != locals.locals.end() && ns.lookup(*it).type.id() == ID_pointer &&
diff --git a/src/analyses/local_bitvector_analysis.h b/src/analyses/local_bitvector_analysis.h
index 429a1d2ad24..1e172b3b069 100644
--- a/src/analyses/local_bitvector_analysis.h
+++ b/src/analyses/local_bitvector_analysis.h
@@ -201,7 +201,7 @@ class local_bitvector_analysist
     const exprt &rhs,
     points_tot &loc_info_src);
 
-  bool is_tracked(const irep_idt &identifier);
+  bool is_tracked(irep_idt identifier);
 };
 
 inline std::ostream &operator<<(
diff --git a/src/analyses/local_may_alias.h b/src/analyses/local_may_alias.h
index febc741dbae..b28222e47ba 100644
--- a/src/analyses/local_may_alias.h
+++ b/src/analyses/local_may_alias.h
@@ -109,7 +109,7 @@ class local_may_alias_factoryt
     }
   }
 
-  local_may_aliast &operator()(const irep_idt &fkt)
+  local_may_aliast &operator()(irep_idt fkt)
   {
     PRECONDITION(goto_functions!=nullptr);
     fkt_mapt::iterator f_it=fkt_map.find(fkt);
diff --git a/src/analyses/locals.h b/src/analyses/locals.h
index 5b275223597..b98d4b3079a 100644
--- a/src/analyses/locals.h
+++ b/src/analyses/locals.h
@@ -34,7 +34,7 @@ class localst
   // Returns true for all procedure-local variables,
   // not including those with static storage duration,
   // but including the function parameters.
-  bool is_local(const irep_idt &identifier) const
+  bool is_local(irep_idt identifier) const
   {
     return locals.find(identifier) != locals.end();
   }
diff --git a/src/analyses/reaching_definitions.cpp b/src/analyses/reaching_definitions.cpp
index c5d4adeb209..0285246e266 100644
--- a/src/analyses/reaching_definitions.cpp
+++ b/src/analyses/reaching_definitions.cpp
@@ -70,7 +70,7 @@ reaching_definitions_analysist::~reaching_definitions_analysist()=default;
 ///
 /// This function is only used to fill in the cache `export_cache` for the
 /// `output` method.
-void rd_range_domaint::populate_cache(const irep_idt &identifier) const
+void rd_range_domaint::populate_cache(irep_idt identifier) const
 {
   PRECONDITION(bv_container);
 
@@ -91,9 +91,9 @@ void rd_range_domaint::populate_cache(const irep_idt &identifier) const
 }
 
 void rd_range_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
@@ -177,9 +177,9 @@ void rd_range_domaint::transform_start_thread(
 
 void rd_range_domaint::transform_function_call(
   const namespacet &ns,
-  const irep_idt &function_from,
+  irep_idt function_from,
   locationt from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   reaching_definitions_analysist &rd)
 {
   // only if there is an actual call, i.e., we have a body
@@ -242,9 +242,9 @@ void rd_range_domaint::transform_function_call(
 
 void rd_range_domaint::transform_end_function(
   const namespacet &ns,
-  const irep_idt &function_from,
+  irep_idt function_from,
   locationt from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   locationt to,
   reaching_definitions_analysist &rd)
 {
@@ -305,7 +305,7 @@ void rd_range_domaint::transform_end_function(
 void rd_range_domaint::transform_assign(
   const namespacet &ns,
   locationt from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   locationt to,
   reaching_definitions_analysist &rd)
 {
@@ -341,7 +341,7 @@ void rd_range_domaint::transform_assign(
 }
 
 void rd_range_domaint::kill(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const range_spect &range_start,
   const range_spect &range_end)
 {
@@ -440,9 +440,7 @@ void rd_range_domaint::kill(
   }
 }
 
-void rd_range_domaint::kill_inf(
-  const irep_idt &,
-  const range_spect &range_start)
+void rd_range_domaint::kill_inf(irep_idt, const range_spect &range_start)
 {
   PRECONDITION(range_start >= range_spect{0});
 
@@ -480,7 +478,7 @@ void rd_range_domaint::kill_inf(
 /// by `range_start` and `range_end`.
 bool rd_range_domaint::gen(
   locationt from,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const range_spect &range_start,
   const range_spect &range_end)
 {
@@ -718,8 +716,8 @@ bool rd_range_domaint::merge_shared(
   return changed;
 }
 
-const rd_range_domaint::ranges_at_loct &rd_range_domaint::get(
-  const irep_idt &identifier) const
+const rd_range_domaint::ranges_at_loct &
+rd_range_domaint::get(irep_idt identifier) const
 {
   populate_cache(identifier);
 
diff --git a/src/analyses/reaching_definitions.h b/src/analyses/reaching_definitions.h
index faa8c46224a..e16b0a4b8cb 100644
--- a/src/analyses/reaching_definitions.h
+++ b/src/analyses/reaching_definitions.h
@@ -96,7 +96,7 @@ struct reaching_definitiont
   range_spect bit_end;
 
   reaching_definitiont(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const ai_domain_baset::locationt &definition_at,
     const range_spect &bit_begin,
     const range_spect &bit_end)
@@ -182,9 +182,9 @@ class rd_range_domaint:public ai_domain_baset
   /// \param ai: A reference to 'reaching_definitions_analysist' instance.
   /// \param ns: Just passed to callees.
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
@@ -252,8 +252,8 @@ class rd_range_domaint:public ai_domain_baset
   typedef std::map<locationt, rangest, goto_programt::target_less_than>
     ranges_at_loct;
 
-  const ranges_at_loct &get(const irep_idt &identifier) const;
-  void clear_cache(const irep_idt &identifier) const
+  const ranges_at_loct &get(irep_idt identifier) const;
+  void clear_cache(irep_idt identifier) const
   {
     export_cache[identifier].clear();
   }
@@ -296,7 +296,7 @@ class rd_range_domaint:public ai_domain_baset
   /// moved to the `output` method or removed entirely.
   mutable export_cachet export_cache;
 
-  void populate_cache(const irep_idt &identifier) const;
+  void populate_cache(irep_idt identifier) const;
 
   void transform_dead(
     const namespacet &ns,
@@ -306,34 +306,32 @@ class rd_range_domaint:public ai_domain_baset
     reaching_definitions_analysist &rd);
   void transform_function_call(
     const namespacet &ns,
-    const irep_idt &function_from,
+    irep_idt function_from,
     locationt from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     reaching_definitions_analysist &rd);
   void transform_end_function(
     const namespacet &ns,
-    const irep_idt &function_from,
+    irep_idt function_from,
     locationt from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     locationt to,
     reaching_definitions_analysist &rd);
   void transform_assign(
     const namespacet &ns,
     locationt from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     locationt to,
     reaching_definitions_analysist &rd);
 
   void kill(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const range_spect &range_start,
     const range_spect &range_end);
-  void kill_inf(
-    const irep_idt &identifier,
-    const range_spect &range_start);
+  void kill_inf(irep_idt identifier, const range_spect &range_start);
   bool gen(
     locationt from,
-    const irep_idt &identifier,
+    irep_idt identifier,
     const range_spect &range_start,
     const range_spect &range_end);
 
diff --git a/src/analyses/uncaught_exceptions_analysis.cpp b/src/analyses/uncaught_exceptions_analysis.cpp
index aa6b3c0e6e4..8764f2d620f 100644
--- a/src/analyses/uncaught_exceptions_analysis.cpp
+++ b/src/analyses/uncaught_exceptions_analysis.cpp
@@ -39,8 +39,7 @@ exprt uncaught_exceptions_domaint::get_exception_symbol(const exprt &expr)
 }
 
 /// The join operator for the uncaught exceptions domain
-void uncaught_exceptions_domaint::join(
-  const irep_idt &element)
+void uncaught_exceptions_domaint::join(irep_idt element)
 {
   thrown.insert(element);
 }
diff --git a/src/analyses/uncaught_exceptions_analysis.h b/src/analyses/uncaught_exceptions_analysis.h
index 617371efdbc..17102769d91 100644
--- a/src/analyses/uncaught_exceptions_analysis.h
+++ b/src/analyses/uncaught_exceptions_analysis.h
@@ -32,7 +32,7 @@ class uncaught_exceptions_domaint
                  uncaught_exceptions_analysist &,
                  const namespacet &);
 
-  void join(const irep_idt &);
+  void join(irep_idt);
   void join(const std::set<irep_idt> &);
   void join(const std::vector<irep_idt> &);
 
diff --git a/src/analyses/uninitialized_domain.cpp b/src/analyses/uninitialized_domain.cpp
index fef7b2a8708..e8c19260fd7 100644
--- a/src/analyses/uninitialized_domain.cpp
+++ b/src/analyses/uninitialized_domain.cpp
@@ -18,9 +18,9 @@ Date: January 2010
 #include <list>
 
 void uninitialized_domaint::transform(
-  const irep_idt &,
+  irep_idt,
   trace_ptrt trace_from,
-  const irep_idt &,
+  irep_idt,
   trace_ptrt,
   ai_baset &,
   const namespacet &ns)
diff --git a/src/analyses/uninitialized_domain.h b/src/analyses/uninitialized_domain.h
index 89789dc4c09..61f448e6b4a 100644
--- a/src/analyses/uninitialized_domain.h
+++ b/src/analyses/uninitialized_domain.h
@@ -30,9 +30,9 @@ class uninitialized_domaint:public ai_domain_baset
   uninitializedt uninitialized;
 
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) final override;
diff --git a/src/analyses/variable-sensitivity/abstract_environment.cpp b/src/analyses/variable-sensitivity/abstract_environment.cpp
index c5fa3a3f6fd..f20ad83e1a2 100644
--- a/src/analyses/variable-sensitivity/abstract_environment.cpp
+++ b/src/analyses/variable-sensitivity/abstract_environment.cpp
@@ -86,7 +86,7 @@ static bool is_access_expr(const exprt &expr)
          expr.id() == ID_dereference;
 }
 
-static bool is_object_creation(const irep_idt &id)
+static bool is_object_creation(irep_idt id)
 {
   return id == ID_array || id == ID_struct || id == ID_constant ||
          id == ID_address_of;
diff --git a/src/analyses/variable-sensitivity/constant_pointer_abstract_object.cpp b/src/analyses/variable-sensitivity/constant_pointer_abstract_object.cpp
index 76fb1a6d7b7..224eec403c1 100644
--- a/src/analyses/variable-sensitivity/constant_pointer_abstract_object.cpp
+++ b/src/analyses/variable-sensitivity/constant_pointer_abstract_object.cpp
@@ -321,7 +321,7 @@ static exprt to_bool_expr(bool v)
 }
 
 exprt struct_member_ptr_comparison_expr(
-  irep_idt const &id,
+  irep_idt id,
   exprt const &lhs,
   exprt const &rhs)
 {
@@ -336,7 +336,7 @@ exprt struct_member_ptr_comparison_expr(
 }
 
 exprt symbol_ptr_comparison_expr(
-  irep_idt const &id,
+  irep_idt id,
   exprt const &lhs,
   exprt const &rhs)
 {
diff --git a/src/analyses/variable-sensitivity/interval_abstract_value.cpp b/src/analyses/variable-sensitivity/interval_abstract_value.cpp
index f939bbfea3e..8efd3bb35a6 100644
--- a/src/analyses/variable-sensitivity/interval_abstract_value.cpp
+++ b/src/analyses/variable-sensitivity/interval_abstract_value.cpp
@@ -172,7 +172,7 @@ static inline constant_interval_exprt make_interval_expr(const exprt &expr)
   }
 }
 
-static inline irep_idt invert_relation(const irep_idt &relation)
+static inline irep_idt invert_relation(irep_idt relation)
 {
   PRECONDITION(
     relation == ID_le || relation == ID_lt || relation == ID_ge ||
diff --git a/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.cpp b/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.cpp
index 86b588e4c28..1807093c3ed 100644
--- a/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.cpp
+++ b/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.cpp
@@ -23,10 +23,10 @@ Date: August 2020
 #include <analyses/variable-sensitivity/variable_sensitivity_domain.h>
 
 bool ai_three_way_merget::visit_edge_function_call(
-  const irep_idt &calling_function_id,
+  irep_idt calling_function_id,
   trace_ptrt p_call,
   locationt l_return,
-  const irep_idt &callee_function_id,
+  irep_idt callee_function_id,
   working_sett &working_set,
   const goto_programt &callee,
   const goto_functionst &goto_functions,
diff --git a/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.h b/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.h
index e60d94f73b5..d3349543d6e 100644
--- a/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.h
+++ b/src/analyses/variable-sensitivity/three_way_merge_abstract_interpreter.h
@@ -45,10 +45,10 @@ class ai_three_way_merget : public ai_recursive_interproceduralt
   // Much of this is the same as ai_recursive_interproceduralt's handling but
   // on function return the three-way merge is used.
   bool visit_edge_function_call(
-    const irep_idt &calling_function_id,
+    irep_idt calling_function_id,
     trace_ptrt p_call,
     locationt l_return,
-    const irep_idt &callee_function_id,
+    irep_idt callee_function_id,
     working_sett &working_set,
     const goto_programt &callee,
     const goto_functionst &goto_functions,
diff --git a/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.cpp b/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.cpp
index 80afe243632..73e136d5cea 100644
--- a/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.cpp
+++ b/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.cpp
@@ -66,9 +66,9 @@ void variable_sensitivity_dependence_domaint::eval_data_deps(
  * \param ns: the namespace
  */
 void variable_sensitivity_dependence_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
@@ -202,9 +202,9 @@ void variable_sensitivity_dependence_domaint::data_dependencies(
 }
 
 void variable_sensitivity_dependence_domaint::control_dependencies(
-  const irep_idt &from_function,
+  irep_idt from_function,
   goto_programt::const_targett from,
-  const irep_idt &to_function,
+  irep_idt to_function,
   goto_programt::const_targett to,
   variable_sensitivity_dependence_grapht &dep_graph)
 {
diff --git a/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.h b/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.h
index c3a8cad69f3..1edb551a853 100644
--- a/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.h
+++ b/src/analyses/variable-sensitivity/variable_sensitivity_dependence_graph.h
@@ -85,9 +85,9 @@ class variable_sensitivity_dependence_domaint
   }
 
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) override;
@@ -193,9 +193,9 @@ class variable_sensitivity_dependence_domaint
     const;
 
   void control_dependencies(
-    const irep_idt &from_function,
+    irep_idt from_function,
     goto_programt::const_targett from,
-    const irep_idt &to_function,
+    irep_idt to_function,
     goto_programt::const_targett to,
     variable_sensitivity_dependence_grapht &dep_graph);
 
@@ -247,8 +247,7 @@ class variable_sensitivity_dependence_grapht : public ai_three_way_merget,
     const vsd_configt &_configuration,
     message_handlert &message_handler);
 
-  void
-  initialize(const irep_idt &function_id, const goto_programt &goto_program)
+  void initialize(irep_idt function_id, const goto_programt &goto_program)
   {
     ai_recursive_interproceduralt::initialize(function_id, goto_program);
   }
diff --git a/src/analyses/variable-sensitivity/variable_sensitivity_domain.cpp b/src/analyses/variable-sensitivity/variable_sensitivity_domain.cpp
index 10efb04e147..0010b26dd62 100644
--- a/src/analyses/variable-sensitivity/variable_sensitivity_domain.cpp
+++ b/src/analyses/variable-sensitivity/variable_sensitivity_domain.cpp
@@ -22,9 +22,9 @@ Date: April 2016
 #endif
 
 void variable_sensitivity_domaint::transform(
-  const irep_idt &function_from,
+  irep_idt function_from,
   trace_ptrt trace_from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt trace_to,
   ai_baset &ai,
   const namespacet &ns)
@@ -401,7 +401,7 @@ void variable_sensitivity_domaint::transform_function_call(
 }
 
 bool variable_sensitivity_domaint::ignore_function_call_transform(
-  const irep_idt &function_id) const
+  irep_idt function_id) const
 {
   static const std::set<irep_idt> ignored_internal_function = {
     CPROVER_PREFIX "set_must",
@@ -437,7 +437,7 @@ void variable_sensitivity_domaint::merge_three_way_function_return(
     modified_symbol_names.begin(),
     modified_symbol_names.end(),
     std::back_inserter(modified_symbols),
-    [&ns](const irep_idt &id) { return ns.lookup(id).symbol_expr(); });
+    [&ns](irep_idt id) { return ns.lookup(id).symbol_expr(); });
 
   for(const auto &symbol : modified_symbols)
   {
diff --git a/src/analyses/variable-sensitivity/variable_sensitivity_domain.h b/src/analyses/variable-sensitivity/variable_sensitivity_domain.h
index 707de155078..6a181e40bfb 100644
--- a/src/analyses/variable-sensitivity/variable_sensitivity_domain.h
+++ b/src/analyses/variable-sensitivity/variable_sensitivity_domain.h
@@ -132,9 +132,9 @@ class variable_sensitivity_domaint : public ai_domain_baset
   /// \param ai: the abstract interpreter
   /// \param ns: the namespace
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt trace_from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt trace_to,
     ai_baset &ai,
     const namespacet &ns) override;
@@ -238,7 +238,7 @@ class variable_sensitivity_domaint : public ai_domain_baset
   /// \param function_id: the name of the function being called
   ///
   /// \return Returns true if the function should be ignored
-  bool ignore_function_call_transform(const irep_idt &function_id) const;
+  bool ignore_function_call_transform(irep_idt function_id) const;
 
   void assume(exprt expr, namespacet ns);
 
diff --git a/src/ansi-c/allocate_objects.cpp b/src/ansi-c/allocate_objects.cpp
index b691e06e0a9..ec9724c7c2a 100644
--- a/src/ansi-c/allocate_objects.cpp
+++ b/src/ansi-c/allocate_objects.cpp
@@ -36,7 +36,7 @@ exprt allocate_objectst::allocate_object(
   const exprt &target_expr,
   const typet &allocate_type,
   const lifetimet lifetime,
-  const irep_idt &basename_prefix)
+  irep_idt basename_prefix)
 {
   switch(lifetime)
   {
@@ -73,7 +73,7 @@ exprt allocate_objectst::allocate_automatic_local_object(
   code_blockt &assignments,
   const exprt &target_expr,
   const typet &allocate_type,
-  const irep_idt &basename_prefix)
+  irep_idt basename_prefix)
 {
   return allocate_non_dynamic_object(
     assignments, target_expr, allocate_type, false, basename_prefix);
@@ -94,7 +94,7 @@ exprt allocate_objectst::allocate_static_global_object(
   code_blockt &assignments,
   const exprt &target_expr,
   const typet &allocate_type,
-  const irep_idt &basename_prefix)
+  irep_idt basename_prefix)
 {
   return allocate_non_dynamic_object(
     assignments, target_expr, allocate_type, true, basename_prefix);
@@ -108,7 +108,7 @@ exprt allocate_objectst::allocate_static_global_object(
 /// \return A symbol expression denoting the variable
 symbol_exprt allocate_objectst::allocate_automatic_local_object(
   const typet &allocate_type,
-  const irep_idt &basename_prefix)
+  irep_idt basename_prefix)
 {
   symbolt &aux_symbol = get_fresh_aux_symbol(
     allocate_type,
@@ -185,7 +185,7 @@ exprt allocate_objectst::allocate_non_dynamic_object(
   const exprt &target_expr,
   const typet &allocate_type,
   const bool static_lifetime,
-  const irep_idt &basename_prefix)
+  irep_idt basename_prefix)
 {
   symbolt &aux_symbol = get_fresh_aux_symbol(
     allocate_type,
diff --git a/src/ansi-c/allocate_objects.h b/src/ansi-c/allocate_objects.h
index bdef7c5edf8..3b175fec292 100644
--- a/src/ansi-c/allocate_objects.h
+++ b/src/ansi-c/allocate_objects.h
@@ -27,9 +27,9 @@ class allocate_objectst
 {
 public:
   allocate_objectst(
-    const irep_idt &symbol_mode,
+    irep_idt symbol_mode,
     const source_locationt &source_location,
-    const irep_idt &name_prefix,
+    irep_idt name_prefix,
     symbol_table_baset &symbol_table)
     : symbol_mode(symbol_mode),
       source_location(source_location),
@@ -44,19 +44,19 @@ class allocate_objectst
     const exprt &target_expr,
     const typet &allocate_type,
     const lifetimet lifetime,
-    const irep_idt &basename_prefix = "tmp");
+    irep_idt basename_prefix = "tmp");
 
   exprt allocate_automatic_local_object(
     code_blockt &assignments,
     const exprt &target_expr,
     const typet &allocate_type,
-    const irep_idt &basename_prefix = "tmp");
+    irep_idt basename_prefix = "tmp");
 
   exprt allocate_static_global_object(
     code_blockt &assignments,
     const exprt &target_expr,
     const typet &allocate_type,
-    const irep_idt &basename_prefix = "tmp");
+    irep_idt basename_prefix = "tmp");
 
   /// Generates code for allocating a dynamic object. A new variable with
   /// basename prefix `alloc_site` is introduced to which the allocated memory
@@ -88,7 +88,7 @@ class allocate_objectst
 
   symbol_exprt allocate_automatic_local_object(
     const typet &allocate_type,
-    const irep_idt &basename_prefix = "tmp");
+    irep_idt basename_prefix = "tmp");
 
   void add_created_symbol(const symbolt &symbol);
 
@@ -111,7 +111,7 @@ class allocate_objectst
     const exprt &target_expr,
     const typet &allocate_type,
     const bool static_lifetime,
-    const irep_idt &basename_prefix);
+    irep_idt basename_prefix);
 };
 
 /// Create code allocating an object of size `size` and assigning it to `lhs`
diff --git a/src/ansi-c/anonymous_member.cpp b/src/ansi-c/anonymous_member.cpp
index e2ed779df93..6ee7e68c0cb 100644
--- a/src/ansi-c/anonymous_member.cpp
+++ b/src/ansi-c/anonymous_member.cpp
@@ -39,7 +39,7 @@ static member_exprt make_member_expr(
 
 exprt get_component_rec(
   const exprt &struct_union,
-  const irep_idt &component_name,
+  irep_idt component_name,
   const namespacet &ns)
 {
   const auto &tag_type = to_struct_or_union_tag_type(struct_union.type());
@@ -68,7 +68,7 @@ exprt get_component_rec(
 
 bool has_component_rec(
   const typet &type,
-  const irep_idt &component_name,
+  irep_idt component_name,
   const namespacet &ns)
 {
   const auto &tag_type = to_struct_or_union_tag_type(type);
diff --git a/src/ansi-c/anonymous_member.h b/src/ansi-c/anonymous_member.h
index ee490ddc4ab..085cb6cbd68 100644
--- a/src/ansi-c/anonymous_member.h
+++ b/src/ansi-c/anonymous_member.h
@@ -18,12 +18,12 @@ class namespacet;
 
 exprt get_component_rec(
   const exprt &struct_union,
-  const irep_idt &component_name,
+  irep_idt component_name,
   const namespacet &ns);
 
 bool has_component_rec(
   const typet &struct_union_type,
-  const irep_idt &component_name,
+  irep_idt component_name,
   const namespacet &ns);
 
 #endif // CPROVER_ANSI_C_ANONYMOUS_MEMBER_H
diff --git a/src/ansi-c/ansi_c_declaration.h b/src/ansi-c/ansi_c_declaration.h
index 7088c93f884..7e91de67e90 100644
--- a/src/ansi-c/ansi_c_declaration.h
+++ b/src/ansi-c/ansi_c_declaration.h
@@ -33,7 +33,7 @@ class ansi_c_declaratort : public nullary_exprt
     return static_cast<const exprt &>(find(ID_value));
   }
 
-  void set_name(const irep_idt &name)
+  void set_name(irep_idt name)
   {
     return set(ID_name, name);
   }
@@ -48,7 +48,7 @@ class ansi_c_declaratort : public nullary_exprt
     return get(ID_base_name);
   }
 
-  void set_base_name(const irep_idt &base_name)
+  void set_base_name(irep_idt base_name)
   {
     return set(ID_base_name, base_name);
   }
diff --git a/src/ansi-c/ansi_c_parser.cpp b/src/ansi-c/ansi_c_parser.cpp
index 749d9f92fa5..dc178e6dc7e 100644
--- a/src/ansi-c/ansi_c_parser.cpp
+++ b/src/ansi-c/ansi_c_parser.cpp
@@ -11,7 +11,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "c_storage_spec.h"
 
 ansi_c_id_classt ansi_c_parsert::lookup(
-  const irep_idt &base_name,
+  irep_idt base_name,
   irep_idt &identifier, // output
   bool tag,
   bool label)
@@ -181,9 +181,7 @@ void ansi_c_parsert::pragma_cprover_pop()
   pragma_cprover_stack.pop_back();
 }
 
-void ansi_c_parsert::pragma_cprover_add_check(
-  const irep_idt &name,
-  bool enabled)
+void ansi_c_parsert::pragma_cprover_add_check(irep_idt name, bool enabled)
 {
   if(pragma_cprover_stack.empty())
     pragma_cprover_push();
@@ -191,7 +189,7 @@ void ansi_c_parsert::pragma_cprover_add_check(
   pragma_cprover_stack.back()[name] = enabled;
 }
 
-bool ansi_c_parsert::pragma_cprover_clash(const irep_idt &name, bool enabled)
+bool ansi_c_parsert::pragma_cprover_clash(irep_idt name, bool enabled)
 {
   auto top = pragma_cprover_stack.back();
   auto found = top.find(name);
diff --git a/src/ansi-c/ansi_c_parser.h b/src/ansi-c/ansi_c_parser.h
index 169a74dc4cf..7354729fd1a 100644
--- a/src/ansi-c/ansi_c_parser.h
+++ b/src/ansi-c/ansi_c_parser.h
@@ -123,7 +123,7 @@ class ansi_c_parsert:public parsert
   }
 
   ansi_c_id_classt lookup(
-    const irep_idt &base_name, // in
+    irep_idt base_name,   // in
     irep_idt &identifier, // out
     bool tag,
     bool label);
@@ -147,11 +147,11 @@ class ansi_c_parsert:public parsert
   void pragma_cprover_pop();
 
   /// \brief Adds a check to the CPROVER pragma stack
-  void pragma_cprover_add_check(const irep_idt &name, bool enabled);
+  void pragma_cprover_add_check(irep_idt name, bool enabled);
 
   /// Returns true iff the same check with  polarity
   /// is already present at top of the stack
-  bool pragma_cprover_clash(const irep_idt &name, bool enabled);
+  bool pragma_cprover_clash(irep_idt name, bool enabled);
 
   /// \brief Tags \ref source_location with
   /// the current CPROVER pragma stack
diff --git a/src/ansi-c/builtin_factory.cpp b/src/ansi-c/builtin_factory.cpp
index 172cb96b05a..b4f15dcb468 100644
--- a/src/ansi-c/builtin_factory.cpp
+++ b/src/ansi-c/builtin_factory.cpp
@@ -40,7 +40,7 @@ static bool find_pattern(
 }
 
 static bool convert(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const std::ostringstream &s,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
@@ -102,7 +102,7 @@ static bool convert(
 //! If so, add declaration to symbol table.
 //! \return 'true' on error
 bool builtin_factory(
-  const irep_idt &identifier,
+  irep_idt identifier,
   bool support_float16_type,
   symbol_table_baset &symbol_table,
   message_handlert &mh)
diff --git a/src/ansi-c/builtin_factory.h b/src/ansi-c/builtin_factory.h
index 6a74b3c6759..520b12c05f4 100644
--- a/src/ansi-c/builtin_factory.h
+++ b/src/ansi-c/builtin_factory.h
@@ -16,7 +16,7 @@ class symbol_table_baset;
 
 //! \return 'true' in case of error
 bool builtin_factory(
-  const irep_idt &identifier,
+  irep_idt identifier,
   bool support_float16_type,
   symbol_table_baset &,
   message_handlert &);
diff --git a/src/ansi-c/c_expr.h b/src/ansi-c/c_expr.h
index d0bac3fc77b..7fe73259f9f 100644
--- a/src/ansi-c/c_expr.h
+++ b/src/ansi-c/c_expr.h
@@ -118,7 +118,7 @@ class side_effect_expr_overflowt : public side_effect_exprt
 {
 public:
   side_effect_expr_overflowt(
-    const irep_idt &kind,
+    irep_idt kind,
     exprt _lhs,
     exprt _rhs,
     exprt _result,
@@ -205,7 +205,7 @@ inline side_effect_expr_overflowt &to_side_effect_expr_overflow(exprt &expr)
 class history_exprt : public unary_exprt
 {
 public:
-  explicit history_exprt(exprt variable, const irep_idt &id)
+  explicit history_exprt(exprt variable, irep_idt id)
     : unary_exprt(id, std::move(variable))
   {
   }
@@ -216,8 +216,7 @@ class history_exprt : public unary_exprt
   }
 };
 
-inline const history_exprt &
-to_history_expr(const exprt &expr, const irep_idt &id)
+inline const history_exprt &to_history_expr(const exprt &expr, irep_idt id)
 {
   PRECONDITION(id == ID_old || id == ID_loop_entry);
   PRECONDITION(expr.id() == id);
diff --git a/src/ansi-c/c_nondet_symbol_factory.h b/src/ansi-c/c_nondet_symbol_factory.h
index 2d7d768233c..b57f0bb090c 100644
--- a/src/ansi-c/c_nondet_symbol_factory.h
+++ b/src/ansi-c/c_nondet_symbol_factory.h
@@ -35,7 +35,7 @@ class symbol_factoryt
   symbol_factoryt(
     symbol_table_baset &_symbol_table,
     const source_locationt &loc,
-    const irep_idt &name_prefix,
+    irep_idt name_prefix,
     const c_object_factory_parameterst &object_factory_params,
     const lifetimet lifetime)
     : symbol_table(_symbol_table),
diff --git a/src/ansi-c/c_typecheck_base.cpp b/src/ansi-c/c_typecheck_base.cpp
index 41c7d532690..4135685314e 100644
--- a/src/ansi-c/c_typecheck_base.cpp
+++ b/src/ansi-c/c_typecheck_base.cpp
@@ -654,9 +654,7 @@ void c_typecheck_baset::typecheck_function_body(symbolt &symbol)
   }
 }
 
-void c_typecheck_baset::apply_asm_label(
-  const irep_idt &asm_label,
-  symbolt &symbol)
+void c_typecheck_baset::apply_asm_label(irep_idt asm_label, symbolt &symbol)
 {
   const irep_idt orig_name=symbol.name;
 
diff --git a/src/ansi-c/c_typecheck_base.h b/src/ansi-c/c_typecheck_base.h
index 11f106995e5..7a8225315d3 100644
--- a/src/ansi-c/c_typecheck_base.h
+++ b/src/ansi-c/c_typecheck_base.h
@@ -227,24 +227,22 @@ class c_typecheck_baset:
   virtual exprt do_special_functions(side_effect_expr_function_callt &expr);
   exprt typecheck_builtin_overflow(
     side_effect_expr_function_callt &expr,
-    const irep_idt &arith_op);
+    irep_idt arith_op);
   exprt
   typecheck_saturating_arithmetic(const side_effect_expr_function_callt &expr);
   virtual std::optional<symbol_exprt> typecheck_gcc_polymorphic_builtin(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const exprt::operandst &arguments,
     const source_locationt &source_location);
   virtual code_blockt instantiate_gcc_polymorphic_builtin(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const symbol_exprt &function_symbol);
   virtual std::optional<symbol_exprt>
   typecheck_shadow_memory_builtin(const side_effect_expr_function_callt &expr);
   virtual exprt
   typecheck_shuffle_vector(const side_effect_expr_function_callt &expr);
-  void disallow_subexpr_by_id(
-    const exprt &,
-    const irep_idt &,
-    const std::string &) const;
+  void
+  disallow_subexpr_by_id(const exprt &, irep_idt, const std::string &) const;
 
   virtual void make_index_type(exprt &expr);
   virtual void make_constant(exprt &expr);
@@ -252,7 +250,7 @@ class c_typecheck_baset:
 
   virtual bool gcc_types_compatible_p(const typet &, const typet &);
 
-  virtual bool builtin_factory(const irep_idt &);
+  virtual bool builtin_factory(irep_idt);
 
   // types
   virtual void typecheck_type(typet &type);
@@ -319,7 +317,7 @@ class c_typecheck_baset:
   typedef std::unordered_map<irep_idt, irep_idt> asm_label_mapt;
   asm_label_mapt asm_label_map;
 
-  void apply_asm_label(const irep_idt &asm_label, symbolt &symbol);
+  void apply_asm_label(irep_idt asm_label, symbolt &symbol);
 };
 
 class already_typechecked_exprt : public expr_protectedt
diff --git a/src/ansi-c/c_typecheck_expr.cpp b/src/ansi-c/c_typecheck_expr.cpp
index afc0f3ca884..093059d5f71 100644
--- a/src/ansi-c/c_typecheck_expr.cpp
+++ b/src/ansi-c/c_typecheck_expr.cpp
@@ -2122,7 +2122,7 @@ void c_typecheck_baset::typecheck_obeys_contract_call(
   expr.type() = bool_typet();
 }
 
-bool c_typecheck_baset::builtin_factory(const irep_idt &identifier)
+bool c_typecheck_baset::builtin_factory(irep_idt identifier)
 {
   return ::builtin_factory(
     identifier,
@@ -3888,7 +3888,7 @@ exprt c_typecheck_baset::do_special_functions(
 
 exprt c_typecheck_baset::typecheck_builtin_overflow(
   side_effect_expr_function_callt &expr,
-  const irep_idt &arith_op)
+  irep_idt arith_op)
 {
   const irep_idt &identifier = to_symbol_expr(expr.function()).identifier();
 
@@ -4843,7 +4843,7 @@ void c_typecheck_baset::make_constant_index(exprt &expr)
 
 void c_typecheck_baset::disallow_subexpr_by_id(
   const exprt &expr,
-  const irep_idt &id,
+  irep_idt id,
   const std::string &message) const
 {
   if(!has_subexpr(expr, id))
diff --git a/src/ansi-c/c_typecheck_gcc_polymorphic_builtins.cpp b/src/ansi-c/c_typecheck_gcc_polymorphic_builtins.cpp
index dd56ef7b239..54a715c4f88 100644
--- a/src/ansi-c/c_typecheck_gcc_polymorphic_builtins.cpp
+++ b/src/ansi-c/c_typecheck_gcc_polymorphic_builtins.cpp
@@ -25,7 +25,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include <atomic>
 
 static symbol_exprt typecheck_sync_with_pointer_parameter(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -64,7 +64,7 @@ static symbol_exprt typecheck_sync_with_pointer_parameter(
 }
 
 static symbol_exprt typecheck_sync_compare_swap(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -107,7 +107,7 @@ static symbol_exprt typecheck_sync_compare_swap(
 }
 
 static symbol_exprt typecheck_sync_lock_release(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -142,7 +142,7 @@ static symbol_exprt typecheck_sync_lock_release(
 }
 
 static symbol_exprt typecheck_atomic_load_n(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -177,7 +177,7 @@ static symbol_exprt typecheck_atomic_load_n(
 }
 
 static symbol_exprt typecheck_atomic_store_n(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -215,7 +215,7 @@ static symbol_exprt typecheck_atomic_store_n(
 }
 
 static symbol_exprt typecheck_atomic_exchange_n(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -253,7 +253,7 @@ static symbol_exprt typecheck_atomic_exchange_n(
 }
 
 static symbol_exprt typecheck_atomic_load_store(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -298,7 +298,7 @@ static symbol_exprt typecheck_atomic_load_store(
 }
 
 static symbol_exprt typecheck_atomic_exchange(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -351,7 +351,7 @@ static symbol_exprt typecheck_atomic_exchange(
 }
 
 static symbol_exprt typecheck_atomic_compare_exchange(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -417,7 +417,7 @@ static symbol_exprt typecheck_atomic_compare_exchange(
 }
 
 static symbol_exprt typecheck_atomic_op_fetch(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -454,7 +454,7 @@ static symbol_exprt typecheck_atomic_op_fetch(
 }
 
 static symbol_exprt typecheck_atomic_fetch_op(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location,
   message_handlert &message_handler)
@@ -492,7 +492,7 @@ static symbol_exprt typecheck_atomic_fetch_op(
 
 std::optional<symbol_exprt>
 c_typecheck_baset::typecheck_gcc_polymorphic_builtin(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const exprt::operandst &arguments,
   const source_locationt &source_location)
 {
@@ -608,7 +608,7 @@ c_typecheck_baset::typecheck_gcc_polymorphic_builtin(
 }
 
 static symbolt result_symbol(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const typet &type,
   const source_locationt &source_location,
   symbol_table_baset &symbol_table)
@@ -626,8 +626,8 @@ static symbolt result_symbol(
 }
 
 static void instantiate_atomic_fetch_op(
-  const irep_idt &identifier,
-  const irep_idt &identifier_with_type,
+  irep_idt identifier,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -689,8 +689,8 @@ static void instantiate_atomic_fetch_op(
 }
 
 static void instantiate_atomic_op_fetch(
-  const irep_idt &identifier,
-  const irep_idt &identifier_with_type,
+  irep_idt identifier,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -753,8 +753,8 @@ static void instantiate_atomic_op_fetch(
 }
 
 static void instantiate_sync_fetch(
-  const irep_idt &identifier,
-  const irep_idt &identifier_with_type,
+  irep_idt identifier,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -777,7 +777,7 @@ static void instantiate_sync_fetch(
 }
 
 static void instantiate_sync_bool_compare_and_swap(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -805,7 +805,7 @@ static void instantiate_sync_bool_compare_and_swap(
 }
 
 static void instantiate_sync_val_compare_and_swap(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -855,7 +855,7 @@ static void instantiate_sync_val_compare_and_swap(
 }
 
 static void instantiate_sync_lock_test_and_set(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -911,7 +911,7 @@ static void instantiate_sync_lock_test_and_set(
 }
 
 static void instantiate_sync_lock_release(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -951,7 +951,7 @@ static void instantiate_sync_lock_release(
 }
 
 static void instantiate_atomic_load(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -985,7 +985,7 @@ static void instantiate_atomic_load(
 }
 
 static void instantiate_atomic_load_n(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1013,7 +1013,7 @@ static void instantiate_atomic_load_n(
 }
 
 static void instantiate_atomic_store(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1047,7 +1047,7 @@ static void instantiate_atomic_store(
 }
 
 static void instantiate_atomic_store_n(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1068,7 +1068,7 @@ static void instantiate_atomic_store_n(
 }
 
 static void instantiate_atomic_exchange(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1104,7 +1104,7 @@ static void instantiate_atomic_exchange(
 }
 
 static void instantiate_atomic_exchange_n(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1135,7 +1135,7 @@ static void instantiate_atomic_exchange_n(
 }
 
 static void instantiate_atomic_compare_exchange(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1213,7 +1213,7 @@ static void instantiate_atomic_compare_exchange(
 }
 
 static void instantiate_atomic_compare_exchange_n(
-  const irep_idt &identifier_with_type,
+  irep_idt identifier_with_type,
   const code_typet &code_type,
   const source_locationt &source_location,
   const std::vector<symbol_exprt> &parameter_exprs,
@@ -1236,7 +1236,7 @@ static void instantiate_atomic_compare_exchange_n(
 }
 
 code_blockt c_typecheck_baset::instantiate_gcc_polymorphic_builtin(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const symbol_exprt &function_symbol)
 {
   const irep_idt &identifier_with_type = function_symbol.identifier();
diff --git a/src/ansi-c/c_typecheck_shadow_memory_builtin.cpp b/src/ansi-c/c_typecheck_shadow_memory_builtin.cpp
index 7c6ee139a76..2decd9b4e4d 100644
--- a/src/ansi-c/c_typecheck_shadow_memory_builtin.cpp
+++ b/src/ansi-c/c_typecheck_shadow_memory_builtin.cpp
@@ -16,7 +16,7 @@
 /// \throws invalid_source_file_exceptiont if the typecheck fails.
 static symbol_exprt typecheck_field_decl(
   const side_effect_expr_function_callt &expr,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const namespacet &ns)
 {
   // Check correct number of arguments
@@ -81,7 +81,7 @@ static symbol_exprt typecheck_field_decl(
 /// \throws invalid_source_file_exceptiont if the typecheck fails.
 static symbol_exprt typecheck_get_field(
   const side_effect_expr_function_callt &expr,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const namespacet &ns)
 {
   // Check correct number of arguments
@@ -146,7 +146,7 @@ static symbol_exprt typecheck_get_field(
 /// \throws invalid_source_file_exceptiont if the typecheck fails.
 static symbol_exprt typecheck_set_field(
   const side_effect_expr_function_callt &expr,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const namespacet &ns)
 {
   // Check correct number of arguments
diff --git a/src/ansi-c/expr2c.cpp b/src/ansi-c/expr2c.cpp
index 19416c4ac96..6f79df68467 100644
--- a/src/ansi-c/expr2c.cpp
+++ b/src/ansi-c/expr2c.cpp
@@ -72,7 +72,7 @@ Precedences are as follows. Higher values mean higher precedence.
 
 */
 
-irep_idt expr2ct::id_shorthand(const irep_idt &identifier) const
+irep_idt expr2ct::id_shorthand(irep_idt identifier) const
 {
   const symbolt *symbol;
 
@@ -90,7 +90,7 @@ irep_idt expr2ct::id_shorthand(const irep_idt &identifier) const
   return sh;
 }
 
-static std::string clean_identifier(const irep_idt &id)
+static std::string clean_identifier(irep_idt id)
 {
   std::string dest=id2string(id);
 
diff --git a/src/ansi-c/expr2c_class.h b/src/ansi-c/expr2c_class.h
index e60af80fa33..25508b806c2 100644
--- a/src/ansi-c/expr2c_class.h
+++ b/src/ansi-c/expr2c_class.h
@@ -90,7 +90,7 @@ class expr2ct
 
   unsigned sizeof_nesting;
 
-  irep_idt id_shorthand(const irep_idt &identifier) const;
+  irep_idt id_shorthand(irep_idt identifier) const;
 
   std::string convert_typecast(
     const typecast_exprt &src, unsigned &precedence);
diff --git a/src/ansi-c/goto-conversion/builtin_functions.cpp b/src/ansi-c/goto-conversion/builtin_functions.cpp
index 3a825087932..db3d0ce6b21 100644
--- a/src/ansi-c/goto-conversion/builtin_functions.cpp
+++ b/src/ansi-c/goto-conversion/builtin_functions.cpp
@@ -568,7 +568,7 @@ exprt goto_convertt::get_array_argument(const exprt &src)
 }
 
 void goto_convertt::do_array_op(
-  const irep_idt &id,
+  irep_idt id,
   const exprt &lhs,
   const symbol_exprt &function,
   const exprt::operandst &arguments,
@@ -631,7 +631,7 @@ void goto_convertt::do_havoc_slice(
   const symbol_exprt &function,
   const exprt::operandst &arguments,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   irep_idt identifier = CPROVER_PREFIX "havoc_slice";
 
@@ -714,7 +714,7 @@ void goto_convertt::do_alloca(
   const symbol_exprt &function,
   const exprt::operandst &arguments,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const source_locationt &source_location = function.source_location();
   const auto alloca_type = to_code_type(function.type());
@@ -823,7 +823,7 @@ void goto_convertt::do_function_call_symbol(
   const symbol_exprt &function,
   const exprt::operandst &arguments,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   if(function.get_bool(ID_C_invalid_object))
     return; // ignore
diff --git a/src/ansi-c/goto-conversion/goto_check_c.cpp b/src/ansi-c/goto-conversion/goto_check_c.cpp
index ad0419853a9..f6822a03347 100644
--- a/src/ansi-c/goto-conversion/goto_check_c.cpp
+++ b/src/ansi-c/goto-conversion/goto_check_c.cpp
@@ -82,9 +82,7 @@ class goto_check_ct
 
   typedef goto_functionst::goto_functiont goto_functiont;
 
-  void goto_check(
-    const irep_idt &function_identifier,
-    goto_functiont &goto_function);
+  void goto_check(irep_idt function_identifier, goto_functiont &goto_function);
 
   /// Fill the list of allocations \ref allocationst with <address, size> for
   ///   every allocation instruction. Also check that each allocation is
@@ -189,7 +187,7 @@ class goto_check_ct
   void undefined_shift_check(const shift_exprt &, const guardt &);
   void pointer_rel_check(const binary_exprt &, const guardt &);
   void pointer_overflow_check(const exprt &, const guardt &);
-  void memory_leak_check(const irep_idt &function_id);
+  void memory_leak_check(irep_idt function_id);
 
   /// Generates VCCs for the validity of the given dereferencing operation.
   /// \param expr the expression to be checked
@@ -339,7 +337,7 @@ class goto_check_ct
   ///
   /// \returns a pair (name, status) if the match succeeds
   /// and the name is known, nothing otherwise.
-  named_check_statust match_named_check(const irep_idt &named_check) const;
+  named_check_statust match_named_check(irep_idt named_check) const;
 };
 
 /// Allows to:
@@ -362,7 +360,7 @@ class flag_overridet
   ///
   /// - calling `set_flag` after `disable_flag` is a no-op
   /// - calling `set_flag` twice triggers an INVARIANT
-  void set_flag(bool &flag, bool new_value, const irep_idt &flag_name)
+  void set_flag(bool &flag, bool new_value, irep_idt flag_name)
   {
     // make this a no-op if the flag is disabled
     if(disabled_flags.find(&flag) != disabled_flags.end())
@@ -384,7 +382,7 @@ class flag_overridet
   ///
   /// - calling `disable_flag` after `set_flag` overrides the set value
   /// - calling `disable_flag` twice triggers an INVARIANT
-  void disable_flag(bool &flag, const irep_idt &flag_name)
+  void disable_flag(bool &flag, irep_idt flag_name)
   {
     INVARIANT(
       disabled_flags.find(&flag) == disabled_flags.end(),
@@ -2076,7 +2074,7 @@ void goto_check_ct::check(const exprt &expr, bool is_assigned)
   check_rec(expr, identity, is_assigned);
 }
 
-void goto_check_ct::memory_leak_check(const irep_idt &function_id)
+void goto_check_ct::memory_leak_check(irep_idt function_id)
 {
   const symbolt &leak = ns.lookup(CPROVER_PREFIX "memory_leak");
   const symbol_exprt leak_expr = leak.symbol_expr();
@@ -2100,7 +2098,7 @@ void goto_check_ct::memory_leak_check(const irep_idt &function_id)
 }
 
 void goto_check_ct::goto_check(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functiont &goto_function)
 {
   const auto &function_symbol = ns.lookup(function_identifier);
@@ -2468,7 +2466,7 @@ exprt goto_check_ct::is_in_bounds_of_some_explicit_allocation(
 }
 
 void goto_check_c(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functionst::goto_functiont &goto_function,
   const namespacet &ns,
   const optionst &options,
@@ -2519,7 +2517,7 @@ void goto_check_ct::add_all_checked_named_check_pragmas(
 }
 
 goto_check_ct::named_check_statust
-goto_check_ct::match_named_check(const irep_idt &named_check) const
+goto_check_ct::match_named_check(irep_idt named_check) const
 {
   auto s = id2string(named_check);
   auto col = s.find(":");
diff --git a/src/ansi-c/goto-conversion/goto_check_c.h b/src/ansi-c/goto-conversion/goto_check_c.h
index e560634cf16..1487c42b8a7 100644
--- a/src/ansi-c/goto-conversion/goto_check_c.h
+++ b/src/ansi-c/goto-conversion/goto_check_c.h
@@ -26,7 +26,7 @@ void goto_check_c(
   message_handlert &message_handler);
 
 void goto_check_c(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_functionst::goto_functiont &goto_function,
   const namespacet &ns,
   const optionst &options,
diff --git a/src/ansi-c/goto-conversion/goto_clean_expr.cpp b/src/ansi-c/goto-conversion/goto_clean_expr.cpp
index 72217bac88a..6cf086755c7 100644
--- a/src/ansi-c/goto-conversion/goto_clean_expr.cpp
+++ b/src/ansi-c/goto-conversion/goto_clean_expr.cpp
@@ -60,7 +60,7 @@ static symbol_exprt find_base_symbol(const exprt &expr)
 static exprt convert_statement_expression(
   const quantifier_exprt &qex,
   const code_expressiont &code,
-  const irep_idt &mode,
+  irep_idt mode,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
@@ -278,7 +278,7 @@ static exprt convert_statement_expression(
 symbol_exprt goto_convertt::make_compound_literal(
   const exprt &expr,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const source_locationt source_location = expr.find_source_location();
 
@@ -437,10 +437,8 @@ void goto_convertt::rewrite_boolean(exprt &expr)
   expr.swap(tmp);
 }
 
-goto_convertt::clean_expr_resultt goto_convertt::clean_expr(
-  exprt &expr,
-  const irep_idt &mode,
-  bool result_is_used)
+goto_convertt::clean_expr_resultt
+goto_convertt::clean_expr(exprt &expr, irep_idt mode, bool result_is_used)
 {
   // this cleans:
   //   && || ==> ?: comma (control-dependency)
@@ -754,7 +752,7 @@ goto_convertt::clean_expr_resultt goto_convertt::clean_expr(
 }
 
 goto_convertt::clean_expr_resultt
-goto_convertt::clean_expr_address_of(exprt &expr, const irep_idt &mode)
+goto_convertt::clean_expr_address_of(exprt &expr, irep_idt mode)
 {
   clean_expr_resultt side_effects;
 
@@ -827,9 +825,7 @@ goto_convertt::clean_expr_address_of(exprt &expr, const irep_idt &mode)
 }
 
 goto_convertt::clean_expr_resultt
-goto_convertt::remove_gcc_conditional_expression(
-  exprt &expr,
-  const irep_idt &mode)
+goto_convertt::remove_gcc_conditional_expression(exprt &expr, irep_idt mode)
 {
   clean_expr_resultt side_effects;
 
diff --git a/src/ansi-c/goto-conversion/goto_convert.cpp b/src/ansi-c/goto-conversion/goto_convert.cpp
index 4ef706f24dd..c3ee39a9c79 100644
--- a/src/ansi-c/goto-conversion/goto_convert.cpp
+++ b/src/ansi-c/goto-conversion/goto_convert.cpp
@@ -249,7 +249,7 @@ Function: goto_convertt::finish_gotos
 
 \*******************************************************************/
 
-void goto_convertt::finish_gotos(goto_programt &dest, const irep_idt &mode)
+void goto_convertt::finish_gotos(goto_programt &dest, irep_idt mode)
 {
   std::unordered_map<irep_idt, symbolt, irep_id_hash> label_flags;
   declaration_hop_instrumentationt instructions_to_insert;
@@ -459,7 +459,7 @@ void goto_convertt::optimize_guarded_gotos(goto_programt &dest)
 void goto_convertt::goto_convert(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   goto_convert_rec(code, dest, mode);
 }
@@ -467,7 +467,7 @@ void goto_convertt::goto_convert(
 void goto_convertt::goto_convert_rec(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   convert(code, dest, mode);
 
@@ -489,7 +489,7 @@ void goto_convertt::copy(
 void goto_convertt::convert_label(
   const code_labelt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   // grab the label
   const irep_idt &label = code.get_label();
@@ -535,7 +535,7 @@ void goto_convertt::convert_gcc_local_label(const codet &, goto_programt &)
 void goto_convertt::convert_switch_case(
   const code_switch_caset &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   goto_programt tmp;
   convert(code.code(), tmp, mode);
@@ -575,7 +575,7 @@ void goto_convertt::convert_switch_case(
 void goto_convertt::convert_gcc_switch_case_range(
   const code_gcc_switch_case_ranget &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const auto lb = numeric_cast<mp_integer>(code.lower());
   const auto ub = numeric_cast<mp_integer>(code.upper());
@@ -616,7 +616,7 @@ void goto_convertt::convert_gcc_switch_case_range(
 void goto_convertt::convert(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const irep_idt &statement = code.get_statement();
 
@@ -730,7 +730,7 @@ void goto_convertt::convert(
 void goto_convertt::convert_block(
   const code_blockt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const source_locationt &end_location = code.end_location();
 
@@ -759,7 +759,7 @@ void goto_convertt::convert_block(
 void goto_convertt::convert_expression(
   const code_expressiont &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   exprt expr = code.expression();
 
@@ -800,7 +800,7 @@ void goto_convertt::convert_expression(
 void goto_convertt::convert_frontend_decl(
   const code_frontend_declt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const irep_idt &identifier = code.get_identifier();
 
@@ -877,7 +877,7 @@ void goto_convertt::convert_decl_type(const codet &, goto_programt &)
 void goto_convertt::convert_assign(
   const code_assignt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   exprt lhs = code.lhs(), rhs = code.rhs();
 
@@ -1035,7 +1035,7 @@ void goto_convertt::convert_cpp_delete(const codet &code, goto_programt &dest)
 void goto_convertt::convert_assert(
   const code_assertt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   exprt cond = code.assertion();
 
@@ -1058,7 +1058,7 @@ void goto_convertt::convert_skip(const codet &code, goto_programt &dest)
 void goto_convertt::convert_assume(
   const code_assumet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   exprt op = code.assumption();
 
@@ -1101,7 +1101,7 @@ void goto_convertt::convert_loop_contracts(
 void goto_convertt::convert_for(
   const code_fort &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   // turn for(A; c; B) { P } into
   //  A; while(c) { P; B; }
@@ -1199,7 +1199,7 @@ void goto_convertt::convert_for(
 void goto_convertt::convert_while(
   const code_whilet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const exprt &cond = code.cond();
   const source_locationt &source_location = code.source_location();
@@ -1255,7 +1255,7 @@ void goto_convertt::convert_while(
 void goto_convertt::convert_dowhile(
   const code_dowhilet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     code.operands().size() == 2,
@@ -1363,7 +1363,7 @@ exprt goto_convertt::case_guard(
 void goto_convertt::convert_switch(
   const code_switcht &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   // switch(v) {
   //   case x: Px;
@@ -1503,7 +1503,7 @@ void goto_convertt::convert_switch(
 void goto_convertt::convert_break(
   const code_breakt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     targets.break_set, "break without target", code.find_source_location());
@@ -1520,7 +1520,7 @@ void goto_convertt::convert_break(
 void goto_convertt::convert_return(
   const code_frontend_returnt &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   if(!targets.return_set)
   {
@@ -1580,7 +1580,7 @@ void goto_convertt::convert_return(
 void goto_convertt::convert_continue(
   const code_continuet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     targets.continue_set,
@@ -1664,7 +1664,7 @@ void goto_convertt::convert_atomic_end(const codet &code, goto_programt &dest)
 void goto_convertt::convert_ifthenelse(
   const code_ifthenelset &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   DATA_INVARIANT(code.then_case().is_not_nil(), "cannot accept an empty body");
 
@@ -1728,7 +1728,7 @@ void goto_convertt::convert_ifthenelse(
 
 void goto_convertt::collect_operands(
   const exprt &expr,
-  const irep_idt &id,
+  irep_idt id,
   std::list<exprt> &dest)
 {
   if(expr.id() != id)
@@ -1761,7 +1761,7 @@ void goto_convertt::generate_ifthenelse(
   goto_programt &false_case,
   const source_locationt &else_end_location,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   if(is_empty(true_case) && is_empty(false_case))
   {
@@ -1938,7 +1938,7 @@ void goto_convertt::generate_conditional_branch(
   goto_programt::targett target_true,
   const source_locationt &source_location,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   if(has_and_or(guard) && needs_cleaning(guard))
   {
@@ -1978,7 +1978,7 @@ void goto_convertt::generate_conditional_branch(
   goto_programt::targett target_false,
   const source_locationt &source_location,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   if(guard.id() == ID_not)
   {
@@ -2143,7 +2143,7 @@ symbolt &goto_convertt::new_tmp_symbol(
   const std::string &suffix,
   goto_programt &dest,
   const source_locationt &source_location,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   PRECONDITION(!mode.empty());
   symbolt &new_symbol = get_fresh_aux_symbol(
@@ -2167,7 +2167,7 @@ irep_idt goto_convertt::make_temp_symbol(
   exprt &expr,
   const std::string &suffix,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const source_locationt source_location = expr.find_source_location();
 
@@ -2191,7 +2191,7 @@ void goto_convert(
   symbol_table_baset &symbol_table,
   goto_programt &dest,
   message_handlert &message_handler,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   symbol_table_buildert symbol_table_builder =
     symbol_table_buildert::wrap(symbol_table);
@@ -2234,7 +2234,7 @@ void goto_convert(
 void goto_convertt::generate_thread_block(
   const code_blockt &thread_body,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   goto_programt preamble, body, postamble;
 
diff --git a/src/ansi-c/goto-conversion/goto_convert.h b/src/ansi-c/goto-conversion/goto_convert.h
index 5be10aa9634..d7adfb7cff4 100644
--- a/src/ansi-c/goto-conversion/goto_convert.h
+++ b/src/ansi-c/goto-conversion/goto_convert.h
@@ -25,7 +25,7 @@ void goto_convert(
   symbol_table_baset &symbol_table,
   goto_programt &dest,
   message_handlert &message_handler,
-  const irep_idt &mode);
+  irep_idt mode);
 
 // start from "main"
 void goto_convert(
diff --git a/src/ansi-c/goto-conversion/goto_convert_class.h b/src/ansi-c/goto-conversion/goto_convert_class.h
index 6ea485eeb59..9aeb403efde 100644
--- a/src/ansi-c/goto-conversion/goto_convert_class.h
+++ b/src/ansi-c/goto-conversion/goto_convert_class.h
@@ -33,8 +33,7 @@ struct build_declaration_hops_inputst;
 class goto_convertt : public messaget
 {
 public:
-  void
-  goto_convert(const codet &code, goto_programt &dest, const irep_idt &mode);
+  void goto_convert(const codet &code, goto_programt &dest, irep_idt mode);
 
   goto_convertt(
     symbol_table_baset &_symbol_table,
@@ -81,16 +80,13 @@ class goto_convertt : public messaget
       side_effects.destructive_append(other.side_effects);
     }
 
-    void add_temporary(const irep_idt &id)
+    void add_temporary(irep_idt id)
     {
       temporaries.push_front(id);
     }
   };
 
-  void goto_convert_rec(
-    const codet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+  void goto_convert_rec(const codet &code, goto_programt &dest, irep_idt mode);
 
   //
   // tools for symbols
@@ -100,12 +96,10 @@ class goto_convertt : public messaget
     const std::string &suffix,
     goto_programt &dest,
     const source_locationt &,
-    const irep_idt &mode);
+    irep_idt mode);
 
-  symbol_exprt make_compound_literal(
-    const exprt &expr,
-    goto_programt &dest,
-    const irep_idt &mode);
+  symbol_exprt
+  make_compound_literal(const exprt &expr, goto_programt &dest, irep_idt mode);
 
   //
   // translation of C expressions (with side effects)
@@ -113,10 +107,10 @@ class goto_convertt : public messaget
   //
 
   [[nodiscard]] clean_expr_resultt
-  clean_expr(exprt &expr, const irep_idt &mode, bool result_is_used = true);
+  clean_expr(exprt &expr, irep_idt mode, bool result_is_used = true);
 
   [[nodiscard]] clean_expr_resultt
-  clean_expr_address_of(exprt &expr, const irep_idt &mode);
+  clean_expr_address_of(exprt &expr, irep_idt mode);
 
   static bool needs_cleaning(const exprt &expr);
 
@@ -133,52 +127,48 @@ class goto_convertt : public messaget
     exprt &expr,
     const std::string &suffix,
     goto_programt &,
-    const irep_idt &mode);
+    irep_idt mode);
 
   void rewrite_boolean(exprt &dest);
 
   [[nodiscard]] clean_expr_resultt remove_side_effect(
     side_effect_exprt &expr,
-    const irep_idt &mode,
+    irep_idt mode,
     bool result_is_used,
     bool address_taken);
   [[nodiscard]] clean_expr_resultt remove_assignment(
     side_effect_exprt &expr,
     bool result_is_used,
     bool address_taken,
-    const irep_idt &mode);
+    irep_idt mode);
   [[nodiscard]] clean_expr_resultt remove_pre(
     side_effect_exprt &expr,
     bool result_is_used,
     bool address_taken,
-    const irep_idt &mode);
-  [[nodiscard]] clean_expr_resultt remove_post(
-    side_effect_exprt &expr,
-    const irep_idt &mode,
-    bool result_is_used);
+    irep_idt mode);
+  [[nodiscard]] clean_expr_resultt
+  remove_post(side_effect_exprt &expr, irep_idt mode, bool result_is_used);
   [[nodiscard]] clean_expr_resultt remove_function_call(
     side_effect_expr_function_callt &expr,
-    const irep_idt &mode,
+    irep_idt mode,
     bool result_is_used);
   [[nodiscard]] clean_expr_resultt
   remove_cpp_new(side_effect_exprt &expr, bool result_is_used);
   [[nodiscard]] clean_expr_resultt remove_cpp_delete(side_effect_exprt &expr);
-  [[nodiscard]] clean_expr_resultt remove_malloc(
-    side_effect_exprt &expr,
-    const irep_idt &mode,
-    bool result_is_used);
+  [[nodiscard]] clean_expr_resultt
+  remove_malloc(side_effect_exprt &expr, irep_idt mode, bool result_is_used);
   [[nodiscard]] clean_expr_resultt
   remove_temporary_object(side_effect_exprt &expr);
   [[nodiscard]] clean_expr_resultt remove_statement_expression(
     side_effect_exprt &expr,
-    const irep_idt &mode,
+    irep_idt mode,
     bool result_is_used);
   [[nodiscard]] clean_expr_resultt
-  remove_gcc_conditional_expression(exprt &expr, const irep_idt &mode);
+  remove_gcc_conditional_expression(exprt &expr, irep_idt mode);
   [[nodiscard]] clean_expr_resultt remove_overflow(
     side_effect_expr_overflowt &expr,
     bool result_is_used,
-    const irep_idt &mode);
+    irep_idt mode);
 
   virtual void do_cpp_new(
     const exprt &lhs,
@@ -211,21 +201,21 @@ class goto_convertt : public messaget
     const exprt &function,
     const exprt::operandst &arguments,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   virtual void do_function_call_if(
     const exprt &lhs,
     const if_exprt &function,
     const exprt::operandst &arguments,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   virtual void do_function_call_symbol(
     const exprt &lhs,
     const symbol_exprt &function,
     const exprt::operandst &arguments,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   virtual void do_function_call_symbol(const symbolt &)
   {
@@ -240,83 +230,66 @@ class goto_convertt : public messaget
   //
   // conversion
   //
-  void convert_block(
-    const code_blockt &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+  void
+  convert_block(const code_blockt &code, goto_programt &dest, irep_idt mode);
   void convert_frontend_decl(
     const code_frontend_declt &,
     goto_programt &,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_decl_type(const codet &code, goto_programt &dest);
   void convert_expression(
     const code_expressiont &code,
     goto_programt &dest,
-    const irep_idt &mode);
-  void convert_assign(
-    const code_assignt &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
+  void
+  convert_assign(const code_assignt &code, goto_programt &dest, irep_idt mode);
   void convert_cpp_delete(const codet &code, goto_programt &dest);
   void convert_loop_contracts(const codet &code, goto_programt::targett loop);
+  void convert_for(const code_fort &code, goto_programt &dest, irep_idt mode);
   void
-  convert_for(const code_fort &code, goto_programt &dest, const irep_idt &mode);
-  void convert_while(
-    const code_whilet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+  convert_while(const code_whilet &code, goto_programt &dest, irep_idt mode);
   void convert_dowhile(
     const code_dowhilet &code,
     goto_programt &dest,
-    const irep_idt &mode);
-  void convert_assume(
-    const code_assumet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
-  void convert_assert(
-    const code_assertt &code,
-    goto_programt &dest,
-    const irep_idt &mode);
-  void convert_switch(
-    const code_switcht &code,
-    goto_programt &dest,
-    const irep_idt &mode);
-  void convert_break(
-    const code_breakt &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
+  void
+  convert_assume(const code_assumet &code, goto_programt &dest, irep_idt mode);
+  void
+  convert_assert(const code_assertt &code, goto_programt &dest, irep_idt mode);
+  void
+  convert_switch(const code_switcht &code, goto_programt &dest, irep_idt mode);
+  void
+  convert_break(const code_breakt &code, goto_programt &dest, irep_idt mode);
   void convert_return(
     const code_frontend_returnt &,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_continue(
     const code_continuet &code,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_ifthenelse(
     const code_ifthenelset &code,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_goto(const code_gotot &code, goto_programt &dest);
   void convert_gcc_computed_goto(const codet &code, goto_programt &dest);
   void convert_skip(const codet &code, goto_programt &dest);
-  void convert_label(
-    const code_labelt &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+  void
+  convert_label(const code_labelt &code, goto_programt &dest, irep_idt mode);
   void convert_gcc_local_label(const codet &code, goto_programt &dest);
   void convert_switch_case(
     const code_switch_caset &code,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_gcc_switch_case_range(
     const code_gcc_switch_case_ranget &,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_function_call(
     const code_function_callt &code,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_start_thread(const codet &code, goto_programt &dest);
   void convert_end_thread(const codet &code, goto_programt &dest);
   void convert_atomic_begin(const codet &code, goto_programt &dest);
@@ -324,34 +297,24 @@ class goto_convertt : public messaget
   void convert_msc_try_finally(
     const codet &code,
     goto_programt &dest,
-    const irep_idt &mode);
-  void convert_msc_try_except(
-    const codet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
-  void convert_msc_leave(
-    const codet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
-  void convert_try_catch(
-    const codet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
+  void
+  convert_msc_try_except(const codet &code, goto_programt &dest, irep_idt mode);
+  void convert_msc_leave(const codet &code, goto_programt &dest, irep_idt mode);
+  void convert_try_catch(const codet &code, goto_programt &dest, irep_idt mode);
   void convert_CPROVER_try_catch(
     const codet &code,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void convert_CPROVER_try_finally(
     const codet &code,
     goto_programt &dest,
-    const irep_idt &mode);
-  void convert_CPROVER_throw(
-    const codet &code,
-    goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
+  void
+  convert_CPROVER_throw(const codet &code, goto_programt &dest, irep_idt mode);
   void convert_asm(const code_asmt &code, goto_programt &dest);
 
-  void convert(const codet &code, goto_programt &dest, const irep_idt &mode);
+  void convert(const codet &code, goto_programt &dest, irep_idt mode);
 
   void copy(
     const codet &code,
@@ -362,12 +325,12 @@ class goto_convertt : public messaget
   // exceptions
   //
 
-  symbol_exprt exception_flag(const irep_idt &mode);
+  symbol_exprt exception_flag(irep_idt mode);
 
   void unwind_destructor_stack(
     const source_locationt &source_location,
     goto_programt &dest,
-    const irep_idt &mode,
+    irep_idt mode,
     std::optional<node_indext> destructor_end_point = {},
     std::optional<node_indext> destructor_start_point = {});
 
@@ -383,7 +346,7 @@ class goto_convertt : public messaget
   // gotos
   //
 
-  void finish_gotos(goto_programt &dest, const irep_idt &mode);
+  void finish_gotos(goto_programt &dest, irep_idt mode);
   void finish_computed_gotos(goto_programt &dest);
   void optimize_guarded_gotos(goto_programt &dest);
 
@@ -591,7 +554,7 @@ class goto_convertt : public messaget
     goto_programt &false_case,
     const source_locationt &,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   // if(guard) goto target_true; else goto target_false;
   void generate_conditional_branch(
@@ -600,7 +563,7 @@ class goto_convertt : public messaget
     goto_programt::targett target_false,
     const source_locationt &,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   // if(guard) goto target;
   void generate_conditional_branch(
@@ -608,19 +571,17 @@ class goto_convertt : public messaget
     goto_programt::targett target_true,
     const source_locationt &,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   // turn a OP b OP c into a list a, b, c
-  static void collect_operands(
-    const exprt &expr,
-    const irep_idt &id,
-    std::list<exprt> &dest);
+  static void
+  collect_operands(const exprt &expr, irep_idt id, std::list<exprt> &dest);
 
   // START_THREAD; ... END_THREAD;
   void generate_thread_block(
     const code_blockt &thread_body,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   //
   // misc
@@ -651,7 +612,7 @@ class goto_convertt : public messaget
     const exprt::operandst &arguments,
     goto_programt &dest);
   void do_array_op(
-    const irep_idt &id,
+    irep_idt id,
     const exprt &lhs,
     const symbol_exprt &function,
     const exprt::operandst &arguments,
@@ -689,13 +650,13 @@ class goto_convertt : public messaget
     const symbol_exprt &function,
     const exprt::operandst &arguments,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
   void do_alloca(
     const exprt &lhs,
     const symbol_exprt &function,
     const exprt::operandst &arguments,
     goto_programt &dest,
-    const irep_idt &mode);
+    irep_idt mode);
 
   exprt get_array_argument(const exprt &src);
 };
diff --git a/src/ansi-c/goto-conversion/goto_convert_exceptions.cpp b/src/ansi-c/goto-conversion/goto_convert_exceptions.cpp
index f7a87a0554c..0ad1eefff74 100644
--- a/src/ansi-c/goto-conversion/goto_convert_exceptions.cpp
+++ b/src/ansi-c/goto-conversion/goto_convert_exceptions.cpp
@@ -17,7 +17,7 @@ Author: Daniel Kroening, kroening@kroening.com
 void goto_convertt::convert_msc_try_finally(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     code.operands().size() == 2,
@@ -55,7 +55,7 @@ void goto_convertt::convert_msc_try_finally(
 void goto_convertt::convert_msc_try_except(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     code.operands().size() == 3,
@@ -70,7 +70,7 @@ void goto_convertt::convert_msc_try_except(
 void goto_convertt::convert_msc_leave(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     targets.leave_set, "leave without target", code.find_source_location());
@@ -86,7 +86,7 @@ void goto_convertt::convert_msc_leave(
 void goto_convertt::convert_try_catch(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     code.operands().size() >= 2,
@@ -145,7 +145,7 @@ void goto_convertt::convert_try_catch(
 void goto_convertt::convert_CPROVER_try_catch(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     code.operands().size() == 2,
@@ -181,7 +181,7 @@ void goto_convertt::convert_CPROVER_try_catch(
 void goto_convertt::convert_CPROVER_throw(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   // set the 'exception' flag
   dest.add(goto_programt::make_assignment(
@@ -212,7 +212,7 @@ void goto_convertt::convert_CPROVER_throw(
 void goto_convertt::convert_CPROVER_try_finally(
   const codet &code,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     code.operands().size() == 2,
@@ -233,7 +233,7 @@ void goto_convertt::convert_CPROVER_try_finally(
   convert(to_code(code.op1()), dest, mode);
 }
 
-symbol_exprt goto_convertt::exception_flag(const irep_idt &mode)
+symbol_exprt goto_convertt::exception_flag(irep_idt mode)
 {
   irep_idt id = "$exception_flag";
 
@@ -280,7 +280,7 @@ symbol_exprt goto_convertt::exception_flag(const irep_idt &mode)
 void goto_convertt::unwind_destructor_stack(
   const source_locationt &source_location,
   goto_programt &dest,
-  const irep_idt &mode,
+  irep_idt mode,
   std::optional<node_indext> end_index,
   std::optional<node_indext> starting_index)
 {
diff --git a/src/ansi-c/goto-conversion/goto_convert_function_call.cpp b/src/ansi-c/goto-conversion/goto_convert_function_call.cpp
index 2fdc5c3e616..895d62feeda 100644
--- a/src/ansi-c/goto-conversion/goto_convert_function_call.cpp
+++ b/src/ansi-c/goto-conversion/goto_convert_function_call.cpp
@@ -20,7 +20,7 @@ Author: Daniel Kroening, kroening@kroening.com
 void goto_convertt::convert_function_call(
   const code_function_callt &function_call,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   do_function_call(
     function_call.lhs(),
@@ -35,7 +35,7 @@ void goto_convertt::do_function_call(
   const exprt &function,
   const exprt::operandst &arguments,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   // make it all side effect free
 
@@ -93,7 +93,7 @@ void goto_convertt::do_function_call_if(
   const if_exprt &function,
   const exprt::operandst &arguments,
   goto_programt &dest,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   // case split
 
diff --git a/src/ansi-c/goto-conversion/goto_convert_functions.cpp b/src/ansi-c/goto-conversion/goto_convert_functions.cpp
index 8c24dedeee9..9fccf89d3da 100644
--- a/src/ansi-c/goto-conversion/goto_convert_functions.cpp
+++ b/src/ansi-c/goto-conversion/goto_convert_functions.cpp
@@ -137,7 +137,7 @@ void goto_convert_functionst::add_return(
 }
 
 void goto_convert_functionst::convert_function(
-  const irep_idt &identifier,
+  irep_idt identifier,
   goto_functionst::goto_functiont &f)
 {
   const symbolt &symbol = ns.lookup(identifier);
@@ -264,7 +264,7 @@ void goto_convert(
 }
 
 void goto_convert(
-  const irep_idt &identifier,
+  irep_idt identifier,
   symbol_table_baset &symbol_table,
   goto_functionst &functions,
   message_handlert &message_handler)
diff --git a/src/ansi-c/goto-conversion/goto_convert_functions.h b/src/ansi-c/goto-conversion/goto_convert_functions.h
index 70d1f856f66..0cc2e8c4791 100644
--- a/src/ansi-c/goto-conversion/goto_convert_functions.h
+++ b/src/ansi-c/goto-conversion/goto_convert_functions.h
@@ -31,7 +31,7 @@ void goto_convert(goto_modelt &, message_handlert &);
 
 // just convert a specific function
 void goto_convert(
-  const irep_idt &identifier,
+  irep_idt identifier,
   symbol_table_baset &symbol_table,
   goto_functionst &functions,
   message_handlert &);
@@ -41,7 +41,7 @@ class goto_convert_functionst : public goto_convertt
 public:
   void goto_convert(goto_functionst &functions);
   void convert_function(
-    const irep_idt &identifier,
+    irep_idt identifier,
     goto_functionst::goto_functiont &result);
 
   goto_convert_functionst(
diff --git a/src/ansi-c/goto-conversion/goto_convert_side_effect.cpp b/src/ansi-c/goto-conversion/goto_convert_side_effect.cpp
index 3282bd6dbfc..6aa514f2401 100644
--- a/src/ansi-c/goto-conversion/goto_convert_side_effect.cpp
+++ b/src/ansi-c/goto-conversion/goto_convert_side_effect.cpp
@@ -28,7 +28,7 @@ goto_convertt::clean_expr_resultt goto_convertt::remove_assignment(
   side_effect_exprt &expr,
   bool result_is_used,
   bool address_taken,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const irep_idt statement = expr.get_statement();
 
@@ -180,7 +180,7 @@ goto_convertt::clean_expr_resultt goto_convertt::remove_pre(
   side_effect_exprt &expr,
   bool result_is_used,
   bool address_taken,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   INVARIANT_WITH_DIAGNOSTICS(
     expr.operands().size() == 1,
@@ -273,7 +273,7 @@ goto_convertt::clean_expr_resultt goto_convertt::remove_pre(
 
 goto_convertt::clean_expr_resultt goto_convertt::remove_post(
   side_effect_exprt &expr,
-  const irep_idt &mode,
+  irep_idt mode,
   bool result_is_used)
 {
   goto_programt tmp1, tmp2;
@@ -360,7 +360,7 @@ goto_convertt::clean_expr_resultt goto_convertt::remove_post(
 
 goto_convertt::clean_expr_resultt goto_convertt::remove_function_call(
   side_effect_expr_function_callt &expr,
-  const irep_idt &mode,
+  irep_idt mode,
   bool result_is_used)
 {
   clean_expr_resultt side_effects;
@@ -476,7 +476,7 @@ goto_convertt::remove_cpp_delete(side_effect_exprt &expr)
 
 goto_convertt::clean_expr_resultt goto_convertt::remove_malloc(
   side_effect_exprt &expr,
-  const irep_idt &mode,
+  irep_idt mode,
   bool result_is_used)
 {
   clean_expr_resultt side_effects;
@@ -557,7 +557,7 @@ goto_convertt::remove_temporary_object(side_effect_exprt &expr)
 
 goto_convertt::clean_expr_resultt goto_convertt::remove_statement_expression(
   side_effect_exprt &expr,
-  const irep_idt &mode,
+  irep_idt mode,
   bool result_is_used)
 {
   clean_expr_resultt side_effects;
@@ -632,7 +632,7 @@ goto_convertt::clean_expr_resultt goto_convertt::remove_statement_expression(
 goto_convertt::clean_expr_resultt goto_convertt::remove_overflow(
   side_effect_expr_overflowt &expr,
   bool result_is_used,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const irep_idt &statement = expr.get_statement();
   const exprt &lhs = expr.lhs();
@@ -710,7 +710,7 @@ goto_convertt::clean_expr_resultt goto_convertt::remove_overflow(
 
 goto_convertt::clean_expr_resultt goto_convertt::remove_side_effect(
   side_effect_exprt &expr,
-  const irep_idt &mode,
+  irep_idt mode,
   bool result_is_used,
   bool address_taken)
 {
diff --git a/src/ansi-c/goto-conversion/link_to_library.cpp b/src/ansi-c/goto-conversion/link_to_library.cpp
index 9885832b970..bf85407837c 100644
--- a/src/ansi-c/goto-conversion/link_to_library.cpp
+++ b/src/ansi-c/goto-conversion/link_to_library.cpp
@@ -29,7 +29,7 @@ add_one_function(
     const symbol_tablet &,
     symbol_tablet &,
     message_handlert &)> &library,
-  const irep_idt &missing_function)
+  irep_idt missing_function)
 {
   goto_modelt library_model;
   library(
diff --git a/src/ansi-c/typedef_type.h b/src/ansi-c/typedef_type.h
index de19004ed6f..c715f3d73ff 100644
--- a/src/ansi-c/typedef_type.h
+++ b/src/ansi-c/typedef_type.h
@@ -15,12 +15,12 @@ Author: Daniel Kroening, kroening@kroening.com
 class typedef_typet : public typet
 {
 public:
-  explicit typedef_typet(const irep_idt &identifier) : typet(ID_typedef_type)
+  explicit typedef_typet(irep_idt identifier) : typet(ID_typedef_type)
   {
     set_identifier(identifier);
   }
 
-  void set_identifier(const irep_idt &identifier)
+  void set_identifier(irep_idt identifier)
   {
     set(ID_identifier, identifier);
   }
diff --git a/src/assembler/remove_asm.cpp b/src/assembler/remove_asm.cpp
index 43426ace345..11ce8d60e54 100644
--- a/src/assembler/remove_asm.cpp
+++ b/src/assembler/remove_asm.cpp
@@ -51,28 +51,26 @@ class remove_asmt
   goto_functionst &goto_functions;
   message_handlert &message_handler;
 
-  void process_function(const irep_idt &, goto_functionst::goto_functiont &);
+  void process_function(irep_idt, goto_functionst::goto_functiont &);
 
   void process_instruction(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::instructiont &instruction,
     goto_programt &dest);
 
   void process_instruction_gcc(const code_asm_gcct &, goto_programt &dest);
 
-  void process_instruction_msc(
-    const irep_idt &,
-    const code_asmt &,
-    goto_programt &dest);
+  void
+  process_instruction_msc(irep_idt, const code_asmt &, goto_programt &dest);
 
   void gcc_asm_function_call(
-    const irep_idt &function_base_name,
+    irep_idt function_base_name,
     const code_asm_gcct &code,
     std::size_t n_args,
     goto_programt &dest);
 
   void msc_asm_function_call(
-    const irep_idt &function_base_name,
+    irep_idt function_base_name,
     const exprt::operandst &operands,
     const code_asmt &code,
     goto_programt &dest);
@@ -87,7 +85,7 @@ class remove_asmt
 /// \param n_args: Number of arguments required by \p function_base_name
 /// \param dest: Goto program to append the function call to
 void remove_asmt::gcc_asm_function_call(
-  const irep_idt &function_base_name,
+  irep_idt function_base_name,
   const code_asm_gcct &code,
   std::size_t n_args,
   goto_programt &dest)
@@ -171,7 +169,7 @@ void remove_asmt::gcc_asm_function_call(
 ///   call
 /// \param dest: Goto program to append the function call to
 void remove_asmt::msc_asm_function_call(
-  const irep_idt &function_base_name,
+  irep_idt function_base_name,
   const exprt::operandst &operands,
   const code_asmt &code,
   goto_programt &dest)
@@ -223,7 +221,7 @@ void remove_asmt::msc_asm_function_call(
 ///   assembly statements
 /// \param dest: The goto program to append the new instructions to
 void remove_asmt::process_instruction(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::instructiont &instruction,
   goto_programt &dest)
 {
@@ -415,7 +413,7 @@ void remove_asmt::process_instruction_gcc(
 /// \param code: The inline assembly code statement to translate
 /// \param dest: The goto program to append the new instructions to
 void remove_asmt::process_instruction_msc(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const code_asmt &code,
   goto_programt &dest)
 {
@@ -542,7 +540,7 @@ void remove_asmt::process_instruction_msc(
 /// \param function_id: Name of function being processed
 /// \param goto_function: The goto function
 void remove_asmt::process_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functionst::goto_functiont &goto_function)
 {
   bool did_something = false;
diff --git a/src/cpp/cpp_declaration.h b/src/cpp/cpp_declaration.h
index db8088f7222..8c185d5e6a2 100644
--- a/src/cpp/cpp_declaration.h
+++ b/src/cpp/cpp_declaration.h
@@ -115,7 +115,7 @@ class cpp_declarationt:public exprt
       find(ID_partial_specialization_args));
   }
 
-  void set_specialization_of(const irep_idt &id)
+  void set_specialization_of(irep_idt id)
   {
     set(ID_specialization_of, id);
   }
diff --git a/src/cpp/cpp_name.h b/src/cpp/cpp_name.h
index 6d6e7cb5931..3de08d48329 100644
--- a/src/cpp/cpp_name.h
+++ b/src/cpp/cpp_name.h
@@ -30,14 +30,13 @@ class cpp_namet:public irept
     {
     }
 
-    explicit namet(const irep_idt &base_name):irept(ID_name)
+    explicit namet(irep_idt base_name) : irept(ID_name)
     {
       set(ID_identifier, base_name);
     }
 
-    namet(
-      const irep_idt &_base_name,
-      const source_locationt &_source_location):irept(ID_name)
+    namet(irep_idt _base_name, const source_locationt &_source_location)
+      : irept(ID_name)
     {
       set(ID_identifier, _base_name);
       add_source_location()=_source_location;
@@ -58,14 +57,13 @@ class cpp_namet:public irept
   {
   }
 
-  explicit cpp_namet(const irep_idt &base_name):irept(ID_cpp_name)
+  explicit cpp_namet(irep_idt base_name) : irept(ID_cpp_name)
   {
     get_sub().push_back(namet(base_name));
   }
 
-  cpp_namet(
-    const irep_idt &_base_name,
-    const source_locationt &_source_location):irept(ID_cpp_name)
+  cpp_namet(irep_idt _base_name, const source_locationt &_source_location)
+    : irept(ID_cpp_name)
   {
     get_sub().push_back(namet(_base_name, _source_location));
   }
diff --git a/src/cpp/cpp_namespace_spec.h b/src/cpp/cpp_namespace_spec.h
index 68f50206031..f38b7f9dd1c 100644
--- a/src/cpp/cpp_namespace_spec.h
+++ b/src/cpp/cpp_namespace_spec.h
@@ -41,7 +41,7 @@ class cpp_namespace_spect:public exprt
     return get(ID_namespace);
   }
 
-  void set_namespace(const irep_idt &_namespace)
+  void set_namespace(irep_idt _namespace)
   {
     set(ID_namespace, _namespace);
   }
diff --git a/src/cpp/cpp_scope.cpp b/src/cpp/cpp_scope.cpp
index eb0831dbb73..40015575b73 100644
--- a/src/cpp/cpp_scope.cpp
+++ b/src/cpp/cpp_scope.cpp
@@ -25,7 +25,7 @@ std::ostream &operator << (std::ostream &out, cpp_scopet::lookup_kindt kind)
 }
 
 void cpp_scopet::lookup_rec(
-  const irep_idt &base_name_to_lookup,
+  irep_idt base_name_to_lookup,
   lookup_kindt kind,
   id_sett &id_set)
 {
@@ -81,7 +81,7 @@ void cpp_scopet::lookup_rec(
 }
 
 void cpp_scopet::lookup_rec(
-  const irep_idt &base_name_to_lookup,
+  irep_idt base_name_to_lookup,
   lookup_kindt kind,
   cpp_idt::id_classt identifier_class,
   id_sett &id_set)
@@ -154,9 +154,8 @@ void cpp_scopet::lookup_rec(
       base_name_to_lookup, kind, identifier_class, id_set);
 }
 
-cpp_scopet::id_sett cpp_scopet::lookup_identifier(
-  const irep_idt &id,
-  cpp_idt::id_classt identifier_class)
+cpp_scopet::id_sett
+cpp_scopet::lookup_identifier(irep_idt id, cpp_idt::id_classt identifier_class)
 {
   id_sett id_set;
 
@@ -187,7 +186,7 @@ cpp_scopet::id_sett cpp_scopet::lookup_identifier(
   return id_set;
 }
 
-cpp_scopet &cpp_scopet::new_scope(const irep_idt &new_scope_name)
+cpp_scopet &cpp_scopet::new_scope(irep_idt new_scope_name)
 {
   cpp_idt &id=insert(new_scope_name);
   id.identifier=prefix+id2string(new_scope_name);
@@ -198,7 +197,7 @@ cpp_scopet &cpp_scopet::new_scope(const irep_idt &new_scope_name)
   return (cpp_scopet &)id;
 }
 
-bool cpp_scopet::contains(const irep_idt &base_name_to_lookup)
+bool cpp_scopet::contains(irep_idt base_name_to_lookup)
 {
   return !lookup(base_name_to_lookup, SCOPE_ONLY).empty();
 }
diff --git a/src/cpp/cpp_scope.h b/src/cpp/cpp_scope.h
index 228734f1c36..a3085dfdf64 100644
--- a/src/cpp/cpp_scope.h
+++ b/src/cpp/cpp_scope.h
@@ -29,7 +29,7 @@ class cpp_scopet:public cpp_idt
 
   enum lookup_kindt { SCOPE_ONLY, QUALIFIED, RECURSIVE };
 
-  id_sett lookup(const irep_idt &base_name_to_lookup, lookup_kindt kind)
+  id_sett lookup(irep_idt base_name_to_lookup, lookup_kindt kind)
   {
     id_sett result;
     lookup_rec(base_name_to_lookup, kind, result);
@@ -37,7 +37,7 @@ class cpp_scopet:public cpp_idt
   }
 
   id_sett lookup(
-    const irep_idt &base_name_to_lookup,
+    irep_idt base_name_to_lookup,
     lookup_kindt kind,
     cpp_idt::id_classt identifier_class)
   {
@@ -46,10 +46,9 @@ class cpp_scopet:public cpp_idt
     return result;
   }
 
-  id_sett
-  lookup_identifier(const irep_idt &id, cpp_idt::id_classt identifier_class);
+  id_sett lookup_identifier(irep_idt id, cpp_idt::id_classt identifier_class);
 
-  cpp_idt &insert(const irep_idt &_base_name)
+  cpp_idt &insert(irep_idt _base_name)
   {
     cpp_id_mapt::iterator it=
       sub.insert(std::pair<irep_idt, cpp_idt>
@@ -72,7 +71,7 @@ class cpp_scopet:public cpp_idt
     return it->second;
   }
 
-  bool contains(const irep_idt &base_name_to_lookup);
+  bool contains(irep_idt base_name_to_lookup);
 
   bool is_root_scope() const
   {
@@ -112,13 +111,13 @@ class cpp_scopet:public cpp_idt
     using_scopes.push_back(&other);
   }
 
-  class cpp_scopet &new_scope(const irep_idt &new_scope_name);
+  class cpp_scopet &new_scope(irep_idt new_scope_name);
 
 protected:
-  void lookup_rec(const irep_idt &base_name, lookup_kindt kind, id_sett &);
+  void lookup_rec(irep_idt base_name, lookup_kindt kind, id_sett &);
 
   void lookup_rec(
-    const irep_idt &base_name,
+    irep_idt base_name,
     lookup_kindt kind,
     cpp_idt::id_classt id_class,
     id_sett &);
diff --git a/src/cpp/cpp_scopes.h b/src/cpp/cpp_scopes.h
index dd3830003f3..edd65b6ca02 100644
--- a/src/cpp/cpp_scopes.h
+++ b/src/cpp/cpp_scopes.h
@@ -34,9 +34,7 @@ class cpp_scopest
     return *current_scope_ptr;
   }
 
-  cpp_scopet &new_scope(
-    const irep_idt &new_scope_name,
-    cpp_idt::id_classt id_class)
+  cpp_scopet &new_scope(irep_idt new_scope_name, cpp_idt::id_classt id_class)
   {
     PRECONDITION(!new_scope_name.empty());
     cpp_scopet &n=current_scope_ptr->new_scope(new_scope_name);
@@ -46,7 +44,7 @@ class cpp_scopest
     return n;
   }
 
-  cpp_scopet &new_namespace(const irep_idt &new_scope_name)
+  cpp_scopet &new_namespace(irep_idt new_scope_name)
   {
     return new_scope(new_scope_name, cpp_idt::id_classt::NAMESPACE);
   }
@@ -69,7 +67,7 @@ class cpp_scopest
 
   cpp_scopet *current_scope_ptr;
 
-  cpp_idt &get_id(const irep_idt &identifier)
+  cpp_idt &get_id(irep_idt identifier)
   {
     id_mapt::const_iterator it=id_map.find(identifier);
     if(it==id_map.end())
@@ -77,14 +75,14 @@ class cpp_scopest
     return *(it->second);
   }
 
-  cpp_scopet &get_scope(const irep_idt &identifier)
+  cpp_scopet &get_scope(irep_idt identifier)
   {
     cpp_idt &n=get_id(identifier);
     CHECK_RETURN(n.is_scope);
     return (cpp_scopet &)n;
   }
 
-  cpp_scopet &set_scope(const irep_idt &identifier)
+  cpp_scopet &set_scope(irep_idt identifier)
   {
     current_scope_ptr=&get_scope(identifier);
     return current_scope();
diff --git a/src/cpp/cpp_template_parameter.h b/src/cpp/cpp_template_parameter.h
index c55b6c30a19..f4a2cd1c850 100644
--- a/src/cpp/cpp_template_parameter.h
+++ b/src/cpp/cpp_template_parameter.h
@@ -65,13 +65,13 @@ struct template_parametert:public exprt
 struct template_parameter_symbol_typet : public typet
 {
 public:
-  explicit template_parameter_symbol_typet(const irep_idt &identifier)
+  explicit template_parameter_symbol_typet(irep_idt identifier)
     : typet(ID_template_parameter_symbol_type)
   {
     set_identifier(identifier);
   }
 
-  void set_identifier(const irep_idt &identifier)
+  void set_identifier(irep_idt identifier)
   {
     set(ID_identifier, identifier);
   }
diff --git a/src/cpp/cpp_typecheck.cpp b/src/cpp/cpp_typecheck.cpp
index 4a8fb80c8e7..d372a1db3a8 100644
--- a/src/cpp/cpp_typecheck.cpp
+++ b/src/cpp/cpp_typecheck.cpp
@@ -375,7 +375,7 @@ void cpp_typecheckt::clean_up()
   }
 }
 
-bool cpp_typecheckt::builtin_factory(const irep_idt &identifier)
+bool cpp_typecheckt::builtin_factory(irep_idt identifier)
 {
   return ::builtin_factory(
     identifier, support_float16_type, symbol_table, get_message_handler());
diff --git a/src/cpp/cpp_typecheck.h b/src/cpp/cpp_typecheck.h
index 3737974fa2f..ef744a92997 100644
--- a/src/cpp/cpp_typecheck.h
+++ b/src/cpp/cpp_typecheck.h
@@ -111,7 +111,7 @@ class cpp_typecheckt:public c_typecheck_baset
 
   void convert_anon_struct_union_member(
     const cpp_declarationt &declaration,
-    const irep_idt &access,
+    irep_idt access,
     struct_typet::componentst &components);
 
   //
@@ -138,12 +138,12 @@ class cpp_typecheckt:public c_typecheck_baset
   void typecheck_class_template_member(cpp_declarationt &declaration);
 
   std::string class_template_identifier(
-    const irep_idt &base_name,
+    irep_idt base_name,
     const template_typet &template_type,
     const cpp_template_args_non_tct &partial_specialization_args);
 
   std::string function_template_identifier(
-    const irep_idt &base_name,
+    irep_idt base_name,
     const template_typet &template_type,
     const typet &function_type);
 
@@ -217,12 +217,10 @@ class cpp_typecheckt:public c_typecheck_baset
     cpp_scopet &template_scope,
     const std::string &suffix);
 
-  void
-  convert_parameters(const irep_idt &current_mode, code_typet &function_type);
+  void convert_parameters(irep_idt current_mode, code_typet &function_type);
 
-  void convert_parameter(
-    const irep_idt &current_mode,
-    code_typet::parametert &parameter);
+  void
+  convert_parameter(irep_idt current_mode, code_typet::parametert &parameter);
 
   //
   // Misc
@@ -230,7 +228,7 @@ class cpp_typecheckt:public c_typecheck_baset
 
   void default_ctor(
     const source_locationt &source_location,
-    const irep_idt &base_name,
+    irep_idt base_name,
     cpp_declarationt &ctor) const;
 
   void default_cpctor(
@@ -263,15 +261,13 @@ class cpp_typecheckt:public c_typecheck_baset
   bool find_assignop(const symbolt &symbol)const;
   bool find_dtor(const symbolt &symbol)const;
 
-  bool find_parent(
-    const symbolt &symb,
-    const irep_idt &base_name,
-    irep_idt &identifier);
+  bool
+  find_parent(const symbolt &symb, irep_idt base_name, irep_idt &identifier);
 
   bool get_component(
     const source_locationt &source_location,
     const exprt &object,
-    const irep_idt &component_name,
+    irep_idt component_name,
     exprt &member);
 
   void new_temporary(const source_locationt &source_location,
@@ -289,12 +285,12 @@ class cpp_typecheckt:public c_typecheck_baset
   void clean_up();
 
   void add_base_components(
-        const struct_typet &from,
-        const irep_idt &access,
-        struct_typet &to,
-        std::set<irep_idt> &bases,
-        std::set<irep_idt> &vbases,
-        bool is_virtual);
+    const struct_typet &from,
+    irep_idt access,
+    struct_typet &to,
+    std::set<irep_idt> &bases,
+    std::set<irep_idt> &vbases,
+    bool is_virtual);
 
   bool cast_away_constness(const typet &t1,
                            const typet &t2) const;
@@ -328,7 +324,7 @@ class cpp_typecheckt:public c_typecheck_baset
 
   void add_method_body(symbolt *_method_symbol);
 
-  bool builtin_factory(const irep_idt &) override;
+  bool builtin_factory(irep_idt) override;
 
   // types
 
@@ -343,17 +339,15 @@ class cpp_typecheckt:public c_typecheck_baset
 
   // determine the scope into which a tag goes
   // (enums, structs, union, classes)
-  cpp_scopet &tag_scope(
-    const irep_idt &_base_name,
-    bool has_body,
-    bool tag_only_declaration);
+  cpp_scopet &
+  tag_scope(irep_idt _base_name, bool has_body, bool tag_only_declaration);
 
   void typecheck_compound_declarator(
     const symbolt &symbol,
     const cpp_declarationt &declaration,
     cpp_declaratort &declarator,
     struct_typet::componentst &components,
-    const irep_idt &access,
+    irep_idt access,
     bool is_static,
     bool is_typedef,
     bool is_mutable);
diff --git a/src/cpp/cpp_typecheck_bases.cpp b/src/cpp/cpp_typecheck_bases.cpp
index 0cc1f7e57ec..9daeeb6a2c2 100644
--- a/src/cpp/cpp_typecheck_bases.cpp
+++ b/src/cpp/cpp_typecheck_bases.cpp
@@ -118,7 +118,7 @@ void cpp_typecheckt::typecheck_compound_bases(struct_typet &type)
 
 void cpp_typecheckt::add_base_components(
   const struct_typet &from,
-  const irep_idt &access,
+  irep_idt access,
   struct_typet &to,
   std::set<irep_idt> &bases,
   std::set<irep_idt> &vbases,
diff --git a/src/cpp/cpp_typecheck_compound_type.cpp b/src/cpp/cpp_typecheck_compound_type.cpp
index 48c62767aae..407a43774b8 100644
--- a/src/cpp/cpp_typecheck_compound_type.cpp
+++ b/src/cpp/cpp_typecheck_compound_type.cpp
@@ -86,7 +86,7 @@ bool cpp_typecheckt::has_auto(const typet &type)
 }
 
 cpp_scopet &cpp_typecheckt::tag_scope(
-  const irep_idt &base_name,
+  irep_idt base_name,
   bool has_body,
   bool tag_only_declaration)
 {
@@ -294,7 +294,7 @@ void cpp_typecheckt::typecheck_compound_declarator(
   const cpp_declarationt &declaration,
   cpp_declaratort &declarator,
   struct_typet::componentst &components,
-  const irep_idt &access,
+  irep_idt access,
   bool is_static,
   bool is_typedef,
   bool is_mutable)
@@ -1425,7 +1425,7 @@ void cpp_typecheckt::add_anonymous_members_to_scope(
 
 void cpp_typecheckt::convert_anon_struct_union_member(
   const cpp_declarationt &declaration,
-  const irep_idt &access,
+  irep_idt access,
   struct_typet::componentst &components)
 {
   const struct_union_typet &final_type =
@@ -1485,7 +1485,7 @@ void cpp_typecheckt::convert_anon_struct_union_member(
 bool cpp_typecheckt::get_component(
   const source_locationt &source_location,
   const exprt &object,
-  const irep_idt &component_name,
+  irep_idt component_name,
   exprt &member)
 {
   PRECONDITION(
diff --git a/src/cpp/cpp_typecheck_constructor.cpp b/src/cpp/cpp_typecheck_constructor.cpp
index 79709e447a2..7c8a170fbd7 100644
--- a/src/cpp/cpp_typecheck_constructor.cpp
+++ b/src/cpp/cpp_typecheck_constructor.cpp
@@ -25,8 +25,8 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 /// \param [out] block: non-typechecked block
 static void copy_parent(
   const source_locationt &source_location,
-  const irep_idt &parent_base_name,
-  const irep_idt &arg_name,
+  irep_idt parent_base_name,
+  irep_idt arg_name,
   exprt &block)
 {
   exprt op0(
@@ -56,8 +56,8 @@ static void copy_parent(
 /// \param [out] block: non-typechecked block
 static void copy_member(
   const source_locationt &source_location,
-  const irep_idt &member_base_name,
-  const irep_idt &arg_name,
+  irep_idt member_base_name,
+  irep_idt arg_name,
   exprt &block)
 {
   cpp_namet op0(member_base_name, source_location);
@@ -84,9 +84,9 @@ static void copy_member(
 /// \param [out] block: non-typechecked block
 static void copy_array(
   const source_locationt &source_location,
-  const irep_idt &member_base_name,
+  irep_idt member_base_name,
   mp_integer i,
-  const irep_idt &arg_name,
+  irep_idt arg_name,
   exprt &block)
 {
   // Build the index expression
@@ -117,7 +117,7 @@ static void copy_array(
 /// Generate code for implicit default constructors
 void cpp_typecheckt::default_ctor(
   const source_locationt &source_location,
-  const irep_idt &base_name,
+  irep_idt base_name,
   cpp_declarationt &ctor) const
 {
   cpp_declaratort decl;
diff --git a/src/cpp/cpp_typecheck_expr.cpp b/src/cpp/cpp_typecheck_expr.cpp
index 1201882af20..b309cf6c1fe 100644
--- a/src/cpp/cpp_typecheck_expr.cpp
+++ b/src/cpp/cpp_typecheck_expr.cpp
@@ -34,7 +34,7 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 bool cpp_typecheckt::find_parent(
   const symbolt &symb,
-  const irep_idt &base_name,
+  irep_idt base_name,
   irep_idt &identifier)
 {
   for(const auto &b : to_struct_type(symb.type).bases())
diff --git a/src/cpp/cpp_typecheck_function.cpp b/src/cpp/cpp_typecheck_function.cpp
index 154b037dae4..b563c1cfb3f 100644
--- a/src/cpp/cpp_typecheck_function.cpp
+++ b/src/cpp/cpp_typecheck_function.cpp
@@ -17,7 +17,7 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 #include "cpp_typecheck.h"
 
 void cpp_typecheckt::convert_parameter(
-  const irep_idt &current_mode,
+  irep_idt current_mode,
   code_typet::parametert &parameter)
 {
   irep_idt base_name=id2string(parameter.get_base_name());
@@ -66,7 +66,7 @@ void cpp_typecheckt::convert_parameter(
 }
 
 void cpp_typecheckt::convert_parameters(
-  const irep_idt &current_mode,
+  irep_idt current_mode,
   code_typet &function_type)
 {
   code_typet::parameterst &parameters=
diff --git a/src/cpp/cpp_typecheck_resolve.cpp b/src/cpp/cpp_typecheck_resolve.cpp
index fb8d19068f4..3232522c67e 100644
--- a/src/cpp/cpp_typecheck_resolve.cpp
+++ b/src/cpp/cpp_typecheck_resolve.cpp
@@ -668,7 +668,7 @@ void cpp_typecheck_resolvet::resolve_argument(
 }
 
 exprt cpp_typecheck_resolvet::do_builtin(
-  const irep_idt &base_name,
+  irep_idt base_name,
   const cpp_typecheck_fargst &fargs,
   const cpp_template_args_non_tct &template_args)
 {
@@ -998,7 +998,7 @@ cpp_scopet &cpp_typecheck_resolvet::resolve_scope(
 
 /// disambiguate partial specialization
 struct_tag_typet cpp_typecheck_resolvet::disambiguate_template_classes(
-  const irep_idt &base_name,
+  irep_idt base_name,
   const cpp_scopest::id_sett &id_set,
   const cpp_template_args_non_tct &full_template_args)
 {
@@ -1277,7 +1277,7 @@ cpp_scopet &cpp_typecheck_resolvet::resolve_namespace(
 }
 
 void cpp_typecheck_resolvet::show_identifiers(
-  const irep_idt &base_name,
+  irep_idt base_name,
   const resolve_identifierst &identifiers,
   std::ostream &out)
 {
@@ -2343,7 +2343,7 @@ void cpp_typecheck_resolvet::filter_for_namespaces(
 
 void cpp_typecheck_resolvet::resolve_with_arguments(
   cpp_scopest::id_sett &id_set,
-  const irep_idt &base_name,
+  irep_idt base_name,
   const cpp_typecheck_fargst &fargs)
 {
   // not clear what this is good for
diff --git a/src/cpp/cpp_typecheck_resolve.h b/src/cpp/cpp_typecheck_resolve.h
index 82471fa554f..84b1a42b919 100644
--- a/src/cpp/cpp_typecheck_resolve.h
+++ b/src/cpp/cpp_typecheck_resolve.h
@@ -75,7 +75,7 @@ class cpp_typecheck_resolvet
     const wantt want);
 
   struct_tag_typet disambiguate_template_classes(
-    const irep_idt &base_name,
+    irep_idt base_name,
     const cpp_scopest::id_sett &id_set,
     const cpp_template_args_non_tct &template_args);
 
@@ -124,18 +124,18 @@ class cpp_typecheck_resolvet
     const cpp_typecheck_fargst &fargs);
 
   exprt do_builtin(
-    const irep_idt &base_name,
+    irep_idt base_name,
     const cpp_typecheck_fargst &fargs,
     const cpp_template_args_non_tct &template_args);
 
   void show_identifiers(
-    const irep_idt &base_name,
+    irep_idt base_name,
     const resolve_identifierst &identifiers,
     std::ostream &out);
 
   void resolve_with_arguments(
     cpp_scopest::id_sett &id_set,
-    const irep_idt &base_name,
+    irep_idt base_name,
     const cpp_typecheck_fargst &fargs);
 
   void filter_for_named_scopes(cpp_scopest::id_sett &id_set);
diff --git a/src/cpp/cpp_typecheck_template.cpp b/src/cpp/cpp_typecheck_template.cpp
index 6dfcd4a05e2..e7e67ee336e 100644
--- a/src/cpp/cpp_typecheck_template.cpp
+++ b/src/cpp/cpp_typecheck_template.cpp
@@ -412,7 +412,7 @@ void cpp_typecheckt::typecheck_class_template_member(
 }
 
 std::string cpp_typecheckt::class_template_identifier(
-  const irep_idt &base_name,
+  irep_idt base_name,
   const template_typet &template_type,
   const cpp_template_args_non_tct &partial_specialization_args)
 {
@@ -471,7 +471,7 @@ std::string cpp_typecheckt::class_template_identifier(
 }
 
 std::string cpp_typecheckt::function_template_identifier(
-  const irep_idt &base_name,
+  irep_idt base_name,
   const template_typet &template_type,
   const typet &function_type)
 {
diff --git a/src/cpp/parse.cpp b/src/cpp/parse.cpp
index 777f4b2f0bd..570b11f6a66 100644
--- a/src/cpp/parse.cpp
+++ b/src/cpp/parse.cpp
@@ -220,9 +220,9 @@ class Parser // NOLINT(readability/identifiers)
   new_scopet root_scope;
   new_scopet *current_scope;
   new_scopet &add_id(const irept &name, new_scopet::kindt);
-  new_scopet &add_id(const irep_idt &, new_scopet::kindt);
+  new_scopet &add_id(irep_idt, new_scopet::kindt);
   void make_sub_scope(const irept &name, new_scopet::kindt);
-  void make_sub_scope(const irep_idt &, new_scopet::kindt);
+  void make_sub_scope(irep_idt, new_scopet::kindt);
 
   enum DeclKind { kDeclarator, kArgDeclarator, kCastDeclarator };
   enum TemplateDeclKind { tdk_unknown, tdk_decl, tdk_instantiation,
@@ -436,7 +436,7 @@ new_scopet &Parser::add_id(const irept &cpp_name, new_scopet::kindt kind)
   return add_id(id, kind);
 }
 
-new_scopet &Parser::add_id(const irep_idt &id, new_scopet::kindt kind)
+new_scopet &Parser::add_id(irep_idt id, new_scopet::kindt kind)
 {
   new_scopet &s=current_scope->id_map[id];
 
@@ -453,7 +453,7 @@ void Parser::make_sub_scope(const irept &cpp_name, new_scopet::kindt kind)
   current_scope=&s;
 }
 
-void Parser::make_sub_scope(const irep_idt &id, new_scopet::kindt kind)
+void Parser::make_sub_scope(irep_idt id, new_scopet::kindt kind)
 {
   new_scopet &s=add_id(id, kind);
   current_scope=&s;
diff --git a/src/cpp/template_map.cpp b/src/cpp/template_map.cpp
index 16767e6e5a3..b12c3ed9ac9 100644
--- a/src/cpp/template_map.cpp
+++ b/src/cpp/template_map.cpp
@@ -90,7 +90,7 @@ void template_mapt::apply(exprt &expr) const
     apply(*it);
 }
 
-exprt template_mapt::lookup(const irep_idt &identifier) const
+exprt template_mapt::lookup(irep_idt identifier) const
 {
   type_mapt::const_iterator t_it=
     type_map.find(identifier);
@@ -111,7 +111,7 @@ exprt template_mapt::lookup(const irep_idt &identifier) const
   return static_cast<const exprt &>(get_nil_irep());
 }
 
-typet template_mapt::lookup_type(const irep_idt &identifier) const
+typet template_mapt::lookup_type(irep_idt identifier) const
 {
   type_mapt::const_iterator t_it=
     type_map.find(identifier);
@@ -122,7 +122,7 @@ typet template_mapt::lookup_type(const irep_idt &identifier) const
   return static_cast<const typet &>(get_nil_irep());
 }
 
-exprt template_mapt::lookup_expr(const irep_idt &identifier) const
+exprt template_mapt::lookup_expr(irep_idt identifier) const
 {
   expr_mapt::const_iterator e_it=
     expr_map.find(identifier);
diff --git a/src/cpp/template_map.h b/src/cpp/template_map.h
index 52be1f217f9..544eff8bc70 100644
--- a/src/cpp/template_map.h
+++ b/src/cpp/template_map.h
@@ -40,9 +40,9 @@ class template_mapt
     expr_map.swap(template_map.expr_map);
   }
 
-  exprt lookup(const irep_idt &identifier) const;
-  typet lookup_type(const irep_idt &identifier) const;
-  exprt lookup_expr(const irep_idt &identifier) const;
+  exprt lookup(irep_idt identifier) const;
+  typet lookup_type(irep_idt identifier) const;
+  exprt lookup_expr(irep_idt identifier) const;
 
   void print(std::ostream &out) const;
 
diff --git a/src/cprover/instrument_contracts.cpp b/src/cprover/instrument_contracts.cpp
index e386f98512d..4306e7d4262 100644
--- a/src/cprover/instrument_contracts.cpp
+++ b/src/cprover/instrument_contracts.cpp
@@ -24,7 +24,7 @@ Author: Daniel Kroening, dkr@amazon.com
 #define MAX_TEXT 20
 
 std::optional<code_with_contract_typet>
-get_contract(const irep_idt &function_identifier, const namespacet &ns)
+get_contract(irep_idt function_identifier, const namespacet &ns)
 {
   // contracts are in a separate symbol, with prefix "contract::"
   auto contract_identifier = "contract::" + id2string(function_identifier);
@@ -35,7 +35,7 @@ get_contract(const irep_idt &function_identifier, const namespacet &ns)
     return to_code_with_contract_type(symbol_ptr->type);
 }
 
-bool has_contract(const irep_idt &function_identifier, const namespacet &ns)
+bool has_contract(irep_idt function_identifier, const namespacet &ns)
 {
   return get_contract(function_identifier, ns).has_value();
 }
@@ -179,8 +179,7 @@ static exprt make_assigns_assertion(
   return disjunction(disjuncts);
 }
 
-static bool
-is_procedure_local(const irep_idt &function_identifier, const exprt &lhs)
+static bool is_procedure_local(irep_idt function_identifier, const exprt &lhs)
 {
   if(lhs.id() == ID_member)
     return is_procedure_local(
diff --git a/src/cprover/instrument_contracts.h b/src/cprover/instrument_contracts.h
index 04f269a9970..0f4025370c0 100644
--- a/src/cprover/instrument_contracts.h
+++ b/src/cprover/instrument_contracts.h
@@ -23,6 +23,6 @@ class namespacet;
 void instrument_contracts(goto_modelt &);
 
 std::optional<code_with_contract_typet>
-get_contract(const irep_idt &function_identifier, const namespacet &);
+get_contract(irep_idt function_identifier, const namespacet &);
 
 #endif // CPROVER_CPOVER_INSTRUMENT_CONTRACTS_H
diff --git a/src/goto-analyzer/unreachable_instructions.cpp b/src/goto-analyzer/unreachable_instructions.cpp
index 5f0cc4b8fff..b23d3b33550 100644
--- a/src/goto-analyzer/unreachable_instructions.cpp
+++ b/src/goto-analyzer/unreachable_instructions.cpp
@@ -66,7 +66,7 @@ static void build_dead_map_from_ai(
 
 static void output_dead_plain(
   const namespacet &ns,
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   const goto_programt &goto_program,
   const dead_mapt &dead_map,
   std::ostream &os)
@@ -80,7 +80,7 @@ static void output_dead_plain(
 }
 
 static void add_to_xml(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   const goto_programt &goto_program,
   const dead_mapt &dead_map,
   xmlt &dest)
@@ -115,7 +115,7 @@ file_name_string_opt(const source_locationt &source_location)
 
 static void add_to_json(
   const namespacet &ns,
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   const goto_programt &goto_program,
   const dead_mapt &dead_map,
   json_arrayt &dest)
@@ -263,7 +263,7 @@ line_string_opt(const source_locationt &source_location)
 }
 
 static void json_output_function(
-  const irep_idt &function,
+  irep_idt function,
   const source_locationt &first_location,
   const source_locationt &last_location,
   json_arrayt &dest)
@@ -280,7 +280,7 @@ static void json_output_function(
 }
 
 static void xml_output_function(
-  const irep_idt &function,
+  irep_idt function,
   const source_locationt &first_location,
   const source_locationt &last_location,
   xmlt &dest)
diff --git a/src/goto-cc/linker_script_merge.cpp b/src/goto-cc/linker_script_merge.cpp
index 12319f59021..c7c7d6ae0f9 100644
--- a/src/goto-cc/linker_script_merge.cpp
+++ b/src/goto-cc/linker_script_merge.cpp
@@ -276,11 +276,11 @@ int linker_script_merget::pointerize_linker_defined_symbols(
 }
 
 int linker_script_merget::replace_expr(
-    exprt &old_expr,
-    const linker_valuest &linker_values,
-    const symbol_exprt &old_symbol,
-    const irep_idt &ident,
-    const std::string &shape)
+  exprt &old_expr,
+  const linker_valuest &linker_values,
+  const symbol_exprt &old_symbol,
+  irep_idt ident,
+  const std::string &shape)
 {
   auto it=linker_values.find(ident);
   if(it==linker_values.end())
diff --git a/src/goto-cc/linker_script_merge.h b/src/goto-cc/linker_script_merge.h
index 37b91d37a65..cbadd96e650 100644
--- a/src/goto-cc/linker_script_merge.h
+++ b/src/goto-cc/linker_script_merge.h
@@ -173,11 +173,11 @@ class linker_script_merget
 
   /// \brief do the actual replacement of an expr with a new pointer expr
   int replace_expr(
-      exprt &old_expr,
-      const linker_valuest &linker_values,
-      const symbol_exprt &old_symbol,
-      const irep_idt &ident,
-      const std::string &shape);
+    exprt &old_expr,
+    const linker_valuest &linker_values,
+    const symbol_exprt &old_symbol,
+    irep_idt ident,
+    const std::string &shape);
 
   /// \brief fill `to_pointerize` with names of linker symbols appearing in expr
   void symbols_to_pointerize(
diff --git a/src/goto-checker/bmc_util.cpp b/src/goto-checker/bmc_util.cpp
index 5bb3d9ce459..09e87b3ebe9 100644
--- a/src/goto-checker/bmc_util.cpp
+++ b/src/goto-checker/bmc_util.cpp
@@ -47,8 +47,7 @@ void build_error_trace(
   build_goto_trace(symex_target_equation, decision_procedure, ns, goto_trace);
 }
 
-ssa_step_predicatet
-ssa_step_matches_failing_property(const irep_idt &property_id)
+ssa_step_predicatet ssa_step_matches_failing_property(irep_idt property_id)
 {
   return [property_id](
            symex_target_equationt::SSA_stepst::const_iterator step,
@@ -386,9 +385,8 @@ void run_property_decider(
     << messaget::eom;
 
   property_decider.add_constraint_from_goals(
-    [&properties](const irep_idt &property_id) {
-      return is_property_to_check(properties.at(property_id).status);
-    });
+    [&properties](irep_idt property_id)
+    { return is_property_to_check(properties.at(property_id).status); });
 
   auto const sat_solver_start = std::chrono::steady_clock::now();
 
diff --git a/src/goto-checker/bmc_util.h b/src/goto-checker/bmc_util.h
index c604856d7ba..6f2fad7c63c 100644
--- a/src/goto-checker/bmc_util.h
+++ b/src/goto-checker/bmc_util.h
@@ -41,8 +41,7 @@ void convert_symex_target_equation(
 
 /// Returns a function that checks whether an SSA step is an assertion
 /// with \p property_id. Usually used for `build_goto_trace`.
-ssa_step_predicatet
-ssa_step_matches_failing_property(const irep_idt &property_id);
+ssa_step_predicatet ssa_step_matches_failing_property(irep_idt property_id);
 
 /// Outputs a message that an error trace is being built
 void message_building_error_trace(messaget &);
diff --git a/src/goto-checker/fault_localization_provider.h b/src/goto-checker/fault_localization_provider.h
index 39a303bfcff..4b0b8d1ad5d 100644
--- a/src/goto-checker/fault_localization_provider.h
+++ b/src/goto-checker/fault_localization_provider.h
@@ -36,8 +36,7 @@ class fault_localization_providert
 public:
   /// Returns the most likely fault locations
   /// for the given FAILed \p property_id
-  virtual fault_location_infot
-  localize_fault(const irep_idt &property_id) const = 0;
+  virtual fault_location_infot localize_fault(irep_idt property_id) const = 0;
 
   virtual ~fault_localization_providert() = default;
 };
diff --git a/src/goto-checker/goto_symex_fault_localizer.cpp b/src/goto-checker/goto_symex_fault_localizer.cpp
index bd7200e3fec..4afa696c505 100644
--- a/src/goto-checker/goto_symex_fault_localizer.cpp
+++ b/src/goto-checker/goto_symex_fault_localizer.cpp
@@ -29,8 +29,8 @@ goto_symex_fault_localizert::goto_symex_fault_localizert(
 {
 }
 
-fault_location_infot goto_symex_fault_localizert::
-operator()(const irep_idt &failed_property_id)
+fault_location_infot
+goto_symex_fault_localizert::operator()(irep_idt failed_property_id)
 {
   fault_location_infot fault_location;
   localization_pointst localization_points;
@@ -51,7 +51,7 @@ operator()(const irep_idt &failed_property_id)
 }
 
 const SSA_stept &goto_symex_fault_localizert::collect_guards(
-  const irep_idt &failed_property_id,
+  irep_idt failed_property_id,
   localization_pointst &localization_points,
   fault_location_infot &fault_location)
 {
diff --git a/src/goto-checker/goto_symex_fault_localizer.h b/src/goto-checker/goto_symex_fault_localizer.h
index 6a6b1d1c5dd..839eceb064e 100644
--- a/src/goto-checker/goto_symex_fault_localizer.h
+++ b/src/goto-checker/goto_symex_fault_localizer.h
@@ -31,7 +31,7 @@ class goto_symex_fault_localizert
     const symex_target_equationt &equation,
     stack_decision_proceduret &solver);
 
-  fault_location_infot operator()(const irep_idt &failed_property_id);
+  fault_location_infot operator()(irep_idt failed_property_id);
 
 protected:
   const optionst &options;
@@ -47,7 +47,7 @@ class goto_symex_fault_localizert
   /// and initializes fault_location_info, and returns the SSA step of
   /// the failed property
   const SSA_stept &collect_guards(
-    const irep_idt &failed_property_id,
+    irep_idt failed_property_id,
     localization_pointst &localization_points,
     fault_location_infot &fault_location);
 
diff --git a/src/goto-checker/goto_symex_property_decider.cpp b/src/goto-checker/goto_symex_property_decider.cpp
index fdec0b18c19..63a9d84ad32 100644
--- a/src/goto-checker/goto_symex_property_decider.cpp
+++ b/src/goto-checker/goto_symex_property_decider.cpp
@@ -81,7 +81,7 @@ void goto_symex_property_decidert::convert_goals()
 }
 
 void goto_symex_property_decidert::add_constraint_from_goals(
-  std::function<bool(const irep_idt &)> select_property)
+  std::function<bool(irep_idt)> select_property)
 {
   exprt::operandst disjuncts;
   decision_proceduret &decision_procedure = solver->decision_procedure();
diff --git a/src/goto-checker/goto_symex_property_decider.h b/src/goto-checker/goto_symex_property_decider.h
index 368416763b2..c23eb19a47a 100644
--- a/src/goto-checker/goto_symex_property_decider.h
+++ b/src/goto-checker/goto_symex_property_decider.h
@@ -39,7 +39,7 @@ class goto_symex_property_decidert
 
   /// Add disjunction of negated selected properties to the equation
   void add_constraint_from_goals(
-    std::function<bool(const irep_idt &property_id)> select_property);
+    std::function<bool(irep_idt property_id)> select_property);
 
   /// Calls solve() on the solver instance
   decision_proceduret::resultt solve();
diff --git a/src/goto-checker/goto_trace_provider.h b/src/goto-checker/goto_trace_provider.h
index e56902c3d3f..a42d553fbb0 100644
--- a/src/goto-checker/goto_trace_provider.h
+++ b/src/goto-checker/goto_trace_provider.h
@@ -32,7 +32,7 @@ class goto_trace_providert
 
   /// Builds and returns the trace for the FAILed property
   /// with the given \p property_id
-  virtual goto_tracet build_trace(const irep_idt &property_id) const = 0;
+  virtual goto_tracet build_trace(irep_idt property_id) const = 0;
 
   /// Returns the namespace associated with the traces
   virtual const namespacet &get_namespace() const = 0;
diff --git a/src/goto-checker/goto_trace_storage.cpp b/src/goto-checker/goto_trace_storage.cpp
index dfb8c572080..8f07eea2e82 100644
--- a/src/goto-checker/goto_trace_storage.cpp
+++ b/src/goto-checker/goto_trace_storage.cpp
@@ -56,8 +56,7 @@ const std::list<goto_tracet> &goto_trace_storaget::all() const
   return traces;
 }
 
-const goto_tracet &goto_trace_storaget::
-operator[](const irep_idt &property_id) const
+const goto_tracet &goto_trace_storaget::operator[](irep_idt property_id) const
 {
   const auto trace_found = property_id_to_trace_index.find(property_id);
   PRECONDITION(trace_found != property_id_to_trace_index.end());
diff --git a/src/goto-checker/goto_trace_storage.h b/src/goto-checker/goto_trace_storage.h
index 36c1596fdc3..0b1c9bc45f9 100644
--- a/src/goto-checker/goto_trace_storage.h
+++ b/src/goto-checker/goto_trace_storage.h
@@ -33,7 +33,7 @@ class goto_trace_storaget
   const goto_tracet &insert_all(goto_tracet &&);
 
   const std::list<goto_tracet> &all() const;
-  const goto_tracet &operator[](const irep_idt &property_id) const;
+  const goto_tracet &operator[](irep_idt property_id) const;
 
   const namespacet &get_namespace() const;
 
diff --git a/src/goto-checker/multi_path_symex_checker.cpp b/src/goto-checker/multi_path_symex_checker.cpp
index 40f60b6ed85..56532d72637 100644
--- a/src/goto-checker/multi_path_symex_checker.cpp
+++ b/src/goto-checker/multi_path_symex_checker.cpp
@@ -123,8 +123,7 @@ goto_tracet multi_path_symex_checkert::build_shortest_trace() const
   return goto_trace;
 }
 
-goto_tracet
-multi_path_symex_checkert::build_trace(const irep_idt &property_id) const
+goto_tracet multi_path_symex_checkert::build_trace(irep_idt property_id) const
 {
   goto_tracet goto_trace;
   build_goto_trace(
@@ -154,7 +153,7 @@ void multi_path_symex_checkert::output_error_witness(
 }
 
 fault_location_infot
-multi_path_symex_checkert::localize_fault(const irep_idt &property_id) const
+multi_path_symex_checkert::localize_fault(irep_idt property_id) const
 {
   goto_symex_fault_localizert fault_localizer(
     options,
diff --git a/src/goto-checker/multi_path_symex_checker.h b/src/goto-checker/multi_path_symex_checker.h
index b604681a32b..93f55f21c92 100644
--- a/src/goto-checker/multi_path_symex_checker.h
+++ b/src/goto-checker/multi_path_symex_checker.h
@@ -45,14 +45,13 @@ class multi_path_symex_checkert : public multi_path_symex_only_checkert,
 
   goto_tracet build_full_trace() const override;
   goto_tracet build_shortest_trace() const override;
-  goto_tracet build_trace(const irep_idt &) const override;
+  goto_tracet build_trace(irep_idt) const override;
   const namespacet &get_namespace() const override;
 
   void output_error_witness(const goto_tracet &) override;
   void output_proof() override;
 
-  fault_location_infot
-  localize_fault(const irep_idt &property_id) const override;
+  fault_location_infot localize_fault(irep_idt property_id) const override;
 
   void report() override;
 
diff --git a/src/goto-checker/properties.cpp b/src/goto-checker/properties.cpp
index 676b75efdae..871c040e2b2 100644
--- a/src/goto-checker/properties.cpp
+++ b/src/goto-checker/properties.cpp
@@ -100,14 +100,13 @@ void update_properties_from_goto_model(
   }
 }
 
-std::string
-as_string(const irep_idt &property_id, const property_infot &property_info)
+std::string as_string(irep_idt property_id, const property_infot &property_info)
 {
   return "[" + id2string(property_id) + "] " + property_info.description +
          ": " + as_string(property_info.status);
 }
 
-xmlt xml(const irep_idt &property_id, const property_infot &property_info)
+xmlt xml(irep_idt property_id, const property_infot &property_info)
 {
   xmlt xml_result("result");
   xml_result.set_attribute("property", id2string(property_id));
@@ -119,7 +118,7 @@ xmlt xml(const irep_idt &property_id, const property_infot &property_info)
 template <class json_objectT>
 static void json(
   json_objectT &result,
-  const irep_idt &property_id,
+  irep_idt property_id,
   const property_infot &property_info)
 {
   result["property"] = json_stringt(property_id);
@@ -128,8 +127,7 @@ static void json(
   result["sourceLocation"] = json(property_info.pc->source_location());
 }
 
-json_objectt
-json(const irep_idt &property_id, const property_infot &property_info)
+json_objectt json(irep_idt property_id, const property_infot &property_info)
 {
   json_objectt result;
   json<json_objectt>(result, property_id, property_info);
@@ -138,7 +136,7 @@ json(const irep_idt &property_id, const property_infot &property_info)
 
 void json(
   json_stream_objectt &result,
-  const irep_idt &property_id,
+  irep_idt property_id,
   const property_infot &property_info)
 {
   json<json_stream_objectt>(result, property_id, property_info);
diff --git a/src/goto-checker/properties.h b/src/goto-checker/properties.h
index 9a74b700fd3..c561e1da96c 100644
--- a/src/goto-checker/properties.h
+++ b/src/goto-checker/properties.h
@@ -84,15 +84,14 @@ void update_properties_from_goto_model(
   const abstract_goto_modelt &goto_model);
 
 std::string
-as_string(const irep_idt &property_id, const property_infot &property_info);
+as_string(irep_idt property_id, const property_infot &property_info);
 
-xmlt xml(const irep_idt &property_id, const property_infot &property_info);
+xmlt xml(irep_idt property_id, const property_infot &property_info);
 
-json_objectt
-json(const irep_idt &property_id, const property_infot &property_info);
+json_objectt json(irep_idt property_id, const property_infot &property_info);
 
 /// Write the property info into the given JSON stream object
-void json(json_stream_objectt &, const irep_idt &, const property_infot &);
+void json(json_stream_objectt &, irep_idt, const property_infot &);
 
 int result_to_exit_code(resultt result);
 
diff --git a/src/goto-checker/report_util.cpp b/src/goto-checker/report_util.cpp
index 1bf165f4ab8..4e37c2cacf3 100644
--- a/src/goto-checker/report_util.cpp
+++ b/src/goto-checker/report_util.cpp
@@ -142,7 +142,7 @@ void report_error(ui_message_handlert &ui_message_handler)
 }
 
 static void output_single_property_plain(
-  const irep_idt &property_id,
+  irep_idt property_id,
   const property_infot &property_info,
   messaget &log,
   irep_idt current_file = irep_idt())
@@ -206,7 +206,8 @@ is_property_less_than(const propertyt &property1, const propertyt &property2)
            std::stoul(id2string(p2.get_line()));
 
   const auto split_property_id =
-    [](const irep_idt &property_id) -> std::pair<std::string, std::size_t> {
+    [](irep_idt property_id) -> std::pair<std::string, std::size_t>
+  {
     const auto property_string = id2string(property_id);
     const auto last_dot = property_string.rfind('.');
     std::string property_name;
@@ -450,7 +451,7 @@ max_fault_localization_score(const fault_location_infot &fault_location)
 }
 
 static void output_fault_localization_plain(
-  const irep_idt &property_id,
+  irep_idt property_id,
   const fault_location_infot &fault_location,
   messaget &log)
 {
@@ -481,7 +482,7 @@ static void output_fault_localization_plain(
 }
 
 static xmlt xml(
-  const irep_idt &property_id,
+  irep_idt property_id,
   const fault_location_infot &fault_location,
   messaget &log)
 {
diff --git a/src/goto-checker/single_loop_incremental_symex_checker.cpp b/src/goto-checker/single_loop_incremental_symex_checker.cpp
index f264a728f58..7d843119a38 100644
--- a/src/goto-checker/single_loop_incremental_symex_checker.cpp
+++ b/src/goto-checker/single_loop_incremental_symex_checker.cpp
@@ -124,9 +124,8 @@ operator()(propertiest &properties)
       }
 
       property_decider.add_constraint_from_goals(
-        [&properties](const irep_idt &property_id) {
-          return is_property_to_check(properties.at(property_id).status);
-        });
+        [&properties](irep_idt property_id)
+        { return is_property_to_check(properties.at(property_id).status); });
 
       log.status()
         << "Running "
@@ -218,8 +217,8 @@ goto_tracet single_loop_incremental_symex_checkert::build_shortest_trace() const
   return goto_trace;
 }
 
-goto_tracet single_loop_incremental_symex_checkert::build_trace(
-  const irep_idt &property_id) const
+goto_tracet
+single_loop_incremental_symex_checkert::build_trace(irep_idt property_id) const
 {
   goto_tracet goto_trace;
   build_goto_trace(
diff --git a/src/goto-checker/single_loop_incremental_symex_checker.h b/src/goto-checker/single_loop_incremental_symex_checker.h
index e5fd98bde13..6b7c8f36246 100644
--- a/src/goto-checker/single_loop_incremental_symex_checker.h
+++ b/src/goto-checker/single_loop_incremental_symex_checker.h
@@ -45,7 +45,7 @@ class single_loop_incremental_symex_checkert : public incremental_goto_checkert,
   resultt operator()(propertiest &) override;
 
   goto_tracet build_full_trace() const override;
-  goto_tracet build_trace(const irep_idt &) const override;
+  goto_tracet build_trace(irep_idt) const override;
   goto_tracet build_shortest_trace() const override;
   const namespacet &get_namespace() const override;
 
diff --git a/src/goto-checker/single_path_symex_checker.cpp b/src/goto-checker/single_path_symex_checker.cpp
index 0e616252879..ae0ffde4994 100644
--- a/src/goto-checker/single_path_symex_checker.cpp
+++ b/src/goto-checker/single_path_symex_checker.cpp
@@ -158,8 +158,7 @@ goto_tracet single_path_symex_checkert::build_shortest_trace() const
   return goto_trace;
 }
 
-goto_tracet
-single_path_symex_checkert::build_trace(const irep_idt &property_id) const
+goto_tracet single_path_symex_checkert::build_trace(irep_idt property_id) const
 {
   goto_tracet goto_trace;
   build_goto_trace(
diff --git a/src/goto-checker/single_path_symex_checker.h b/src/goto-checker/single_path_symex_checker.h
index eca9ad0af80..b1048216346 100644
--- a/src/goto-checker/single_path_symex_checker.h
+++ b/src/goto-checker/single_path_symex_checker.h
@@ -33,7 +33,7 @@ class single_path_symex_checkert : public single_path_symex_only_checkert,
 
   goto_tracet build_full_trace() const override;
   goto_tracet build_shortest_trace() const override;
-  goto_tracet build_trace(const irep_idt &) const override;
+  goto_tracet build_trace(irep_idt) const override;
   const namespacet &get_namespace() const override;
 
   void output_error_witness(const goto_tracet &) override;
diff --git a/src/goto-checker/symex_bmc.cpp b/src/goto-checker/symex_bmc.cpp
index cd99776aea2..b068f470b2b 100644
--- a/src/goto-checker/symex_bmc.cpp
+++ b/src/goto-checker/symex_bmc.cpp
@@ -171,7 +171,7 @@ bool symex_bmct::should_stop_unwind(
 }
 
 bool symex_bmct::get_unwind_recursion(
-  const irep_idt &id,
+  irep_idt id,
   unsigned thread_nr,
   unsigned unwind)
 {
diff --git a/src/goto-checker/symex_bmc.h b/src/goto-checker/symex_bmc.h
index 81d15eed13f..840de213f7b 100644
--- a/src/goto-checker/symex_bmc.h
+++ b/src/goto-checker/symex_bmc.h
@@ -51,7 +51,7 @@ class symex_bmct : public goto_symext
   /// information for the user (e.g. "unwinding iteration N, max M"),
   /// and is not enforced. They return true to halt unwinding, false to
   /// authorise unwinding, or Unknown to indicate they have no opinion.
-  typedef std::function<tvt(const irep_idt &, unsigned, unsigned &)>
+  typedef std::function<tvt(irep_idt, unsigned, unsigned &)>
     recursion_unwind_handlert;
 
   /// Add a callback function that will be called to determine whether to unwind
@@ -105,7 +105,7 @@ class symex_bmct : public goto_symext
     unsigned unwind) override;
 
   bool get_unwind_recursion(
-    const irep_idt &identifier,
+    irep_idt identifier,
     unsigned thread_nr,
     unsigned unwind) override;
 
diff --git a/src/goto-checker/symex_bmc_incremental_one_loop.cpp b/src/goto-checker/symex_bmc_incremental_one_loop.cpp
index 0492797d6a6..9bef57049e1 100644
--- a/src/goto-checker/symex_bmc_incremental_one_loop.cpp
+++ b/src/goto-checker/symex_bmc_incremental_one_loop.cpp
@@ -112,7 +112,7 @@ bool symex_bmc_incremental_one_loopt::should_stop_unwind(
 /// \return True if the back edge encountered during symbolic execution
 ///   corresponds to the given loop (incr_loop_id)
 bool symex_bmc_incremental_one_loopt::check_break(
-  const irep_idt &loop_id,
+  irep_idt loop_id,
   unsigned unwind)
 {
   if(unwind < incr_min_unwind)
diff --git a/src/goto-checker/symex_bmc_incremental_one_loop.h b/src/goto-checker/symex_bmc_incremental_one_loop.h
index b5081081617..8b9cb4d8844 100644
--- a/src/goto-checker/symex_bmc_incremental_one_loop.h
+++ b/src/goto-checker/symex_bmc_incremental_one_loop.h
@@ -41,7 +41,7 @@ class symex_bmc_incremental_one_loopt : public symex_bmct
   std::unique_ptr<goto_symext::statet> state;
 
   // returns true if the symbolic execution is to be interrupted for checking
-  bool check_break(const irep_idt &loop_id, unsigned unwind) override;
+  bool check_break(irep_idt loop_id, unsigned unwind) override;
 
   bool should_stop_unwind(
     const symex_targett::sourcet &source,
diff --git a/src/goto-checker/symex_coverage.cpp b/src/goto-checker/symex_coverage.cpp
index 6e4edbe81d3..83f06b2e8ec 100644
--- a/src/goto-checker/symex_coverage.cpp
+++ b/src/goto-checker/symex_coverage.cpp
@@ -52,7 +52,7 @@ class goto_program_coverage_recordt : public coverage_recordt
 public:
   goto_program_coverage_recordt(
     const namespacet &ns,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     const symex_coveraget::coveraget &coverage);
 
@@ -131,7 +131,7 @@ rate_detailed(std::size_t covered, std::size_t total, bool per_cent = false)
 
 goto_program_coverage_recordt::goto_program_coverage_recordt(
   const namespacet &ns,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   const symex_coveraget::coveraget &coverage)
   : coverage_recordt("method")
diff --git a/src/goto-diff/change_impact.cpp b/src/goto-diff/change_impact.cpp
index 1a0d7c1ffb2..82aac6b572a 100644
--- a/src/goto-diff/change_impact.cpp
+++ b/src/goto-diff/change_impact.cpp
@@ -245,10 +245,10 @@ class change_impactt
 
   goto_functions_change_impactt old_change_impact, new_change_impact;
 
-  void change_impact(const irep_idt &function_id);
+  void change_impact(irep_idt function_id);
 
   void change_impact(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &old_goto_program,
     const goto_programt &new_goto_program,
     const unified_difft::goto_program_difft &diff,
@@ -256,25 +256,25 @@ class change_impactt
     goto_program_change_impactt &new_impact);
 
   void propogate_dep_back(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const dependence_grapht::nodet &d_node,
     const dependence_grapht &dep_graph,
     goto_functions_change_impactt &change_impact,
     bool del);
   void propogate_dep_forward(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const dependence_grapht::nodet &d_node,
     const dependence_grapht &dep_graph,
     goto_functions_change_impactt &change_impact,
     bool del);
 
   void output_change_impact(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_program_change_impactt &c_i,
     const goto_functionst &goto_functions,
     const namespacet &ns) const;
   void output_change_impact(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_program_change_impactt &o_c_i,
     const goto_functionst &o_goto_functions,
     const namespacet &o_ns,
@@ -316,7 +316,7 @@ change_impactt::change_impactt(
   new_dep_graph(new_goto_functions, ns_new);
 }
 
-void change_impactt::change_impact(const irep_idt &function_id)
+void change_impactt::change_impact(irep_idt function_id)
 {
   unified_difft::goto_program_difft diff = unified_diff.get_diff(function_id);
 
@@ -349,7 +349,7 @@ void change_impactt::change_impact(const irep_idt &function_id)
 }
 
 void change_impactt::change_impact(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &old_goto_program,
   const goto_programt &new_goto_program,
   const unified_difft::goto_program_difft &diff,
@@ -421,7 +421,7 @@ void change_impactt::change_impact(
 }
 
 void change_impactt::propogate_dep_forward(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const dependence_grapht::nodet &d_node,
   const dependence_grapht &dep_graph,
   goto_functions_change_impactt &change_impact,
@@ -454,7 +454,7 @@ void change_impactt::propogate_dep_forward(
 }
 
 void change_impactt::propogate_dep_back(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const dependence_grapht::nodet &d_node,
   const dependence_grapht &dep_graph,
   goto_functions_change_impactt &change_impact,
@@ -568,7 +568,7 @@ void change_impactt::operator()()
 }
 
 void change_impactt::output_change_impact(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_program_change_impactt &c_i,
   const goto_functionst &goto_functions,
   const namespacet &ns) const
@@ -613,7 +613,7 @@ void change_impactt::output_change_impact(
 }
 
 void change_impactt::output_change_impact(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_program_change_impactt &o_c_i,
   const goto_functionst &o_goto_functions,
   const namespacet &o_ns,
diff --git a/src/goto-diff/goto_diff.h b/src/goto-diff/goto_diff.h
index cce63bce7b8..4187ff74028 100644
--- a/src/goto-diff/goto_diff.h
+++ b/src/goto-diff/goto_diff.h
@@ -57,9 +57,8 @@ class goto_difft
     const std::string &group_name,
     const std::set<irep_idt> &function_group,
     const goto_modelt &goto_model) const;
-  void output_function(
-    const irep_idt &function_name,
-    const goto_modelt &goto_model) const;
+  void
+  output_function(irep_idt function_name, const goto_modelt &goto_model) const;
 
   void convert_function_group_json(
     json_arrayt &result,
@@ -67,7 +66,7 @@ class goto_difft
     const goto_modelt &goto_model) const;
   void convert_function_json(
     json_objectt &result,
-    const irep_idt &function_name,
+    irep_idt function_name,
     const goto_modelt &goto_model) const;
 };
 
diff --git a/src/goto-diff/goto_diff_base.cpp b/src/goto-diff/goto_diff_base.cpp
index 66872711d00..3d960e6e8b7 100644
--- a/src/goto-diff/goto_diff_base.cpp
+++ b/src/goto-diff/goto_diff_base.cpp
@@ -81,7 +81,7 @@ void goto_difft::output_function_group(
 /// \param function_name: the function id
 /// \param goto_model: the goto model
 void goto_difft::output_function(
-  const irep_idt &function_name,
+  irep_idt function_name,
   const goto_modelt &goto_model) const
 {
   messaget msg(message_handler);
@@ -135,7 +135,7 @@ void goto_difft::convert_function_group_json(
 /// \param goto_model: the goto model
 void goto_difft::convert_function_json(
   json_objectt &result,
-  const irep_idt &function_name,
+  irep_idt function_name,
   const goto_modelt &goto_model) const
 {
   namespacet ns(goto_model.symbol_table);
diff --git a/src/goto-diff/unified_diff.cpp b/src/goto-diff/unified_diff.cpp
index da1001f6a32..11f27aafbca 100644
--- a/src/goto-diff/unified_diff.cpp
+++ b/src/goto-diff/unified_diff.cpp
@@ -28,7 +28,7 @@ unified_difft::unified_difft(
 }
 
 unified_difft::goto_program_difft
-unified_difft::get_diff(const irep_idt &function) const
+unified_difft::get_diff(irep_idt function) const
 {
   differences_mapt::const_iterator entry = differences_map_.find(function);
   if(entry == differences_map_.end())
@@ -101,7 +101,7 @@ unified_difft::goto_program_difft unified_difft::get_diff(
 }
 
 void unified_difft::output_diff(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const goto_programt &old_goto_program,
   const goto_programt &new_goto_program,
   const differencest &differences,
@@ -303,7 +303,7 @@ unified_difft::differencest unified_difft::lcss(
 }
 
 void unified_difft::unified_diff(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const goto_programt &old_goto_program,
   const goto_programt &new_goto_program)
 {
diff --git a/src/goto-diff/unified_diff.h b/src/goto-diff/unified_diff.h
index 7c78ca91e1f..bb5007f2d56 100644
--- a/src/goto-diff/unified_diff.h
+++ b/src/goto-diff/unified_diff.h
@@ -45,7 +45,7 @@ class unified_difft
   typedef std::list<std::pair<goto_programt::const_targett, differencet>>
     goto_program_difft;
 
-  goto_program_difft get_diff(const irep_idt &function) const;
+  goto_program_difft get_diff(irep_idt function) const;
 
 private:
   const goto_functionst &old_goto_functions;
@@ -57,7 +57,7 @@ class unified_difft
   typedef std::map<irep_idt, differencest> differences_mapt;
 
   void unified_diff(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const goto_programt &old_goto_program,
     const goto_programt &new_goto_program);
 
@@ -71,7 +71,7 @@ class unified_difft
     const differencest &differences);
 
   void output_diff(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const goto_programt &old_goto_program,
     const goto_programt &new_goto_program,
     const differencest &differences,
diff --git a/src/goto-harness/function_call_harness_generator.cpp b/src/goto-harness/function_call_harness_generator.cpp
index 93810d52787..29bd2dcf2ca 100644
--- a/src/goto-harness/function_call_harness_generator.cpp
+++ b/src/goto-harness/function_call_harness_generator.cpp
@@ -61,7 +61,7 @@ struct function_call_harness_generatort::implt
   std::set<symbol_exprt> global_pointers;
 
   /// \see goto_harness_generatort::generate
-  void generate(goto_modelt &goto_model, const irep_idt &harness_function_name);
+  void generate(goto_modelt &goto_model, irep_idt harness_function_name);
   /// Iterate over the symbol table and generate initialisation code for
   /// globals into the function body.
   void generate_nondet_globals(code_blockt &function_body);
@@ -218,14 +218,14 @@ void function_call_harness_generatort::handle_option(
 
 void function_call_harness_generatort::generate(
   goto_modelt &goto_model,
-  const irep_idt &harness_function_name)
+  irep_idt harness_function_name)
 {
   p_impl->generate(goto_model, harness_function_name);
 }
 
 void function_call_harness_generatort::implt::generate(
   goto_modelt &goto_model,
-  const irep_idt &harness_function_name)
+  irep_idt harness_function_name)
 {
   symbol_table = &goto_model.symbol_table;
   goto_functions = &goto_model.goto_functions;
diff --git a/src/goto-harness/function_call_harness_generator.h b/src/goto-harness/function_call_harness_generator.h
index 5a3a3eef336..fab10e125f4 100644
--- a/src/goto-harness/function_call_harness_generator.h
+++ b/src/goto-harness/function_call_harness_generator.h
@@ -25,8 +25,8 @@ class function_call_harness_generatort : public goto_harness_generatort
   explicit function_call_harness_generatort(
     ui_message_handlert &message_handler);
   ~function_call_harness_generatort() override;
-  void generate(goto_modelt &goto_model, const irep_idt &harness_function_name)
-    override;
+  void
+  generate(goto_modelt &goto_model, irep_idt harness_function_name) override;
 
 protected:
   void handle_option(
diff --git a/src/goto-harness/goto_harness_generator.h b/src/goto-harness/goto_harness_generator.h
index 95bbfc2252e..fd76da0546c 100644
--- a/src/goto-harness/goto_harness_generator.h
+++ b/src/goto-harness/goto_harness_generator.h
@@ -43,7 +43,7 @@ class goto_harness_generatort
 public:
   /// Generate a harness according to the set options
   virtual void
-  generate(goto_modelt &goto_model, const irep_idt &harness_function_name) = 0;
+  generate(goto_modelt &goto_model, irep_idt harness_function_name) = 0;
 
   virtual ~goto_harness_generatort() = default;
   friend class goto_harness_generator_factoryt;
diff --git a/src/goto-harness/memory_snapshot_harness_generator.cpp b/src/goto-harness/memory_snapshot_harness_generator.cpp
index c91da54f11d..45d6b07a387 100644
--- a/src/goto-harness/memory_snapshot_harness_generator.cpp
+++ b/src/goto-harness/memory_snapshot_harness_generator.cpp
@@ -228,7 +228,7 @@ code_blockt memory_snapshot_harness_generatort::add_assignments_to_globals(
       {
         collect_references(
           snapshot_pair.second.value,
-          [&reference_relation, &snapshot_pair](const irep_idt &id) {
+          [&reference_relation, &snapshot_pair](irep_idt id) {
             reference_relation.insert(std::make_pair(snapshot_pair.first, id));
           });
         selected_snapshot_symbols.push_back(snapshot_pair);
@@ -368,7 +368,7 @@ void memory_snapshot_harness_generatort::get_memory_snapshot(
 
 void memory_snapshot_harness_generatort::generate(
   goto_modelt &goto_model,
-  const irep_idt &harness_function_name)
+  irep_idt harness_function_name)
 {
   symbol_tablet snapshot;
   get_memory_snapshot(memory_snapshot_file, snapshot);
diff --git a/src/goto-harness/memory_snapshot_harness_generator.h b/src/goto-harness/memory_snapshot_harness_generator.h
index 4e2f94e868b..17bebdf1982 100644
--- a/src/goto-harness/memory_snapshot_harness_generator.h
+++ b/src/goto-harness/memory_snapshot_harness_generator.h
@@ -44,8 +44,8 @@ class memory_snapshot_harness_generatort : public goto_harness_generatort
   /// 6. Insert harness function into \p goto_model.
   /// \param goto_model: goto model to be modified
   /// \param harness_function_name: name of the resulting harness function
-  void generate(goto_modelt &goto_model, const irep_idt &harness_function_name)
-    override;
+  void
+  generate(goto_modelt &goto_model, irep_idt harness_function_name) override;
 
 protected:
   /// User provided goto location: function name and (maybe) location number;
@@ -143,7 +143,7 @@ class memory_snapshot_harness_generatort : public goto_harness_generatort
 
     void match_up(
       const size_t &candidate_distance,
-      const irep_idt &candidate_function_name,
+      irep_idt candidate_function_name,
       const goto_programt::const_targett &candidate_instruction)
     {
       if(match_found && distance <= candidate_distance)
diff --git a/src/goto-harness/recursive_initialization.cpp b/src/goto-harness/recursive_initialization.cpp
index a2f566db749..5b52a3c7b22 100644
--- a/src/goto-harness/recursive_initialization.cpp
+++ b/src/goto-harness/recursive_initialization.cpp
@@ -373,14 +373,14 @@ irep_idt recursive_initializationt::build_constructor(const exprt &expr)
 }
 
 bool recursive_initializationt::should_be_treated_as_array(
-  const irep_idt &array_name) const
+  irep_idt array_name) const
 {
   return initialization_config.pointers_to_treat_as_arrays.find(array_name) !=
          initialization_config.pointers_to_treat_as_arrays.end();
 }
 
 std::optional<recursive_initializationt::equal_cluster_idt>
-recursive_initializationt::find_equal_cluster(const irep_idt &name) const
+recursive_initializationt::find_equal_cluster(irep_idt name) const
 {
   for(equal_cluster_idt index = 0;
       index != initialization_config.pointers_to_treat_equal.size();
@@ -393,7 +393,7 @@ recursive_initializationt::find_equal_cluster(const irep_idt &name) const
 }
 
 bool recursive_initializationt::is_array_size_parameter(
-  const irep_idt &cmdline_arg) const
+  irep_idt cmdline_arg) const
 {
   return initialization_config.variables_that_hold_array_sizes.find(
            cmdline_arg) !=
@@ -401,7 +401,7 @@ bool recursive_initializationt::is_array_size_parameter(
 }
 
 std::optional<irep_idt> recursive_initializationt::get_associated_size_variable(
-  const irep_idt &array_name) const
+  irep_idt array_name) const
 {
   return optional_lookup(
     initialization_config.array_name_to_associated_array_size_variable,
@@ -409,7 +409,7 @@ std::optional<irep_idt> recursive_initializationt::get_associated_size_variable(
 }
 
 bool recursive_initializationt::should_be_treated_as_cstring(
-  const irep_idt &pointer_name) const
+  irep_idt pointer_name) const
 {
   return initialization_config.pointers_to_treat_as_cstrings.count(
            pointer_name) != 0;
@@ -578,7 +578,7 @@ symbolt &recursive_initializationt::get_fresh_param_symbol(
 }
 
 symbol_exprt
-recursive_initializationt::get_symbol_expr(const irep_idt &symbol_name) const
+recursive_initializationt::get_symbol_expr(irep_idt symbol_name) const
 {
   auto maybe_symbol = goto_model.symbol_table.lookup(symbol_name);
   CHECK_RETURN(maybe_symbol != nullptr);
diff --git a/src/goto-harness/recursive_initialization.h b/src/goto-harness/recursive_initialization.h
index 2b13ce9981b..bf2fed2ca3e 100644
--- a/src/goto-harness/recursive_initialization.h
+++ b/src/goto-harness/recursive_initialization.h
@@ -120,13 +120,12 @@ class recursive_initializationt
   type_constructor_namest type_constructor_names;
   std::vector<std::optional<exprt>> common_arguments_origins;
 
-  bool should_be_treated_as_array(const irep_idt &pointer_name) const;
-  std::optional<equal_cluster_idt>
-  find_equal_cluster(const irep_idt &name) const;
-  bool is_array_size_parameter(const irep_idt &cmdline_arg) const;
+  bool should_be_treated_as_array(irep_idt pointer_name) const;
+  std::optional<equal_cluster_idt> find_equal_cluster(irep_idt name) const;
+  bool is_array_size_parameter(irep_idt cmdline_arg) const;
   std::optional<irep_idt>
-  get_associated_size_variable(const irep_idt &array_name) const;
-  bool should_be_treated_as_cstring(const irep_idt &pointer_name) const;
+  get_associated_size_variable(irep_idt array_name) const;
+  bool should_be_treated_as_cstring(irep_idt pointer_name) const;
 
   /// Construct a new global symbol of type `int` and set it's value to \p
   ///   initial_value.
@@ -174,7 +173,7 @@ class recursive_initializationt
   /// Recover the symbol expression from symbol table.
   /// \param symbol_name: the name of the symbol to get
   /// \return symbol expression of the symbol with given name
-  symbol_exprt get_symbol_expr(const irep_idt &symbol_name) const;
+  symbol_exprt get_symbol_expr(irep_idt symbol_name) const;
 
   /// Simple pretty-printer for \ref typet. Produces strings that can decorate
   ///   variable names in C.
diff --git a/src/goto-instrument/accelerate/scratch_program.cpp b/src/goto-instrument/accelerate/scratch_program.cpp
index daae044e9cd..ffa36875c9e 100644
--- a/src/goto-instrument/accelerate/scratch_program.cpp
+++ b/src/goto-instrument/accelerate/scratch_program.cpp
@@ -36,9 +36,9 @@ bool scratch_programt::check_sat(bool do_slice, guard_managert &guard_manager)
 
   goto_functiont this_goto_function;
   this_goto_function.body.copy_from(*this);
-  auto get_goto_function =
-    [this, &this_goto_function](
-      const irep_idt &key) -> const goto_functionst::goto_functiont & {
+  auto get_goto_function = [this, &this_goto_function](irep_idt key)
+    -> const goto_functionst::goto_functiont &
+  {
     if(key == goto_functionst::entry_point())
       return this_goto_function;
     else
diff --git a/src/goto-instrument/aggressive_slicer.cpp b/src/goto-instrument/aggressive_slicer.cpp
index 46f092774b4..917c066f164 100644
--- a/src/goto-instrument/aggressive_slicer.cpp
+++ b/src/goto-instrument/aggressive_slicer.cpp
@@ -22,8 +22,7 @@ Author: Elizabeth Polgreen, elizabeth.polgreen@cs.ox.ac.uk
 
 #include "remove_function.h"
 
-void aggressive_slicert::note_functions_to_keep(
-  const irep_idt &destination_function)
+void aggressive_slicert::note_functions_to_keep(irep_idt destination_function)
 {
   if(preserve_all_direct_paths)
   {
diff --git a/src/goto-instrument/aggressive_slicer.h b/src/goto-instrument/aggressive_slicer.h
index b5ebf25217d..948a1a24d19 100644
--- a/src/goto-instrument/aggressive_slicer.h
+++ b/src/goto-instrument/aggressive_slicer.h
@@ -85,7 +85,7 @@ class aggressive_slicert
   /// slicer, i.e., shortest path between two functions, or all direct paths.
   /// Inserts functions to preserve into the functions_to_keep set
   /// \param destination_function: name of destination function for slice
-  void note_functions_to_keep(const irep_idt &destination_function);
+  void note_functions_to_keep(irep_idt destination_function);
 
   /// \brief Finds all functions that contain a property,
   /// and adds them to the list of functions to keep. This
diff --git a/src/goto-instrument/branch.cpp b/src/goto-instrument/branch.cpp
index 50198aa74c1..afe75963275 100644
--- a/src/goto-instrument/branch.cpp
+++ b/src/goto-instrument/branch.cpp
@@ -18,9 +18,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include "function.h"
 
-void branch(
-  goto_modelt &goto_model,
-  const irep_idt &id)
+void branch(goto_modelt &goto_model, irep_idt id)
 {
   for(auto &gf_entry : goto_model.goto_functions.function_map)
   {
diff --git a/src/goto-instrument/branch.h b/src/goto-instrument/branch.h
index dd6f1d2d85d..2125631ab09 100644
--- a/src/goto-instrument/branch.h
+++ b/src/goto-instrument/branch.h
@@ -16,8 +16,6 @@ Author: Daniel Kroening, kroening@kroening.com
 
 class goto_modelt;
 
-void branch(
-  goto_modelt &,
-  const irep_idt &id);
+void branch(goto_modelt &, irep_idt id);
 
 #endif // CPROVER_GOTO_INSTRUMENT_BRANCH_H
diff --git a/src/goto-instrument/call_sequences.cpp b/src/goto-instrument/call_sequences.cpp
index 765ac523b5c..fada57fc686 100644
--- a/src/goto-instrument/call_sequences.cpp
+++ b/src/goto-instrument/call_sequences.cpp
@@ -24,9 +24,7 @@ Date: April 2013
 
 #include <linking/static_lifetime_init.h>
 
-void show_call_sequences(
-  const irep_idt &caller,
-  const goto_programt &goto_program)
+void show_call_sequences(irep_idt caller, const goto_programt &goto_program)
 {
   // show calls in  blocks within caller body
   // dfs on code blocks using stack
diff --git a/src/goto-instrument/contracts/cfg_info.h b/src/goto-instrument/contracts/cfg_info.h
index 3fd7db72ca7..1e8d166224a 100644
--- a/src/goto-instrument/contracts/cfg_info.h
+++ b/src/goto-instrument/contracts/cfg_info.h
@@ -40,11 +40,11 @@ class cfg_infot
 {
 public:
   /// Returns true iff `ident` is locally declared.
-  virtual bool is_local(const irep_idt &ident) const = 0;
+  virtual bool is_local(irep_idt ident) const = 0;
 
   /// Returns true iff the given `ident` is either non-locally declared
   /// or is locally-declared but dirty.
-  virtual bool is_not_local_or_dirty_local(const irep_idt &ident) const = 0;
+  virtual bool is_not_local_or_dirty_local(irep_idt ident) const = 0;
 
   /// Returns true iff `expr` is an access to a locally declared symbol
   /// and does not contain `dereference` or `address_of` operations.
@@ -119,7 +119,7 @@ class function_cfg_infot : public cfg_infot
   }
 
   /// Returns true iff `ident` is a local or parameter of the goto_function.
-  bool is_local(const irep_idt &ident) const override
+  bool is_local(irep_idt ident) const override
   {
     return locals.is_local(ident) ||
            (parameters.find(ident) != parameters.end());
@@ -127,7 +127,7 @@ class function_cfg_infot : public cfg_infot
 
   /// Returns true iff the given `ident` is either not a goto_function local
   /// or is a local that is dirty.
-  bool is_not_local_or_dirty_local(const irep_idt &ident) const override
+  bool is_not_local_or_dirty_local(irep_idt ident) const override
   {
     return is_local(ident) ? is_dirty(ident) : true;
   }
@@ -153,14 +153,14 @@ class loop_cfg_infot : public cfg_infot
   }
 
   /// Returns true iff `ident` is a loop local.
-  bool is_local(const irep_idt &ident) const override
+  bool is_local(irep_idt ident) const override
   {
     return locals.find(ident) != locals.end();
   }
 
   /// Returns true iff the given `ident` is either not a loop local
   /// or is a loop local that is dirty.
-  bool is_not_local_or_dirty_local(const irep_idt &ident) const override
+  bool is_not_local_or_dirty_local(irep_idt ident) const override
   {
     if(is_local(ident))
       return is_dirty(ident);
@@ -176,9 +176,10 @@ class loop_cfg_infot : public cfg_infot
       const std::unordered_set<irep_idt> symbols = find_symbol_identifiers(*it);
 
       if(
-        std::find_if(symbols.begin(), symbols.end(), [this](const irep_idt &s) {
-          return is_local(s);
-        }) != symbols.end())
+        std::find_if(
+          symbols.begin(),
+          symbols.end(),
+          [this](irep_idt s) { return is_local(s); }) != symbols.end())
       {
         it = exprs.erase(it);
       }
@@ -214,14 +215,14 @@ class goto_program_cfg_infot : public cfg_infot
   }
 
   /// Returns true iff `ident` is a loop local.
-  bool is_local(const irep_idt &ident) const override
+  bool is_local(irep_idt ident) const override
   {
     return locals.find(ident) != locals.end();
   }
 
   /// Returns true iff the given `ident` is either not a loop local
   /// or is a loop local that is dirty.
-  bool is_not_local_or_dirty_local(const irep_idt &ident) const override
+  bool is_not_local_or_dirty_local(irep_idt ident) const override
   {
     if(is_local(ident))
       return dirty.find(ident) != dirty.end();
diff --git a/src/goto-instrument/contracts/contracts.cpp b/src/goto-instrument/contracts/contracts.cpp
index 5d192c6cd78..3f126174e8f 100644
--- a/src/goto-instrument/contracts/contracts.cpp
+++ b/src/goto-instrument/contracts/contracts.cpp
@@ -38,7 +38,7 @@ Date: February 2016
 #include <map>
 
 void code_contractst::check_apply_loop_contracts(
-  const irep_idt &function_name,
+  irep_idt function_name,
   goto_functionst::goto_functiont &goto_function,
   const local_may_aliast &local_may_alias,
   goto_programt::targett loop_head,
@@ -47,7 +47,7 @@ void code_contractst::check_apply_loop_contracts(
   exprt assigns_clause,
   exprt invariant,
   exprt decreases_clause,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   const auto loop_head_location = loop_head->source_location();
   const auto loop_number = loop_end->loop_number;
@@ -553,7 +553,7 @@ static void generate_contract_constraints(
   symbol_tablet &symbol_table,
   goto_convertt &converter,
   exprt &instantiated_clause,
-  const irep_idt &mode,
+  irep_idt mode,
   const std::function<void(goto_programt &)> &is_fresh_update,
   goto_programt &program,
   const source_locationt &location)
@@ -577,7 +577,7 @@ static void generate_contract_constraints(
 }
 
 static const code_with_contract_typet &
-get_contract(const irep_idt &function, const namespacet &ns)
+get_contract(irep_idt function, const namespacet &ns)
 {
   const std::string &function_str = id2string(function);
   const auto &function_symbol = ns.lookup(function);
@@ -598,7 +598,7 @@ get_contract(const irep_idt &function, const namespacet &ns)
 }
 
 void code_contractst::apply_function_contract(
-  const irep_idt &function,
+  irep_idt function,
   const source_locationt &location,
   goto_programt &function_body,
   goto_programt::targett &target)
@@ -629,7 +629,7 @@ void code_contractst::apply_function_contract(
   }
 
   // Isolate each component of the contract.
-  const auto &type = get_contract(target_function, ns);
+  const auto type = get_contract(target_function, ns);
 
   // Prepare to instantiate expressions in the callee
   // with expressions from the call site (e.g. the return value).
@@ -839,7 +839,7 @@ void code_contractst::apply_function_contract(
 }
 
 void code_contractst::apply_loop_contract(
-  const irep_idt &function_name,
+  irep_idt function_name,
   goto_functionst::goto_functiont &goto_function)
 {
   const bool may_have_loops = std::any_of(
@@ -1121,7 +1121,7 @@ void code_contractst::apply_loop_contract(
   }
 }
 
-void code_contractst::check_frame_conditions_function(const irep_idt &function)
+void code_contractst::check_frame_conditions_function(irep_idt function)
 {
   // Get the function object before instrumentation.
   auto function_obj = goto_functions.function_map.find(function);
@@ -1186,7 +1186,8 @@ void code_contractst::check_frame_conditions_function(const irep_idt &function)
     instantiation_values.push_back(
       ns.lookup(param.get_identifier()).symbol_expr());
   }
-  for(auto &target : get_contract(function, ns).c_assigns())
+  const auto contract_type = get_contract(function, ns);
+  for(auto &target : contract_type.c_assigns())
   {
     goto_programt payload;
     instrument_spec_assigns.track_spec_target(
@@ -1212,7 +1213,7 @@ void code_contractst::check_frame_conditions_function(const irep_idt &function)
     function_body, instruction_it, function_body.instructions.end());
 }
 
-void code_contractst::enforce_contract(const irep_idt &function)
+void code_contractst::enforce_contract(irep_idt function)
 {
   // Add statements to the source function
   // to ensure assigns clause is respected.
@@ -1269,8 +1270,8 @@ void code_contractst::enforce_contract(const irep_idt &function)
 }
 
 void code_contractst::add_contract_check(
-  const irep_idt &wrapper_function,
-  const irep_idt &mangled_function,
+  irep_idt wrapper_function,
+  irep_idt mangled_function,
   goto_programt &dest)
 {
   PRECONDITION(!dest.instructions.empty());
@@ -1283,7 +1284,7 @@ void code_contractst::add_contract_check(
   // ret=function(parameter1, ...)
   // assert(ensures)
 
-  const auto &code_type = get_contract(wrapper_function, ns);
+  const auto code_type = get_contract(wrapper_function, ns);
   goto_programt check;
 
   // prepare function call including all declarations
diff --git a/src/goto-instrument/contracts/contracts.h b/src/goto-instrument/contracts/contracts.h
index 20cf3f049c3..4930c8ec035 100644
--- a/src/goto-instrument/contracts/contracts.h
+++ b/src/goto-instrument/contracts/contracts.h
@@ -124,7 +124,7 @@ class code_contractst
     const std::set<std::string> &to_exclude_from_nondet_init = {});
 
   void check_apply_loop_contracts(
-    const irep_idt &function_name,
+    irep_idt function_name,
     goto_functionst::goto_functiont &goto_function,
     const local_may_aliast &local_may_alias,
     goto_programt::targett loop_head,
@@ -133,7 +133,7 @@ class code_contractst
     exprt assigns_clause,
     exprt invariant,
     exprt decreases_clause,
-    const irep_idt &mode);
+    irep_idt mode);
 
   std::unordered_map<goto_programt::const_targett, unsigned, const_target_hash>
   get_original_loop_number_map() const
@@ -177,22 +177,22 @@ class code_contractst
 
 public:
   /// \brief Enforce contract of a single function
-  void enforce_contract(const irep_idt &function);
+  void enforce_contract(irep_idt function);
 
   /// Instrument functions to check frame conditions.
-  void check_frame_conditions_function(const irep_idt &function);
+  void check_frame_conditions_function(irep_idt function);
 
   /// Apply loop contracts, whenever available, to all loops in `function`.
   /// Loop invariants, loop variants, and loop assigns clauses.
   void apply_loop_contract(
-    const irep_idt &function,
+    irep_idt function,
     goto_functionst::goto_functiont &goto_function);
 
   /// Replaces function calls with assertions based on requires clauses,
   /// non-deterministic assignments for the write set, and assumptions
   /// based on ensures clauses.
   void apply_function_contract(
-    const irep_idt &function,
+    irep_idt function,
     const source_locationt &location,
     goto_programt &function_body,
     goto_programt::targett &target);
@@ -200,8 +200,8 @@ class code_contractst
   /// Instruments `wrapper_function` adding assumptions based on requires
   /// clauses and assertions based on ensures clauses.
   void add_contract_check(
-    const irep_idt &wrapper_function,
-    const irep_idt &mangled_function,
+    irep_idt wrapper_function,
+    irep_idt mangled_function,
     goto_programt &dest);
 };
 
diff --git a/src/goto-instrument/contracts/contracts_wrangler.cpp b/src/goto-instrument/contracts/contracts_wrangler.cpp
index e66d6f52421..72612f242b3 100644
--- a/src/goto-instrument/contracts/contracts_wrangler.cpp
+++ b/src/goto-instrument/contracts/contracts_wrangler.cpp
@@ -99,7 +99,7 @@ void contracts_wranglert::add_builtin_pointer_function_symbol(
 
 void contracts_wranglert::mangle(
   const loop_contracts_clauset &loop_contracts,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   messaget log(message_handler);
   // Loop contracts mangling consists of four steps.
diff --git a/src/goto-instrument/contracts/contracts_wrangler.h b/src/goto-instrument/contracts/contracts_wrangler.h
index 819754ea2e3..5ff6514466e 100644
--- a/src/goto-instrument/contracts/contracts_wrangler.h
+++ b/src/goto-instrument/contracts/contracts_wrangler.h
@@ -81,9 +81,8 @@ class contracts_wranglert
   /// @brief Mangle `loop_contracts` in the function with `function_id`
   /// @param loop_contracts The contracts mangled in the function.
   /// @param function_id The function containing the loop we mangle to.
-  void mangle(
-    const loop_contracts_clauset &loop_contracts,
-    const irep_idt &function_id);
+  void
+  mangle(const loop_contracts_clauset &loop_contracts, irep_idt function_id);
 
   /// @brief Add builtin function symbol with `function_name` into symbol table.
   /// @param function_name Name of the function to add.
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc.cpp
index 1403b04f403..bdd6e11df38 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc.cpp
@@ -51,7 +51,7 @@ std::string invalid_function_contract_pair_exceptiont::what() const
 }
 
 static std::pair<irep_idt, irep_idt>
-parse_function_contract_pair(const irep_idt &cli_flag)
+parse_function_contract_pair(irep_idt cli_flag)
 {
   auto const correct_format_message =
     "the format for function and contract pairs is "
@@ -93,7 +93,7 @@ parse_function_contract_pair(const irep_idt &cli_flag)
 void dfcc(
   const optionst &options,
   goto_modelt &goto_model,
-  const irep_idt &harness_id,
+  irep_idt harness_id,
   const std::optional<irep_idt> &to_check,
   const bool allow_recursive_calls,
   const std::set<irep_idt> &to_replace,
@@ -121,7 +121,7 @@ void dfcc(
 dfcct::dfcct(
   const optionst &options,
   goto_modelt &goto_model,
-  const irep_idt &harness_id,
+  irep_idt harness_id,
   const std::optional<std::pair<irep_idt, irep_idt>> &to_check,
   const bool allow_recursive_calls,
   const std::map<irep_idt, irep_idt> &to_replace,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc.h b/src/goto-instrument/contracts/dynamic-frames/dfcc.h
index b385f9e0233..e83fb26ad1d 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc.h
@@ -102,7 +102,7 @@ class invalid_function_contract_pair_exceptiont : public cprover_exception_baset
 void dfcc(
   const optionst &options,
   goto_modelt &goto_model,
-  const irep_idt &harness_id,
+  irep_idt harness_id,
   const std::optional<irep_idt> &to_check,
   const bool allow_recursive_calls,
   const std::set<irep_idt> &to_replace,
@@ -129,7 +129,7 @@ class dfcct
   dfcct(
     const optionst &options,
     goto_modelt &goto_model,
-    const irep_idt &harness_id,
+    irep_idt harness_id,
     const std::optional<std::pair<irep_idt, irep_idt>> &to_check,
     const bool allow_recursive_calls,
     const std::map<irep_idt, irep_idt> &to_replace,
@@ -166,7 +166,7 @@ class dfcct
 protected:
   const optionst &options;
   goto_modelt &goto_model;
-  const irep_idt &harness_id;
+  irep_idt harness_id;
   const std::optional<std::pair<irep_idt, irep_idt>> &to_check;
   const bool allow_recursive_calls;
   const std::map<irep_idt, irep_idt> &to_replace;
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.cpp
index af61dac31ed..be1ef609d2b 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.cpp
@@ -224,7 +224,7 @@ static void tag_loop_instructions(
   }
 }
 
-static bool is_assigned(dirtyt &dirty, const irep_idt &ident, assignst assigns)
+static bool is_assigned(dirtyt &dirty, irep_idt ident, assignst assigns)
 {
   PRECONDITION(!dirty(ident));
   // For each assigns clause target
@@ -307,7 +307,7 @@ struct contract_clausest
 static struct contract_clausest default_loop_contract_clauses(
   const dfcc_loop_nesting_grapht &loop_nesting_graph,
   const std::size_t loop_id,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const assignst &inferred_assigns,
   const bool check_side_effect,
   message_handlert &message_handler,
@@ -392,7 +392,7 @@ static struct contract_clausest default_loop_contract_clauses(
 static dfcc_loop_infot gen_dfcc_loop_info(
   const dfcc_loop_nesting_grapht &loop_nesting_graph,
   const std::size_t loop_id,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   const std::map<std::size_t, dfcc_loop_infot> &loop_info_map,
   dirtyt &dirty,
@@ -484,7 +484,7 @@ static dfcc_loop_infot gen_dfcc_loop_info(
 
 dfcc_cfg_infot::dfcc_cfg_infot(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   const exprt &top_level_write_set,
   const loop_contract_configt &loop_contract_config,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.h
index 59583869780..f4d0cbf133c 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_cfg_info.h
@@ -244,7 +244,7 @@ class dfcc_cfg_infot
 public:
   dfcc_cfg_infot(
     goto_modelt &goto_model,
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functiont &goto_function,
     const exprt &top_level_write_set,
     const loop_contract_configt &loop_contract_config,
@@ -315,7 +315,7 @@ class dfcc_cfg_infot
   }
 
 private:
-  const irep_idt &function_id;
+  irep_idt function_id;
   goto_functiont &goto_function;
   const exprt &top_level_write_set;
   const namespacet ns;
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.cpp
index 6c1d6d23fd0..348abdb8118 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.cpp
@@ -41,7 +41,7 @@ dfcc_contract_clauses_codegent::dfcc_contract_clauses_codegent(
 }
 
 void dfcc_contract_clauses_codegent::gen_spec_assigns_instructions(
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const exprt::operandst &assigns_clause,
   goto_programt &dest)
 {
@@ -69,7 +69,7 @@ void dfcc_contract_clauses_codegent::gen_spec_assigns_instructions(
 }
 
 void dfcc_contract_clauses_codegent::gen_spec_frees_instructions(
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const exprt::operandst &frees_clause,
   goto_programt &dest)
 {
@@ -96,7 +96,7 @@ void dfcc_contract_clauses_codegent::gen_spec_frees_instructions(
 }
 
 void dfcc_contract_clauses_codegent::encode_assignable_target_group(
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const conditional_target_group_exprt &group,
   goto_programt &dest)
 {
@@ -123,7 +123,7 @@ void dfcc_contract_clauses_codegent::encode_assignable_target_group(
 }
 
 void dfcc_contract_clauses_codegent::encode_assignable_target(
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const exprt &target,
   goto_programt &dest)
 {
@@ -185,7 +185,7 @@ void dfcc_contract_clauses_codegent::encode_assignable_target(
 }
 
 void dfcc_contract_clauses_codegent::encode_freeable_target_group(
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const conditional_target_group_exprt &group,
   goto_programt &dest)
 {
@@ -212,7 +212,7 @@ void dfcc_contract_clauses_codegent::encode_freeable_target_group(
 }
 
 void dfcc_contract_clauses_codegent::encode_freeable_target(
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const exprt &target,
   goto_programt &dest)
 {
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.h
index e3db30d054c..761a2bc4e11 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_clauses_codegen.h
@@ -47,7 +47,7 @@ class dfcc_contract_clauses_codegent
   /// \param assigns_clause Sequence of targets to encode
   /// \param dest Destination program
   void gen_spec_assigns_instructions(
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     const exprt::operandst &assigns_clause,
     goto_programt &dest);
 
@@ -62,7 +62,7 @@ class dfcc_contract_clauses_codegent
   /// \param frees_clause Sequence of targets to encode
   /// \param dest Destination program
   void gen_spec_frees_instructions(
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     const exprt::operandst &frees_clause,
     goto_programt &dest);
 
@@ -76,28 +76,28 @@ class dfcc_contract_clauses_codegent
   /// Generates GOTO instructions to build the representation of the given
   /// conditional target group.
   void encode_assignable_target_group(
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     const conditional_target_group_exprt &group,
     goto_programt &dest);
 
   /// Generates GOTO instructions to build the representation of the given
   /// assignable target.
   void encode_assignable_target(
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     const exprt &target,
     goto_programt &dest);
 
   /// Generates GOTO instructions to build the representation of the given
   /// conditional target group.
   void encode_freeable_target_group(
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     const conditional_target_group_exprt &group,
     goto_programt &dest);
 
   /// Generates GOTO instructions to build the representation of the given
   /// freeable target.
   void encode_freeable_target(
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     const exprt &target,
     goto_programt &dest);
 
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.cpp
index d57da7795a1..eb646bab56c 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.cpp
@@ -65,7 +65,7 @@ dfcc_contract_functionst::dfcc_contract_functionst(
 
 void dfcc_contract_functionst::
   instrument_without_loop_contracts_check_no_pointer_contracts(
-    const irep_idt &spec_function_id)
+    irep_idt spec_function_id)
 {
   std::set<irep_idt> function_pointer_contracts;
   instrument.instrument_function(
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.h
index f3702ddfc6d..0b01f688807 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_functions.h
@@ -74,7 +74,7 @@ class dfcc_contract_functionst
   /// Instruments the given function without loop contracts and checks that no
   /// function pointer contracts were discovered.
   void instrument_without_loop_contracts_check_no_pointer_contracts(
-    const irep_idt &spec_function_id);
+    irep_idt spec_function_id);
 
   /// Returns the contract::c_assigns function symbol
   const symbolt &get_spec_assigns_function_symbol() const;
@@ -107,7 +107,7 @@ class dfcc_contract_functionst
   const irep_idt spec_frees_function_id;
 
   /// Language mode of the contract symbol
-  const irep_idt &language_mode;
+  irep_idt language_mode;
 
 protected:
   goto_modelt &goto_model;
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.cpp
index d01a927f8a3..c407bfd9851 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.cpp
@@ -43,7 +43,7 @@ dfcc_contract_handlert::dfcc_contract_handlert(
 }
 
 const dfcc_contract_functionst &
-dfcc_contract_handlert::get_contract_functions(const irep_idt &contract_id)
+dfcc_contract_handlert::get_contract_functions(irep_idt contract_id)
 {
   auto iter = dfcc_contract_handlert::contract_cache.find(contract_id);
 
@@ -67,16 +67,16 @@ dfcc_contract_handlert::get_contract_functions(const irep_idt &contract_id)
 }
 
 const std::size_t
-dfcc_contract_handlert::get_assigns_clause_size(const irep_idt &contract_id)
+dfcc_contract_handlert::get_assigns_clause_size(irep_idt contract_id)
 {
   return get_contract_functions(contract_id).get_nof_assigns_targets();
 }
 
 void dfcc_contract_handlert::add_contract_instructions(
   const dfcc_contract_modet contract_mode,
-  const irep_idt &wrapper_id,
-  const irep_idt &wrapped_id,
-  const irep_idt &contract_id,
+  irep_idt wrapper_id,
+  irep_idt wrapped_id,
+  irep_idt contract_id,
   const symbolt &wrapper_write_set_symbol,
   goto_programt &dest,
   std::set<irep_idt> &function_pointer_contracts)
@@ -96,7 +96,7 @@ void dfcc_contract_handlert::add_contract_instructions(
 }
 
 const symbolt &dfcc_contract_handlert::get_pure_contract_symbol(
-  const irep_idt &contract_id,
+  irep_idt contract_id,
   const std::optional<irep_idt> function_id_opt)
 {
   auto pure_contract_id = "contract::" + id2string(contract_id);
@@ -106,7 +106,7 @@ const symbolt &dfcc_contract_handlert::get_pure_contract_symbol(
     if(function_id_opt.has_value())
     {
       auto function_id = function_id_opt.value();
-      const auto &function_symbol =
+      const symbolt function_symbol =
         dfcc_utilst::get_function_symbol(goto_model.symbol_table, function_id);
       check_signature_compat(
         function_id,
@@ -141,9 +141,9 @@ const symbolt &dfcc_contract_handlert::get_pure_contract_symbol(
 }
 
 void dfcc_contract_handlert::check_signature_compat(
-  const irep_idt &contract_id,
+  irep_idt contract_id,
   const code_typet &contract_type,
-  const irep_idt &pure_contract_id,
+  irep_idt pure_contract_id,
   const code_typet &pure_contract_type)
 {
   // can we turn a call to `contract` into a call to `pure_contract` ?
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.h
index 46b9e04b468..6b4d3d0662d 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_contract_handler.h
@@ -84,15 +84,15 @@ class dfcc_contract_handlert
   /// be swapped_and_wrapped in replacement mode if they are not already.
   void add_contract_instructions(
     const dfcc_contract_modet contract_mode,
-    const irep_idt &wrapper_id,
-    const irep_idt &wrapped_id,
-    const irep_idt &contract_id,
+    irep_idt wrapper_id,
+    irep_idt wrapped_id,
+    irep_idt contract_id,
     const symbolt &wrapper_write_set_symbol,
     goto_programt &dest,
     std::set<irep_idt> &function_pointer_contracts);
 
   /// Returns the size assigns clause of the given contract in number of targets
-  const std::size_t get_assigns_clause_size(const irep_idt &contract_id);
+  const std::size_t get_assigns_clause_size(irep_idt contract_id);
 
   /// Searches for a symbol named "contract::contract_id" in the symbol table.
   /// If the "contract::contract_id" is found and \p function_id_opt is present,
@@ -104,7 +104,7 @@ class dfcc_contract_handlert
   /// If the symbol was not found and \p function_id_opt was not provided, a
   /// PRECONDITION is triggered.
   const symbolt &get_pure_contract_symbol(
-    const irep_idt &contract_id,
+    irep_idt contract_id,
     const std::optional<irep_idt> function_id_opt = {});
 
 protected:
@@ -123,8 +123,7 @@ class dfcc_contract_handlert
 
   /// Returns the `dfcc_contract_functionst` object for the given contract
   /// from the cache, creates it if it does not exists.
-  const dfcc_contract_functionst &
-  get_contract_functions(const irep_idt &contract_id);
+  const dfcc_contract_functionst &get_contract_functions(irep_idt contract_id);
 
   /// \brief Throws an error if the type signatures are not compatible
   /// \param contract_id name of the function that carries the contract
@@ -132,9 +131,9 @@ class dfcc_contract_handlert
   /// \param pure_contract_id name of the pure contract symbol for contract_id
   /// \param pure_contract_type code_type of pure_contract_id
   void check_signature_compat(
-    const irep_idt &contract_id,
+    irep_idt contract_id,
     const code_typet &contract_type,
-    const irep_idt &pure_contract_id,
+    irep_idt pure_contract_id,
     const code_typet &pure_contract_type);
 };
 
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.cpp
index caf87eb62fa..d650e246d07 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.cpp
@@ -53,7 +53,7 @@ depends_on(const exprt &expr, std::unordered_set<irep_idt> identifiers)
 /// 2. there is no write or read of it outside the loop.
 /// 3. it is not used in loop contracts.
 std::unordered_set<irep_idt> gen_loop_locals_set(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   const dfcc_loop_nesting_graph_nodet &loop_node,
   message_handlert &message_handler,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.h
index 955213b8ef2..3891686bff3 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_infer_loop_assigns.h
@@ -20,7 +20,7 @@ struct dfcc_loop_nesting_graph_nodet;
 
 /// Collect identifiers that are local to `loop`.
 std::unordered_set<irep_idt> gen_loop_locals_set(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   const dfcc_loop_nesting_graph_nodet &loop,
   message_handlert &message_handler,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.cpp
index 1979cdc8a88..d2d6faf4cad 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.cpp
@@ -225,19 +225,19 @@ std::size_t dfcc_instrumentt::get_max_assigns_clause_size() const
 */
 
 /// True iff the symbol must not be instrumented
-bool dfcc_instrumentt::is_internal_symbol(const irep_idt &id) const
+bool dfcc_instrumentt::is_internal_symbol(irep_idt id) const
 {
   return internal_symbols.find(id) != internal_symbols.end();
 }
 
-bool dfcc_instrumentt::do_not_instrument(const irep_idt &id) const
+bool dfcc_instrumentt::do_not_instrument(irep_idt id) const
 {
   return !has_prefix(id2string(id), CPROVER_PREFIX "file_local") &&
          (dfcc_is_cprover_function_symbol(id) || is_internal_symbol(id));
 }
 
 void dfcc_instrumentt::instrument_harness_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const loop_contract_configt &loop_contract_config,
   std::set<irep_idt> &function_pointer_contracts)
 {
@@ -255,7 +255,7 @@ void dfcc_instrumentt::instrument_harness_function(
     to_pointer_type(library.dfcc_type[dfcc_typet::WRITE_SET_PTR]));
 
   // create a local write set symbol
-  const auto &function_symbol =
+  const symbolt function_symbol =
     dfcc_utilst::get_function_symbol(goto_model.symbol_table, function_id);
   const auto write_set = dfcc_utilst::create_symbol(
     goto_model.symbol_table,
@@ -296,8 +296,7 @@ void dfcc_instrumentt::instrument_harness_function(
   goto_model.goto_functions.update();
 }
 
-std::set<symbol_exprt>
-dfcc_instrumentt::get_local_statics(const irep_idt &function_id)
+std::set<symbol_exprt> dfcc_instrumentt::get_local_statics(irep_idt function_id)
 {
   std::set<symbol_exprt> local_statics;
   for(const auto &sym_pair : goto_model.symbol_table)
@@ -316,7 +315,7 @@ dfcc_instrumentt::get_local_statics(const irep_idt &function_id)
 }
 
 void dfcc_instrumentt::instrument_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const loop_contract_configt &loop_contract_config,
   std::set<irep_idt> &function_pointer_contracts)
 {
@@ -351,8 +350,8 @@ void dfcc_instrumentt::instrument_function(
 }
 
 void dfcc_instrumentt::instrument_wrapped_function(
-  const irep_idt &wrapped_function_id,
-  const irep_idt &initial_function_id,
+  irep_idt wrapped_function_id,
+  irep_idt initial_function_id,
   const loop_contract_configt &loop_contract_config,
   std::set<irep_idt> &function_pointer_contracts)
 {
@@ -389,7 +388,7 @@ void dfcc_instrumentt::instrument_wrapped_function(
 }
 
 void dfcc_instrumentt::instrument_goto_program(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const exprt &write_set,
   std::set<irep_idt> &function_pointer_contracts)
@@ -427,7 +426,7 @@ void dfcc_instrumentt::instrument_goto_program(
 }
 
 void dfcc_instrumentt::instrument_goto_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   const exprt &write_set,
   const std::set<symbol_exprt> &local_statics,
@@ -519,7 +518,7 @@ void dfcc_instrumentt::instrument_goto_function(
 }
 
 void dfcc_instrumentt::instrument_instructions(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett first_instruction,
   const goto_programt::targett &last_instruction,
@@ -587,7 +586,7 @@ void dfcc_instrumentt::instrument_instructions(
 }
 
 void dfcc_instrumentt::insert_add_decl_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const exprt &write_set,
   const symbol_exprt &symbol_expr,
   goto_programt::targett &target,
@@ -617,7 +616,7 @@ void dfcc_instrumentt::insert_add_decl_call(
 /// insert_add_decl_call(...);
 /// ```
 void dfcc_instrumentt::instrument_decl(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett &target,
   goto_programt &goto_program,
   dfcc_cfg_infot &cfg_info)
@@ -634,7 +633,7 @@ void dfcc_instrumentt::instrument_decl(
 }
 
 void dfcc_instrumentt::insert_record_dead_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const exprt &write_set,
   const symbol_exprt &symbol_expr,
   goto_programt::targett &target,
@@ -665,7 +664,7 @@ void dfcc_instrumentt::insert_record_dead_call(
 /// DEAD x;
 /// ```
 void dfcc_instrumentt::instrument_dead(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett &target,
   goto_programt &goto_program,
   dfcc_cfg_infot &cfg_info)
@@ -680,7 +679,7 @@ void dfcc_instrumentt::instrument_dead(
 }
 
 void dfcc_instrumentt::instrument_lhs(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett &target,
   const exprt &lhs,
   goto_programt &goto_program,
@@ -742,7 +741,7 @@ void dfcc_instrumentt::instrument_lhs(
 }
 
 void dfcc_instrumentt::instrument_assign(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett &target,
   goto_programt &goto_program,
   dfcc_cfg_infot &cfg_info)
@@ -868,7 +867,7 @@ void dfcc_instrumentt::instrument_call_instruction(
 }
 
 void dfcc_instrumentt::instrument_deallocate_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const exprt &write_set,
   goto_programt::targett &target,
   goto_programt &goto_program)
@@ -937,7 +936,7 @@ void dfcc_instrumentt::instrument_deallocate_call(
 }
 
 void dfcc_instrumentt::instrument_function_call(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett &target,
   goto_programt &goto_program,
   dfcc_cfg_infot &cfg_info)
@@ -971,7 +970,7 @@ void dfcc_instrumentt::instrument_function_call(
 }
 
 void dfcc_instrumentt::instrument_other(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett &target,
   goto_programt &goto_program,
   dfcc_cfg_infot &cfg_info)
@@ -1169,7 +1168,7 @@ void dfcc_instrumentt::instrument_other(
 }
 
 void dfcc_instrumentt::apply_loop_contracts(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   dfcc_cfg_infot &cfg_info,
   const loop_contract_configt &loop_contract_config,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.h
index 809542d1919..a218876ae9f 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument.h
@@ -51,11 +51,11 @@ class dfcc_instrumentt
     dfcc_contract_clauses_codegent &contract_clauses_codegen);
 
   /// True iff the symbol an internal symbol
-  bool is_internal_symbol(const irep_idt &id) const;
+  bool is_internal_symbol(irep_idt id) const;
 
   /// True iff the symbol must not be instrumented because it is an internal
   /// symbol or a CPROVER symbol
-  bool do_not_instrument(const irep_idt &id) const;
+  bool do_not_instrument(irep_idt id) const;
 
   /// Instruments a GOTO function used as a proof harness. Proof harnesses
   /// are closed functions without parameters, so we declare a local write set
@@ -80,7 +80,7 @@ class dfcc_instrumentt
   /// \param function_pointer_contracts Contract names discovered in calls to
   /// the `obeys_contract` predicate are added to this set.
   void instrument_harness_function(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const loop_contract_configt &loop_contract_config,
     std::set<irep_idt> &function_pointer_contracts);
 
@@ -101,7 +101,7 @@ class dfcc_instrumentt
   /// \param function_pointer_contracts Contracts discovered in calls to
   /// the obeys_contract predicate are added to this set.
   void instrument_function(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const loop_contract_configt &loop_contract_config,
     std::set<irep_idt> &function_pointer_contracts);
 
@@ -126,8 +126,8 @@ class dfcc_instrumentt
   /// \param function_pointer_contracts contracts discovered in calls to
   /// the obeys_contract predicate are added to this set.
   void instrument_wrapped_function(
-    const irep_idt &wrapped_function_id,
-    const irep_idt &initial_function_id,
+    irep_idt wrapped_function_id,
+    irep_idt initial_function_id,
     const loop_contract_configt &loop_contract_config,
     std::set<irep_idt> &function_pointer_contracts);
 
@@ -149,7 +149,7 @@ class dfcc_instrumentt
   /// \param write_set Write set variable to use for instrumentation.
   /// \param function_pointer_contracts Discovered function pointer contracts
   void instrument_goto_program(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     const exprt &write_set,
     std::set<irep_idt> &function_pointer_contracts);
@@ -185,7 +185,7 @@ class dfcc_instrumentt
   /// have the static flag set to true and have a source location where the
   /// function field is equal to the given \p function_id .
   /// \param[in] function_id Function name used to collect the statics.
-  std::set<symbol_exprt> get_local_statics(const irep_idt &function_id);
+  std::set<symbol_exprt> get_local_statics(irep_idt function_id);
 
   /// \brief Generates a guarded call to record a locally allocated symbol
   /// and inserts it in the goto_program at the target, and moves the target
@@ -201,7 +201,7 @@ class dfcc_instrumentt
   /// \param target The instruction pointer to insert at
   /// \param goto_program the goto_program being instrumented
   void insert_add_decl_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const exprt &write_set,
     const symbol_exprt &symbol_expr,
     goto_programt::targett &target,
@@ -221,7 +221,7 @@ class dfcc_instrumentt
   /// \param target The instruction pointer to insert at
   /// \param goto_program the goto_program being instrumented
   void insert_record_dead_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const exprt &write_set,
     const symbol_exprt &symbol_expr,
     goto_programt::targett &target,
@@ -231,7 +231,7 @@ class dfcc_instrumentt
   /// Adds the given local statics to the write set in pre and removes them
   /// post.
   void instrument_goto_function(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functiont &goto_function,
     const exprt &write_set,
     const std::set<symbol_exprt> &local_statics,
@@ -251,7 +251,7 @@ class dfcc_instrumentt
   /// \param function_pointer_contracts Contracts discovered in calls to
   /// the obeys_contract predicate are added to this set.
   void instrument_instructions(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     goto_programt::targett first_instruction,
     const goto_programt::targett &last_instruction, // excluding the last
@@ -261,7 +261,7 @@ class dfcc_instrumentt
   /// Instruments a `DECL x` instruction.
   /// \pre \p target points to a `DECL` instruction
   void instrument_decl(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett &target,
     goto_programt &goto_program,
     dfcc_cfg_infot &cfg_info);
@@ -269,7 +269,7 @@ class dfcc_instrumentt
   /// Instruments a `DEAD x` instruction.
   /// \pre \p target points to a `DEAD` instruction
   void instrument_dead(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett &target,
     goto_programt &goto_program,
     dfcc_cfg_infot &cfg_info);
@@ -277,7 +277,7 @@ class dfcc_instrumentt
   /// \brief Instruments the LHS of an assignment instruction instruction by
   /// adding an inclusion check of \p lhs in \p write_set.
   void instrument_lhs(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett &target,
     const exprt &lhs,
     goto_programt &goto_program,
@@ -289,7 +289,7 @@ class dfcc_instrumentt
   /// added to the \p write_set.
   /// \pre \p target points to an `ASSIGN` instruction.
   void instrument_assign(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett &target,
     goto_programt &goto_program,
     dfcc_cfg_infot &cfg_info);
@@ -319,7 +319,7 @@ class dfcc_instrumentt
   /// to the __CPROVER_deallocate function.
   /// \pre \p target points to a `CALL __CPROVER_deallocate` instruction.
   void instrument_deallocate_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const exprt &write_set,
     goto_programt::targett &target,
     goto_programt &goto_program);
@@ -329,7 +329,7 @@ class dfcc_instrumentt
   /// and passing `write_set` as an extra argument to the function call.
   /// \pre \p target points to a `CALL` instruction.
   void instrument_function_call(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett &target,
     goto_programt &goto_program,
     dfcc_cfg_infot &cfg_info);
@@ -339,7 +339,7 @@ class dfcc_instrumentt
   /// a havoc_object instruction.
   /// \pre \p target points to an `OTHER` instruction.
   void instrument_other(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett &target,
     goto_programt &goto_program,
     dfcc_cfg_infot &cfg_info);
@@ -350,7 +350,7 @@ class dfcc_instrumentt
   /// \pre Instructions of the function must already have been instrumented for
   /// DFCC using the same cfg_info.
   void apply_loop_contracts(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functiont &goto_function,
     dfcc_cfg_infot &cfg_info,
     const loop_contract_configt &loop_contract_config,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.cpp
index 314890a5ca0..9bf92ab760b 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.cpp
@@ -43,7 +43,7 @@ dfcc_instrument_loopt::dfcc_instrument_loopt(
 
 void dfcc_instrument_loopt::operator()(
   const std::size_t loop_id,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functiont &goto_function,
   dfcc_cfg_infot &cfg_info,
   const std::set<symbol_exprt> &local_statics,
@@ -207,7 +207,7 @@ void dfcc_instrument_loopt::operator()(
 std::unordered_map<exprt, symbol_exprt, irep_hash>
 dfcc_instrument_loopt::add_prehead_instructions(
   const std::size_t loop_id,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functionst::goto_functiont &goto_function,
   symbol_table_baset &symbol_table,
   goto_programt::targett loop_head,
@@ -220,7 +220,7 @@ dfcc_instrument_loopt::add_prehead_instructions(
   const symbol_exprt &entered_loop,
   const symbol_exprt &initial_invariant,
   const symbol_exprt &in_base_case,
-  const irep_idt &language_mode)
+  irep_idt language_mode)
 {
   auto loop_head_location(loop_head->source_location());
   dfcc_remove_loop_tags(loop_head_location);
@@ -324,7 +324,7 @@ goto_programt::instructiont::targett
 dfcc_instrument_loopt::add_step_instructions(
   const std::size_t loop_id,
   const std::size_t cbmc_loop_id,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functionst::goto_functiont &goto_function,
   symbol_table_baset &symbol_table,
   goto_programt::targett loop_head,
@@ -473,7 +473,7 @@ dfcc_instrument_loopt::add_step_instructions(
 void dfcc_instrument_loopt::add_body_instructions(
   const std::size_t loop_id,
   const std::size_t cbmc_loop_id,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functionst::goto_functiont &goto_function,
   symbol_table_baset &symbol_table,
   goto_programt::targett loop_head,
@@ -485,7 +485,7 @@ void dfcc_instrument_loopt::add_body_instructions(
   const std::vector<symbol_exprt> &old_decreases_vars,
   const std::vector<symbol_exprt> &new_decreases_vars,
   const goto_programt::instructiont::targett &step_case_target,
-  const irep_idt &language_mode)
+  irep_idt language_mode)
 {
   auto loop_head_location(loop_head->source_location());
   dfcc_remove_loop_tags(loop_head_location);
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.h
index 0db2bb5889c..750b4c68271 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_instrument_loop.h
@@ -131,7 +131,7 @@ class dfcc_instrument_loopt
   ///
   void operator()(
     const std::size_t loop_id,
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functiont &goto_function,
     dfcc_cfg_infot &cfg_info,
     const std::set<symbol_exprt> &local_statics,
@@ -196,7 +196,7 @@ class dfcc_instrument_loopt
   /// \return `history_var_map` that maps variables to loop_entry variables.
   std::unordered_map<exprt, symbol_exprt, irep_hash> add_prehead_instructions(
     const std::size_t loop_id,
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functionst::goto_functiont &goto_function,
     symbol_table_baset &symbol_table,
     goto_programt::targett loop_head,
@@ -209,7 +209,7 @@ class dfcc_instrument_loopt
     const symbol_exprt &entered_loop,
     const symbol_exprt &initial_invariant,
     const symbol_exprt &in_base_case,
-    const irep_idt &symbol_mode);
+    irep_idt symbol_mode);
 
   /// \brief Adds instructions of the step block, and returns the STEP
   /// jump target so that it can be used to jump back from the loop body block.
@@ -246,7 +246,7 @@ class dfcc_instrument_loopt
   goto_programt::instructiont::targett add_step_instructions(
     const std::size_t loop_id,
     const std::size_t cbmc_loop_id,
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functionst::goto_functiont &goto_function,
     symbol_table_baset &symbol_table,
     goto_programt::targett loop_head,
@@ -295,7 +295,7 @@ class dfcc_instrument_loopt
   void add_body_instructions(
     const std::size_t loop_id,
     const std::size_t cbmc_loop_id,
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functionst::goto_functiont &goto_function,
     symbol_table_baset &symbol_table,
     goto_programt::targett loop_head,
@@ -307,7 +307,7 @@ class dfcc_instrument_loopt
     const std::vector<symbol_exprt> &old_decreases_vars,
     const std::vector<symbol_exprt> &new_decreases_vars,
     const goto_programt::instructiont::targett &step_case_target,
-    const irep_idt &symbol_mode);
+    irep_idt symbol_mode);
 
   /// \brief Adds instructions of the exit block.
   ///
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.cpp
index 321a6bdbadb..25320d89169 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.cpp
@@ -138,7 +138,7 @@ static void init_static_symbols(std::unordered_set<irep_idt> &static_symbols)
   }
 }
 
-bool dfcc_is_cprover_function_symbol(const irep_idt &id)
+bool dfcc_is_cprover_function_symbol(irep_idt id)
 {
   std::unordered_set<irep_idt> function_symbols;
   init_function_symbols(function_symbols);
@@ -148,7 +148,7 @@ bool dfcc_is_cprover_function_symbol(const irep_idt &id)
          has_prefix(str, "__VERIFIER") || has_prefix(str, "nondet");
 }
 
-bool dfcc_is_cprover_static_symbol(const irep_idt &id)
+bool dfcc_is_cprover_static_symbol(irep_idt id)
 {
   std::unordered_set<irep_idt> static_symbols;
   init_static_symbols(static_symbols);
@@ -159,7 +159,7 @@ bool dfcc_is_cprover_static_symbol(const irep_idt &id)
          has_prefix(id2string(id), CPROVER_PREFIX "going_to");
 }
 
-bool dfcc_is_cprover_pointer_predicate(const irep_idt &id)
+bool dfcc_is_cprover_pointer_predicate(irep_idt id)
 {
   return id == CPROVER_PREFIX "pointer_equals" ||
          id == CPROVER_PREFIX "is_fresh" ||
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.h
index e6848cecf4a..17add9361f0 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_is_cprover_symbol.h
@@ -17,14 +17,14 @@ Date: March 2023
 
 /// Returns `true` iff id is one of the known CPROVER functions or starts with
 /// `__VERIFIER` or `nondet`.
-bool dfcc_is_cprover_function_symbol(const irep_idt &id);
+bool dfcc_is_cprover_function_symbol(irep_idt id);
 
 /// Returns `true` iff the symbol is one of the known CPROVER static
 /// instrumentation variables or ends with `$object` and represents an
 /// auto-generated object following a pointer dereference.
-bool dfcc_is_cprover_static_symbol(const irep_idt &id);
+bool dfcc_is_cprover_static_symbol(irep_idt id);
 
 /// Returns `true` iff the symbol is one of the CPROVER pointer predicates
-bool dfcc_is_cprover_pointer_predicate(const irep_idt &id);
+bool dfcc_is_cprover_pointer_predicate(irep_idt id);
 
 #endif
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_library.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_library.cpp
index ed6389310a4..e7027b1cb1f 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_library.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_library.cpp
@@ -195,13 +195,13 @@ dfcc_libraryt::dfcc_libraryt(
 }
 
 /// Returns the instrumentation function to use for a given front-end function
-bool dfcc_libraryt::is_front_end_builtin(const irep_idt &function_id) const
+bool dfcc_libraryt::is_front_end_builtin(irep_idt function_id) const
 {
   return dfcc_hook.find(function_id) != dfcc_hook.end();
 }
 
 /// Returns the instrumentation function to use for a given front-end function
-dfcc_funt dfcc_libraryt::get_hook(const irep_idt &function_id) const
+dfcc_funt dfcc_libraryt::get_hook(irep_idt function_id) const
 {
   PRECONDITION(is_front_end_builtin(function_id));
   return dfcc_hook.find(function_id)->second;
@@ -209,7 +209,7 @@ dfcc_funt dfcc_libraryt::get_hook(const irep_idt &function_id) const
 
 // Returns the havoc function to use for a given front-end function
 std::optional<dfcc_funt>
-dfcc_libraryt::get_havoc_hook(const irep_idt &function_id) const
+dfcc_libraryt::get_havoc_hook(irep_idt function_id) const
 {
   auto found = havoc_hook.find(function_id);
   if(found != havoc_hook.end())
@@ -368,7 +368,7 @@ void dfcc_libraryt::load(std::set<irep_idt> &to_instrument)
     goto_model.goto_functions.function_map.at(it.second.name).make_hidden();
 }
 
-std::optional<dfcc_funt> dfcc_libraryt::get_dfcc_fun(const irep_idt &id) const
+std::optional<dfcc_funt> dfcc_libraryt::get_dfcc_fun(irep_idt id) const
 {
   auto found = dfcc_name_to_fun.find(id);
   if(found != dfcc_name_to_fun.end())
@@ -377,7 +377,7 @@ std::optional<dfcc_funt> dfcc_libraryt::get_dfcc_fun(const irep_idt &id) const
     return {};
 }
 
-bool dfcc_libraryt::is_dfcc_library_symbol(const irep_idt &id) const
+bool dfcc_libraryt::is_dfcc_library_symbol(irep_idt id) const
 {
   return get_dfcc_fun(id).has_value();
 }
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_library.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_library.h
index a103da404a5..19e9ee65d26 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_library.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_library.h
@@ -229,13 +229,13 @@ class dfcc_libraryt
   void load(std::set<irep_idt> &to_instrument);
 
   /// Returns the dfcc_funt that corresponds to the given id if any.
-  std::optional<dfcc_funt> get_dfcc_fun(const irep_idt &id) const;
+  std::optional<dfcc_funt> get_dfcc_fun(irep_idt id) const;
 
   /// Returns the name of the given dfcc_funt.
   const irep_idt &get_dfcc_fun_name(dfcc_funt fun) const;
 
   /// True iff the given id is one of the library symbols.
-  bool is_dfcc_library_symbol(const irep_idt &id) const;
+  bool is_dfcc_library_symbol(irep_idt id) const;
 
   /// Specializes the library by unwinding loops in library functions
   /// to the given assigns clause size.
@@ -260,17 +260,17 @@ class dfcc_libraryt
   /// Returns true iff the given function_id is one of `__CPROVER_assignable`,
   /// `__CPROVER_object_whole`, `__CPROVER_object_from`,
   /// `__CPROVER_object_upto`, `__CPROVER_freeable`
-  bool is_front_end_builtin(const irep_idt &function_id) const;
+  bool is_front_end_builtin(irep_idt function_id) const;
 
   /// Returns the library instrumentation hook for the given front-end function.
   /// \pre  \p function_id is a front end built-in as defined by
   /// \ref is_front_end_builtin.
-  dfcc_funt get_hook(const irep_idt &function_id) const;
+  dfcc_funt get_hook(irep_idt function_id) const;
 
   /// Returns the library instrumentation hook for the given built-in.
   /// function_id must be one of `__CPROVER_assignable`,
   /// `__CPROVER_object_whole`, `__CPROVER_object_from`, `__CPROVER_object_upto`
-  std::optional<dfcc_funt> get_havoc_hook(const irep_idt &function_id) const;
+  std::optional<dfcc_funt> get_havoc_hook(irep_idt function_id) const;
 
   /// \brief Returns the "__dfcc_instrumented_functions" symbol or creates it if
   /// it does not exist already.
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.cpp
index 3e4dab5c637..d40f5951de9 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.cpp
@@ -39,14 +39,13 @@ dfcc_lift_memory_predicatest::dfcc_lift_memory_predicatest(
 }
 
 /// True if a function had at least one of its parameters lifted
-bool dfcc_lift_memory_predicatest::is_lifted_function(
-  const irep_idt &function_id)
+bool dfcc_lift_memory_predicatest::is_lifted_function(irep_idt function_id)
 {
   return lifted_parameters.find(function_id) != lifted_parameters.end();
 }
 
 /// True iff function_id is a core memory predicate
-static bool is_core_memory_predicate(const irep_idt &function_id)
+static bool is_core_memory_predicate(irep_idt function_id)
 {
   return (function_id == CPROVER_PREFIX "pointer_equals") ||
          (function_id == CPROVER_PREFIX "is_fresh") ||
@@ -125,9 +124,8 @@ std::set<irep_idt> dfcc_lift_memory_predicatest::lift_predicates(
   // some predicates were found, build dependency graph
   struct dep_graph_nodet : public graph_nodet<empty_edget>
   {
-    const irep_idt &function_id;
-    explicit dep_graph_nodet(const irep_idt &function_id)
-      : function_id(function_id)
+    irep_idt function_id;
+    explicit dep_graph_nodet(irep_idt function_id) : function_id(function_id)
     {
     }
   };
@@ -215,9 +213,9 @@ static std::optional<std::size_t> is_param_expr(
 }
 
 void dfcc_lift_memory_predicatest::collect_parameters_to_lift(
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
-  const symbolt &function_symbol =
+  const symbolt function_symbol =
     dfcc_utilst::get_function_symbol(goto_model.symbol_table, function_id);
   // map of parameter name to its rank in the signature
   std::map<irep_idt, std::size_t> parameter_rank;
@@ -287,7 +285,7 @@ void dfcc_lift_memory_predicatest::collect_parameters_to_lift(
 }
 
 void dfcc_lift_memory_predicatest::add_pointer_type(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::size_t parameter_rank,
   replace_symbolt &replace_lifted_param)
 {
@@ -328,7 +326,7 @@ void dfcc_lift_memory_predicatest::add_pointer_type(
 }
 
 void dfcc_lift_memory_predicatest::lift_parameters_and_update_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   std::set<irep_idt> &discovered_function_pointer_contracts)
 {
   replace_symbolt replace_lifted_params;
@@ -373,7 +371,7 @@ void dfcc_lift_memory_predicatest::lift_parameters_and_update_body(
 }
 
 void dfcc_lift_memory_predicatest::lift_predicate(
-  const irep_idt &function_id,
+  irep_idt function_id,
   std::set<irep_idt> &discovered_function_pointer_contracts)
 {
   // when this function_id gets processed, any memory predicate it calls has
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.h
index 848d5aaf600..120678bfb97 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_lift_memory_predicates.h
@@ -79,11 +79,11 @@ class dfcc_lift_memory_predicatest
     const std::set<irep_idt> &predicates);
 
   void lift_predicate(
-    const irep_idt &function_id,
+    irep_idt function_id,
     std::set<irep_idt> &discovered_function_pointer_contracts);
 
   void lift_parameters_and_update_body(
-    const irep_idt &function_id,
+    irep_idt function_id,
     std::set<irep_idt> &discovered_function_pointer_contracts);
 
   /// \brief adds a pointer_type to the parameter of a function
@@ -93,16 +93,16 @@ class dfcc_lift_memory_predicatest
   /// The parameter symbol gets updated in the symbol table and the function
   /// signature gets updated with the new type.
   void add_pointer_type(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const std::size_t parameter_rank,
     replace_symbolt &replace_lifted_param);
 
   /// \brief Computes the subset of function parameters of function_id
   /// that are passed directly to core predicates and must be lifted.
-  void collect_parameters_to_lift(const irep_idt &function_id);
+  void collect_parameters_to_lift(irep_idt function_id);
 
   /// \brief True if a function at least had one of its parameters lifted
-  bool is_lifted_function(const irep_idt &function_id);
+  bool is_lifted_function(irep_idt function_id);
 };
 
 #endif
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_loop_tags.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_loop_tags.cpp
index 6f1be29ad7d..32fd2571655 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_loop_tags.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_loop_tags.cpp
@@ -40,16 +40,15 @@ bool dfcc_has_loop_id(
   return loop_id_opt.has_value() && loop_id_opt.value() == loop_id;
 }
 
-static void dfcc_set_loop_tag(
-  goto_programt::instructiont::targett &target,
-  const irep_idt &tag)
+static void
+dfcc_set_loop_tag(goto_programt::instructiont::targett &target, irep_idt tag)
 {
   target->source_location_nonconst().set(tag, true);
 }
 
 static bool has_loop_tag(
   const goto_programt::instructiont::const_targett &target,
-  const irep_idt &tag)
+  irep_idt tag)
 {
   return target->source_location().get_bool(tag);
 }
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.cpp
index 48a55bbc323..08bd175cdc1 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.cpp
@@ -42,8 +42,8 @@ const typet &dfcc_spec_functionst::get_target_type(const exprt &expr)
 }
 
 void dfcc_spec_functionst::generate_havoc_function(
-  const irep_idt &function_id,
-  const irep_idt &havoc_function_id,
+  irep_idt function_id,
+  irep_idt havoc_function_id,
   std::size_t &nof_targets)
 {
   INVARIANT(
@@ -51,7 +51,7 @@ void dfcc_spec_functionst::generate_havoc_function(
     "DFCC: havoc function id '" + id2string(havoc_function_id) +
       "' already exists");
 
-  const auto &function_symbol =
+  const symbolt function_symbol =
     dfcc_utilst::get_function_symbol(goto_model.symbol_table, function_id);
 
   // create the code type that goes on the function symbol
@@ -143,7 +143,7 @@ void dfcc_spec_functionst::generate_havoc_function(
 }
 
 void dfcc_spec_functionst::generate_havoc_instructions(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &original_program,
   const exprt &write_set_to_havoc,
   dfcc_ptr_havoc_modet ptr_havoc_mode,
@@ -277,7 +277,7 @@ void dfcc_spec_functionst::generate_havoc_instructions(
 }
 
 void dfcc_spec_functionst::to_spec_assigns_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   std::size_t &nof_targets)
 {
   auto &goto_function = goto_model.goto_functions.function_map.at(function_id);
@@ -304,7 +304,7 @@ void dfcc_spec_functionst::to_spec_assigns_function(
 
 void dfcc_spec_functionst::to_spec_assigns_instructions(
   const exprt &write_set_to_fill,
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   goto_programt &program,
   std::size_t &nof_targets)
 {
@@ -360,7 +360,7 @@ void dfcc_spec_functionst::to_spec_assigns_instructions(
 }
 
 void dfcc_spec_functionst::to_spec_frees_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   std::size_t &nof_targets)
 {
   auto &goto_function = goto_model.goto_functions.function_map.at(function_id);
@@ -387,7 +387,7 @@ void dfcc_spec_functionst::to_spec_frees_function(
 
 void dfcc_spec_functionst::to_spec_frees_instructions(
   const exprt &write_set_to_fill,
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   goto_programt &program,
   std::size_t &nof_targets)
 {
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.h
index 2f64f551275..c37a1bfd202 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_spec_functions.h
@@ -74,8 +74,8 @@ class dfcc_spec_functionst
   /// \param[in] havoc_function_id write set variable to havoc
   /// \param[out] nof_targets maximum number of targets to havoc
   void generate_havoc_function(
-    const irep_idt &function_id,
-    const irep_idt &havoc_function_id,
+    irep_idt function_id,
+    irep_idt havoc_function_id,
     std::size_t &nof_targets);
 
   /// Translates \p original_program that specifies assignable targets
@@ -100,7 +100,7 @@ class dfcc_spec_functionst
   /// \param[out] havoc_program destination program for havoc instructions
   /// \param[out] nof_targets max number of havoc targets discovered
   void generate_havoc_instructions(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &original_program,
     const exprt &write_set_to_havoc,
     dfcc_ptr_havoc_modet ptr_havoc_mode,
@@ -128,9 +128,7 @@ class dfcc_spec_functionst
   /// \param function_id function to transform in place
   /// \param nof_targets receives the estimated size of the write set
   ///
-  void to_spec_assigns_function(
-    const irep_idt &function_id,
-    std::size_t &nof_targets);
+  void to_spec_assigns_function(irep_idt function_id, std::size_t &nof_targets);
 
   /// Rewrites in place \p program expressed in terms of built-ins specifying
   /// assignable targets declaratively using `__CPROVER_assignable`,
@@ -153,7 +151,7 @@ class dfcc_spec_functionst
   ///
   void to_spec_assigns_instructions(
     const exprt &write_set_to_fill,
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     goto_programt &program,
     std::size_t &nof_targets);
 
@@ -180,8 +178,7 @@ class dfcc_spec_functionst
   /// \param function_id function to transform in place
   /// \param nof_targets receives the estimated size of the write set
   ///
-  void
-  to_spec_frees_function(const irep_idt &function_id, std::size_t &nof_targets);
+  void to_spec_frees_function(irep_idt function_id, std::size_t &nof_targets);
 
   /// Rewrites in place \p program expressed in terms of built-ins specifying
   /// freeable targets declaratively using `__CPROVER_freeable` into a program
@@ -202,7 +199,7 @@ class dfcc_spec_functionst
   ///
   void to_spec_frees_instructions(
     const exprt &write_set_to_fill,
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     goto_programt &program,
     std::size_t &nof_targets);
 
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.cpp
index 2f57751f7dd..7ab2bc7d952 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.cpp
@@ -42,8 +42,8 @@ std::map<
 void dfcc_swap_and_wrapt::swap_and_wrap(
   const dfcc_contract_modet contract_mode,
   const loop_contract_configt &loop_contract_config,
-  const irep_idt &function_id,
-  const irep_idt &contract_id,
+  irep_idt function_id,
+  irep_idt contract_id,
   std::set<irep_idt> &function_pointer_contracts,
   bool allow_recursive_calls)
 {
@@ -133,8 +133,8 @@ void dfcc_swap_and_wrapt::get_swapped_functions(std::set<irep_idt> &dest) const
 /// ```
 void dfcc_swap_and_wrapt::check_contract(
   const loop_contract_configt &loop_contract_config,
-  const irep_idt &function_id,
-  const irep_idt &contract_id,
+  irep_idt function_id,
+  irep_idt contract_id,
   std::set<irep_idt> &function_pointer_contracts,
   bool allow_recursive_calls)
 {
@@ -147,7 +147,7 @@ void dfcc_swap_and_wrapt::check_contract(
   // wrapper body
   goto_programt body;
 
-  const auto &wrapper_symbol =
+  const symbolt wrapper_symbol =
     dfcc_utilst::get_function_symbol(goto_model.symbol_table, wrapper_id);
 
   auto check_started = dfcc_utilst::create_static_symbol(
@@ -264,8 +264,8 @@ void dfcc_swap_and_wrapt::check_contract(
 }
 
 void dfcc_swap_and_wrapt::replace_with_contract(
-  const irep_idt &function_id,
-  const irep_idt &contract_id,
+  irep_idt function_id,
+  irep_idt contract_id,
   std::set<irep_idt> &function_pointer_contracts)
 {
   const irep_idt &wrapper_id = function_id;
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.h
index 73c2e909ae3..545dbcc69e5 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_swap_and_wrap.h
@@ -49,8 +49,8 @@ class dfcc_swap_and_wrapt
 
   void swap_and_wrap_check(
     const loop_contract_configt &loop_contract_config,
-    const irep_idt &function_id,
-    const irep_idt &contract_id,
+    irep_idt function_id,
+    irep_idt contract_id,
     std::set<irep_idt> &function_pointer_contracts,
     bool allow_recursive_calls)
   {
@@ -64,8 +64,8 @@ class dfcc_swap_and_wrapt
   }
 
   void swap_and_wrap_replace(
-    const irep_idt &function_id,
-    const irep_idt &contract_id,
+    irep_idt function_id,
+    irep_idt contract_id,
     std::set<irep_idt> &function_pointer_contracts)
   {
     swap_and_wrap(
@@ -99,8 +99,8 @@ class dfcc_swap_and_wrapt
   void swap_and_wrap(
     const dfcc_contract_modet contract_mode,
     const loop_contract_configt &loop_contract_config,
-    const irep_idt &function_id,
-    const irep_idt &contract_id,
+    irep_idt function_id,
+    irep_idt contract_id,
     std::set<irep_idt> &function_pointer_contracts,
     bool allow_recursive_calls);
 
@@ -108,16 +108,16 @@ class dfcc_swap_and_wrapt
   /// checks the given `contract_id`.
   void check_contract(
     const loop_contract_configt &loop_contract_config,
-    const irep_idt &function_id,
-    const irep_idt &contract_id,
+    irep_idt function_id,
+    irep_idt contract_id,
     std::set<irep_idt> &function_pointer_contracts,
     bool allow_recursive_calls);
 
   /// Swaps-and-wraps the given `function_id` in a wrapper function that
   /// models the abstract behaviour of contract `contract_id`.
   void replace_with_contract(
-    const irep_idt &function_id,
-    const irep_idt &contract_id,
+    irep_idt function_id,
+    irep_idt contract_id,
     std::set<irep_idt> &function_pointer_contracts);
 };
 #endif
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.cpp b/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.cpp
index bd501d020a1..508f592dcce 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.cpp
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.cpp
@@ -32,7 +32,7 @@ Date: August 2022
 /// Returns true iff the given symbol exists and satisfies requirements.
 static bool symbol_exists(
   const goto_modelt &goto_model,
-  const irep_idt &name,
+  irep_idt name,
   const bool require_has_code_type,
   const bool require_body_available)
 {
@@ -57,21 +57,21 @@ static bool symbol_exists(
 
 bool dfcc_utilst::function_symbol_exists(
   const goto_modelt &goto_model,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   return symbol_exists(goto_model, function_id, true, false);
 }
 
 bool dfcc_utilst::function_symbol_with_body_exists(
   const goto_modelt &goto_model,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   return symbol_exists(goto_model, function_id, true, true);
 }
 
 symbolt &dfcc_utilst::get_function_symbol(
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   symbolt &function_symbol = symbol_table.get_writeable_ref(function_id);
   CHECK_RETURN(function_symbol.type.id() == ID_code);
@@ -81,11 +81,11 @@ symbolt &dfcc_utilst::get_function_symbol(
 symbol_exprt dfcc_utilst::create_symbol(
   symbol_table_baset &symbol_table,
   const typet &type,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::string &base_name,
   const source_locationt &source_location)
 {
-  const symbolt &function_symbol =
+  const symbolt function_symbol =
     get_function_symbol(symbol_table, function_id);
 
   symbolt &symbol = get_fresh_aux_symbol(
@@ -106,8 +106,8 @@ const symbolt &dfcc_utilst::create_static_symbol(
   const std::string &prefix,
   const std::string &base_name,
   const source_locationt &source_location,
-  const irep_idt &mode,
-  const irep_idt &module,
+  irep_idt mode,
+  irep_idt module,
   const exprt &initial_value,
   const bool no_nondet_initialization)
 {
@@ -123,11 +123,11 @@ const symbolt &dfcc_utilst::create_static_symbol(
 
 const symbolt &dfcc_utilst::create_new_parameter_symbol(
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::string &base_name,
   const typet &type)
 {
-  const symbolt &function_symbol =
+  const symbolt function_symbol =
     get_function_symbol(symbol_table, function_id);
 
   symbolt &symbol = get_fresh_aux_symbol(
@@ -156,7 +156,7 @@ static void add_parameter(const symbolt &symbol, code_typet &code_type)
 void dfcc_utilst::add_parameter(
   goto_modelt &goto_model,
   const symbolt &symbol,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   auto &function_symbol =
     get_function_symbol(goto_model.symbol_table, function_id);
@@ -169,7 +169,7 @@ void dfcc_utilst::add_parameter(
 
 const symbolt &dfcc_utilst::add_parameter(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::string &base_name,
   const typet &type)
 {
@@ -184,11 +184,11 @@ const symbolt &dfcc_utilst::add_parameter(
 static void clone_parameters(
   symbol_table_baset &symbol_table,
   const code_typet::parameterst &old_params,
-  const irep_idt &mode,
-  const irep_idt &module,
+  irep_idt mode,
+  irep_idt module,
   const source_locationt &location,
-  std::function<const irep_idt(const irep_idt &)> &trans_param,
-  const irep_idt &new_function_id,
+  std::function<const irep_idt(irep_idt)> &trans_param,
+  irep_idt new_function_id,
   code_typet::parameterst &new_params)
 {
   // rename function parameters in the wrapper function's code_type
@@ -248,13 +248,13 @@ static void clone_parameters(
 /// \return the new function symbol
 static const symbolt &clone_and_rename_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
-  std::function<const irep_idt(const irep_idt &)> &trans_fun,
-  std::function<const irep_idt(const irep_idt &)> &trans_param,
+  irep_idt function_id,
+  std::function<const irep_idt(irep_idt)> &trans_fun,
+  std::function<const irep_idt(irep_idt)> &trans_param,
   std::function<const typet(const typet &)> &trans_ret_type,
   std::function<const source_locationt(const source_locationt &)> &trans_loc)
 {
-  const symbolt &old_function_symbol =
+  const symbolt old_function_symbol =
     dfcc_utilst::get_function_symbol(goto_model.symbol_table, function_id);
   code_typet old_code_type = to_code_type(old_function_symbol.type);
 
@@ -299,15 +299,15 @@ static const symbolt &clone_and_rename_function(
 
 const symbolt &dfcc_utilst::clone_and_rename_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
-  const irep_idt &new_function_id,
+  irep_idt function_id,
+  irep_idt new_function_id,
   std::optional<typet> new_return_type = {})
 {
-  std::function<const irep_idt(const irep_idt &)> trans_fun =
-    [&](const irep_idt &old_name) { return new_function_id; };
+  std::function<const irep_idt(irep_idt)> trans_fun = [&](irep_idt old_name)
+  { return new_function_id; };
 
-  std::function<const irep_idt(const irep_idt &)> trans_param =
-    [&](const irep_idt &old_name) { return old_name; };
+  std::function<const irep_idt(irep_idt)> trans_param = [&](irep_idt old_name)
+  { return old_name; };
 
   std::function<const typet(const typet &)> trans_ret_type =
     [&](const typet &old_type) {
@@ -323,8 +323,8 @@ const symbolt &dfcc_utilst::clone_and_rename_function(
 
 void dfcc_utilst::wrap_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
-  const irep_idt &wrapped_function_id)
+  irep_idt function_id,
+  irep_idt wrapped_function_id)
 {
   auto &goto_functions = goto_model.goto_functions;
   auto &symbol_table = goto_model.symbol_table;
@@ -360,10 +360,8 @@ void dfcc_utilst::wrap_function(
   // Re-insert a symbol for `function_id` which is now the wrapper function
   symbolt wrapper_sym = *old_sym;
 
-  std::function<const irep_idt(const irep_idt &)> trans_param =
-    [&](const irep_idt &old_param) {
-      return id2string(old_param) + "_wrapper";
-    };
+  std::function<const irep_idt(irep_idt)> trans_param = [&](irep_idt old_param)
+  { return id2string(old_param) + "_wrapper"; };
 
   // create new code_type with renamed parameters for the wrapper
   const auto &old_code_type = to_code_type(old_sym->type);
@@ -423,7 +421,7 @@ exprt dfcc_utilst::make_sizeof_expr(const exprt &expr, const namespacet &ns)
 
 static inlining_decoratort inline_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   message_handlert &message_handler)
 {
   auto &goto_function = goto_model.goto_functions.function_map.at(function_id);
@@ -442,7 +440,7 @@ static inlining_decoratort inline_function(
 
 void dfcc_utilst::inline_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   message_handlert &message_handler)
 {
   inlining_decoratort decorated =
@@ -459,7 +457,7 @@ void dfcc_utilst::inline_function(
 
 void dfcc_utilst::inline_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   std::set<irep_idt> &no_body,
   std::set<irep_idt> &recursive_call,
   std::set<irep_idt> &missing_function,
diff --git a/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.h b/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.h
index 341371cddef..11cb82a3f59 100644
--- a/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.h
+++ b/src/goto-instrument/contracts/dynamic-frames/dfcc_utils.h
@@ -26,15 +26,13 @@ class symbolt;
 struct dfcc_utilst
 {
   /// Returns true iff the given symbol exists and satisfies requirements.
+  static bool function_symbol_exists(const goto_modelt &, irep_idt function_id);
   static bool
-  function_symbol_exists(const goto_modelt &, const irep_idt &function_id);
-  static bool function_symbol_with_body_exists(
-    const goto_modelt &,
-    const irep_idt &function_id);
+  function_symbol_with_body_exists(const goto_modelt &, irep_idt function_id);
 
   /// Returns the `symbolt` for `function_id`.
   static symbolt &
-  get_function_symbol(symbol_table_baset &, const irep_idt &function_id);
+  get_function_symbol(symbol_table_baset &, irep_idt function_id);
 
   /// Adds a new symbol named `function_id::base_name` of type `type`
   /// with given attributes in the symbol table, and returns a symbol expression
@@ -44,7 +42,7 @@ struct dfcc_utilst
   static symbol_exprt create_symbol(
     symbol_table_baset &,
     const typet &type,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const std::string &base_name,
     const source_locationt &source_location);
 
@@ -65,8 +63,8 @@ struct dfcc_utilst
     const std::string &prefix,
     const std::string &base_name,
     const source_locationt &source_location,
-    const irep_idt &mode,
-    const irep_idt &module,
+    irep_idt mode,
+    irep_idt module,
     const exprt &initial_value,
     const bool no_nondet_initialization = true);
 
@@ -77,23 +75,21 @@ struct dfcc_utilst
   static const symbolt &
   create_new_parameter_symbol(
     symbol_table_baset &,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const std::string &base_name,
     const typet &type);
 
   /// \brief Adds the given symbol as parameter to the function symbol's
   /// code_type. Also adds the corresponding parameter to its goto_function if
   /// it exists in the function map of the goto model.
-  static void add_parameter(
-    goto_modelt &,
-    const symbolt &symbol,
-    const irep_idt &function_id);
+  static void
+  add_parameter(goto_modelt &, const symbolt &symbol, irep_idt function_id);
 
   /// \brief Adds a parameter with given `base_name` and `type` to the given
   /// `function_id`. Both the symbol and the goto_function are updated.
   static const symbolt &add_parameter(
     goto_modelt &,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const std::string &base_name,
     const typet &type);
 
@@ -109,8 +105,8 @@ struct dfcc_utilst
   static const symbolt &
   clone_and_rename_function(
     goto_modelt &goto_model,
-    const irep_idt &function_id,
-    const irep_idt &new_function_id,
+    irep_idt function_id,
+    irep_idt new_function_id,
     std::optional<typet> new_return_type);
 
   /// Given a function to wrap `foo` and a new name `wrapped_foo`
@@ -143,8 +139,8 @@ struct dfcc_utilst
   /// checking logic, contract replacement logic, etc.
   static void wrap_function(
     goto_modelt &goto_model,
-    const irep_idt &function_id,
-    const irep_idt &wrapped_function_id);
+    irep_idt function_id,
+    irep_idt wrapped_function_id);
 
   /// \brief Returns the expression `expr == NULL`.
   static const exprt make_null_check_expr(const exprt &ptr);
@@ -156,14 +152,14 @@ struct dfcc_utilst
   /// inlining.
   static void inline_function(
     goto_modelt &goto_model,
-    const irep_idt &function_id,
+    irep_idt function_id,
     message_handlert &message_handler);
 
   /// \brief Inlines the given function, and returns function symbols that
   /// caused warnings.
   static void inline_function(
     goto_modelt &goto_model,
-    const irep_idt &function_id,
+    irep_idt function_id,
     std::set<irep_idt> &no_body,
     std::set<irep_idt> &recursive_call,
     std::set<irep_idt> &missing_function,
diff --git a/src/goto-instrument/contracts/havoc_assigns_clause_targets.h b/src/goto-instrument/contracts/havoc_assigns_clause_targets.h
index dc25bfecda8..4f3fee252ca 100644
--- a/src/goto-instrument/contracts/havoc_assigns_clause_targets.h
+++ b/src/goto-instrument/contracts/havoc_assigns_clause_targets.h
@@ -52,7 +52,7 @@ class havoc_assigns_clause_targetst : public instrument_spec_assignst
   /// \param _message_handler handler used to log translation warnings/errors
   ///
   havoc_assigns_clause_targetst(
-    const irep_idt &_function_id,
+    irep_idt _function_id,
     const std::vector<exprt> &_targets,
     const goto_functionst &_functions,
     cfg_infot &_cfg_info,
diff --git a/src/goto-instrument/contracts/instrument_spec_assigns.cpp b/src/goto-instrument/contracts/instrument_spec_assigns.cpp
index b346f64007c..14add356292 100644
--- a/src/goto-instrument/contracts/instrument_spec_assigns.cpp
+++ b/src/goto-instrument/contracts/instrument_spec_assigns.cpp
@@ -460,7 +460,7 @@ static symbol_exprt create_fresh_symbol(
   const std::string &suffix,
   const typet &type,
   const source_locationt &location,
-  const irep_idt &mode,
+  irep_idt mode,
   symbol_table_baset &symbol_table)
 {
   return get_fresh_aux_symbol(
@@ -992,8 +992,7 @@ bool instrument_spec_assignst::must_check_assign(
 }
 
 /// Track the symbol is not a local or is a dirty local.
-bool instrument_spec_assignst::must_track_decl_or_dead(
-  const irep_idt &ident) const
+bool instrument_spec_assignst::must_track_decl_or_dead(irep_idt ident) const
 {
   return cfg_info.is_not_local_or_dirty_local(ident);
 }
diff --git a/src/goto-instrument/contracts/instrument_spec_assigns.h b/src/goto-instrument/contracts/instrument_spec_assigns.h
index 2534f61427d..07c24f0f46e 100644
--- a/src/goto-instrument/contracts/instrument_spec_assigns.h
+++ b/src/goto-instrument/contracts/instrument_spec_assigns.h
@@ -194,7 +194,7 @@ class instrument_spec_assignst
   ///  \param _st symbol table of the goto_model
   ///  \param _message_handler used to output warning/error messages
   instrument_spec_assignst(
-    const irep_idt &_function_id,
+    irep_idt _function_id,
     const goto_functionst &_functions,
     cfg_infot &_cfg_info,
     symbol_table_baset &_st,
@@ -471,7 +471,7 @@ class instrument_spec_assignst
 
 protected:
   /// Name of the instrumented function
-  const irep_idt &function_id;
+  irep_idt function_id;
 
   /// Other functions of the model
   const goto_functionst &functions;
@@ -489,7 +489,7 @@ class instrument_spec_assignst
   messaget log;
 
   /// Language mode
-  const irep_idt &mode;
+  irep_idt mode;
 
   /// Track and generate snaphsot instructions and target validity
   /// checking assertions for a conditional target group from an assigns clause
@@ -575,7 +575,7 @@ class instrument_spec_assignst
   /// passed C compiler checks, non-dirty locals can only be assigned to
   /// directly by name, cannot escape their lexical scope, and are always safe
   /// to assign. Hence, we only track dirty locals in the write set.
-  bool must_track_decl_or_dead(const irep_idt &ident) const;
+  bool must_track_decl_or_dead(irep_idt ident) const;
 
   /// Returns true iff an `ASSIGN lhs := rhs` instruction must be instrumented.
   bool must_check_assign(const goto_programt::const_targett &target);
diff --git a/src/goto-instrument/contracts/memory_predicates.cpp b/src/goto-instrument/contracts/memory_predicates.cpp
index c78eb140966..906e99f4c2f 100644
--- a/src/goto-instrument/contracts/memory_predicates.cpp
+++ b/src/goto-instrument/contracts/memory_predicates.cpp
@@ -242,7 +242,7 @@ void is_fresh_baset::update_fn_call(
 is_fresh_enforcet::is_fresh_enforcet(
   goto_modelt &goto_model,
   message_handlert &message_handler,
-  const irep_idt &_fun_id)
+  irep_idt _fun_id)
   : is_fresh_baset(goto_model, message_handler, _fun_id)
 {
   std::stringstream ssreq, ssensure, ssmemmap;
@@ -321,7 +321,7 @@ void is_fresh_enforcet::create_ensures_fn_call(goto_programt::targett &ins)
 is_fresh_replacet::is_fresh_replacet(
   goto_modelt &goto_model,
   message_handlert &message_handler,
-  const irep_idt &_fun_id)
+  irep_idt _fun_id)
   : is_fresh_baset(goto_model, message_handler, _fun_id)
 {
   std::stringstream ssreq, ssensure, ssmemmap;
diff --git a/src/goto-instrument/contracts/memory_predicates.h b/src/goto-instrument/contracts/memory_predicates.h
index 543ef9c7386..3ef4c7953db 100644
--- a/src/goto-instrument/contracts/memory_predicates.h
+++ b/src/goto-instrument/contracts/memory_predicates.h
@@ -28,7 +28,7 @@ class is_fresh_baset
   is_fresh_baset(
     goto_modelt &goto_model,
     message_handlert &message_handler,
-    const irep_idt &_fun_id)
+    irep_idt _fun_id)
     : goto_model(goto_model), message_handler(message_handler), fun_id(_fun_id)
   {
   }
@@ -53,7 +53,7 @@ class is_fresh_baset
 
   goto_modelt &goto_model;
   message_handlert &message_handler;
-  const irep_idt &fun_id;
+  irep_idt fun_id;
 
   // written by the child classes.
   std::string memmap_name;
@@ -70,7 +70,7 @@ class is_fresh_enforcet : public is_fresh_baset
   is_fresh_enforcet(
     goto_modelt &goto_model,
     message_handlert &message_handler,
-    const irep_idt &_fun_id);
+    irep_idt _fun_id);
 
   virtual void create_declarations();
 
@@ -85,7 +85,7 @@ class is_fresh_replacet : public is_fresh_baset
   is_fresh_replacet(
     goto_modelt &goto_model,
     message_handlert &message_handler,
-    const irep_idt &_fun_id);
+    irep_idt _fun_id);
 
   virtual void create_declarations();
 
diff --git a/src/goto-instrument/contracts/utils.cpp b/src/goto-instrument/contracts/utils.cpp
index f01bd73f97e..cb481844315 100644
--- a/src/goto-instrument/contracts/utils.cpp
+++ b/src/goto-instrument/contracts/utils.cpp
@@ -328,14 +328,14 @@ static const char ASSIGNS_CLAUSE_REPLACEMENT_TRACKING[] =
 
 irep_idt make_assigns_clause_replacement_tracking_comment(
   const exprt &target,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const namespacet &ns)
 {
   return from_expr(ns, target.id(), target) +
          ASSIGNS_CLAUSE_REPLACEMENT_TRACKING + id2string(function_id) + ")";
 }
 
-bool is_assigns_clause_replacement_tracking_comment(const irep_idt &comment)
+bool is_assigns_clause_replacement_tracking_comment(irep_idt comment)
 {
   return id2string(comment).find(ASSIGNS_CLAUSE_REPLACEMENT_TRACKING) !=
          std::string::npos;
@@ -388,9 +388,9 @@ static void replace_history_parameter_rec(
   exprt &expr,
   std::unordered_map<exprt, symbol_exprt, irep_hash> &parameter2history,
   const source_locationt &location,
-  const irep_idt &mode,
+  irep_idt mode,
   goto_programt &history,
-  const irep_idt &history_id)
+  irep_idt history_id)
 {
   for(auto &op : expr.operands())
   {
@@ -401,7 +401,7 @@ static void replace_history_parameter_rec(
   if(expr.id() != ID_old && expr.id() != ID_loop_entry)
     return;
 
-  const auto &parameter = to_history_expr(expr, history_id).expression();
+  const auto parameter = to_history_expr(expr, history_id).expression();
   const auto &id = parameter.id();
   DATA_INVARIANT_WITH_DIAGNOSTICS(
     id == ID_dereference || id == ID_member || id == ID_symbol ||
@@ -457,7 +457,7 @@ replace_history_parametert replace_history_old(
   symbol_table_baset &symbol_table,
   const exprt &expr,
   const source_locationt &location,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   replace_history_parametert result;
   result.expression_after_replacement = expr;
@@ -476,7 +476,7 @@ replace_history_parametert replace_history_loop_entry(
   symbol_table_baset &symbol_table,
   const exprt &expr,
   const source_locationt &location,
-  const irep_idt &mode)
+  irep_idt mode)
 {
   replace_history_parametert result;
   result.expression_after_replacement = expr;
@@ -494,7 +494,7 @@ replace_history_parametert replace_history_loop_entry(
 void generate_history_variables_initialization(
   symbol_table_baset &symbol_table,
   exprt &clause,
-  const irep_idt &mode,
+  irep_idt mode,
   goto_programt &program)
 {
   // Find and replace "old" expression in the "expression" variable
diff --git a/src/goto-instrument/contracts/utils.h b/src/goto-instrument/contracts/utils.h
index 2b81b81c27c..40ea8d8cc1c 100644
--- a/src/goto-instrument/contracts/utils.h
+++ b/src/goto-instrument/contracts/utils.h
@@ -42,7 +42,7 @@ class cleanert : public goto_convertt
   }
 
   [[nodiscard]] std::list<irep_idt>
-  clean(exprt &guard, goto_programt &dest, const irep_idt &mode)
+  clean(exprt &guard, goto_programt &dest, irep_idt mode)
   {
     auto clean_result = goto_convertt::clean_expr(guard, mode, true);
     dest.destructive_append(clean_result.side_effects);
@@ -53,7 +53,7 @@ class cleanert : public goto_convertt
     const symbol_exprt &function,
     const exprt::operandst &arguments,
     goto_programt &dest,
-    const irep_idt &mode)
+    irep_idt mode)
   {
     goto_convertt::do_havoc_slice(nil_exprt{}, function, arguments, dest, mode);
   }
@@ -93,7 +93,7 @@ class havoc_assigns_targetst : public havoc_if_validt
     const assignst &mod,
     symbol_tablet &st,
     message_handlert &message_handler,
-    const irep_idt &mode)
+    irep_idt mode)
     : havoc_if_validt(mod, ns),
       ns(st),
       cleaner(st, message_handler),
@@ -121,7 +121,7 @@ class havoc_assigns_targetst : public havoc_if_validt
   namespacet ns;
   cleanert cleaner;
   messaget log;
-  const irep_idt &mode;
+  irep_idt mode;
 };
 
 /// \brief Generate a validity check over all dereferences in an expression
@@ -210,12 +210,12 @@ bool is_loop_free(
 /// `target` was assigned by the contract of `function_id`.
 irep_idt make_assigns_clause_replacement_tracking_comment(
   const exprt &target,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const namespacet &ns);
 
 /// Returns true if the given comment matches the type of comments created by
 /// \ref make_assigns_clause_replacement_tracking_comment.
-bool is_assigns_clause_replacement_tracking_comment(const irep_idt &comment);
+bool is_assigns_clause_replacement_tracking_comment(irep_idt comment);
 
 /// Infer loop assigns using alias analysis result `local_may_alias`.
 void infer_loop_assigns(
@@ -243,7 +243,7 @@ replace_history_parametert replace_history_old(
   symbol_table_baset &symbol_table,
   const exprt &expr,
   const source_locationt &location,
-  const irep_idt &mode);
+  irep_idt mode);
 
 /// This function recursively identifies the "loop_entry" expressions within
 /// \p expr and replaces them with corresponding history variables.
@@ -251,14 +251,14 @@ replace_history_parametert replace_history_loop_entry(
   symbol_table_baset &symbol_table,
   const exprt &expr,
   const source_locationt &location,
-  const irep_idt &mode);
+  irep_idt mode);
 
 /// This function generates all the instructions required to initialize
 /// history variables.
 void generate_history_variables_initialization(
   symbol_table_baset &symbol_table,
   exprt &clause,
-  const irep_idt &mode,
+  irep_idt mode,
   goto_programt &program);
 
 /// Return true if `target` is the head of some transformed loop.
diff --git a/src/goto-instrument/cover.cpp b/src/goto-instrument/cover.cpp
index 96fb6020e22..22eab7cbde0 100644
--- a/src/goto-instrument/cover.cpp
+++ b/src/goto-instrument/cover.cpp
@@ -34,10 +34,10 @@ Date: May 2016
 ///   asserted is expected to include the expression passed in, but may include
 ///   other additional conditions.
 static void instrument_cover_goals(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const cover_instrumenterst &instrumenters,
-  const irep_idt &mode,
+  irep_idt mode,
   message_handlert &message_handler,
   const cover_instrumenter_baset::assertion_factoryt &make_assertion)
 {
@@ -246,7 +246,7 @@ cover_configt get_cover_config(
 /// \return a cover_configt on success, or null otherwise.
 cover_configt get_cover_config(
   const optionst &options,
-  const irep_idt &main_function_id,
+  irep_idt main_function_id,
   const symbol_tablet &symbol_table,
   message_handlert &message_handler)
 {
diff --git a/src/goto-instrument/cover.h b/src/goto-instrument/cover.h
index 548ded5eb6b..184c7cc79b2 100644
--- a/src/goto-instrument/cover.h
+++ b/src/goto-instrument/cover.h
@@ -88,7 +88,7 @@ get_cover_config(const optionst &, const symbol_tablet &, message_handlert &);
 
 cover_configt get_cover_config(
   const optionst &,
-  const irep_idt &main_function_id,
+  irep_idt main_function_id,
   const symbol_tablet &,
   message_handlert &);
 
diff --git a/src/goto-instrument/cover_basic_blocks.cpp b/src/goto-instrument/cover_basic_blocks.cpp
index 23df805b4dc..aa9c4208944 100644
--- a/src/goto-instrument/cover_basic_blocks.cpp
+++ b/src/goto-instrument/cover_basic_blocks.cpp
@@ -123,7 +123,7 @@ cover_basic_blockst::source_lines_of(const std::size_t block_nr) const
 }
 
 void cover_basic_blockst::report_block_anomalies(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   message_handlert &message_handler)
 {
diff --git a/src/goto-instrument/cover_basic_blocks.h b/src/goto-instrument/cover_basic_blocks.h
index 8c9bd2c2a89..1a7056409c5 100644
--- a/src/goto-instrument/cover_basic_blocks.h
+++ b/src/goto-instrument/cover_basic_blocks.h
@@ -51,7 +51,7 @@ class cover_blocks_baset
   /// \param goto_program: The goto program
   /// \param message_handler: The message handler
   virtual void report_block_anomalies(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     message_handlert &message_handler)
   {
@@ -93,7 +93,7 @@ class cover_basic_blockst final : public cover_blocks_baset
   /// \param goto_program: The goto program
   /// \param message_handler: The message handler
   void report_block_anomalies(
-    const irep_idt &function_id,
+    irep_idt function_id,
     const goto_programt &goto_program,
     message_handlert &message_handler) override;
 
diff --git a/src/goto-instrument/cover_filter.h b/src/goto-instrument/cover_filter.h
index c1a479f258e..28e1d1aeb09 100644
--- a/src/goto-instrument/cover_filter.h
+++ b/src/goto-instrument/cover_filter.h
@@ -142,7 +142,7 @@ class internal_functions_filtert : public function_filter_baset
 class file_filtert : public function_filter_baset
 {
 public:
-  explicit file_filtert(const irep_idt &file_id) : file_id(file_id)
+  explicit file_filtert(irep_idt file_id) : file_id(file_id)
   {
   }
 
@@ -157,7 +157,7 @@ class file_filtert : public function_filter_baset
 class single_function_filtert : public function_filter_baset
 {
 public:
-  explicit single_function_filtert(const irep_idt &function_id)
+  explicit single_function_filtert(irep_idt function_id)
     : function_id(function_id)
   {
   }
diff --git a/src/goto-instrument/cover_instrument.h b/src/goto-instrument/cover_instrument.h
index a535987fd91..c5b82384e4d 100644
--- a/src/goto-instrument/cover_instrument.h
+++ b/src/goto-instrument/cover_instrument.h
@@ -30,7 +30,7 @@ class cover_instrumenter_baset
   cover_instrumenter_baset(
     const symbol_table_baset &_symbol_table,
     const goal_filterst &_goal_filters,
-    const irep_idt &_coverage_criterion)
+    irep_idt _coverage_criterion)
     : coverage_criterion(_coverage_criterion),
       ns(_symbol_table),
       goal_filters(_goal_filters)
@@ -54,7 +54,7 @@ class cover_instrumenter_baset
   /// \param make_assertion: A function which makes goto program assertions.
   ///    This parameter may be used to customise the expressions asserted.
   void operator()(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     const cover_blocks_baset &basic_blocks,
     const assertion_factoryt &make_assertion) const
@@ -74,7 +74,7 @@ class cover_instrumenter_baset
 
   /// Override this method to implement an instrumenter
   virtual void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -83,7 +83,7 @@ class cover_instrumenter_baset
   void initialize_source_location(
     source_locationt &source_location,
     const std::string &comment,
-    const irep_idt &function_id) const
+    irep_idt function_id) const
   {
     source_location.set_comment(comment);
     source_location.set(ID_coverage_criterion, coverage_criterion);
@@ -114,7 +114,7 @@ class cover_instrumenterst
   /// \param make_assertion: A function which makes goto program assertions.
   ///    This parameter may be used to customise the expressions asserted.
   void operator()(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     const cover_blocks_baset &basic_blocks,
     const cover_instrumenter_baset::assertion_factoryt &make_assertion) const
@@ -140,7 +140,7 @@ class cover_location_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -160,7 +160,7 @@ class cover_branch_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -180,7 +180,7 @@ class cover_condition_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -200,7 +200,7 @@ class cover_decision_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -220,7 +220,7 @@ class cover_mcdc_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -240,7 +240,7 @@ class cover_path_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -260,7 +260,7 @@ class cover_assertion_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -280,7 +280,7 @@ class cover_cover_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
@@ -288,7 +288,7 @@ class cover_cover_instrumentert : public cover_instrumenter_baset
 };
 
 void cover_instrument_end_of_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const cover_instrumenter_baset::assertion_factoryt &);
 
@@ -305,7 +305,7 @@ class cover_assume_instrumentert : public cover_instrumenter_baset
 
 protected:
   void instrument(
-    const irep_idt &,
+    irep_idt,
     goto_programt &,
     goto_programt::targett &,
     const cover_blocks_baset &,
diff --git a/src/goto-instrument/cover_instrument_assume.cpp b/src/goto-instrument/cover_instrument_assume.cpp
index 0b0591ec4d6..4ed73537eb8 100644
--- a/src/goto-instrument/cover_instrument_assume.cpp
+++ b/src/goto-instrument/cover_instrument_assume.cpp
@@ -14,7 +14,7 @@
 /// \param i_it The current instruction (instruction under instrumentation).
 /// \param make_assertion The assertion generator function.
 void cover_assume_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
diff --git a/src/goto-instrument/cover_instrument_branch.cpp b/src/goto-instrument/cover_instrument_branch.cpp
index 803b4f4b78c..e038e418759 100644
--- a/src/goto-instrument/cover_instrument_branch.cpp
+++ b/src/goto-instrument/cover_instrument_branch.cpp
@@ -14,7 +14,7 @@ Author: Daniel Kroening
 #include "cover_instrument.h"
 
 void cover_branch_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &i_it,
   const cover_blocks_baset &basic_blocks,
diff --git a/src/goto-instrument/cover_instrument_condition.cpp b/src/goto-instrument/cover_instrument_condition.cpp
index 9e5c319db8f..8bd925fd219 100644
--- a/src/goto-instrument/cover_instrument_condition.cpp
+++ b/src/goto-instrument/cover_instrument_condition.cpp
@@ -16,7 +16,7 @@ Author: Daniel Kroening
 #include "cover_util.h"
 
 void cover_condition_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
diff --git a/src/goto-instrument/cover_instrument_decision.cpp b/src/goto-instrument/cover_instrument_decision.cpp
index adefbd528da..3cfc386fa9c 100644
--- a/src/goto-instrument/cover_instrument_decision.cpp
+++ b/src/goto-instrument/cover_instrument_decision.cpp
@@ -16,7 +16,7 @@ Author: Daniel Kroening
 #include "cover_util.h"
 
 void cover_decision_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
diff --git a/src/goto-instrument/cover_instrument_location.cpp b/src/goto-instrument/cover_instrument_location.cpp
index 64b93dc1936..200fa78d6c2 100644
--- a/src/goto-instrument/cover_instrument_location.cpp
+++ b/src/goto-instrument/cover_instrument_location.cpp
@@ -15,7 +15,7 @@ Author: Daniel Kroening
 #include "cover_filter.h"
 
 void cover_location_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &i_it,
   const cover_blocks_baset &basic_blocks,
diff --git a/src/goto-instrument/cover_instrument_mcdc.cpp b/src/goto-instrument/cover_instrument_mcdc.cpp
index 08db0b0092b..25a9314de3d 100644
--- a/src/goto-instrument/cover_instrument_mcdc.cpp
+++ b/src/goto-instrument/cover_instrument_mcdc.cpp
@@ -621,7 +621,7 @@ void minimize_mcdc_controlling(
 }
 
 void cover_mcdc_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
diff --git a/src/goto-instrument/cover_instrument_other.cpp b/src/goto-instrument/cover_instrument_other.cpp
index 5ab081c9490..00c50796b16 100644
--- a/src/goto-instrument/cover_instrument_other.cpp
+++ b/src/goto-instrument/cover_instrument_other.cpp
@@ -18,7 +18,7 @@ Author: Daniel Kroening
 #include <algorithm>
 
 void cover_path_instrumentert::instrument(
-  const irep_idt &,
+  irep_idt,
   goto_programt &,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
@@ -31,7 +31,7 @@ void cover_path_instrumentert::instrument(
 }
 
 void cover_assertion_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
@@ -49,7 +49,7 @@ void cover_assertion_instrumentert::instrument(
 }
 
 void cover_cover_instrumentert::instrument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &,
   goto_programt::targett &i_it,
   const cover_blocks_baset &,
@@ -76,7 +76,7 @@ void cover_cover_instrumentert::instrument(
 }
 
 void cover_instrument_end_of_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const cover_instrumenter_baset::assertion_factoryt &make_assertion)
 {
diff --git a/src/goto-instrument/dot.cpp b/src/goto-instrument/dot.cpp
index 45da7c038cb..42668c4fc53 100644
--- a/src/goto-instrument/dot.cpp
+++ b/src/goto-instrument/dot.cpp
@@ -44,8 +44,7 @@ class dott
   std::list<std::pair<std::string, exprt>> function_calls;
   std::list<exprt> clusters;
 
-  void
-  write_dot_subgraph(std::ostream &, const irep_idt &, const goto_programt &);
+  void write_dot_subgraph(std::ostream &, irep_idt, const goto_programt &);
 
   void do_dot_function_calls(std::ostream &);
 
@@ -70,7 +69,7 @@ class dott
 /// \param goto_program: goto program the dot graph of which is written
 void dott::write_dot_subgraph(
   std::ostream &out,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program)
 {
   clusters.push_back(exprt("cluster"));
diff --git a/src/goto-instrument/dump_c.cpp b/src/goto-instrument/dump_c.cpp
index 89e785ca3f3..6ad89df5638 100644
--- a/src/goto-instrument/dump_c.cpp
+++ b/src/goto-instrument/dump_c.cpp
@@ -32,7 +32,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include "goto_program2code.h"
 
-static std::string clean_identifier(const irep_idt &id)
+static std::string clean_identifier(irep_idt id)
 {
   std::string result;
   result.reserve(id2string(id).size());
@@ -1194,9 +1194,9 @@ void dump_ct::convert_function_declaration(
 }
 
 static bool find_block_position_rec(
-  const irep_idt &identifier,
+  irep_idt identifier,
   codet &root,
-  code_blockt* &dest,
+  code_blockt *&dest,
   exprt::operandst::iterator &before)
 {
   if(!root.has_operands())
diff --git a/src/goto-instrument/dump_c_class.h b/src/goto-instrument/dump_c_class.h
index 0fb1e2b3a06..6713b204ff9 100644
--- a/src/goto-instrument/dump_c_class.h
+++ b/src/goto-instrument/dump_c_class.h
@@ -117,7 +117,7 @@ class dump_ct
     const bool use_all_headers,
     const bool include_harness,
     const namespacet &_ns,
-    const irep_idt &mode,
+    irep_idt mode,
     const dump_c_configurationt config)
     : goto_functions(_goto_functions),
       copied_symbol_table(_ns.get_symbol_table()),
@@ -136,7 +136,7 @@ class dump_ct
     const bool use_all_headers,
     const bool include_harness,
     const namespacet &_ns,
-    const irep_idt &mode)
+    irep_idt mode)
     : dump_ct(
         _goto_functions,
         use_system_headers,
@@ -177,9 +177,7 @@ class dump_ct
     bool early;
     std::unordered_set<irep_idt> dependencies;
 
-    explicit typedef_infot(const irep_idt &name):
-      typedef_name(name),
-      early(false)
+    explicit typedef_infot(irep_idt name) : typedef_name(name), early(false)
     {
     }
   };
@@ -196,9 +194,7 @@ class dump_ct
     return std::string(2*n, ' ');
   }
 
-  std::string make_decl(
-      const irep_idt &identifier,
-      const typet &type)
+  std::string make_decl(irep_idt identifier, const typet &type)
   {
     symbol_exprt sym(identifier, type);
     code_frontend_declt d(sym);
diff --git a/src/goto-instrument/full_slicer.h b/src/goto-instrument/full_slicer.h
index e18f37f1103..ab5cf56f637 100644
--- a/src/goto-instrument/full_slicer.h
+++ b/src/goto-instrument/full_slicer.h
@@ -37,9 +37,8 @@ class slicing_criteriont
 {
 public:
   virtual ~slicing_criteriont();
-  virtual bool operator()(
-    const irep_idt &function_id,
-    goto_programt::const_targett) const = 0;
+  virtual bool
+  operator()(irep_idt function_id, goto_programt::const_targett) const = 0;
 };
 
 void full_slicer(
diff --git a/src/goto-instrument/full_slicer_class.h b/src/goto-instrument/full_slicer_class.h
index 4ad06772ce6..342e83d40d6 100644
--- a/src/goto-instrument/full_slicer_class.h
+++ b/src/goto-instrument/full_slicer_class.h
@@ -111,8 +111,7 @@ class full_slicert
 class assert_criteriont:public slicing_criteriont
 {
 public:
-  virtual bool
-  operator()(const irep_idt &, goto_programt::const_targett target) const
+  virtual bool operator()(irep_idt, goto_programt::const_targett target) const
   {
     return target->is_assert();
   }
@@ -127,7 +126,7 @@ class in_function_criteriont : public slicing_criteriont
   }
 
   virtual bool
-  operator()(const irep_idt &function_id, goto_programt::const_targett) const
+  operator()(irep_idt function_id, goto_programt::const_targett) const
   {
     return function_id == target_function;
   }
@@ -145,8 +144,7 @@ class properties_criteriont:public slicing_criteriont
   {
   }
 
-  virtual bool
-  operator()(const irep_idt &, goto_programt::const_targett target) const
+  virtual bool operator()(irep_idt, goto_programt::const_targett target) const
   {
     if(!target->is_assert())
       return false;
diff --git a/src/goto-instrument/function.cpp b/src/goto-instrument/function.cpp
index 246c0ddec81..02e13f21d0b 100644
--- a/src/goto-instrument/function.cpp
+++ b/src/goto-instrument/function.cpp
@@ -21,8 +21,8 @@ Author: Daniel Kroening, kroening@kroening.com
 
 code_function_callt function_to_call(
   symbol_table_baset &symbol_table,
-  const irep_idt &id,
-  const irep_idt &argument)
+  irep_idt id,
+  irep_idt argument)
 {
   // already there?
 
@@ -74,9 +74,7 @@ code_function_callt function_to_call(
   return call;
 }
 
-void function_enter(
-  goto_modelt &goto_model,
-  const irep_idt &id)
+void function_enter(goto_modelt &goto_model, irep_idt id)
 {
   for(auto &gf_entry : goto_model.goto_functions.function_map)
   {
@@ -99,9 +97,7 @@ void function_enter(
   }
 }
 
-void function_exit(
-  goto_modelt &goto_model,
-  const irep_idt &id)
+void function_exit(goto_modelt &goto_model, irep_idt id)
 {
   for(auto &gf_entry : goto_model.goto_functions.function_map)
   {
diff --git a/src/goto-instrument/function.h b/src/goto-instrument/function.h
index 98652f00641..6cae85ddb15 100644
--- a/src/goto-instrument/function.h
+++ b/src/goto-instrument/function.h
@@ -17,17 +17,11 @@ Author: Daniel Kroening, kroening@kroening.com
 class goto_modelt;
 class symbol_table_baset;
 
-class code_function_callt function_to_call(
-  symbol_table_baset &,
-  const irep_idt &id,
-  const irep_idt &argument);
-
-void function_enter(
-  goto_modelt &,
-  const irep_idt &id);
-
-void function_exit(
-  goto_modelt &,
-  const irep_idt &id);
+class code_function_callt
+function_to_call(symbol_table_baset &, irep_idt id, irep_idt argument);
+
+void function_enter(goto_modelt &, irep_idt id);
+
+void function_exit(goto_modelt &, irep_idt id);
 
 #endif // CPROVER_GOTO_INSTRUMENT_FUNCTION_H
diff --git a/src/goto-instrument/generate_function_bodies.cpp b/src/goto-instrument/generate_function_bodies.cpp
index dc4c27de008..e3d289adb69 100644
--- a/src/goto-instrument/generate_function_bodies.cpp
+++ b/src/goto-instrument/generate_function_bodies.cpp
@@ -24,7 +24,7 @@ Author: Diffblue Ltd.
 void generate_function_bodiest::generate_function_body(
   goto_functiont &function,
   symbol_tablet &symbol_table,
-  const irep_idt &function_name) const
+  irep_idt function_name) const
 {
   PRECONDITION(!function.body_available());
   generate_parameter_names(function, symbol_table, function_name);
@@ -34,7 +34,7 @@ void generate_function_bodiest::generate_function_body(
 void generate_function_bodiest::generate_parameter_names(
   goto_functiont &function,
   symbol_tablet &symbol_table,
-  const irep_idt &function_name) const
+  irep_idt function_name) const
 {
   auto &function_symbol = symbol_table.get_writeable_ref(function_name);
   auto &parameters = to_code_type(function_symbol.type).parameters();
@@ -71,7 +71,7 @@ class assume_false_generate_function_bodiest : public generate_function_bodiest
   void generate_function_body_impl(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const override
+    irep_idt function_name) const override
   {
     auto const &function_symbol = symbol_table.lookup_ref(function_name);
     source_locationt location = function_symbol.location;
@@ -88,7 +88,7 @@ class assert_false_generate_function_bodiest : public generate_function_bodiest
   void generate_function_body_impl(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const override
+    irep_idt function_name) const override
   {
     auto const &function_symbol = symbol_table.lookup_ref(function_name);
 
@@ -112,7 +112,7 @@ class assert_false_then_assume_false_generate_function_bodiest
   void generate_function_body_impl(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const override
+    irep_idt function_name) const override
   {
     auto const &function_symbol = symbol_table.lookup_ref(function_name);
 
@@ -164,7 +164,7 @@ class havoc_generate_function_bodiest : public generate_function_bodiest
     const exprt &lhs,
     const std::size_t initial_depth,
     const source_locationt &source_location,
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_tablet &symbol_table,
     goto_programt &dest) const
   {
@@ -218,7 +218,7 @@ class havoc_generate_function_bodiest : public generate_function_bodiest
   void generate_function_body_impl(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const override
+    irep_idt function_name) const override
   {
     const namespacet ns(symbol_table);
     // some user input checking
diff --git a/src/goto-instrument/generate_function_bodies.h b/src/goto-instrument/generate_function_bodies.h
index 11014c7d06f..68f04ccf4f6 100644
--- a/src/goto-instrument/generate_function_bodies.h
+++ b/src/goto-instrument/generate_function_bodies.h
@@ -33,7 +33,7 @@ class generate_function_bodiest
   virtual void generate_function_body_impl(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const = 0;
+    irep_idt function_name) const = 0;
 
 public:
   virtual ~generate_function_bodiest() = default;
@@ -46,7 +46,7 @@ class generate_function_bodiest
   void generate_function_body(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const;
+    irep_idt function_name) const;
 
 private:
   /// Generate parameter names for unnamed parameters.
@@ -55,7 +55,7 @@ class generate_function_bodiest
   void generate_parameter_names(
     goto_functiont &function,
     symbol_tablet &symbol_table,
-    const irep_idt &function_name) const;
+    irep_idt function_name) const;
 };
 
 std::unique_ptr<generate_function_bodiest> generate_function_bodies_factory(
diff --git a/src/goto-instrument/goto_program2code.h b/src/goto-instrument/goto_program2code.h
index 8bb837cb48a..f81473f97a3 100644
--- a/src/goto-instrument/goto_program2code.h
+++ b/src/goto-instrument/goto_program2code.h
@@ -51,7 +51,7 @@ class goto_program2codet
 
 public:
   goto_program2codet(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const goto_programt &_goto_program,
     symbol_tablet &_symbol_table,
     code_blockt &_dest,
@@ -81,7 +81,7 @@ class goto_program2codet
   void operator()();
 
 protected:
-  const irep_idt &func_name;
+  irep_idt func_name;
   const goto_programt &goto_program;
   symbol_tablet &symbol_table;
   const namespacet ns;
diff --git a/src/goto-instrument/interrupt.cpp b/src/goto-instrument/interrupt.cpp
index cfc83340aec..4f54ee9c699 100644
--- a/src/goto-instrument/interrupt.cpp
+++ b/src/goto-instrument/interrupt.cpp
@@ -58,7 +58,7 @@ static bool potential_race_on_write(
 static void interrupt(
   value_setst &value_sets,
   const symbol_tablet &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
 #ifdef LOCAL_MAY
   const goto_functionst::goto_functiont &goto_function,
 #endif
@@ -151,7 +151,7 @@ static void interrupt(
 }
 
 static symbol_exprt
-get_isr(const symbol_tablet &symbol_table, const irep_idt &interrupt_handler)
+get_isr(const symbol_tablet &symbol_table, irep_idt interrupt_handler)
 {
   std::list<symbol_exprt> matches;
 
@@ -188,7 +188,7 @@ get_isr(const symbol_tablet &symbol_table, const irep_idt &interrupt_handler)
 void interrupt(
   value_setst &value_sets,
   goto_modelt &goto_model,
-  const irep_idt &interrupt_handler,
+  irep_idt interrupt_handler,
   message_handlert &message_handler)
 {
   // look up the ISR
diff --git a/src/goto-instrument/interrupt.h b/src/goto-instrument/interrupt.h
index 9d2446a60b0..c50f79e8d06 100644
--- a/src/goto-instrument/interrupt.h
+++ b/src/goto-instrument/interrupt.h
@@ -23,7 +23,7 @@ class value_setst;
 void interrupt(
   value_setst &,
   goto_modelt &,
-  const irep_idt &interrupt_handler,
+  irep_idt interrupt_handler,
   message_handlert &);
 
 #endif // CPROVER_GOTO_INSTRUMENT_INTERRUPT_H
diff --git a/src/goto-instrument/k_induction.cpp b/src/goto-instrument/k_induction.cpp
index 05fcc37a6f1..826278c3e7d 100644
--- a/src/goto-instrument/k_induction.cpp
+++ b/src/goto-instrument/k_induction.cpp
@@ -24,7 +24,7 @@ class k_inductiont
 {
 public:
   k_inductiont(
-    const irep_idt &_function_id,
+    irep_idt _function_id,
     goto_functiont &_goto_function,
     bool _base_case,
     bool _step_case,
@@ -43,7 +43,7 @@ class k_inductiont
   }
 
 protected:
-  const irep_idt &function_id;
+  irep_idt function_id;
   goto_functiont &goto_function;
   local_may_aliast local_may_alias;
   natural_loops_mutablet natural_loops;
diff --git a/src/goto-instrument/mmio.cpp b/src/goto-instrument/mmio.cpp
index 65ecad0c63b..158eb754d41 100644
--- a/src/goto-instrument/mmio.cpp
+++ b/src/goto-instrument/mmio.cpp
@@ -24,7 +24,7 @@ Date: September 2011
 static void mmio(
   value_setst &value_sets,
   const symbol_tablet &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
 #ifdef LOCAL_MAY
   const goto_functionst::goto_functiont &goto_function,
 #endif
diff --git a/src/goto-instrument/nondet_static.cpp b/src/goto-instrument/nondet_static.cpp
index 56266f83372..cf52230bd44 100644
--- a/src/goto-instrument/nondet_static.cpp
+++ b/src/goto-instrument/nondet_static.cpp
@@ -80,10 +80,8 @@ bool is_nondet_initializable_static(
 /// \param [inout] goto_model: Existing goto-functions and symbol table to
 ///   be updated.
 /// \param fct_name: Name of the goto-function to be updated.
-static void nondet_static(
-  const namespacet &ns,
-  goto_modelt &goto_model,
-  const irep_idt &fct_name)
+static void
+nondet_static(const namespacet &ns, goto_modelt &goto_model, irep_idt fct_name)
 {
   goto_functionst::function_mapt::iterator fct_entry =
     goto_model.goto_functions.function_map.find(fct_name);
diff --git a/src/goto-instrument/nondet_volatile.cpp b/src/goto-instrument/nondet_volatile.cpp
index a8146df8806..f3cf83f73fd 100644
--- a/src/goto-instrument/nondet_volatile.cpp
+++ b/src/goto-instrument/nondet_volatile.cpp
@@ -73,12 +73,10 @@ class nondet_volatilet
     symbol_table_baset &symbol_table,
     goto_programt &goto_program);
 
-  const symbolt &typecheck_variable(const irep_idt &id, const namespacet &ns);
+  const symbolt &typecheck_variable(irep_idt id, const namespacet &ns);
 
-  void typecheck_model(
-    const irep_idt &id,
-    const symbolt &variable,
-    const namespacet &ns);
+  void
+  typecheck_model(irep_idt id, const symbolt &variable, const namespacet &ns);
 
   void typecheck_options(const optionst &options);
 
@@ -269,7 +267,7 @@ void nondet_volatilet::nondet_volatile(
 }
 
 const symbolt &
-nondet_volatilet::typecheck_variable(const irep_idt &id, const namespacet &ns)
+nondet_volatilet::typecheck_variable(irep_idt id, const namespacet &ns)
 {
   const symbolt *symbol;
 
@@ -297,7 +295,7 @@ nondet_volatilet::typecheck_variable(const irep_idt &id, const namespacet &ns)
 }
 
 void nondet_volatilet::typecheck_model(
-  const irep_idt &id,
+  irep_idt id,
   const symbolt &variable,
   const namespacet &ns)
 {
diff --git a/src/goto-instrument/object_id.h b/src/goto-instrument/object_id.h
index c6fee15c37f..4ce7a3fe6ac 100644
--- a/src/goto-instrument/object_id.h
+++ b/src/goto-instrument/object_id.h
@@ -29,7 +29,7 @@ class object_idt
     id = symbol_expr.identifier();
   }
 
-  explicit object_idt(const irep_idt &identifier)
+  explicit object_idt(irep_idt identifier)
   {
     id=identifier;
   }
diff --git a/src/goto-instrument/race_check.cpp b/src/goto-instrument/race_check.cpp
index 6a4c48e493f..55d4a81fd02 100644
--- a/src/goto-instrument/race_check.cpp
+++ b/src/goto-instrument/race_check.cpp
@@ -40,9 +40,9 @@ class w_guardst
 
   std::list<irep_idt> w_guards;
 
-  const symbolt &get_guard_symbol(const irep_idt &object);
+  const symbolt &get_guard_symbol(irep_idt object);
 
-  const exprt get_guard_symbol_expr(const irep_idt &object)
+  const exprt get_guard_symbol_expr(irep_idt object)
   {
     return get_guard_symbol(object).symbol_expr();
   }
@@ -63,7 +63,7 @@ class w_guardst
   symbol_table_baset &symbol_table;
 };
 
-const symbolt &w_guardst::get_guard_symbol(const irep_idt &object)
+const symbolt &w_guardst::get_guard_symbol(irep_idt object)
 {
   const irep_idt identifier=id2string(object)+"$w_guard";
 
@@ -160,7 +160,7 @@ static bool has_shared_entries(const namespacet &ns, const rw_set_baset &rw_set)
 static void race_check(
   value_setst &value_sets,
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   L_M_ARG(const goto_functionst::goto_functiont &goto_function)
   goto_programt &goto_program,
   w_guardst &w_guards,
@@ -269,7 +269,7 @@ static void race_check(
 void race_check(
   value_setst &value_sets,
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
 #ifdef LOCAL_MAY
   const goto_functionst::goto_functiont &goto_function,
 #endif
diff --git a/src/goto-instrument/race_check.h b/src/goto-instrument/race_check.h
index e4d6daa3443..23946919e27 100644
--- a/src/goto-instrument/race_check.h
+++ b/src/goto-instrument/race_check.h
@@ -28,7 +28,7 @@ class value_setst;
 void race_check(
   value_setst &,
   class symbol_table_baset &,
-  const irep_idt &function_id,
+  irep_idt function_id,
 #ifdef LOCAL_MAY
   const goto_functionst::goto_functiont &goto_function,
 #endif
diff --git a/src/goto-instrument/remove_function.cpp b/src/goto-instrument/remove_function.cpp
index 2b7ab9119b8..be79df7756f 100644
--- a/src/goto-instrument/remove_function.cpp
+++ b/src/goto-instrument/remove_function.cpp
@@ -27,7 +27,7 @@ Date: April 2017
 /// message_handler  Error/status output
 void remove_function(
   goto_modelt &goto_model,
-  const irep_idt &identifier,
+  irep_idt identifier,
   message_handlert &message_handler)
 {
   messaget message(message_handler);
diff --git a/src/goto-instrument/remove_function.h b/src/goto-instrument/remove_function.h
index 9130908af17..27fa7bcfb85 100644
--- a/src/goto-instrument/remove_function.h
+++ b/src/goto-instrument/remove_function.h
@@ -22,10 +22,7 @@ Date: April 2017
 class goto_modelt;
 class message_handlert;
 
-void remove_function(
-  goto_modelt &,
-  const irep_idt &identifier,
-  message_handlert &);
+void remove_function(goto_modelt &, irep_idt identifier, message_handlert &);
 
 void remove_functions(
   goto_modelt &,
diff --git a/src/goto-instrument/rw_set.h b/src/goto-instrument/rw_set.h
index 3eefa66b554..275dafdddd5 100644
--- a/src/goto-instrument/rw_set.h
+++ b/src/goto-instrument/rw_set.h
@@ -49,7 +49,7 @@ class rw_set_baset
 
     entryt(
       const symbol_exprt &_symbol_expr,
-      const irep_idt &_object,
+      irep_idt _object,
       const exprt &_guard)
       : symbol_expr(_symbol_expr), object(_object), guard(_guard)
     {
@@ -130,7 +130,7 @@ class _rw_set_loct:public rw_set_baset
   _rw_set_loct(
     const namespacet &_ns,
     value_setst &_value_sets,
-    const irep_idt &_function_id,
+    irep_idt _function_id,
     goto_programt::const_targett _target,
     message_handlert &message_handler)
     : rw_set_baset(_ns, message_handler),
@@ -199,7 +199,7 @@ class rw_set_loct:public _rw_set_loct
   rw_set_loct(
     const namespacet &_ns,
     value_setst &_value_sets,
-    const irep_idt &_function_id,
+    irep_idt _function_id,
     goto_programt::const_targett _target,
     message_handlert &message_handler)
     : _rw_set_loct(_ns, _value_sets, _function_id, _target, message_handler)
@@ -270,7 +270,7 @@ class rw_set_with_trackt:public _rw_set_loct
   rw_set_with_trackt(
     const namespacet &_ns,
     value_setst &_value_sets,
-    const irep_idt &_function_id,
+    irep_idt _function_id,
     goto_programt::const_targett _target,
     message_handlert &message_handler)
     : _rw_set_loct(_ns, _value_sets, _function_id, _target, message_handler),
diff --git a/src/goto-instrument/uninitialized.cpp b/src/goto-instrument/uninitialized.cpp
index 93c1e13d879..4bc5126d1a0 100644
--- a/src/goto-instrument/uninitialized.cpp
+++ b/src/goto-instrument/uninitialized.cpp
@@ -23,9 +23,7 @@ class uninitializedt
   {
   }
 
-  void add_assertions(
-    const irep_idt &function_identifer,
-    goto_programt &goto_program);
+  void add_assertions(irep_idt function_identifer, goto_programt &goto_program);
 
 protected:
   symbol_table_baset &symbol_table;
@@ -61,7 +59,7 @@ void uninitializedt::get_tracking(goto_programt::const_targett i_it)
 }
 
 void uninitializedt::add_assertions(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_programt &goto_program)
 {
   uninitialized_analysis(function_identifier, goto_program, ns);
diff --git a/src/goto-instrument/unwind.cpp b/src/goto-instrument/unwind.cpp
index 88936c78983..f5b93cde684 100644
--- a/src/goto-instrument/unwind.cpp
+++ b/src/goto-instrument/unwind.cpp
@@ -81,7 +81,7 @@ void goto_unwindt::copy_segment(
 }
 
 void goto_unwindt::unwind(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const goto_programt::const_targett loop_head,
   const goto_programt::const_targett loop_exit,
@@ -100,7 +100,7 @@ void goto_unwindt::unwind(
 }
 
 void goto_unwindt::unwind(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const goto_programt::const_targett loop_head,
   const goto_programt::const_targett loop_exit,
@@ -279,7 +279,7 @@ void goto_unwindt::unwind(
 }
 
 void goto_unwindt::unwind(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   const unwindsett &unwindset,
   const unwind_strategyt unwind_strategy)
diff --git a/src/goto-instrument/unwind.h b/src/goto-instrument/unwind.h
index 71736d80310..4b83448699f 100644
--- a/src/goto-instrument/unwind.h
+++ b/src/goto-instrument/unwind.h
@@ -33,7 +33,7 @@ class goto_unwindt
   // unwind loop
 
   void unwind(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     const goto_programt::const_targett loop_head,
     const goto_programt::const_targett loop_exit,
@@ -41,7 +41,7 @@ class goto_unwindt
     const unwind_strategyt unwind_strategy);
 
   void unwind(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     const goto_programt::const_targett loop_head,
     const goto_programt::const_targett loop_exit,
@@ -52,7 +52,7 @@ class goto_unwindt
   // unwind function
 
   void unwind(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     const unwindsett &unwindset,
     const unwind_strategyt unwind_strategy = unwind_strategyt::PARTIAL);
diff --git a/src/goto-instrument/wmm/goto2graph.cpp b/src/goto-instrument/wmm/goto2graph.cpp
index 94955668ee0..12878bfdb53 100644
--- a/src/goto-instrument/wmm/goto2graph.cpp
+++ b/src/goto-instrument/wmm/goto2graph.cpp
@@ -30,7 +30,7 @@ Date: 2012
 
 
 /// is local variable?
-bool inline instrumentert::local(const irep_idt &id)
+bool inline instrumentert::local(irep_idt id)
 {
   std::string identifier=id2string(id);
 
@@ -78,7 +78,7 @@ bool inline instrumentert::local(const irep_idt &id)
   }
 }
 
-bool inline instrumentert::cfg_visitort::local(const irep_idt &i)
+bool inline instrumentert::cfg_visitort::local(irep_idt i)
 {
   return instrumenter.local(i);
 }
@@ -150,7 +150,7 @@ void instrumentert::cfg_visitort::visit_cfg_function(
   memory_modelt model,
   bool no_dependencies,
   loop_strategyt replicate_body,
-  const irep_idt &function_id,
+  irep_idt function_id,
   std::set<instrumentert::cfg_visitort::nodet> &ending_vertex)
 {
   /* flow: egraph */
@@ -406,7 +406,7 @@ event_idt alt_copy_segment(wmm_grapht &alt_egraph,
 }
 
 bool instrumentert::cfg_visitort::contains_shared_array(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::const_targett targ,
   goto_programt::const_targett i_it,
   value_setst &value_sets
@@ -414,7 +414,7 @@ bool instrumentert::cfg_visitort::contains_shared_array(
   ,
   local_may_aliast local_may
 #endif
-  ) const // NOLINT(whitespace/parens)
+) const // NOLINT(whitespace/parens)
 {
   instrumenter.message.debug()
     << "contains_shared_array called for " << targ->source_location().get_line()
@@ -462,7 +462,7 @@ bool instrumentert::cfg_visitort::contains_shared_array(
 
 /// strategy: fwd/bwd alternation
 void inline instrumentert::cfg_visitort::visit_cfg_body(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   goto_programt::const_targett i_it,
   loop_strategyt replicate_body,
@@ -647,7 +647,7 @@ void inline instrumentert::cfg_visitort::visit_cfg_backedge(
 }
 
 void instrumentert::cfg_visitort::visit_cfg_goto(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   goto_programt::instructionst::iterator i_it,
   loop_strategyt replicate_body,
@@ -748,7 +748,7 @@ void instrumentert::cfg_visitort::visit_cfg_function_call(
 
 void instrumentert::cfg_visitort::visit_cfg_lwfence(
   goto_programt::instructionst::iterator i_it,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   const goto_programt::instructiont &instruction=*i_it;
   const abstract_eventt new_fence_event(
@@ -787,7 +787,7 @@ void instrumentert::cfg_visitort::visit_cfg_lwfence(
 
 void instrumentert::cfg_visitort::visit_cfg_asm_fence(
   goto_programt::instructionst::iterator i_it,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   const goto_programt::instructiont &instruction=*i_it;
   bool WRfence = instruction.code().get_bool(ID_WRfence);
@@ -840,7 +840,7 @@ void instrumentert::cfg_visitort::visit_cfg_asm_fence(
 
 void instrumentert::cfg_visitort::visit_cfg_assign(
   value_setst &value_sets,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::instructionst::iterator &i_it,
   bool no_dependencies
 #ifdef LOCAL_MAY
@@ -1177,7 +1177,7 @@ void instrumentert::cfg_visitort::visit_cfg_assign(
 
 void instrumentert::cfg_visitort::visit_cfg_fence(
   goto_programt::instructionst::iterator i_it,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   const goto_programt::instructiont &instruction=*i_it;
   const abstract_eventt new_fence_event(
diff --git a/src/goto-instrument/wmm/goto2graph.h b/src/goto-instrument/wmm/goto2graph.h
index d864ac99461..6e8b26e8126 100644
--- a/src/goto-instrument/wmm/goto2graph.h
+++ b/src/goto-instrument/wmm/goto2graph.h
@@ -46,7 +46,7 @@ class instrumentert
   bool render_by_file;
   bool render_by_function;
 
-  bool inline local(const irep_idt &id);
+  bool inline local(irep_idt id);
 
   void inline add_instr_to_interleaving(
     goto_programt::instructionst::iterator it,
@@ -99,7 +99,7 @@ class instrumentert
     unsigned coming_from;
 
     bool contains_shared_array(
-      const irep_idt &function_id,
+      irep_idt function_id,
       goto_programt::const_targett targ,
       goto_programt::const_targett i_it,
       value_setst &value_sets
@@ -107,13 +107,13 @@ class instrumentert
       ,
       local_may_aliast local_may
 #endif
-      ) const; // NOLINT(whitespace/parens)
+    ) const; // NOLINT(whitespace/parens)
 
     /* transformers */
     void visit_cfg_thread() const;
     void visit_cfg_propagate(goto_programt::instructionst::iterator i_it);
     void visit_cfg_body(
-      const irep_idt &function_id,
+      irep_idt function_id,
       const goto_programt &goto_program,
       goto_programt::const_targett i_it,
       loop_strategyt replicate_body,
@@ -131,7 +131,7 @@ class instrumentert
       goto_programt::const_targett i_it);
     void visit_cfg_assign(
       value_setst &value_sets,
-      const irep_idt &function_id,
+      irep_idt function_id,
       goto_programt::instructionst::iterator &i_it,
       bool no_dependencies
 #ifdef LOCAL_MAY
@@ -141,21 +141,21 @@ class instrumentert
     ); // NOLINT(whitespace/parens)
     void visit_cfg_fence(
       goto_programt::instructionst::iterator i_it,
-      const irep_idt &function_id);
+      irep_idt function_id);
     void visit_cfg_skip(goto_programt::instructionst::iterator i_it);
     void visit_cfg_lwfence(
       goto_programt::instructionst::iterator i_it,
-      const irep_idt &function_id);
+      irep_idt function_id);
     void visit_cfg_asm_fence(
       goto_programt::instructionst::iterator i_it,
-      const irep_idt &function_id);
+      irep_idt function_id);
     void visit_cfg_function_call(value_setst &value_sets,
       goto_programt::instructionst::iterator i_it,
       memory_modelt model,
       bool no_dependenciess,
       loop_strategyt duplicate_body);
     void visit_cfg_goto(
-      const irep_idt &function_id,
+      irep_idt function_id,
       const goto_programt &goto_program,
       goto_programt::instructionst::iterator i_it,
       /* forces the duplication of all the loops, with array or not
@@ -244,14 +244,14 @@ class instrumentert
       coming_from = 0;
     }
 
-    void inline enter_function(const irep_idt &function_id)
+    void inline enter_function(irep_idt function_id)
     {
       if(functions_met.find(function_id) != functions_met.end())
         throw "sorry, doesn't handle recursive function for the moment";
       functions_met.insert(function_id);
     }
 
-    void inline leave_function(const irep_idt &function_id)
+    void inline leave_function(irep_idt function_id)
     {
       functions_met.erase(function_id);
     }
@@ -261,7 +261,7 @@ class instrumentert
       memory_modelt model,
       bool no_dependencies,
       loop_strategyt duplicate_body,
-      const irep_idt &function_id)
+      irep_idt function_id)
     {
       /* ignore recursive calls -- underapproximation */
       try
@@ -297,10 +297,10 @@ class instrumentert
       memory_modelt model,
       bool no_dependencies,
       loop_strategyt duplicate_body,
-      const irep_idt &function_id,
+      irep_idt function_id,
       std::set<nodet> &ending_vertex);
 
-    bool inline local(const irep_idt &i);
+    bool inline local(irep_idt i);
   };
 
 public:
diff --git a/src/goto-instrument/wmm/shared_buffers.cpp b/src/goto-instrument/wmm/shared_buffers.cpp
index 55adf6f536c..9e5639cef5c 100644
--- a/src/goto-instrument/wmm/shared_buffers.cpp
+++ b/src/goto-instrument/wmm/shared_buffers.cpp
@@ -28,8 +28,7 @@ std::string shared_bufferst::unique(void)
 }
 
 /// instruments the variable
-const shared_bufferst::varst &shared_bufferst::operator()(
-  const irep_idt &object)
+const shared_bufferst::varst &shared_bufferst::operator()(irep_idt object)
 {
   var_mapt::const_iterator it=var_map.find(object);
   if(it!=var_map.end())
@@ -141,7 +140,7 @@ void shared_bufferst::assignment(
   goto_programt &goto_program,
   goto_programt::targett &t,
   const source_locationt &source_location,
-  const irep_idt &id_lhs,
+  irep_idt id_lhs,
   const exprt &value)
 {
   const namespacet ns(symbol_table);
@@ -177,8 +176,8 @@ void shared_bufferst::delay_read(
   goto_programt &goto_program,
   goto_programt::targett &target,
   const source_locationt &source_location,
-  const irep_idt &read_object,
-  const irep_idt &write_object)
+  irep_idt read_object,
+  irep_idt write_object)
 {
 /* option 1: */
 /* trick using an additional variable whose value is to be defined later */
@@ -226,7 +225,7 @@ void shared_bufferst::flush_read(
   goto_programt &goto_program,
   goto_programt::targett &target,
   const source_locationt &source_location,
-  const irep_idt &write_object)
+  irep_idt write_object)
 {
 #if 0
   // option 1
@@ -266,7 +265,7 @@ void shared_bufferst::write(
   goto_programt &goto_program,
   goto_programt::targett &target,
   const source_locationt &source_location,
-  const irep_idt &object,
+  irep_idt object,
   goto_programt::instructiont &original_instruction,
   const unsigned current_thread)
 {
@@ -328,7 +327,7 @@ void shared_bufferst::det_flush(
   goto_programt &goto_program,
   goto_programt::targett &target,
   const source_locationt &source_location,
-  const irep_idt &object,
+  irep_idt object,
   const unsigned current_thread)
 {
   const std::string identifier=id2string(object);
@@ -431,11 +430,11 @@ void shared_bufferst::det_flush(
 
 /// instruments read
 void shared_bufferst::nondet_flush(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett &target,
   const source_locationt &source_location,
-  const irep_idt &object,
+  irep_idt object,
   const unsigned current_thread,
   const bool tso_pso_rmo) // true: tso/pso/rmo; false: power
 {
@@ -1047,7 +1046,7 @@ void shared_bufferst::affected_by_delay(
 /// instruments the program for the pairs detected through the CFG
 void shared_bufferst::cfg_visitort::weak_memory(
   value_setst &value_sets,
-  const irep_idt &function_id,
+  irep_idt function_id,
   memory_modelt model)
 {
   shared_buffers.message.debug()
diff --git a/src/goto-instrument/wmm/shared_buffers.h b/src/goto-instrument/wmm/shared_buffers.h
index 729892b7700..f13a29d7f62 100644
--- a/src/goto-instrument/wmm/shared_buffers.h
+++ b/src/goto-instrument/wmm/shared_buffers.h
@@ -86,7 +86,7 @@ class shared_bufferst
   // events in cycles: var->locations (for read instrumentations)
   std::multimap<irep_idt, source_locationt> cycles_r_loc;
 
-  const varst &operator()(const irep_idt &object);
+  const varst &operator()(irep_idt object);
 
   void add_initialization_code(goto_functionst &goto_functions);
 
@@ -94,20 +94,20 @@ class shared_bufferst
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &read_object,
-    const irep_idt &write_object);
+    irep_idt read_object,
+    irep_idt write_object);
 
   void flush_read(
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &write_object);
+    irep_idt write_object);
 
   void write(
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &object,
+    irep_idt object,
     goto_programt::instructiont &original_instruction,
     const unsigned current_thread);
 
@@ -115,15 +115,15 @@ class shared_bufferst
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &object,
+    irep_idt object,
     const unsigned current_thread);
 
   void nondet_flush(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &object,
+    irep_idt object,
     const unsigned current_thread,
     const bool tso_pso_rmo);
 
@@ -131,22 +131,22 @@ class shared_bufferst
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &id_lhs,
+    irep_idt id_lhs,
     const exprt &rhs);
 
   void assignment(
     goto_programt &goto_program,
     goto_programt::targett &t,
     const source_locationt &source_location,
-    const irep_idt &id_lhs,
-    const irep_idt &id_rhs)
+    irep_idt id_lhs,
+    irep_idt id_rhs)
   {
     namespacet ns(symbol_table);
     assignment(goto_program, t, source_location, id_lhs,
       ns.lookup(id_rhs).symbol_expr());
   }
 
-  bool track(const irep_idt &id) const
+  bool track(irep_idt id) const
   {
     namespacet ns(symbol_table);
 
@@ -159,7 +159,7 @@ class shared_bufferst
     return true;
   }
 
-  irep_idt choice(const irep_idt &function_id, const std::string &suffix)
+  irep_idt choice(irep_idt function_id, const std::string &suffix)
   {
     const auto maybe_symbol = symbol_table.lookup(function_id);
     CHECK_RETURN(maybe_symbol);
@@ -217,7 +217,7 @@ class shared_bufferst
 
     void weak_memory(
       value_setst &value_sets,
-      const irep_idt &function_id,
+      irep_idt function_id,
       memory_modelt model);
   };
 
diff --git a/src/goto-instrument/wmm/weak_memory.cpp b/src/goto-instrument/wmm/weak_memory.cpp
index bf4b85c69fe..d82aaccde8a 100644
--- a/src/goto-instrument/wmm/weak_memory.cpp
+++ b/src/goto-instrument/wmm/weak_memory.cpp
@@ -38,7 +38,7 @@ Date: September 2011
 void introduce_temporaries(
   value_setst &value_sets,
   symbol_tablet &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
 #ifdef LOCAL_MAY
   const goto_functionst::goto_functiont &goto_function,
diff --git a/src/goto-instrument/wmm/weak_memory.h b/src/goto-instrument/wmm/weak_memory.h
index 9908a2a42de..477d25d5ea5 100644
--- a/src/goto-instrument/wmm/weak_memory.h
+++ b/src/goto-instrument/wmm/weak_memory.h
@@ -47,7 +47,7 @@ void weak_memory(
 void introduce_temporaries(
   value_setst &,
   symbol_tablet &,
-  const irep_idt &function,
+  irep_idt function,
   goto_programt &,
 #ifdef LOCAL_MAY
   const goto_functionst::goto_functiont &goto_function,
diff --git a/src/goto-programs/abstract_goto_model.h b/src/goto-programs/abstract_goto_model.h
index 150fe02a43f..68e7b5986d3 100644
--- a/src/goto-programs/abstract_goto_model.h
+++ b/src/goto-programs/abstract_goto_model.h
@@ -29,7 +29,7 @@ class abstract_goto_modelt
   /// \param id: function ID to query
   /// \return true if we can produce a function body, or false if we would leave
   ///   it a bodyless stub.
-  virtual bool can_produce_function(const irep_idt &id) const = 0;
+  virtual bool can_produce_function(irep_idt id) const = 0;
 
   /// Get a GOTO function by name, or throw if no such function exists.
   /// May have side-effects on the GOTO function map provided by
@@ -37,8 +37,8 @@ class abstract_goto_modelt
   /// so iterators pointing into either may be invalidated.
   /// \param id: function to get
   /// \return goto function
-  virtual const goto_functionst::goto_functiont &get_goto_function(
-    const irep_idt &id) = 0;
+  virtual const goto_functionst::goto_functiont &
+  get_goto_function(irep_idt id) = 0;
 
   /// Accessor to get a raw goto_functionst. Concurrent use of get_goto_function
   /// may invalidate iterators or otherwise surprise users by modifying the map
diff --git a/src/goto-programs/class_hierarchy.cpp b/src/goto-programs/class_hierarchy.cpp
index a58c2e3baf7..6fb64b0bbb9 100644
--- a/src/goto-programs/class_hierarchy.cpp
+++ b/src/goto-programs/class_hierarchy.cpp
@@ -82,7 +82,7 @@ class_hierarchy_grapht::idst class_hierarchy_grapht::ids_from_indices(
 /// \param c: The class to consider
 /// \return A list containing ids of all direct children of c.
 class_hierarchy_grapht::idst
-class_hierarchy_grapht::get_direct_children(const irep_idt &c) const
+class_hierarchy_grapht::get_direct_children(irep_idt c) const
 {
   const node_indext &node_index = nodes_by_name.at(c);
   const auto &child_indices = get_successors(node_index);
@@ -90,9 +90,8 @@ class_hierarchy_grapht::get_direct_children(const irep_idt &c) const
 }
 
 /// Helper function for `get_children_trans` and `get_parents_trans`
-class_hierarchy_grapht::idst class_hierarchy_grapht::get_other_reachable_ids(
-  const irep_idt &c,
-  bool forwards) const
+class_hierarchy_grapht::idst
+class_hierarchy_grapht::get_other_reachable_ids(irep_idt c, bool forwards) const
 {
   idst direct_child_ids;
   const node_indext &node_index = nodes_by_name.at(c);
@@ -112,7 +111,7 @@ class_hierarchy_grapht::idst class_hierarchy_grapht::get_other_reachable_ids(
 /// \param c: The class to consider
 /// \return A list containing ids of all classes that eventually inherit from c.
 class_hierarchy_grapht::idst
-class_hierarchy_grapht::get_children_trans(const irep_idt &c) const
+class_hierarchy_grapht::get_children_trans(irep_idt c) const
 {
   return get_other_reachable_ids(c, true);
 }
@@ -121,14 +120,12 @@ class_hierarchy_grapht::get_children_trans(const irep_idt &c) const
 /// \param c: The class to consider
 /// \return A list of class ids that c eventually inherits from.
 class_hierarchy_grapht::idst
-class_hierarchy_grapht::get_parents_trans(const irep_idt &c) const
+class_hierarchy_grapht::get_parents_trans(irep_idt c) const
 {
   return get_other_reachable_ids(c, false);
 }
 
-void class_hierarchyt::get_children_trans_rec(
-  const irep_idt &c,
-  idst &dest) const
+void class_hierarchyt::get_children_trans_rec(irep_idt c, idst &dest) const
 {
   class_mapt::const_iterator it=class_map.find(c);
   if(it==class_map.end())
@@ -176,9 +173,7 @@ void class_hierarchyt::operator()(const symbol_table_baset &symbol_table)
 /// the order is all the parents of the first immediate parent
 /// \param c: The class to consider
 /// \param [out] dest: A list of class ids that c eventually inherits from.
-void class_hierarchyt::get_parents_trans_rec(
-  const irep_idt &c,
-  idst &dest) const
+void class_hierarchyt::get_parents_trans_rec(irep_idt c, idst &dest) const
 {
   class_mapt::const_iterator it=class_map.find(c);
   if(it==class_map.end())
diff --git a/src/goto-programs/class_hierarchy.h b/src/goto-programs/class_hierarchy.h
index 7041f8c2571..6bc1cbce34d 100644
--- a/src/goto-programs/class_hierarchy.h
+++ b/src/goto-programs/class_hierarchy.h
@@ -63,7 +63,7 @@ class class_hierarchyt
   class_hierarchyt &operator=(const class_hierarchyt &) = delete;
 
   // transitively gets all children
-  idst get_children_trans(const irep_idt &id) const
+  idst get_children_trans(irep_idt id) const
   {
     idst result;
     get_children_trans_rec(id, result);
@@ -71,7 +71,7 @@ class class_hierarchyt
   }
 
   // transitively gets all parents
-  idst get_parents_trans(const irep_idt &id) const
+  idst get_parents_trans(irep_idt id) const
   {
     idst result;
     get_parents_trans_rec(id, result);
@@ -83,8 +83,8 @@ class class_hierarchyt
   void output(json_stream_arrayt &, bool children_only) const;
 
 protected:
-  void get_children_trans_rec(const irep_idt &, idst &) const;
-  void get_parents_trans_rec(const irep_idt &, idst &) const;
+  void get_children_trans_rec(irep_idt, idst &) const;
+  void get_parents_trans_rec(irep_idt, idst &) const;
 };
 
 /// Class hierarchy graph node: simply contains a class identifier.
@@ -114,11 +114,11 @@ class class_hierarchy_grapht : public grapht<class_hierarchy_graph_nodet>
     return nodes_by_name;
   }
 
-  idst get_direct_children(const irep_idt &c) const;
+  idst get_direct_children(irep_idt c) const;
 
-  idst get_children_trans(const irep_idt &c) const;
+  idst get_children_trans(irep_idt c) const;
 
-  idst get_parents_trans(const irep_idt &c) const;
+  idst get_parents_trans(irep_idt c) const;
 
 private:
   /// Maps class identifiers onto node indices
@@ -126,7 +126,7 @@ class class_hierarchy_grapht : public grapht<class_hierarchy_graph_nodet>
 
   idst ids_from_indices(const std::vector<node_indext> &nodes) const;
 
-  idst get_other_reachable_ids(const irep_idt &c, bool forwards) const;
+  idst get_other_reachable_ids(irep_idt c, bool forwards) const;
 };
 
 /// Output the class hierarchy
diff --git a/src/goto-programs/goto_functions.h b/src/goto-programs/goto_functions.h
index 73f8d06ba1d..b4843df9dc7 100644
--- a/src/goto-programs/goto_functions.h
+++ b/src/goto-programs/goto_functions.h
@@ -69,7 +69,7 @@ class goto_functionst
   /// Remove the function named \p name from the function map, if it exists.
   /// \return Returns 0 when \p name was not present, and 1 when \p name was
   ///   removed.
-  std::size_t unload(const irep_idt &name)
+  std::size_t unload(irep_idt name)
   {
     return function_map.erase(name);
   }
diff --git a/src/goto-programs/goto_inline_class.cpp b/src/goto-programs/goto_inline_class.cpp
index c604403bb8d..72413ea39f0 100644
--- a/src/goto-programs/goto_inline_class.cpp
+++ b/src/goto-programs/goto_inline_class.cpp
@@ -23,7 +23,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 void goto_inlinet::parameter_assignments(
   const goto_programt::targett target,
-  const irep_idt &function_name, // name of called function
+  irep_idt function_name, // name of called function
   const goto_functiont::parameter_identifierst &parameter_identifiers,
   const exprt::operandst &arguments, // arguments of call
   goto_programt &dest)
diff --git a/src/goto-programs/goto_inline_class.h b/src/goto-programs/goto_inline_class.h
index bb4b2e81f54..a881abae4cc 100644
--- a/src/goto-programs/goto_inline_class.h
+++ b/src/goto-programs/goto_inline_class.h
@@ -202,7 +202,7 @@ class goto_inlinet
 
   void parameter_assignments(
     const goto_programt::targett target,
-    const irep_idt &function_name,
+    irep_idt function_name,
     const goto_functiont::parameter_identifierst &parameter_identifiers,
     const exprt::operandst &arguments,
     goto_programt &dest);
diff --git a/src/goto-programs/goto_instruction_code.cpp b/src/goto-programs/goto_instruction_code.cpp
index 65826ee8b7e..253c9912daa 100644
--- a/src/goto-programs/goto_instruction_code.cpp
+++ b/src/goto-programs/goto_instruction_code.cpp
@@ -30,7 +30,7 @@ code_inputt::code_inputt(
 }
 
 code_inputt::code_inputt(
-  const irep_idt &description,
+  irep_idt description,
   exprt expression,
   std::optional<source_locationt> location)
   : code_inputt{
@@ -59,7 +59,7 @@ code_outputt::code_outputt(
 }
 
 code_outputt::code_outputt(
-  const irep_idt &description,
+  irep_idt description,
   exprt expression,
   std::optional<source_locationt> location)
   : code_outputt{
diff --git a/src/goto-programs/goto_instruction_code.h b/src/goto-programs/goto_instruction_code.h
index 298893c01eb..acd091d5873 100644
--- a/src/goto-programs/goto_instruction_code.h
+++ b/src/goto-programs/goto_instruction_code.h
@@ -422,7 +422,7 @@ class code_inputt : public goto_instruction_codet
   ///   recorded as an input.
   /// \param location: A location to associate with this instruction.
   code_inputt(
-    const irep_idt &description,
+    irep_idt description,
     exprt expression,
     std::optional<source_locationt> location = {});
 
@@ -468,7 +468,7 @@ class code_outputt : public goto_instruction_codet
   ///   recorded as an output.
   /// \param location: A location to associate with this instruction.
   code_outputt(
-    const irep_idt &description,
+    irep_idt description,
     exprt expression,
     std::optional<source_locationt> location = {});
 
diff --git a/src/goto-programs/goto_model.h b/src/goto-programs/goto_model.h
index 7debed5795c..0044af5cf84 100644
--- a/src/goto-programs/goto_model.h
+++ b/src/goto-programs/goto_model.h
@@ -69,7 +69,7 @@ class goto_modelt : public abstract_goto_modelt
   /// Remove the function named \p name from the function map, if it exists.
   /// \return Returns 0 when \p name was not present, and 1 when \p name was
   ///   removed.
-  std::size_t unload(const irep_idt &name)
+  std::size_t unload(irep_idt name)
   {
     return goto_functions.unload(name);
   }
@@ -86,13 +86,12 @@ class goto_modelt : public abstract_goto_modelt
     return symbol_table;
   }
 
-  const goto_functionst::goto_functiont &get_goto_function(
-    const irep_idt &id) override
+  const goto_functionst::goto_functiont &get_goto_function(irep_idt id) override
   {
     return goto_functions.function_map.at(id);
   }
 
-  bool can_produce_function(const irep_idt &id) const override
+  bool can_produce_function(irep_idt id) const override
   {
     return goto_functions.function_map.find(id) !=
            goto_functions.function_map.end();
@@ -142,13 +141,12 @@ class wrapper_goto_modelt : public abstract_goto_modelt
     return symbol_table;
   }
 
-  const goto_functionst::goto_functiont &get_goto_function(
-    const irep_idt &id) override
+  const goto_functionst::goto_functiont &get_goto_function(irep_idt id) override
   {
     return goto_functions.function_map.at(id);
   }
 
-  bool can_produce_function(const irep_idt &id) const override
+  bool can_produce_function(irep_idt id) const override
   {
     return goto_functions.function_map.find(id) !=
            goto_functions.function_map.end();
@@ -201,12 +199,12 @@ class goto_model_functiont
   goto_model_functiont(
     journalling_symbol_tablet &symbol_table,
     goto_functionst &goto_functions,
-    const irep_idt &function_id,
-    goto_functionst::goto_functiont &goto_function):
-  symbol_table(symbol_table),
-  goto_functions(goto_functions),
-  function_id(function_id),
-  goto_function(goto_function)
+    irep_idt function_id,
+    goto_functionst::goto_functiont &goto_function)
+    : symbol_table(symbol_table),
+      goto_functions(goto_functions),
+      function_id(function_id),
+      goto_function(goto_function)
   {
   }
 
diff --git a/src/goto-programs/goto_program.cpp b/src/goto-programs/goto_program.cpp
index 360759e4a1e..ec351f9bfb5 100644
--- a/src/goto-programs/goto_program.cpp
+++ b/src/goto-programs/goto_program.cpp
@@ -514,7 +514,7 @@ std::list<exprt> objects_written(
 
 std::string as_string(
   const class namespacet &ns,
-  const irep_idt &function,
+  irep_idt function,
   const goto_programt::instructiont &i)
 {
   std::string result;
diff --git a/src/goto-programs/goto_program.h b/src/goto-programs/goto_program.h
index 234d759f6c9..6057d24d3f1 100644
--- a/src/goto-programs/goto_program.h
+++ b/src/goto-programs/goto_program.h
@@ -787,8 +787,7 @@ class goto_programt
   void update();
 
   /// Human-readable loop name
-  static irep_idt
-  loop_id(const irep_idt &function_id, const instructiont &instruction)
+  static irep_idt loop_id(irep_idt function_id, const instructiont &instruction)
   {
     return id2string(function_id) + "." +
            std::to_string(instruction.loop_number);
@@ -1243,7 +1242,7 @@ std::list<exprt> expressions_written(const goto_programt::instructiont &);
 
 std::string as_string(
   const namespacet &ns,
-  const irep_idt &function,
+  irep_idt function,
   const goto_programt::instructiont &);
 
 #endif // CPROVER_GOTO_PROGRAMS_GOTO_PROGRAM_H
diff --git a/src/goto-programs/graphml_witness.cpp b/src/goto-programs/graphml_witness.cpp
index e48b7aa6484..ba71fe7c229 100644
--- a/src/goto-programs/graphml_witness.cpp
+++ b/src/goto-programs/graphml_witness.cpp
@@ -32,7 +32,7 @@ Author: Daniel Kroening
 #include "goto_trace.h"
 
 static std::string
-expr_to_string(const namespacet &ns, const irep_idt &id, const exprt &expr)
+expr_to_string(const namespacet &ns, irep_idt id, const exprt &expr)
 {
   if(get_mode_from_identifier(ns, id) == ID_C)
     return expr2c(expr, ns, expr2c_configurationt::clean_configuration);
@@ -72,7 +72,7 @@ void graphml_witnesst::remove_l0_l1(exprt &expr)
 }
 
 std::string graphml_witnesst::convert_assign_rec(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const code_assignt &assign)
 {
   const auto cit = cache.find({identifier.get_no(), &assign.read()});
@@ -276,9 +276,8 @@ static bool contains_symbol_prefix(const exprt &expr, const std::string &prefix)
 
 /// Check if a function is built-in (CPROVER library), has no body,
 /// or does not exist in the symbol table
-static bool is_function_built_in_or_extern(
-  const namespacet &ns,
-  const irep_idt &function_id)
+static bool
+is_function_built_in_or_extern(const namespacet &ns, irep_idt function_id)
 {
   const symbolt *symbol_ptr = nullptr;
   if(ns.lookup(function_id, symbol_ptr))
@@ -300,7 +299,7 @@ static bool is_function_built_in_or_extern(
 /// Note: scope is determined by the prefix before the first "::". This is
 /// correct for CBMC's C front-end where locals are named "function::N::var"
 /// and function_id is "function". JBMC does not use graphml witnesses.
-static bool all_symbols_in_scope(const exprt &expr, const irep_idt &function_id)
+static bool all_symbols_in_scope(const exprt &expr, irep_idt function_id)
 {
   find_symbols_sett symbols;
   find_symbols(expr, symbols);
diff --git a/src/goto-programs/graphml_witness.h b/src/goto-programs/graphml_witness.h
index 3192f00a73f..4434b662222 100644
--- a/src/goto-programs/graphml_witness.h
+++ b/src/goto-programs/graphml_witness.h
@@ -41,9 +41,8 @@ class graphml_witnesst
   graphmlt graphml;
 
   void remove_l0_l1(exprt &expr);
-  std::string convert_assign_rec(
-    const irep_idt &identifier,
-    const code_assignt &assign);
+  std::string
+  convert_assign_rec(irep_idt identifier, const code_assignt &assign);
 
   template <typename T>
   static void hash_combine(std::size_t &seed, const T &v)
diff --git a/src/goto-programs/initialize_goto_model.cpp b/src/goto-programs/initialize_goto_model.cpp
index b7aada2c44f..86215af2545 100644
--- a/src/goto-programs/initialize_goto_model.cpp
+++ b/src/goto-programs/initialize_goto_model.cpp
@@ -114,7 +114,7 @@ void initialize_from_source_files(
 void set_up_custom_entry_point(
   language_filest &language_files,
   symbol_tablet &symbol_table,
-  const std::function<std::size_t(const irep_idt &)> &unload,
+  const std::function<std::size_t(irep_idt)> &unload,
   const optionst &options,
   bool try_mode_lookup,
   message_handlert &message_handler)
@@ -207,7 +207,7 @@ goto_modelt initialize_goto_model(
   set_up_custom_entry_point(
     language_files,
     goto_model.symbol_table,
-    [&goto_model](const irep_idt &id) { return goto_model.unload(id); },
+    [&goto_model](irep_idt id) { return goto_model.unload(id); },
     options,
     true,
     message_handler);
diff --git a/src/goto-programs/initialize_goto_model.h b/src/goto-programs/initialize_goto_model.h
index 88849fe71ea..95ccffa9aa1 100644
--- a/src/goto-programs/initialize_goto_model.h
+++ b/src/goto-programs/initialize_goto_model.h
@@ -51,7 +51,7 @@ void initialize_from_source_files(
 void set_up_custom_entry_point(
   language_filest &language_files,
   symbol_tablet &symbol_table,
-  const std::function<std::size_t(const irep_idt &)> &unload,
+  const std::function<std::size_t(irep_idt)> &unload,
   const optionst &options,
   bool try_mode_lookup,
   message_handlert &message_handler);
diff --git a/src/goto-programs/interpreter.cpp b/src/goto-programs/interpreter.cpp
index 83ad4802f6c..7291b2ae253 100644
--- a/src/goto-programs/interpreter.cpp
+++ b/src/goto-programs/interpreter.cpp
@@ -445,7 +445,7 @@ interpretert::get_component(const typet &object_type, const mp_integer &offset)
 }
 
 /// returns the type object corresponding to id
-typet interpretert::get_type(const irep_idt &id) const
+typet interpretert::get_type(irep_idt id) const
 {
   dynamic_typest::const_iterator it=dynamic_types.find(id);
   if(it==dynamic_types.end())
@@ -1022,7 +1022,7 @@ mp_integer interpretert::get_size(const typet &type)
   return 1;
 }
 
-exprt interpretert::get_value(const irep_idt &id)
+exprt interpretert::get_value(irep_idt id)
 {
   // The dynamic type and the static symbol type may differ for VLAs,
   // where the symbol carries a size expression and the dynamic type
diff --git a/src/goto-programs/interpreter_class.h b/src/goto-programs/interpreter_class.h
index e873546db7a..1077dc837ab 100644
--- a/src/goto-programs/interpreter_class.h
+++ b/src/goto-programs/interpreter_class.h
@@ -201,7 +201,7 @@ class interpretert
   struct_typet::componentt
   get_component(const typet &object_type, const mp_integer &offset);
 
-  typet get_type(const irep_idt &id) const;
+  typet get_type(irep_idt id) const;
 
   exprt get_value(
     const typet &type,
@@ -213,7 +213,7 @@ class interpretert
     mp_vectort &rhs,
     const mp_integer &offset=0);
 
-  exprt get_value(const irep_idt &id);
+  exprt get_value(irep_idt id);
 
   void step();
 
diff --git a/src/goto-programs/json_expr.cpp b/src/goto-programs/json_expr.cpp
index 3af77d5e51a..53ed5bb193e 100644
--- a/src/goto-programs/json_expr.cpp
+++ b/src/goto-programs/json_expr.cpp
@@ -75,7 +75,7 @@ static exprt simplify_json_expr(const exprt &src)
 /// \param ns: a namespace
 /// \param mode: language in which the code was written
 /// \return a json object
-json_objectt json(const typet &type, const namespacet &ns, const irep_idt &mode)
+json_objectt json(const typet &type, const namespacet &ns, irep_idt mode)
 {
   json_objectt result;
 
@@ -200,7 +200,7 @@ static std::string binary(const constant_exprt &src)
 /// \param ns: a namespace
 /// \param mode: language in which the code was written
 /// \return a json object
-json_objectt json(const exprt &expr, const namespacet &ns, const irep_idt &mode)
+json_objectt json(const exprt &expr, const namespacet &ns, irep_idt mode)
 {
   json_objectt result;
 
diff --git a/src/goto-programs/json_expr.h b/src/goto-programs/json_expr.h
index 3298003db23..763ee670f4c 100644
--- a/src/goto-programs/json_expr.h
+++ b/src/goto-programs/json_expr.h
@@ -19,8 +19,8 @@ class typet;
 class exprt;
 class namespacet;
 
-json_objectt json(const exprt &, const namespacet &, const irep_idt &mode);
+json_objectt json(const exprt &, const namespacet &, irep_idt mode);
 
-json_objectt json(const typet &, const namespacet &, const irep_idt &mode);
+json_objectt json(const typet &, const namespacet &, irep_idt mode);
 
 #endif // CPROVER_GOTO_PROGRAMS_JSON_EXPR_H
diff --git a/src/goto-programs/loop_ids.cpp b/src/goto-programs/loop_ids.cpp
index e3658577b91..465badc1439 100644
--- a/src/goto-programs/loop_ids.cpp
+++ b/src/goto-programs/loop_ids.cpp
@@ -27,7 +27,7 @@ void show_loop_ids(
 
 void show_loop_ids(
   ui_message_handlert::uit ui,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program)
 {
   switch(ui)
@@ -72,7 +72,7 @@ void show_loop_ids(
 
 void show_loop_ids_json(
   ui_message_handlert::uit ui,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   json_arrayt &loops)
 {
diff --git a/src/goto-programs/loop_ids.h b/src/goto-programs/loop_ids.h
index dc8860fabb5..eee4c3644e2 100644
--- a/src/goto-programs/loop_ids.h
+++ b/src/goto-programs/loop_ids.h
@@ -26,7 +26,7 @@ class goto_programt;
 ///     goto instruction.
 struct loop_idt
 {
-  loop_idt(const irep_idt &function_id, const unsigned int loop_number)
+  loop_idt(irep_idt function_id, const unsigned int loop_number)
     : function_id(function_id), loop_number(loop_number)
   {
   }
@@ -63,7 +63,7 @@ void show_loop_ids(
 
 void show_loop_ids(
   ui_message_handlert::uit,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &);
 
 #endif // CPROVER_GOTO_PROGRAMS_LOOP_IDS_H
diff --git a/src/goto-programs/remove_function_pointers.cpp b/src/goto-programs/remove_function_pointers.cpp
index 9e99580336f..6fb1f43c0ae 100644
--- a/src/goto-programs/remove_function_pointers.cpp
+++ b/src/goto-programs/remove_function_pointers.cpp
@@ -42,9 +42,8 @@ class remove_function_pointerst
 
   void operator()(goto_functionst &goto_functions);
 
-  bool remove_function_pointers(
-    goto_programt &goto_program,
-    const irep_idt &function_id);
+  bool
+  remove_function_pointers(goto_programt &goto_program, irep_idt function_id);
 
 protected:
   message_handlert &message_handler;
@@ -67,7 +66,7 @@ class remove_function_pointerst
   /// \param target: location with function call with function pointer
   void remove_function_pointer(
     goto_programt &goto_program,
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::targett target);
 
   std::unordered_set<irep_idt> address_taken;
@@ -203,7 +202,7 @@ static void fix_argument_types(code_function_callt &function_call)
 }
 
 static void fix_return_type(
-  const irep_idt &in_function_id,
+  irep_idt in_function_id,
   code_function_callt &function_call,
   const source_locationt &source_location,
   symbol_tablet &symbol_table,
@@ -245,7 +244,7 @@ static void fix_return_type(
 
 void remove_function_pointerst::remove_function_pointer(
   goto_programt &goto_program,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett target)
 {
   const auto &function = to_dereference_expr(as_const(*target).call_function());
@@ -380,7 +379,7 @@ void remove_function_pointer(
   message_handlert &message_handler,
   symbol_tablet &symbol_table,
   goto_programt &goto_program,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett target,
   const std::unordered_set<symbol_exprt, irep_hash> &functions_set)
 {
@@ -493,7 +492,7 @@ void remove_function_pointer(
 
 bool remove_function_pointerst::remove_function_pointers(
   goto_programt &goto_program,
-  const irep_idt &function_id)
+  irep_idt function_id)
 {
   bool did_something=false;
 
diff --git a/src/goto-programs/remove_function_pointers.h b/src/goto-programs/remove_function_pointers.h
index 2bcb72ba612..53230728f18 100644
--- a/src/goto-programs/remove_function_pointers.h
+++ b/src/goto-programs/remove_function_pointers.h
@@ -43,7 +43,7 @@ void remove_function_pointer(
   message_handlert &message_handler,
   symbol_tablet &symbol_table,
   goto_programt &goto_program,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::targett target,
   const std::unordered_set<symbol_exprt, irep_hash> &functions);
 
diff --git a/src/goto-programs/remove_returns.cpp b/src/goto-programs/remove_returns.cpp
index 4c80d68167d..b5370d20316 100644
--- a/src/goto-programs/remove_returns.cpp
+++ b/src/goto-programs/remove_returns.cpp
@@ -46,25 +46,24 @@ class remove_returnst
   symbol_table_baset &symbol_table;
 
   void replace_returns(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_functionst::goto_functiont &function);
 
   bool do_function_calls(
     function_is_stubt function_is_stub,
     goto_programt &goto_program);
 
-  bool
-  restore_returns(const irep_idt &function_id, goto_programt &goto_program);
+  bool restore_returns(irep_idt function_id, goto_programt &goto_program);
 
   void undo_function_calls(
     goto_programt &goto_program);
 
   std::optional<symbol_exprt>
-  get_or_create_return_value_symbol(const irep_idt &function_id);
+  get_or_create_return_value_symbol(irep_idt function_id);
 };
 
 std::optional<symbol_exprt>
-remove_returnst::get_or_create_return_value_symbol(const irep_idt &function_id)
+remove_returnst::get_or_create_return_value_symbol(irep_idt function_id)
 {
   const namespacet ns(symbol_table);
   const auto symbol_expr = return_value_symbol(function_id, ns);
@@ -100,7 +99,7 @@ remove_returnst::get_or_create_return_value_symbol(const irep_idt &function_id)
 /// \param function_id: name of the function to transform
 /// \param function: function to transform
 void remove_returnst::replace_returns(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_functionst::goto_functiont &function)
 {
   // look up the function symbol
@@ -220,7 +219,8 @@ void remove_returnst::operator()(goto_functionst &goto_functions)
   for(auto &gf_entry : goto_functions.function_map)
   {
     // NOLINTNEXTLINE
-    auto function_is_stub = [&goto_functions](const irep_idt &function_id) {
+    auto function_is_stub = [&goto_functions](irep_idt function_id)
+    {
       auto findit = goto_functions.function_map.find(function_id);
       INVARIANT(
         findit != goto_functions.function_map.end(),
@@ -292,7 +292,7 @@ void remove_returns(goto_modelt &goto_model)
 
 /// turns an assignment to fkt#return_value back into 'return x'
 bool remove_returnst::restore_returns(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program)
 {
   // do we have X#return_value?
@@ -404,20 +404,19 @@ void restore_returns(goto_modelt &goto_model)
   rr.restore(goto_model.goto_functions);
 }
 
-irep_idt return_value_identifier(const irep_idt &identifier)
+irep_idt return_value_identifier(irep_idt identifier)
 {
   return id2string(identifier) + RETURN_VALUE_SUFFIX;
 }
 
-symbol_exprt
-return_value_symbol(const irep_idt &identifier, const namespacet &ns)
+symbol_exprt return_value_symbol(irep_idt identifier, const namespacet &ns)
 {
   const symbolt &function_symbol = ns.lookup(identifier);
   const typet &return_type = to_code_type(function_symbol.type).return_type();
   return symbol_exprt(return_value_identifier(identifier), return_type);
 }
 
-bool is_return_value_identifier(const irep_idt &id)
+bool is_return_value_identifier(irep_idt id)
 {
   return has_suffix(id2string(id), RETURN_VALUE_SUFFIX);
 }
diff --git a/src/goto-programs/remove_returns.h b/src/goto-programs/remove_returns.h
index 5474e7cc519..8a56e5b1561 100644
--- a/src/goto-programs/remove_returns.h
+++ b/src/goto-programs/remove_returns.h
@@ -85,7 +85,7 @@ class symbol_exprt;
 
 void remove_returns(symbol_table_baset &, goto_functionst &);
 
-typedef std::function<bool(const irep_idt &)> function_is_stubt;
+typedef std::function<bool(irep_idt)> function_is_stubt;
 
 void remove_returns(goto_model_functiont &, function_is_stubt);
 
@@ -98,15 +98,15 @@ void restore_returns(goto_modelt &);
 
 /// produces the identifier that is used to store the return
 /// value of the function with the given identifier
-irep_idt return_value_identifier(const irep_idt &);
+irep_idt return_value_identifier(irep_idt);
 
 /// produces the symbol that is used to store the return
 /// value of the function with the given identifier
-symbol_exprt return_value_symbol(const irep_idt &, const namespacet &);
+symbol_exprt return_value_symbol(irep_idt, const namespacet &);
 
 /// Returns true if \p id is a special return-value symbol produced by
 /// \ref return_value_identifier
-bool is_return_value_identifier(const irep_idt &id);
+bool is_return_value_identifier(irep_idt id);
 
 /// Returns true if \p symbol_expr is a special return-value symbol produced by
 /// \ref return_value_symbol
diff --git a/src/goto-programs/remove_unused_functions.cpp b/src/goto-programs/remove_unused_functions.cpp
index d4f0fbdada3..6a41e6ab658 100644
--- a/src/goto-programs/remove_unused_functions.cpp
+++ b/src/goto-programs/remove_unused_functions.cpp
@@ -55,7 +55,7 @@ void remove_unused_functions(
 }
 
 void find_used_functions(
-  const irep_idt &start,
+  irep_idt start,
   goto_functionst &functions,
   std::set<irep_idt> &seen)
 {
diff --git a/src/goto-programs/remove_unused_functions.h b/src/goto-programs/remove_unused_functions.h
index 56ac797c399..061ee2cdc70 100644
--- a/src/goto-programs/remove_unused_functions.h
+++ b/src/goto-programs/remove_unused_functions.h
@@ -29,7 +29,7 @@ void remove_unused_functions(
   message_handlert &);
 
 void find_used_functions(
-  const irep_idt &current,
+  irep_idt current,
   goto_functionst &functions,
   std::set<irep_idt> &seen);
 
diff --git a/src/goto-programs/remove_virtual_functions.cpp b/src/goto-programs/remove_virtual_functions.cpp
index e3d9822813c..cceba821609 100644
--- a/src/goto-programs/remove_virtual_functions.cpp
+++ b/src/goto-programs/remove_virtual_functions.cpp
@@ -43,19 +43,16 @@ class get_virtual_calleest
 
   const class_hierarchyt &class_hierarchy;
 
-  typedef std::function<
-    std::optional<resolve_inherited_componentt::inherited_componentt>(
-      const irep_idt &,
-      const irep_idt &)>
+  typedef std::function<std::optional<
+    resolve_inherited_componentt::inherited_componentt>(irep_idt, irep_idt)>
     function_call_resolvert;
   void get_child_functions_rec(
-    const irep_idt &,
+    irep_idt,
     const std::optional<symbol_exprt> &,
-    const irep_idt &,
+    irep_idt,
     dispatch_table_entriest &,
     dispatch_table_entries_mapt &) const;
-  exprt
-  get_method(const irep_idt &class_id, const irep_idt &component_name) const;
+  exprt get_method(irep_idt class_id, irep_idt component_name) const;
 };
 
 class remove_virtual_functionst
@@ -72,9 +69,8 @@ class remove_virtual_functionst
 
   void operator()(goto_functionst &functions);
 
-  bool remove_virtual_functions(
-    const irep_idt &function_id,
-    goto_programt &goto_program);
+  bool
+  remove_virtual_functions(irep_idt function_id, goto_programt &goto_program);
 
 private:
   const class_hierarchyt &class_hierarchy;
@@ -82,7 +78,7 @@ class remove_virtual_functionst
   namespacet ns;
 
   goto_programt::targett remove_virtual_function(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt &goto_program,
     goto_programt::targett target);
 };
@@ -201,7 +197,7 @@ static goto_programt analyse_checks_directly_preceding_function_call(
 ///   used for new instructions that are added
 /// \param [out] new_code_for_this_argument: New instructions are added here
 static void process_this_argument(
-  const irep_idt &function_id,
+  irep_idt function_id,
   const goto_programt &goto_program,
   const goto_programt::targett target,
   exprt &argument_for_this,
@@ -264,7 +260,7 @@ static void process_this_argument(
 ///   program after replaced function call
 static goto_programt::targett replace_virtual_function_with_dispatch_table(
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett target,
   const dispatch_table_entriest &functions,
@@ -464,7 +460,7 @@ static goto_programt::targett replace_virtual_function_with_dispatch_table(
 /// \return Returns a pointer to the statement in the supplied GOTO
 ///   program after replaced function call
 goto_programt::targett remove_virtual_functionst::remove_virtual_function(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett target)
 {
@@ -504,9 +500,9 @@ goto_programt::targett remove_virtual_functionst::remove_virtual_function(
 ///   -> [{"C", C.f}, {"B", C.f}, {"A", A.f}]
 /// \param entry_map: map of class identifiers to dispatch table entries
 void get_virtual_calleest::get_child_functions_rec(
-  const irep_idt &this_id,
+  irep_idt this_id,
   const std::optional<symbol_exprt> &last_method_defn,
-  const irep_idt &component_name,
+  irep_idt component_name,
   dispatch_table_entriest &functions,
   dispatch_table_entries_mapt &entry_map) const
 {
@@ -637,8 +633,8 @@ void get_virtual_calleest::get_functions(
 /// \return nil_exprt instance on error and a symbol_exprt pointing to
 ///   the method on success
 exprt get_virtual_calleest::get_method(
-  const irep_idt &class_id,
-  const irep_idt &component_name) const
+  irep_idt class_id,
+  irep_idt component_name) const
 {
   const irep_idt &id=
     resolve_inherited_componentt::build_full_component_identifier(
@@ -655,7 +651,7 @@ exprt get_virtual_calleest::get_method(
 /// them with calls to their most derived implementations. Returns
 /// true if at least one function has been replaced.
 bool remove_virtual_functionst::remove_virtual_functions(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program)
 {
   bool did_something=false;
@@ -807,7 +803,7 @@ void remove_virtual_functions(
 ///   program after replaced function call
 goto_programt::targett remove_virtual_function(
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett instruction,
   const dispatch_table_entriest &dispatch_table,
@@ -828,7 +824,7 @@ goto_programt::targett remove_virtual_function(
 
 goto_programt::targett remove_virtual_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett instruction,
   const dispatch_table_entriest &dispatch_table,
diff --git a/src/goto-programs/remove_virtual_functions.h b/src/goto-programs/remove_virtual_functions.h
index 5dd9d7d1e51..f0579b9f74d 100644
--- a/src/goto-programs/remove_virtual_functions.h
+++ b/src/goto-programs/remove_virtual_functions.h
@@ -68,7 +68,7 @@ enum class virtual_dispatch_fallback_actiont
 class dispatch_table_entryt
 {
 public:
-  explicit dispatch_table_entryt(const irep_idt &_class_id)
+  explicit dispatch_table_entryt(irep_idt _class_id)
     : symbol_expr(), class_id(_class_id)
   {
   }
@@ -104,7 +104,7 @@ typedef std::map<irep_idt, dispatch_table_entryt> dispatch_table_entries_mapt;
 
 goto_programt::targett remove_virtual_function(
   goto_modelt &goto_model,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett instruction,
   const dispatch_table_entriest &dispatch_table,
@@ -112,7 +112,7 @@ goto_programt::targett remove_virtual_function(
 
 goto_programt::targett remove_virtual_function(
   symbol_table_baset &symbol_table,
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt &goto_program,
   goto_programt::targett instruction,
   const dispatch_table_entriest &dispatch_table,
diff --git a/src/goto-programs/resolve_inherited_component.cpp b/src/goto-programs/resolve_inherited_component.cpp
index d3d855bbeff..9573291f9dc 100644
--- a/src/goto-programs/resolve_inherited_component.cpp
+++ b/src/goto-programs/resolve_inherited_component.cpp
@@ -34,8 +34,8 @@ resolve_inherited_componentt::resolve_inherited_componentt(
 /// \return The concrete component that has been resolved
 std::optional<resolve_inherited_componentt::inherited_componentt>
 resolve_inherited_componentt::operator()(
-  const irep_idt &class_id,
-  const irep_idt &component_name,
+  irep_idt class_id,
+  irep_idt component_name,
   bool include_interfaces,
   const std::function<bool(const symbolt &)> user_filter)
 {
@@ -92,7 +92,8 @@ resolve_inherited_componentt::operator()(
 /// \return A name for looking up in the symbol table for classes `class_name`'s
 ///   component `component_name`
 irep_idt resolve_inherited_componentt::build_full_component_identifier(
-  const irep_idt &class_name, const irep_idt &component_name)
+  irep_idt class_name,
+  irep_idt component_name)
 {
   // Verify the parameters are called in the correct order.
   PRECONDITION(id2string(class_name).find("::")!=std::string::npos);
@@ -124,8 +125,8 @@ irep_idt resolve_inherited_componentt::inherited_componentt::
 /// \return The concrete component that has been resolved
 std::optional<resolve_inherited_componentt::inherited_componentt>
 get_inherited_method_implementation(
-  const irep_idt &call_basename,
-  const irep_idt &classname,
+  irep_idt call_basename,
+  irep_idt classname,
   const symbol_table_baset &symbol_table)
 {
   resolve_inherited_componentt call_resolver{symbol_table};
diff --git a/src/goto-programs/resolve_inherited_component.h b/src/goto-programs/resolve_inherited_component.h
index a15d61c68e5..d9f3ed2d32d 100644
--- a/src/goto-programs/resolve_inherited_component.h
+++ b/src/goto-programs/resolve_inherited_component.h
@@ -29,10 +29,8 @@ class resolve_inherited_componentt
   class inherited_componentt
   {
   public:
-    inherited_componentt(
-      const irep_idt &class_id, const irep_idt &component_id):
-        class_identifier(class_id),
-        component_identifier(component_id)
+    inherited_componentt(irep_idt class_id, irep_idt component_id)
+      : class_identifier(class_id), component_identifier(component_id)
     {}
 
     irep_idt get_full_component_identifier() const;
@@ -48,15 +46,14 @@ class resolve_inherited_componentt
   };
 
   std::optional<inherited_componentt> operator()(
-    const irep_idt &class_id,
-    const irep_idt &component_name,
+    irep_idt class_id,
+    irep_idt component_name,
     bool include_interfaces,
-    std::function<bool(const symbolt &)> user_filter = [](const symbolt &) {
-      return true;
-    });
+    std::function<bool(const symbolt &)> user_filter = [](const symbolt &)
+    { return true; });
 
-  static irep_idt build_full_component_identifier(
-    const irep_idt &class_name, const irep_idt &component_name);
+  static irep_idt
+  build_full_component_identifier(irep_idt class_name, irep_idt component_name);
 
 private:
   const symbol_table_baset &symbol_table;
@@ -64,8 +61,8 @@ class resolve_inherited_componentt
 
 std::optional<resolve_inherited_componentt::inherited_componentt>
 get_inherited_method_implementation(
-  const irep_idt &call_basename,
-  const irep_idt &classname,
+  irep_idt call_basename,
+  irep_idt classname,
   const symbol_table_baset &symbol_table);
 
 #endif // CPROVER_GOTO_PROGRAMS_RESOLVE_INHERITED_COMPONENT_H
diff --git a/src/goto-programs/restrict_function_pointers.cpp b/src/goto-programs/restrict_function_pointers.cpp
index ec7a01fa037..fddb6bfe5fe 100644
--- a/src/goto-programs/restrict_function_pointers.cpp
+++ b/src/goto-programs/restrict_function_pointers.cpp
@@ -39,7 +39,7 @@ void for_each_function_call(GotoFunctionT &&goto_function, Handler handler)
   message_handlert &message_handler,
   symbol_tablet &symbol_table,
   goto_programt &goto_program,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const function_pointer_restrictionst &restrictions,
   const goto_programt::targett &location)
 {
diff --git a/src/goto-programs/show_goto_functions_json.cpp b/src/goto-programs/show_goto_functions_json.cpp
index 2d0e26d5eda..8d41826b53f 100644
--- a/src/goto-programs/show_goto_functions_json.cpp
+++ b/src/goto-programs/show_goto_functions_json.cpp
@@ -53,7 +53,7 @@ json_objectt show_goto_functions_jsont::convert(
       make_range(
         function.parameter_identifiers.begin(),
         function.parameter_identifiers.end())
-        .map([](const irep_idt &id) { return json_stringt{id}; });
+        .map([](irep_idt id) { return json_stringt{id}; });
     json_function["parameterIdentifiers"] = json_arrayt{
       json_parameter_id_range.begin(), json_parameter_id_range.end()};
 
@@ -117,7 +117,7 @@ json_objectt show_goto_functions_jsont::convert(
         {
           auto json_label_range =
             make_range(instruction.labels.begin(), instruction.labels.end())
-              .map([](const irep_idt &id) { return json_stringt{id}; });
+              .map([](irep_idt id) { return json_stringt{id}; });
           instruction_entry["labels"] =
             json_arrayt{json_label_range.begin(), json_label_range.end()};
         }
diff --git a/src/goto-programs/show_properties.cpp b/src/goto-programs/show_properties.cpp
index 38e46131f50..b25447c0ba5 100644
--- a/src/goto-programs/show_properties.cpp
+++ b/src/goto-programs/show_properties.cpp
@@ -20,7 +20,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "goto_model.h"
 
 std::optional<source_locationt>
-find_property(const irep_idt &property, const goto_functionst &goto_functions)
+find_property(irep_idt property, const goto_functionst &goto_functions)
 {
   for(const auto &fct : goto_functions.function_map)
   {
@@ -42,7 +42,7 @@ find_property(const irep_idt &property, const goto_functionst &goto_functions)
 
 void show_properties(
   const namespacet &ns,
-  const irep_idt &identifier,
+  irep_idt identifier,
   message_handlert &message_handler,
   ui_message_handlert::uit ui,
   const goto_programt &goto_program)
@@ -126,7 +126,7 @@ void show_properties(
 void convert_properties_json(
   json_arrayt &json_properties,
   const namespacet &ns,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const goto_programt &goto_program)
 {
   for(const auto &ins : goto_program.instructions)
diff --git a/src/goto-programs/show_properties.h b/src/goto-programs/show_properties.h
index 1a7cfa494ca..e9098bf1808 100644
--- a/src/goto-programs/show_properties.h
+++ b/src/goto-programs/show_properties.h
@@ -47,7 +47,7 @@ void show_properties(
 /// \return optional<source_locationt> the location of the
 ///   property, if found.
 std::optional<source_locationt>
-find_property(const irep_idt &property, const goto_functionst &goto_functions);
+find_property(irep_idt property, const goto_functionst &goto_functions);
 
 /// \brief Collects the properties in the goto program into a `json_arrayt`
 /// \param json_properties: JSON array to hold the properties
@@ -57,7 +57,7 @@ find_property(const irep_idt &property, const goto_functionst &goto_functions);
 void convert_properties_json(
   json_arrayt &json_properties,
   const namespacet &ns,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const goto_programt &goto_program);
 
 #endif // CPROVER_GOTO_PROGRAMS_SHOW_PROPERTIES_H
diff --git a/src/goto-programs/string_abstraction.cpp b/src/goto-programs/string_abstraction.cpp
index 6de670c1794..52666a0f8ef 100644
--- a/src/goto-programs/string_abstraction.cpp
+++ b/src/goto-programs/string_abstraction.cpp
@@ -219,7 +219,7 @@ void string_abstractiont::add_str_parameters(
 code_typet::parametert string_abstractiont::add_parameter(
   const symbolt &fct_symbol,
   const typet &type,
-  const irep_idt &identifier)
+  irep_idt identifier)
 {
   typet final_type=is_ptr_argument(type)?
                    type:pointer_type(type);
@@ -298,10 +298,11 @@ void string_abstractiont::declare_define_locals(goto_programt &dest)
   }
 }
 
-void string_abstractiont::make_decl_and_def(goto_programt &dest,
-    goto_programt::targett ref_instr,
-    const irep_idt &identifier,
-    const irep_idt &source_sym)
+void string_abstractiont::make_decl_and_def(
+  goto_programt &dest,
+  goto_programt::targett ref_instr,
+  irep_idt identifier,
+  irep_idt source_sym)
 {
   const symbolt &symbol=ns.lookup(identifier);
   symbol_exprt sym_expr=symbol.symbol_expr();
@@ -395,12 +396,12 @@ exprt string_abstractiont::make_val_or_dummy_rec(goto_programt &dest,
 }
 
 symbol_exprt string_abstractiont::add_dummy_symbol_and_value(
-    goto_programt &dest,
-    goto_programt::targett ref_instr,
-    const symbolt &symbol,
-    const irep_idt &component_name,
-    const typet &type,
-    const typet &source_type)
+  goto_programt &dest,
+  goto_programt::targett ref_instr,
+  const symbolt &symbol,
+  irep_idt component_name,
+  const typet &type,
+  const typet &source_type)
 {
   std::string suffix="$strdummy";
   if(!component_name.empty())
@@ -1040,8 +1041,10 @@ bool string_abstractiont::build_symbol(const symbol_exprt &sym, exprt &dest)
   return false;
 }
 
-void string_abstractiont::build_new_symbol(const symbolt &symbol,
-    const irep_idt &identifier, const typet &type)
+void string_abstractiont::build_new_symbol(
+  const symbolt &symbol,
+  irep_idt identifier,
+  const typet &type)
 {
   if(!symbol.is_static_lifetime)
     locals[symbol.name]=identifier;
diff --git a/src/goto-programs/string_abstraction.h b/src/goto-programs/string_abstraction.h
index 596f3d5a038..a8a99a1c9b0 100644
--- a/src/goto-programs/string_abstraction.h
+++ b/src/goto-programs/string_abstraction.h
@@ -128,8 +128,10 @@ class string_abstractiont
   const typet &build_abstraction_type_rec(const typet &type,
       const abstraction_types_mapt &known);
   bool build_pointer(const exprt &object, exprt &dest, bool write);
-  void build_new_symbol(const symbolt &symbol,
-      const irep_idt &identifier, const typet &type);
+  void build_new_symbol(
+    const symbolt &symbol,
+    irep_idt identifier,
+    const typet &type);
 
   exprt member(const exprt &a, whatt what);
 
@@ -149,10 +151,13 @@ class string_abstractiont
   code_typet::parametert add_parameter(
     const symbolt &fct_symbol,
     const typet &type,
-    const irep_idt &identifier);
+    irep_idt identifier);
 
-  void make_decl_and_def(goto_programt &dest, goto_programt::targett ref_instr,
-    const irep_idt &identifier, const irep_idt &source_sym);
+  void make_decl_and_def(
+    goto_programt &dest,
+    goto_programt::targett ref_instr,
+    irep_idt identifier,
+    irep_idt source_sym);
 
   exprt make_val_or_dummy_rec(goto_programt &dest,
       goto_programt::targett ref_instr,
@@ -162,7 +167,7 @@ class string_abstractiont
     goto_programt &dest,
     goto_programt::targett ref_instr,
     const symbolt &symbol,
-    const irep_idt &component_name,
+    irep_idt component_name,
     const typet &type,
     const typet &source_type);
 
diff --git a/src/goto-programs/unwindset.cpp b/src/goto-programs/unwindset.cpp
index e214c21d27c..2b8bb2efed6 100644
--- a/src/goto-programs/unwindset.cpp
+++ b/src/goto-programs/unwindset.cpp
@@ -190,7 +190,7 @@ void unwindsett::parse_unwindset(
 }
 
 std::optional<unsigned>
-unwindsett::get_limit(const irep_idt &loop_id, unsigned thread_nr) const
+unwindsett::get_limit(irep_idt loop_id, unsigned thread_nr) const
 {
   // We use the most specific limit we have
 
diff --git a/src/goto-programs/unwindset.h b/src/goto-programs/unwindset.h
index a4af6e161ec..4126f8265c3 100644
--- a/src/goto-programs/unwindset.h
+++ b/src/goto-programs/unwindset.h
@@ -42,8 +42,7 @@ class unwindsett
     message_handlert &message_handler);
 
   // queries
-  std::optional<unsigned>
-  get_limit(const irep_idt &loop, unsigned thread_id) const;
+  std::optional<unsigned> get_limit(irep_idt loop, unsigned thread_id) const;
 
   // read unwindset directives from a file
   void parse_unwindset_file(
diff --git a/src/goto-programs/xml_goto_trace.cpp b/src/goto-programs/xml_goto_trace.cpp
index aac13610ced..b51f9159853 100644
--- a/src/goto-programs/xml_goto_trace.cpp
+++ b/src/goto-programs/xml_goto_trace.cpp
@@ -41,7 +41,7 @@ static void replace_string_constants_rec(exprt &expr)
 /// printable in XML 1.0. Produces an empty string if no valid XML 1.0 string
 /// representing \p expr can be generated.
 static std::string
-get_printable_xml(const namespacet &ns, const irep_idt &id, const exprt &expr)
+get_printable_xml(const namespacet &ns, irep_idt id, const exprt &expr)
 {
   std::string result = from_expr(ns, id, expr);
 
diff --git a/src/goto-symex/field_sensitivity.h b/src/goto-symex/field_sensitivity.h
index 12606321ce0..23e2461dd2b 100644
--- a/src/goto-symex/field_sensitivity.h
+++ b/src/goto-symex/field_sensitivity.h
@@ -125,7 +125,7 @@ class field_sensitivityt
   field_sensitivityt(
     std::size_t max_array_size,
     bool should_simplify,
-    const irep_idt &language_mode)
+    irep_idt language_mode)
     : max_field_sensitivity_array_size(max_array_size),
       should_simplify(should_simplify),
       language_mode(language_mode)
@@ -208,7 +208,7 @@ class field_sensitivityt
   const std::size_t max_field_sensitivity_array_size;
 
   const bool should_simplify;
-  const irep_idt &language_mode;
+  irep_idt language_mode;
 
   void field_assignments_rec(
     const namespacet &ns,
diff --git a/src/goto-symex/goto_symex.h b/src/goto-symex/goto_symex.h
index 5980573f0cd..a4fd1aeddec 100644
--- a/src/goto-symex/goto_symex.h
+++ b/src/goto-symex/goto_symex.h
@@ -89,8 +89,7 @@ class goto_symext
   /// \remarks
   /// This allows goto_symext to be divorced from the particular type of
   /// goto_modelt that provides the function bodies
-  typedef
-    std::function<const goto_functionst::goto_functiont &(const irep_idt &)>
+  typedef std::function<const goto_functionst::goto_functiont &(irep_idt)>
     get_goto_functiont;
 
   /// Return a function to get/load a goto function from the given goto model
@@ -179,7 +178,7 @@ class goto_symext
   /// \param loop_id: the loop identifier
   /// \param unwind: current unwinding counter
   /// \return true if the symbolic execution is to be interrupted for checking
-  virtual bool check_break(const irep_idt &loop_id, unsigned unwind);
+  virtual bool check_break(irep_idt loop_id, unsigned unwind);
 
 protected:
   /// The configuration to use for this symbolic execution
@@ -397,7 +396,7 @@ class goto_symext
   /// \param state: Symbolic execution state for current instruction
   virtual void vcc(
     const exprt &cond,
-    const irep_idt &property_id,
+    irep_idt property_id,
     const std::string &msg,
     statet &state);
 
@@ -460,7 +459,7 @@ class goto_symext
   /// \param state The current state
   /// \param goto_function The goto function
   virtual void locality(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     goto_symext::statet &state,
     const goto_functionst::goto_functiont &goto_function);
 
@@ -502,7 +501,7 @@ class goto_symext
     const exprt::operandst &cleaned_arguments);
 
   virtual bool get_unwind_recursion(
-    const irep_idt &identifier,
+    irep_idt identifier,
     unsigned thread_nr,
     unsigned unwind);
 
@@ -513,7 +512,7 @@ class goto_symext
   /// \param [out] state: state of the goto program
   /// \param arguments: arguments that are passed to the function
   void parameter_assignments(
-    const irep_idt &function_identifier,
+    irep_idt function_identifier,
     const goto_functionst::goto_functiont &goto_function,
     statet &state,
     const exprt::operandst &arguments);
diff --git a/src/goto-symex/goto_symex_state.cpp b/src/goto-symex/goto_symex_state.cpp
index d5e597a0925..0ec7804a952 100644
--- a/src/goto-symex/goto_symex_state.cpp
+++ b/src/goto-symex/goto_symex_state.cpp
@@ -34,7 +34,7 @@ goto_symex_statet::goto_symex_statet(
   bool should_simplify,
   const irep_idt language_mode,
   guard_managert &manager,
-  std::function<std::size_t(const irep_idt &)> fresh_l2_name_provider)
+  std::function<std::size_t(irep_idt)> fresh_l2_name_provider)
   : goto_statet(manager),
     source(_source),
     guard_manager(manager),
@@ -699,7 +699,7 @@ static bool requires_renaming(const typet &type, const namespacet &ns)
 template <levelt level>
 void goto_symex_statet::rename(
   typet &type,
-  const irep_idt &l1_identifier,
+  irep_idt l1_identifier,
   const namespacet &ns)
 {
   // check whether there are symbol expressions in the type; if not, there
@@ -803,7 +803,7 @@ void goto_symex_statet::print_backtrace(std::ostream &out) const
 
 ssa_exprt goto_symex_statet::add_object(
   const symbol_exprt &expr,
-  std::function<std::size_t(const irep_idt &)> index_generator,
+  std::function<std::size_t(irep_idt)> index_generator,
   const namespacet &ns)
 {
   framet &frame = call_stack().top();
diff --git a/src/goto-symex/goto_symex_state.h b/src/goto-symex/goto_symex_state.h
index 143d12ea485..f51df4ec8ce 100644
--- a/src/goto-symex/goto_symex_state.h
+++ b/src/goto-symex/goto_symex_state.h
@@ -47,7 +47,7 @@ class goto_symex_statet final : public goto_statet
     bool should_simplify,
     const irep_idt language_mode,
     guard_managert &manager,
-    std::function<std::size_t(const irep_idt &)> fresh_l2_name_provider);
+    std::function<std::size_t(irep_idt)> fresh_l2_name_provider);
   ~goto_symex_statet();
 
   /// \brief Fake "copy constructor" that initializes the `symex_target` member
@@ -106,7 +106,7 @@ class goto_symex_statet final : public goto_statet
   rename_ssa(ssa_exprt ssa, const namespacet &ns);
 
   template <levelt level = L2>
-  void rename(typet &type, const irep_idt &l1_identifier, const namespacet &ns);
+  void rename(typet &type, irep_idt l1_identifier, const namespacet &ns);
 
   [[nodiscard]] exprt l2_rename_rvalues(exprt lvalue, const namespacet &ns);
 
@@ -164,7 +164,7 @@ class goto_symex_statet final : public goto_statet
   /// \return L1-renamed SSA expression
   ssa_exprt add_object(
     const symbol_exprt &expr,
-    std::function<std::size_t(const irep_idt &)> index_generator,
+    std::function<std::size_t(irep_idt)> index_generator,
     const namespacet &ns);
 
   /// Add `invalid` (or a failed symbol) to the value_set if ssa is a pointer,
@@ -230,18 +230,18 @@ class goto_symex_statet final : public goto_statet
   unsigned remaining_vccs = 0;
 
   /// Drops an L1 name from the local L2 map
-  void drop_existing_l1_name(const irep_idt &l1_identifier)
+  void drop_existing_l1_name(irep_idt l1_identifier)
   {
     level2.current_names.erase(l1_identifier);
   }
 
   /// Drops an L1 name from the local L2 map
-  void drop_l1_name(const irep_idt &l1_identifier)
+  void drop_l1_name(irep_idt l1_identifier)
   {
     level2.current_names.erase_if_exists(l1_identifier);
   }
 
-  std::function<std::size_t(const irep_idt &)> get_l2_name_provider() const
+  std::function<std::size_t(irep_idt)> get_l2_name_provider() const
   {
     return fresh_l2_name_provider;
   }
@@ -260,7 +260,7 @@ class goto_symex_statet final : public goto_statet
 
 private:
   const irep_idt language_mode;
-  std::function<std::size_t(const irep_idt &)> fresh_l2_name_provider;
+  std::function<std::size_t(irep_idt)> fresh_l2_name_provider;
 
   /// \brief Dangerous, do not use
   ///
diff --git a/src/goto-symex/path_storage.h b/src/goto-symex/path_storage.h
index 1b230776cd5..02bc4cc2161 100644
--- a/src/goto-symex/path_storage.h
+++ b/src/goto-symex/path_storage.h
@@ -101,12 +101,12 @@ class path_storaget
 
   /// Provide a unique L1 index for a given \p id, starting from
   /// \p minimum_index.
-  std::size_t get_unique_l1_index(const irep_idt &id, std::size_t minimum_index)
+  std::size_t get_unique_l1_index(irep_idt id, std::size_t minimum_index)
   {
     return get_unique_index(l1_indices, id, minimum_index);
   }
 
-  std::size_t get_unique_l2_index(const irep_idt &id)
+  std::size_t get_unique_l2_index(irep_idt id)
   {
     return get_unique_index(l2_indices, id, 1);
   }
@@ -117,7 +117,7 @@ class path_storaget
 
   /// Generates a loop analysis for the instructions in goto_programt and
   /// keys it against function ID.
-  void add_function_loops(const irep_idt &identifier, const goto_programt &body)
+  void add_function_loops(irep_idt identifier, const goto_programt &body)
   {
     auto loop_iter = loop_analysis_map.find(identifier);
     if(loop_iter == loop_analysis_map.end())
@@ -127,8 +127,7 @@ class path_storaget
     }
   }
 
-  inline std::shared_ptr<lexical_loopst>
-  get_loop_analysis(const irep_idt &function_id)
+  inline std::shared_ptr<lexical_loopst> get_loop_analysis(irep_idt function_id)
   {
     return loop_analysis_map.at(function_id);
   }
@@ -146,7 +145,7 @@ class path_storaget
 
   std::size_t get_unique_index(
     name_index_mapt &unique_index_map,
-    const irep_idt &id,
+    irep_idt id,
     std::size_t minimum_index)
   {
     auto entry = unique_index_map.emplace(id, minimum_index);
diff --git a/src/goto-symex/postcondition.cpp b/src/goto-symex/postcondition.cpp
index 5ac2bb6af42..3e42cc7e1f8 100644
--- a/src/goto-symex/postcondition.cpp
+++ b/src/goto-symex/postcondition.cpp
@@ -44,8 +44,8 @@ class postconditiont
 protected:
   void strengthen(exprt &dest);
   void weaken(exprt &dest);
-  bool is_used_address_of(const exprt &expr, const irep_idt &identifier);
-  bool is_used(const exprt &expr, const irep_idt &identifier);
+  bool is_used_address_of(const exprt &expr, irep_idt identifier);
+  bool is_used(const exprt &expr, irep_idt identifier);
 };
 
 void postcondition(
@@ -67,9 +67,7 @@ void postcondition(
   }
 }
 
-bool postconditiont::is_used_address_of(
-  const exprt &expr,
-  const irep_idt &identifier)
+bool postconditiont::is_used_address_of(const exprt &expr, irep_idt identifier)
 {
   if(expr.id()==ID_symbol)
   {
@@ -144,9 +142,7 @@ void postconditiont::strengthen(exprt &dest)
   }
 }
 
-bool postconditiont::is_used(
-  const exprt &expr,
-  const irep_idt &identifier)
+bool postconditiont::is_used(const exprt &expr, irep_idt identifier)
 {
   if(expr.id()==ID_address_of)
   {
diff --git a/src/goto-symex/renaming_level.cpp b/src/goto-symex/renaming_level.cpp
index 0f89e3cccfe..0f0ac2a502e 100644
--- a/src/goto-symex/renaming_level.cpp
+++ b/src/goto-symex/renaming_level.cpp
@@ -128,16 +128,16 @@ void symex_level1t::restore_from(const symex_level1t &other)
   }
 }
 
-unsigned symex_level2t::latest_index(const irep_idt &identifier) const
+unsigned symex_level2t::latest_index(irep_idt identifier) const
 {
   const auto r_opt = current_names.find(identifier);
   return !r_opt ? 0 : r_opt->get().second;
 }
 
 std::size_t symex_level2t::increase_generation(
-  const irep_idt &l1_identifier,
+  irep_idt l1_identifier,
   const ssa_exprt &lhs,
-  std::function<std::size_t(const irep_idt &)> fresh_l2_name_provider)
+  std::function<std::size_t(irep_idt)> fresh_l2_name_provider)
 {
   const std::size_t n = fresh_l2_name_provider(l1_identifier);
 
diff --git a/src/goto-symex/renaming_level.h b/src/goto-symex/renaming_level.h
index eda7865f59a..f76741bb97b 100644
--- a/src/goto-symex/renaming_level.h
+++ b/src/goto-symex/renaming_level.h
@@ -74,14 +74,14 @@ struct symex_level2t
   renamedt<ssa_exprt, L2> operator()(renamedt<ssa_exprt, L1> l1_expr) const;
 
   /// Counter corresponding to an identifier
-  unsigned latest_index(const irep_idt &identifier) const;
+  unsigned latest_index(irep_idt identifier) const;
 
   /// Allocates a fresh L2 name for the given L1 identifier, and makes it the
   ///  latest generation on this path.
   std::size_t increase_generation(
-    const irep_idt &l1_identifier,
+    irep_idt l1_identifier,
     const ssa_exprt &lhs,
-    std::function<std::size_t(const irep_idt &)> fresh_l2_name_provider);
+    std::function<std::size_t(irep_idt)> fresh_l2_name_provider);
 };
 
 /// Undo all levels of renaming
diff --git a/src/goto-symex/shadow_memory.cpp b/src/goto-symex/shadow_memory.cpp
index 4d585fa8295..3667c486ea8 100644
--- a/src/goto-symex/shadow_memory.cpp
+++ b/src/goto-symex/shadow_memory.cpp
@@ -67,7 +67,7 @@ void shadow_memoryt::initialize_shadow_memory(
 const symbol_exprt &shadow_memoryt::add_field(
   goto_symex_statet &state,
   const exprt &expr,
-  const irep_idt &field_name,
+  irep_idt field_name,
   const typet &field_type)
 {
   const auto &function_symbol = ns.lookup(state.source.function_id);
@@ -158,7 +158,7 @@ void shadow_memoryt::symex_set_field(
     }
 
     // Get the type of the shadow memory for this field
-    const typet &sm_field_type = get_field_init_type(field_name, state);
+    const typet sm_field_type = get_field_init_type(field_name, state);
     // Add a conditional cast to the shadow memory field type if `rhs` is not of
     // the expected type
     const exprt casted_rhs =
@@ -222,7 +222,7 @@ void shadow_memoryt::symex_get_field(
   std::vector<std::pair<exprt, exprt>> rhs_conds_values;
   const null_pointer_exprt null_pointer(to_pointer_type(expr.type()));
   // Used to give a default value for invalid pointers and other usages
-  const exprt &field_init_expr = get_field_init_expr(field_name, state);
+  const exprt field_init_expr = get_field_init_expr(field_name, state);
 
   if(contains_null_or_invalid(value_set, null_pointer))
   {
diff --git a/src/goto-symex/shadow_memory.h b/src/goto-symex/shadow_memory.h
index 206d8b51f15..4a71df1543e 100644
--- a/src/goto-symex/shadow_memory.h
+++ b/src/goto-symex/shadow_memory.h
@@ -128,7 +128,7 @@ class shadow_memoryt
   const symbol_exprt &add_field(
     goto_symex_statet &state,
     const exprt &expr,
-    const irep_idt &field_name,
+    irep_idt field_name,
     const typet &field_type);
 
 private:
diff --git a/src/goto-symex/shadow_memory_util.cpp b/src/goto-symex/shadow_memory_util.cpp
index bc1d1ed1476..e86f554fd06 100644
--- a/src/goto-symex/shadow_memory_util.cpp
+++ b/src/goto-symex/shadow_memory_util.cpp
@@ -32,7 +32,7 @@ Author: Peter Schrammel
 void shadow_memory_log_set_field(
   const namespacet &ns,
   const messaget &log,
-  const irep_idt &field_name,
+  irep_idt field_name,
   const exprt &expr,
   const exprt &value)
 {
@@ -49,7 +49,7 @@ void shadow_memory_log_set_field(
 void shadow_memory_log_get_field(
   const namespacet &ns,
   const messaget &log,
-  const irep_idt &field_name,
+  irep_idt field_name,
   const exprt &expr)
 {
 #ifdef DEBUG_SHADOW_MEMORY
@@ -297,7 +297,7 @@ void replace_invalid_object_by_null(exprt &expr)
 }
 
 const exprt &
-get_field_init_expr(const irep_idt &field_name, const goto_symex_statet &state)
+get_field_init_expr(irep_idt field_name, const goto_symex_statet &state)
 {
   auto field_type_it = state.shadow_memory.fields.local_fields.find(field_name);
   if(field_type_it != state.shadow_memory.fields.local_fields.end())
@@ -310,10 +310,9 @@ get_field_init_expr(const irep_idt &field_name, const goto_symex_statet &state)
 }
 
 const typet &
-get_field_init_type(const irep_idt &field_name, const goto_symex_statet &state)
+get_field_init_type(irep_idt field_name, const goto_symex_statet &state)
 {
-  const exprt &field_init_expr = get_field_init_expr(field_name, state);
-  return field_init_expr.type();
+  return get_field_init_expr(field_name, state).type();
 }
 
 bool contains_null_or_invalid(
diff --git a/src/goto-symex/shadow_memory_util.h b/src/goto-symex/shadow_memory_util.h
index 4b12eed37bf..55878ae8be8 100644
--- a/src/goto-symex/shadow_memory_util.h
+++ b/src/goto-symex/shadow_memory_util.h
@@ -27,7 +27,7 @@ class typet;
 void shadow_memory_log_set_field(
   const namespacet &ns,
   const messaget &log,
-  const irep_idt &field_name,
+  irep_idt field_name,
   const exprt &expr,
   const exprt &value);
 
@@ -44,7 +44,7 @@ void shadow_memory_log_value_set(
 void shadow_memory_log_get_field(
   const namespacet &ns,
   const messaget &log,
-  const irep_idt &field_name,
+  irep_idt field_name,
   const exprt &expr);
 
 /// Logs a successful match between an address and a value within the value set.
@@ -94,7 +94,7 @@ void replace_invalid_object_by_null(exprt &expr);
 ///   expression.
 /// \returns The expression the field was initialised with.
 const exprt &
-get_field_init_expr(const irep_idt &field_name, const goto_symex_statet &state);
+get_field_init_expr(irep_idt field_name, const goto_symex_statet &state);
 
 /// Get a list of `(condition, value)` pairs for a certain pointer from
 /// the shadow memory, where each pair denotes the `value` of the pointer
@@ -120,7 +120,7 @@ std::vector<std::pair<exprt, exprt>> get_shadow_dereference_candidates(
 ///    the type of the value the field currently is associated with, but it's
 ///    invariant since the declaration).
 const typet &
-get_field_init_type(const irep_idt &field_name, const goto_symex_statet &state);
+get_field_init_type(irep_idt field_name, const goto_symex_statet &state);
 
 /// Given a pointer expression check to see if it can be a null pointer or an
 /// invalid object within value_set.
diff --git a/src/goto-symex/simplify_expr_with_value_set.cpp b/src/goto-symex/simplify_expr_with_value_set.cpp
index 24a519f6364..3ab6324b222 100644
--- a/src/goto-symex/simplify_expr_with_value_set.cpp
+++ b/src/goto-symex/simplify_expr_with_value_set.cpp
@@ -31,7 +31,7 @@ Author: Michael Tautschnig
 /// \return If we were able to evaluate the condition as true or false then we
 ///   return that, otherwise we return an empty std::optional
 static std::optional<exprt> try_evaluate_pointer_comparison(
-  const irep_idt &operation,
+  irep_idt operation,
   const symbol_exprt &symbol_expr,
   const exprt &other_operand,
   const value_sett &value_set,
diff --git a/src/goto-symex/simplify_expr_with_value_set.h b/src/goto-symex/simplify_expr_with_value_set.h
index 446326cf04a..db2baa71a44 100644
--- a/src/goto-symex/simplify_expr_with_value_set.h
+++ b/src/goto-symex/simplify_expr_with_value_set.h
@@ -18,7 +18,7 @@ class simplify_expr_with_value_sett : public simplify_exprt
 public:
   simplify_expr_with_value_sett(
     const value_sett &_vs,
-    const irep_idt &_mode,
+    irep_idt _mode,
     const namespacet &_ns)
     : simplify_exprt(_ns), value_set(_vs), language_mode(_mode)
   {
diff --git a/src/goto-symex/symex_assign.h b/src/goto-symex/symex_assign.h
index e6a282637d7..345fdff3b8b 100644
--- a/src/goto-symex/symex_assign.h
+++ b/src/goto-symex/symex_assign.h
@@ -33,7 +33,7 @@ class symex_assignt
     symex_targett::assignment_typet assignment_type,
     const namespacet &ns,
     const symex_configt &symex_config,
-    const irep_idt &language_mode,
+    irep_idt language_mode,
     symex_targett &target)
     : shadow_memory(shadow_memory),
       state(state),
@@ -67,7 +67,7 @@ class symex_assignt
   symex_targett::assignment_typet assignment_type;
   const namespacet &ns;
   const symex_configt &symex_config;
-  const irep_idt &language_mode;
+  irep_idt language_mode;
   symex_targett &target;
 
   void assign_from_struct(
diff --git a/src/goto-symex/symex_builtin_functions.cpp b/src/goto-symex/symex_builtin_functions.cpp
index 0ffc7b606f6..6c1fe4f0849 100644
--- a/src/goto-symex/symex_builtin_functions.cpp
+++ b/src/goto-symex/symex_builtin_functions.cpp
@@ -212,7 +212,7 @@ void goto_symext::symex_allocate(
 /// we need to put immediate values or pointers in there, depending on the size
 /// of the parameter.
 static exprt va_list_entry(
-  const irep_idt &parameter,
+  irep_idt parameter,
   const pointer_typet &lhs_type,
   const namespacet &ns)
 {
@@ -336,7 +336,7 @@ static irep_idt get_string_argument_rec(const exprt &src)
 static irep_idt get_string_argument(
   const exprt &src,
   const value_sett &value_set,
-  const irep_idt &language_mode,
+  irep_idt language_mode,
   const namespacet &ns)
 {
   exprt tmp=src;
diff --git a/src/goto-symex/symex_decl.cpp b/src/goto-symex/symex_decl.cpp
index a33352d2b83..fc7c429f010 100644
--- a/src/goto-symex/symex_decl.cpp
+++ b/src/goto-symex/symex_decl.cpp
@@ -31,9 +31,8 @@ void goto_symext::symex_decl(statet &state, const symbol_exprt &expr)
   // doing it this way).
   ssa_exprt ssa = state.add_object(
     expr,
-    [this](const irep_idt &l0_name) {
-      return path_storage.get_unique_l1_index(l0_name, 1);
-    },
+    [this](irep_idt l0_name)
+    { return path_storage.get_unique_l1_index(l0_name, 1); },
     ns);
 
   ssa = state.declare(std::move(ssa), ns);
diff --git a/src/goto-symex/symex_function_call.cpp b/src/goto-symex/symex_function_call.cpp
index a23c6a7b426..a6a33520b69 100644
--- a/src/goto-symex/symex_function_call.cpp
+++ b/src/goto-symex/symex_function_call.cpp
@@ -24,13 +24,13 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "path_storage.h"
 #include "symex_assign.h"
 
-bool goto_symext::get_unwind_recursion(const irep_idt &, unsigned, unsigned)
+bool goto_symext::get_unwind_recursion(irep_idt, unsigned, unsigned)
 {
   return false;
 }
 
 void goto_symext::parameter_assignments(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   const goto_functionst::goto_functiont &goto_function,
   statet &state,
   const exprt::operandst &arguments)
@@ -466,7 +466,7 @@ void goto_symext::symex_end_of_function(statet &state)
 }
 
 void goto_symext::locality(
-  const irep_idt &function_identifier,
+  irep_idt function_identifier,
   goto_symext::statet &state,
   const goto_functionst::goto_functiont &goto_function)
 {
@@ -478,9 +478,8 @@ void goto_symext::locality(
   {
     const ssa_exprt &renamed_param = state.add_object(
       ns.lookup(param).symbol_expr(),
-      [this, &frame_nr](const irep_idt &l0_name) {
-        return path_storage.get_unique_l1_index(l0_name, frame_nr);
-      },
+      [this, &frame_nr](irep_idt l0_name)
+      { return path_storage.get_unique_l1_index(l0_name, frame_nr); },
       ns);
 
     // Allocate shadow memory for parameters.
diff --git a/src/goto-symex/symex_goto.cpp b/src/goto-symex/symex_goto.cpp
index 98eef067653..032a693a426 100644
--- a/src/goto-symex/symex_goto.cpp
+++ b/src/goto-symex/symex_goto.cpp
@@ -454,7 +454,7 @@ void goto_symext::symex_unreachable_goto(statet &state)
   symex_transition(state);
 }
 
-bool goto_symext::check_break(const irep_idt &loop_id, unsigned unwind)
+bool goto_symext::check_break(irep_idt loop_id, unsigned unwind)
 {
   // dummy implementation
   return false;
diff --git a/src/goto-symex/symex_main.cpp b/src/goto-symex/symex_main.cpp
index 9e9e519a68a..50be8133bce 100644
--- a/src/goto-symex/symex_main.cpp
+++ b/src/goto-symex/symex_main.cpp
@@ -179,7 +179,7 @@ void goto_symext::symex_assert(
 
 void goto_symext::vcc(
   const exprt &condition,
-  const irep_idt &property_id,
+  irep_idt property_id,
   const std::string &msg,
   statet &state)
 {
@@ -420,7 +420,7 @@ std::unique_ptr<goto_symext::statet> goto_symext::initialize_entry_point_state(
     symex_config.simplify_opt,
     language_mode,
     guard_manager,
-    [storage](const irep_idt &id) { return storage->get_unique_l2_index(id); });
+    [storage](irep_idt id) { return storage->get_unique_l2_index(id); });
 
   CHECK_RETURN(!state->threads.empty());
   CHECK_RETURN(!state->call_stack().empty());
@@ -492,10 +492,8 @@ void goto_symext::initialize_path_storage_from_entry_point_of(
 goto_symext::get_goto_functiont
 goto_symext::get_goto_function(abstract_goto_modelt &goto_model)
 {
-  return [&goto_model](
-           const irep_idt &id) -> const goto_functionst::goto_functiont & {
-    return goto_model.get_goto_function(id);
-  };
+  return [&goto_model](irep_idt id) -> const goto_functionst::goto_functiont &
+  { return goto_model.get_goto_function(id); };
 }
 
 messaget::mstreamt &
diff --git a/src/goto-symex/symex_target.h b/src/goto-symex/symex_target.h
index 209bc6de49e..6fa1e45fef5 100644
--- a/src/goto-symex/symex_target.h
+++ b/src/goto-symex/symex_target.h
@@ -41,14 +41,12 @@ class symex_targett
     // is in its program sequence
     goto_programt::const_targett pc;
 
-    sourcet(const irep_idt &_function_id, goto_programt::const_targett _pc)
+    sourcet(irep_idt _function_id, goto_programt::const_targett _pc)
       : thread_nr(0), function_id(_function_id), pc(_pc)
     {
     }
 
-    explicit sourcet(
-      const irep_idt &_function_id,
-      const goto_programt &_goto_program)
+    explicit sourcet(irep_idt _function_id, const goto_programt &_goto_program)
       : thread_nr(0),
         function_id(_function_id),
         pc(_goto_program.instructions.begin())
@@ -157,7 +155,7 @@ class symex_targett
   ///  function call
   virtual void function_call(
     const exprt &guard,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const std::vector<renamedt<exprt, L2>> &ssa_function_arguments,
     const sourcet &source,
     bool hidden) = 0;
@@ -170,7 +168,7 @@ class symex_targett
   ///  function return
   virtual void function_return(
     const exprt &guard,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const sourcet &source,
     bool hidden) = 0;
 
@@ -191,7 +189,7 @@ class symex_targett
   virtual void output(
     const exprt &guard,
     const sourcet &source,
-    const irep_idt &output_id,
+    irep_idt output_id,
     const std::list<renamedt<exprt, L2>> &args) = 0;
 
   /// Record formatted output.
@@ -204,9 +202,9 @@ class symex_targett
   virtual void output_fmt(
     const exprt &guard,
     const sourcet &source,
-    const irep_idt &output_id,
-    const irep_idt &fmt,
-    const std::list<exprt> &args)=0;
+    irep_idt output_id,
+    irep_idt fmt,
+    const std::list<exprt> &args) = 0;
 
   /// Record an input.
   /// \param guard: Precondition for reading from the input
@@ -217,8 +215,8 @@ class symex_targett
   virtual void input(
     const exprt &guard,
     const sourcet &source,
-    const irep_idt &input_id,
-    const std::list<exprt> &args)=0;
+    irep_idt input_id,
+    const std::list<exprt> &args) = 0;
 
   /// Record an assumption.
   /// \param guard: Precondition for reaching this assumption
@@ -240,7 +238,7 @@ class symex_targett
   virtual void assertion(
     const exprt &guard,
     const exprt &cond,
-    const irep_idt &property_id,
+    irep_idt property_id,
     const std::string &msg,
     const sourcet &source) = 0;
 
diff --git a/src/goto-symex/symex_target_equation.cpp b/src/goto-symex/symex_target_equation.cpp
index 0bb35155e01..46aa1df5f41 100644
--- a/src/goto-symex/symex_target_equation.cpp
+++ b/src/goto-symex/symex_target_equation.cpp
@@ -180,7 +180,7 @@ void symex_target_equationt::location(
 
 void symex_target_equationt::function_call(
   const exprt &guard,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const std::vector<renamedt<exprt, L2>> &function_arguments,
   const sourcet &source,
   const bool hidden)
@@ -199,7 +199,7 @@ void symex_target_equationt::function_call(
 
 void symex_target_equationt::function_return(
   const exprt &guard,
-  const irep_idt &function_id,
+  irep_idt function_id,
   const sourcet &source,
   const bool hidden)
 {
@@ -216,7 +216,7 @@ void symex_target_equationt::function_return(
 void symex_target_equationt::output(
   const exprt &guard,
   const sourcet &source,
-  const irep_idt &output_id,
+  irep_idt output_id,
   const std::list<renamedt<exprt, L2>> &args)
 {
   SSA_steps.emplace_back(source, goto_trace_stept::typet::OUTPUT);
@@ -233,8 +233,8 @@ void symex_target_equationt::output(
 void symex_target_equationt::output_fmt(
   const exprt &guard,
   const sourcet &source,
-  const irep_idt &output_id,
-  const irep_idt &fmt,
+  irep_idt output_id,
+  irep_idt fmt,
   const std::list<exprt> &args)
 {
   SSA_steps.emplace_back(source, goto_trace_stept::typet::OUTPUT);
@@ -252,7 +252,7 @@ void symex_target_equationt::output_fmt(
 void symex_target_equationt::input(
   const exprt &guard,
   const sourcet &source,
-  const irep_idt &input_id,
+  irep_idt input_id,
   const std::list<exprt> &args)
 {
   SSA_steps.emplace_back(source, goto_trace_stept::typet::INPUT);
@@ -282,7 +282,7 @@ void symex_target_equationt::assumption(
 void symex_target_equationt::assertion(
   const exprt &guard,
   const exprt &cond,
-  const irep_idt &property_id,
+  irep_idt property_id,
   const std::string &msg,
   const sourcet &source)
 {
diff --git a/src/goto-symex/symex_target_equation.h b/src/goto-symex/symex_target_equation.h
index b10a922b113..6f89979e96b 100644
--- a/src/goto-symex/symex_target_equation.h
+++ b/src/goto-symex/symex_target_equation.h
@@ -81,7 +81,7 @@ class symex_target_equationt:public symex_targett
   /// \copydoc symex_targett::function_call()
   virtual void function_call(
     const exprt &guard,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const std::vector<renamedt<exprt, L2>> &ssa_function_arguments,
     const sourcet &source,
     bool hidden);
@@ -89,7 +89,7 @@ class symex_target_equationt:public symex_targett
   /// \copydoc symex_targett::function_return()
   virtual void function_return(
     const exprt &guard,
-    const irep_idt &function_id,
+    irep_idt function_id,
     const sourcet &source,
     bool hidden);
 
@@ -102,22 +102,22 @@ class symex_target_equationt:public symex_targett
   virtual void output(
     const exprt &guard,
     const sourcet &source,
-    const irep_idt &output_id,
+    irep_idt output_id,
     const std::list<renamedt<exprt, L2>> &args);
 
   /// \copydoc symex_targett::output_fmt()
   virtual void output_fmt(
     const exprt &guard,
     const sourcet &source,
-    const irep_idt &output_id,
-    const irep_idt &fmt,
+    irep_idt output_id,
+    irep_idt fmt,
     const std::list<exprt> &args);
 
   /// \copydoc symex_targett::input()
   virtual void input(
     const exprt &guard,
     const sourcet &source,
-    const irep_idt &input_id,
+    irep_idt input_id,
     const std::list<exprt> &args);
 
   /// \copydoc symex_targett::assumption()
@@ -130,7 +130,7 @@ class symex_target_equationt:public symex_targett
   virtual void assertion(
     const exprt &guard,
     const exprt &cond,
-    const irep_idt &property_id,
+    irep_idt property_id,
     const std::string &msg,
     const sourcet &source);
 
diff --git a/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.cpp b/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.cpp
index d1bdd3140ed..e0e5a2cd3c8 100644
--- a/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.cpp
+++ b/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.cpp
@@ -307,7 +307,7 @@ exprt enumerative_loop_contracts_synthesizert::synthesize_same_object_predicate(
 exprt enumerative_loop_contracts_synthesizert::synthesize_strengthening_clause(
   const std::vector<exprt> terminal_symbols,
   const loop_idt &cause_loop_id,
-  const irep_idt &violation_id,
+  irep_idt violation_id,
   const std::vector<cext> &cexs)
 {
   // Synthesis of strengthening clauses is a enumerate-and-check process.
diff --git a/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.h b/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.h
index fd065e7e69f..0a80300b4a9 100644
--- a/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.h
+++ b/src/goto-synthesizer/enumerative_loop_contracts_synthesizer.h
@@ -81,7 +81,7 @@ class enumerative_loop_contracts_synthesizert
   exprt synthesize_strengthening_clause(
     const std::vector<exprt> terminal_symbols,
     const loop_idt &cause_loop_id,
-    const irep_idt &violation_id,
+    irep_idt violation_id,
     const std::vector<cext> &cexs);
 
   /// Synthesize assigns target and update assigns_map.
diff --git a/src/goto-synthesizer/expr_enumerator.cpp b/src/goto-synthesizer/expr_enumerator.cpp
index 373897a2df2..97ad8d4f713 100644
--- a/src/goto-synthesizer/expr_enumerator.cpp
+++ b/src/goto-synthesizer/expr_enumerator.cpp
@@ -285,7 +285,7 @@ std::list<partitiont> non_leaf_enumeratort::get_partitions(
   return result;
 }
 
-bool binary_functional_enumeratort::is_commutative(const irep_idt &op) const
+bool binary_functional_enumeratort::is_commutative(irep_idt op) const
 {
   return op_id == ID_equal || op_id == ID_plus || op_id == ID_notequal ||
          op_id == ID_or || op_id == ID_and || op_id == ID_xor ||
diff --git a/src/goto-synthesizer/expr_enumerator.h b/src/goto-synthesizer/expr_enumerator.h
index 057be543d6d..352f956a005 100644
--- a/src/goto-synthesizer/expr_enumerator.h
+++ b/src/goto-synthesizer/expr_enumerator.h
@@ -217,7 +217,7 @@ class binary_functional_enumeratort : public non_leaf_enumeratort
 {
 public:
   binary_functional_enumeratort(
-    const irep_idt &op,
+    irep_idt op,
     const enumerator_baset &enumerator_1,
     const enumerator_baset &enumerator_2,
     const std::function<bool(const partitiont &)> partition_check,
@@ -230,7 +230,7 @@ class binary_functional_enumeratort : public non_leaf_enumeratort
   }
 
   binary_functional_enumeratort(
-    const irep_idt &op,
+    irep_idt op,
     const enumerator_baset &enumerator_1,
     const enumerator_baset &enumerator_2,
     const std::function<bool(const partitiont &)> partition_check,
@@ -246,7 +246,7 @@ class binary_functional_enumeratort : public non_leaf_enumeratort
   }
 
   binary_functional_enumeratort(
-    const irep_idt &op,
+    irep_idt op,
     const enumerator_baset &enumerator_1,
     const enumerator_baset &enumerator_2,
     const namespacet &ns)
@@ -259,7 +259,7 @@ class binary_functional_enumeratort : public non_leaf_enumeratort
   {
   }
 
-  bool is_commutative(const irep_idt &op) const;
+  bool is_commutative(irep_idt op) const;
 
   /// Determine whether a tuple of expressions is the representation of some
   /// equivalence class.
@@ -273,7 +273,7 @@ class binary_functional_enumeratort : public non_leaf_enumeratort
   // set of expressions.
   const bool is_exchangeable = false;
 
-  const irep_idt &op_id;
+  irep_idt op_id;
 };
 
 /// Enumerators that enumerates expressions in the union of enumerated
diff --git a/src/json-symtab-language/json_goto_function.cpp b/src/json-symtab-language/json_goto_function.cpp
index b8545e95e46..cdfb1f1f095 100644
--- a/src/json-symtab-language/json_goto_function.cpp
+++ b/src/json-symtab-language/json_goto_function.cpp
@@ -38,7 +38,7 @@ static goto_instruction_codet try_get_code(const json_objectt &json)
 /// \param code_id: The expected code type
 /// \return An expression, unless an exception was thrown before.
 static goto_instruction_codet
-try_get_code(const json_objectt &json, const irep_idt &code_id)
+try_get_code(const json_objectt &json, irep_idt code_id)
 {
   goto_instruction_codet code = try_get_code(json);
   if(code.get_statement() != code_id)
diff --git a/src/langapi/language.h b/src/langapi/language.h
index 5b47d4c9475..bb4477e106a 100644
--- a/src/langapi/language.h
+++ b/src/langapi/language.h
@@ -101,7 +101,7 @@ class languaget
   /// advertised the given `function_id` could be provided by this `languaget`
   /// instance.
   virtual void convert_lazy_method(
-    const irep_idt &function_id,
+    irep_idt function_id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler)
   {
diff --git a/src/langapi/language_file.cpp b/src/langapi/language_file.cpp
index b46be2f3d17..9797a38c655 100644
--- a/src/langapi/language_file.cpp
+++ b/src/langapi/language_file.cpp
@@ -38,7 +38,7 @@ void language_filet::get_modules()
 }
 
 void language_filet::convert_lazy_method(
-  const irep_idt &id,
+  irep_idt id,
   symbol_table_baset &symbol_table,
   message_handlert &message_handler)
 {
diff --git a/src/langapi/language_file.h b/src/langapi/language_file.h
index be4722d4ad2..1c1b9d43d3c 100644
--- a/src/langapi/language_file.h
+++ b/src/langapi/language_file.h
@@ -49,7 +49,7 @@ class language_filet final
   void get_modules();
 
   void convert_lazy_method(
-    const irep_idt &id,
+    irep_idt id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler);
 
@@ -132,7 +132,7 @@ class language_filest
   // in lazy_method_map (currently always in language_filest::typecheck)
   // for this to be legal.
   void convert_lazy_method(
-    const irep_idt &id,
+    irep_idt id,
     symbol_table_baset &symbol_table,
     message_handlert &message_handler)
   {
@@ -142,7 +142,7 @@ class language_filest
       it->second->convert_lazy_method(id, symbol_table, message_handler);
   }
 
-  bool can_convert_lazy_method(const irep_idt &id) const
+  bool can_convert_lazy_method(irep_idt id) const
   {
     return lazy_method_map.count(id) != 0;
   }
diff --git a/src/langapi/language_util.cpp b/src/langapi/language_util.cpp
index 324ed0f01da..36a8ca1b53a 100644
--- a/src/langapi/language_util.cpp
+++ b/src/langapi/language_util.cpp
@@ -19,10 +19,8 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 
 #include <memory>
 
-std::string from_expr_using_mode(
-  const namespacet &ns,
-  const irep_idt &mode,
-  const exprt &expr)
+std::string
+from_expr_using_mode(const namespacet &ns, irep_idt mode, const exprt &expr)
 {
   std::unique_ptr<languaget> language = (mode == ID_unknown)
                                           ? get_default_language()
@@ -36,10 +34,8 @@ std::string from_expr_using_mode(
   return result;
 }
 
-std::string from_expr(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const exprt &expr)
+std::string
+from_expr(const namespacet &ns, irep_idt identifier, const exprt &expr)
 {
   std::unique_ptr<languaget> p(get_language_from_identifier(ns, identifier));
 
@@ -49,10 +45,8 @@ std::string from_expr(
   return result;
 }
 
-std::string from_type(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const typet &type)
+std::string
+from_type(const namespacet &ns, irep_idt identifier, const typet &type)
 {
   std::unique_ptr<languaget> p(get_language_from_identifier(ns, identifier));
 
@@ -62,10 +56,8 @@ std::string from_type(
   return result;
 }
 
-std::string type_to_name(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const typet &type)
+std::string
+type_to_name(const namespacet &ns, irep_idt identifier, const typet &type)
 {
   std::unique_ptr<languaget> p(get_language_from_identifier(ns, identifier));
 
@@ -87,10 +79,7 @@ std::string from_type(const typet &type)
   return from_type(namespacet(symbol_table), irep_idt(), type);
 }
 
-exprt to_expr(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const std::string &src)
+exprt to_expr(const namespacet &ns, irep_idt identifier, const std::string &src)
 {
   std::unique_ptr<languaget> p(get_language_from_identifier(ns, identifier));
 
diff --git a/src/langapi/language_util.h b/src/langapi/language_util.h
index 9e7f87466af..5610a865de6 100644
--- a/src/langapi/language_util.h
+++ b/src/langapi/language_util.h
@@ -18,34 +18,26 @@ class typet;
 
 /// Formats an expression using the given namespace,
 /// using the given mode to retrieve the language printer.
-std::string from_expr_using_mode(
-  const namespacet &ns,
-  const irep_idt &mode,
-  const exprt &expr);
+std::string
+from_expr_using_mode(const namespacet &ns, irep_idt mode, const exprt &expr);
 
-std::string from_expr(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const exprt &expr);
+std::string
+from_expr(const namespacet &ns, irep_idt identifier, const exprt &expr);
 
 std::string from_expr(const exprt &expr);
 
-std::string from_type(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const typet &type);
+std::string
+from_type(const namespacet &ns, irep_idt identifier, const typet &type);
 
 std::string from_type(const typet &type);
 
 exprt to_expr(
   const namespacet &ns,
-  const irep_idt &identifier,
+  irep_idt identifier,
   const std::string &src);
 
-std::string type_to_name(
-  const namespacet &ns,
-  const irep_idt &identifier,
-  const typet &type);
+std::string
+type_to_name(const namespacet &ns, irep_idt identifier, const typet &type);
 
 std::string type_to_name(const typet &type);
 
diff --git a/src/langapi/mode.cpp b/src/langapi/mode.cpp
index e401522750f..268988fc925 100644
--- a/src/langapi/mode.cpp
+++ b/src/langapi/mode.cpp
@@ -48,7 +48,7 @@ void register_language(language_factoryt factory)
 /// Get the language corresponding to the given mode
 /// \param mode: the mode, e.g. `ID_C`
 /// \return the language or `nullptr` if the language has not been registered
-std::unique_ptr<languaget> get_language_from_mode(const irep_idt &mode)
+std::unique_ptr<languaget> get_language_from_mode(irep_idt mode)
 {
   for(const auto &language : languages)
     if(mode == language.mode)
@@ -63,7 +63,7 @@ std::unique_ptr<languaget> get_language_from_mode(const irep_idt &mode)
 /// \return the mode, e.g. `ID_C`, if the identifier is in the given
 ///   symbol table, or `ID_unknown` otherwise
 const irep_idt &
-get_mode_from_identifier(const namespacet &ns, const irep_idt &identifier)
+get_mode_from_identifier(const namespacet &ns, irep_idt identifier)
 {
   if(identifier.empty())
     return ID_unknown;
@@ -81,9 +81,9 @@ get_mode_from_identifier(const namespacet &ns, const irep_idt &identifier)
 /// Note: It is assumed as an invariant that languages of symbols in the symbol
 ///   table have been registered.
 std::unique_ptr<languaget>
-get_language_from_identifier(const namespacet &ns, const irep_idt &identifier)
+get_language_from_identifier(const namespacet &ns, irep_idt identifier)
 {
-  const irep_idt &mode = get_mode_from_identifier(ns, identifier);
+  const irep_idt mode = get_mode_from_identifier(ns, identifier);
   if(mode == ID_unknown)
     return get_default_language();
 
diff --git a/src/langapi/mode.h b/src/langapi/mode.h
index 3223cf4a960..b05cc294ef1 100644
--- a/src/langapi/mode.h
+++ b/src/langapi/mode.h
@@ -17,11 +17,11 @@ Author: Daniel Kroening, kroening@cs.cmu.edu
 class languaget;
 class namespacet;
 
-std::unique_ptr<languaget> get_language_from_mode(const irep_idt &mode);
+std::unique_ptr<languaget> get_language_from_mode(irep_idt mode);
 const irep_idt &
-get_mode_from_identifier(const namespacet &ns, const irep_idt &identifier);
+get_mode_from_identifier(const namespacet &ns, irep_idt identifier);
 std::unique_ptr<languaget>
-get_language_from_identifier(const namespacet &ns, const irep_idt &identifier);
+get_language_from_identifier(const namespacet &ns, irep_idt identifier);
 std::unique_ptr<languaget> get_language_from_filename(
   const std::string &filename);
 std::unique_ptr<languaget> get_default_language();
diff --git a/src/linking/linking.cpp b/src/linking/linking.cpp
index 6bde1eb04cd..0606017798d 100644
--- a/src/linking/linking.cpp
+++ b/src/linking/linking.cpp
@@ -40,7 +40,7 @@ static const typet &follow_tags_symbols(
 }
 
 irep_idt
-linkingt::rename(const symbol_table_baset &src_symbol_table, const irep_idt &id)
+linkingt::rename(const symbol_table_baset &src_symbol_table, irep_idt id)
 {
   unsigned cnt=0;
 
diff --git a/src/linking/linking_class.h b/src/linking/linking_class.h
index 0f5c3f1cf23..5d8c610f2f3 100644
--- a/src/linking/linking_class.h
+++ b/src/linking/linking_class.h
@@ -120,7 +120,7 @@ class linkingt
   namespacet ns;
   message_handlert &message_handler;
 
-  irep_idt rename(const symbol_table_baset &, const irep_idt &);
+  irep_idt rename(const symbol_table_baset &, irep_idt);
 
   // the new IDs created by renaming
   std::unordered_set<irep_idt> renamed_ids;
diff --git a/src/linking/static_lifetime_init.cpp b/src/linking/static_lifetime_init.cpp
index 336c848d7dd..0413ade02b9 100644
--- a/src/linking/static_lifetime_init.cpp
+++ b/src/linking/static_lifetime_init.cpp
@@ -22,9 +22,8 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include <set>
 
-static std::optional<codet> static_lifetime_init(
-  const irep_idt &identifier,
-  symbol_table_baset &symbol_table)
+static std::optional<codet>
+static_lifetime_init(irep_idt identifier, symbol_table_baset &symbol_table)
 {
   const namespacet ns(symbol_table);
   const symbolt &symbol = ns.lookup(identifier);
diff --git a/src/memory-analyzer/analyze_symbol.cpp b/src/memory-analyzer/analyze_symbol.cpp
index 0e1d1e7046f..0e968761a5f 100644
--- a/src/memory-analyzer/analyze_symbol.cpp
+++ b/src/memory-analyzer/analyze_symbol.cpp
@@ -35,7 +35,7 @@ gdb_value_extractort::gdb_value_extractort(
 gdb_value_extractort::memory_scopet::memory_scopet(
   const memory_addresst &begin,
   const mp_integer &byte_size,
-  const irep_idt &name)
+  irep_idt name)
   : // the address is given in hex, starting with 0x....
     begin_int(
       safe_string2size_t(std::string_view{begin.address_string}.substr(2), 16)),
@@ -151,7 +151,7 @@ void gdb_value_extractort::analyze_symbols(
   }
 }
 
-void gdb_value_extractort::analyze_symbol(const irep_idt &symbol_name)
+void gdb_value_extractort::analyze_symbol(irep_idt symbol_name)
 {
   const symbolt &symbol = ns.lookup(symbol_name);
   const symbol_exprt symbol_expr = symbol.symbol_expr();
diff --git a/src/memory-analyzer/analyze_symbol.h b/src/memory-analyzer/analyze_symbol.h
index 308fa9590ae..0c3517856d3 100644
--- a/src/memory-analyzer/analyze_symbol.h
+++ b/src/memory-analyzer/analyze_symbol.h
@@ -115,7 +115,7 @@ class gdb_value_extractort
     memory_scopet(
       const memory_addresst &begin,
       const mp_integer &byte_size,
-      const irep_idt &name);
+      irep_idt name);
 
     /// Check if \p point points somewhere in this memory scope
     /// \param point: memory address to be check for presence
@@ -153,7 +153,7 @@ class gdb_value_extractort
   /// Keep track of the memory location for the analyzed symbols
   std::map<irep_idt, pointer_valuet> memory_map;
 
-  bool has_known_memory_location(const irep_idt &id) const
+  bool has_known_memory_location(irep_idt id) const
   {
     return memory_map.count(id) != 0;
   }
@@ -197,7 +197,7 @@ class gdb_value_extractort
   ///   expression and then process outstanding assignments that this
   ///   extraction introduced.
   /// \param symbol_name: symbol table name to be analysed
-  void analyze_symbol(const irep_idt &symbol_name);
+  void analyze_symbol(irep_idt symbol_name);
 
   /// Create assignment \p lhs := \p value (see \ref analyze_symbol)
   /// \param lhs: the left-hand side of the assignment; expected to be a
diff --git a/src/pointer-analysis/add_failed_symbols.cpp b/src/pointer-analysis/add_failed_symbols.cpp
index f53947a767b..b8e978ad226 100644
--- a/src/pointer-analysis/add_failed_symbols.cpp
+++ b/src/pointer-analysis/add_failed_symbols.cpp
@@ -23,7 +23,7 @@ Author: Daniel Kroening, kroening@kroening.com
 /// to by a given pointer-typed symbol.
 /// \param id: base symbol id
 /// \return id of the corresponding unknown-object ("failed") symbol.
-irep_idt failed_symbol_id(const irep_idt &id)
+irep_idt failed_symbol_id(irep_idt id)
 {
   return id2string(id)+"$object";
 }
diff --git a/src/pointer-analysis/add_failed_symbols.h b/src/pointer-analysis/add_failed_symbols.h
index c52a24b3e71..c70668cb5cb 100644
--- a/src/pointer-analysis/add_failed_symbols.h
+++ b/src/pointer-analysis/add_failed_symbols.h
@@ -24,7 +24,7 @@ void add_failed_symbols(symbol_table_baset &symbol_table);
 void add_failed_symbol_if_needed(
   const symbolt &symbol, symbol_table_baset &symbol_table);
 
-irep_idt failed_symbol_id(const irep_idt &identifier);
+irep_idt failed_symbol_id(irep_idt identifier);
 
 /// Get the failed-dereference symbol for the given symbol
 /// \param expr: symbol expression to get a failed symbol for
diff --git a/src/pointer-analysis/goto_program_dereference.cpp b/src/pointer-analysis/goto_program_dereference.cpp
index efa02a89046..b6e0c67c66b 100644
--- a/src/pointer-analysis/goto_program_dereference.cpp
+++ b/src/pointer-analysis/goto_program_dereference.cpp
@@ -245,7 +245,7 @@ void goto_program_dereferencet::dereference_instruction(
 
 /// Set the current target to `target` and remove derefence from expr.
 void goto_program_dereferencet::dereference_expression(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::const_targett target,
   exprt &expr)
 {
@@ -276,7 +276,7 @@ void remove_pointers(
 /// Remove dereferences in `expr` using `value_sets` to determine to what
 /// objects the pointers may be pointing to.
 void dereference(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::const_targett target,
   exprt &expr,
   const namespacet &ns,
diff --git a/src/pointer-analysis/goto_program_dereference.h b/src/pointer-analysis/goto_program_dereference.h
index 1818323d0de..7f5eaae7617 100644
--- a/src/pointer-analysis/goto_program_dereference.h
+++ b/src/pointer-analysis/goto_program_dereference.h
@@ -62,7 +62,7 @@ class goto_program_dereferencet:protected dereference_callbackt
     bool checks_only=false);
 
   void dereference_expression(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::const_targett target,
     exprt &expr);
 
@@ -94,7 +94,7 @@ class goto_program_dereferencet:protected dereference_callbackt
 };
 
 void dereference(
-  const irep_idt &function_id,
+  irep_idt function_id,
   goto_programt::const_targett target,
   exprt &expr,
   const namespacet &,
diff --git a/src/pointer-analysis/show_value_sets.cpp b/src/pointer-analysis/show_value_sets.cpp
index 6e4f8fd6085..b690f5c4fd0 100644
--- a/src/pointer-analysis/show_value_sets.cpp
+++ b/src/pointer-analysis/show_value_sets.cpp
@@ -40,7 +40,7 @@ void show_value_sets(
 void show_value_sets(
   ui_message_handlert::uit ui,
   const namespacet &ns,
-  const irep_idt &function_name,
+  irep_idt function_name,
   const goto_programt &goto_program,
   const value_set_analysist &value_set_analysis)
 {
diff --git a/src/pointer-analysis/value_set.cpp b/src/pointer-analysis/value_set.cpp
index aad9ae75f69..e98fc087b55 100644
--- a/src/pointer-analysis/value_set.cpp
+++ b/src/pointer-analysis/value_set.cpp
@@ -40,7 +40,7 @@ Author: Daniel Kroening, kroening@kroening.com
 const value_sett::object_map_dt value_sett::empty_object_map{};
 object_numberingt value_sett::object_numbering;
 
-bool value_sett::field_sensitive(const irep_idt &id, const typet &type)
+bool value_sett::field_sensitive(irep_idt id, const typet &type)
 {
   // we always track fields on these
   if(
@@ -52,7 +52,7 @@ bool value_sett::field_sensitive(const irep_idt &id, const typet &type)
   return type.id() == ID_struct || type.id() == ID_struct_tag;
 }
 
-const value_sett::entryt *value_sett::find_entry(const irep_idt &id) const
+const value_sett::entryt *value_sett::find_entry(irep_idt id) const
 {
   auto found = values.find(id);
   return !found.has_value() ? nullptr : &(found->get());
@@ -137,81 +137,83 @@ bool value_sett::insert(
 
 void value_sett::output(std::ostream &out, const std::string &indent) const
 {
-  values.iterate([&](const irep_idt &, const entryt &e) {
-    irep_idt identifier, display_name;
-
-    if(e.identifier.starts_with("value_set::dynamic_object"))
-    {
-      display_name = id2string(e.identifier) + e.suffix;
-      identifier.clear();
-    }
-    else if(e.identifier == "value_set::return_value")
-    {
-      display_name = "RETURN_VALUE" + e.suffix;
-      identifier.clear();
-    }
-    else
+  values.iterate(
+    [&](irep_idt, const entryt &e)
     {
+      irep_idt identifier, display_name;
+
+      if(e.identifier.starts_with("value_set::dynamic_object"))
+      {
+        display_name = id2string(e.identifier) + e.suffix;
+        identifier.clear();
+      }
+      else if(e.identifier == "value_set::return_value")
+      {
+        display_name = "RETURN_VALUE" + e.suffix;
+        identifier.clear();
+      }
+      else
+      {
 #if 0
         const symbolt &symbol=ns.lookup(e.identifier);
         display_name=id2string(symbol.display_name())+e.suffix;
         identifier=symbol.name;
 #else
-      identifier = id2string(e.identifier);
-      display_name = id2string(identifier) + e.suffix;
+        identifier = id2string(e.identifier);
+        display_name = id2string(identifier) + e.suffix;
 #endif
-    }
-
-    out << indent << display_name << " = { ";
-
-    const object_map_dt &object_map = e.object_map.read();
+      }
 
-    std::size_t width = 0;
+      out << indent << display_name << " = { ";
 
-    for(object_map_dt::const_iterator o_it = object_map.begin();
-        o_it != object_map.end();
-        o_it++)
-    {
-      const exprt &o = object_numbering[o_it->first];
+      const object_map_dt &object_map = e.object_map.read();
 
-      std::ostringstream stream;
+      std::size_t width = 0;
 
-      if(o.id() == ID_invalid || o.id() == ID_unknown)
-        stream << format(o);
-      else
+      for(object_map_dt::const_iterator o_it = object_map.begin();
+          o_it != object_map.end();
+          o_it++)
       {
-        stream << "<" << format(o) << ", ";
+        const exprt &o = object_numbering[o_it->first];
 
-        if(o_it->second)
-          stream << format(*o_it->second);
-        else
-          stream << '*';
+        std::ostringstream stream;
 
-        if(o.type().is_nil())
-          stream << ", ?";
+        if(o.id() == ID_invalid || o.id() == ID_unknown)
+          stream << format(o);
         else
-          stream << ", " << format(o.type());
+        {
+          stream << "<" << format(o) << ", ";
 
-        stream << '>';
-      }
+          if(o_it->second)
+            stream << format(*o_it->second);
+          else
+            stream << '*';
 
-      const std::string result = stream.str();
-      out << result;
-      width += result.size();
+          if(o.type().is_nil())
+            stream << ", ?";
+          else
+            stream << ", " << format(o.type());
 
-      object_map_dt::const_iterator next(o_it);
-      next++;
+          stream << '>';
+        }
 
-      if(next != object_map.end())
-      {
-        out << ", ";
-        if(width >= 40)
-          out << "\n" << std::string(indent.size(), ' ') << "      ";
+        const std::string result = stream.str();
+        out << result;
+        width += result.size();
+
+        object_map_dt::const_iterator next(o_it);
+        next++;
+
+        if(next != object_map.end())
+        {
+          out << ", ";
+          if(width >= 40)
+            out << "\n" << std::string(indent.size(), ' ') << "      ";
+        }
       }
-    }
 
-    out << " } \n";
-  });
+      out << " } \n";
+    });
 }
 
 xmlt value_sett::output_xml(void) const
@@ -409,10 +411,12 @@ value_sett::object_mapt value_sett::get_value_set(
   if(includes_nondet_pointer && expr.type().id() == ID_pointer)
   {
     // we'll take the union of all objects we see, with unspecified offsets
-    values.iterate([this, &dest](const irep_idt &key, const entryt &value) {
-      for(const auto &object : value.object_map.read())
-        insert(dest, object.first, offsett());
-    });
+    values.iterate(
+      [this, &dest](irep_idt key, const entryt &value)
+      {
+        for(const auto &object : value.object_map.read())
+          insert(dest, object.first, offsett());
+      });
 
     // we'll add null, in case it's not there yet
     insert(
@@ -1785,7 +1789,7 @@ void value_sett::assign_rec(
 }
 
 void value_sett::do_function_call(
-  const irep_idt &function,
+  irep_idt function,
   const exprt::operandst &arguments,
   const namespacet &ns)
 {
@@ -1995,7 +1999,7 @@ void value_sett::guard(
 }
 
 void value_sett::erase_values_from_entry(
-  const irep_idt &index,
+  irep_idt index,
   const std::unordered_set<exprt, irep_hash> &values_to_erase)
 {
   if(values_to_erase.empty())
diff --git a/src/pointer-analysis/value_set.h b/src/pointer-analysis/value_set.h
index 73119a8ffb6..d4de9b8275e 100644
--- a/src/pointer-analysis/value_set.h
+++ b/src/pointer-analysis/value_set.h
@@ -65,7 +65,7 @@ class value_sett
 
   /// Determines whether an identifier of a given type should have its fields
   /// distinguished. Virtual so that subclasses can override this behaviour.
-  virtual bool field_sensitive(const irep_idt &id, const typet &type);
+  virtual bool field_sensitive(irep_idt id, const typet &type);
 
   /// Matches the location_number field of the instruction that corresponds
   /// to this value_sett instance in value_set_domaint's state map
@@ -194,7 +194,7 @@ class value_sett
     {
     }
 
-    entryt(const irep_idt &_identifier, const std::string &_suffix)
+    entryt(irep_idt _identifier, const std::string &_suffix)
       : identifier(_identifier), suffix(_suffix)
     {
     }
@@ -248,7 +248,7 @@ class value_sett
   /// \ref update_entry.
   /// \param id: identifier to find.
   /// \return a constant pointer to an entry if found, or null otherwise.
-  const entryt *find_entry(const irep_idt &id) const;
+  const entryt *find_entry(irep_idt id) const;
 
   /// Adds or replaces an entry in this value-set.
   /// \param e: entry to find. Its `id` and `suffix` fields will be used
@@ -355,7 +355,7 @@ class value_sett
   /// \param arguments: actual arguments
   /// \param ns: global namespace
   void do_function_call(
-    const irep_idt &function,
+    irep_idt function,
     const exprt::operandst &arguments,
     const namespacet &ns);
 
@@ -413,7 +413,7 @@ class value_sett
   /// \param index: index in the value set
   /// \param values_to_erase: set of values to remove from the entry
   void erase_values_from_entry(
-    const irep_idt &index,
+    irep_idt index,
     const std::unordered_set<exprt, irep_hash> &values_to_erase);
 
   void erase_symbol(const symbol_exprt &symbol_expr, const namespacet &ns);
diff --git a/src/pointer-analysis/value_set_analysis.h b/src/pointer-analysis/value_set_analysis.h
index 4003ff47f05..b80f8729ec9 100644
--- a/src/pointer-analysis/value_set_analysis.h
+++ b/src/pointer-analysis/value_set_analysis.h
@@ -40,7 +40,7 @@ class value_set_analysis_templatet : public value_setst, public ait<VSDT>
 
   // interface value_sets
   std::vector<exprt>
-  get_values(const irep_idt &, locationt l, const exprt &expr) override
+  get_values(irep_idt, locationt l, const exprt &expr) override
   {
     auto s = this->abstract_state_before(l);
     auto d = std::dynamic_pointer_cast<const domaint>(s);
diff --git a/src/pointer-analysis/value_set_analysis_fi.cpp b/src/pointer-analysis/value_set_analysis_fi.cpp
index dd407a12115..d62b040cb84 100644
--- a/src/pointer-analysis/value_set_analysis_fi.cpp
+++ b/src/pointer-analysis/value_set_analysis_fi.cpp
@@ -87,7 +87,7 @@ void value_set_analysis_fit::get_entries(
 }
 
 void value_set_analysis_fit::get_entries_rec(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const std::string &suffix,
   const typet &type,
   std::list<value_set_fit::entryt> &dest)
@@ -207,7 +207,7 @@ bool value_set_analysis_fit::check_type(const typet &type)
 }
 
 std::vector<exprt> value_set_analysis_fit::get_values(
-  const irep_idt &function_id,
+  irep_idt function_id,
   flow_insensitive_analysis_baset::locationt l,
   const exprt &expr)
 {
diff --git a/src/pointer-analysis/value_set_analysis_fi.h b/src/pointer-analysis/value_set_analysis_fi.h
index 9d3887c345a..f63bc5610f2 100644
--- a/src/pointer-analysis/value_set_analysis_fi.h
+++ b/src/pointer-analysis/value_set_analysis_fi.h
@@ -53,17 +53,15 @@ class value_set_analysis_fit:
     std::list<value_set_fit::entryt> &dest);
 
   void get_entries_rec(
-    const irep_idt &identifier,
+    irep_idt identifier,
     const std::string &suffix,
     const typet &type,
     std::list<value_set_fit::entryt> &dest);
 
 public:
   // interface value_sets
-  std::vector<exprt> get_values(
-    const irep_idt &function_id,
-    locationt l,
-    const exprt &expr) override;
+  std::vector<exprt>
+  get_values(irep_idt function_id, locationt l, const exprt &expr) override;
 };
 
 #endif // CPROVER_POINTER_ANALYSIS_VALUE_SET_ANALYSIS_FI_H
diff --git a/src/pointer-analysis/value_set_dereference.cpp b/src/pointer-analysis/value_set_dereference.cpp
index f9a99530a6c..406fce23270 100644
--- a/src/pointer-analysis/value_set_dereference.cpp
+++ b/src/pointer-analysis/value_set_dereference.cpp
@@ -423,7 +423,7 @@ bool value_set_dereferencet::dereference_type_compare(
 bool value_set_dereferencet::should_ignore_value(
   const exprt &what,
   bool exclude_null_derefs,
-  const irep_idt &language_mode)
+  irep_idt language_mode)
 {
   if(what.id() == ID_unknown || what.id() == ID_invalid)
   {
diff --git a/src/pointer-analysis/value_set_dereference.h b/src/pointer-analysis/value_set_dereference.h
index 96552e66af9..49045ca0bcf 100644
--- a/src/pointer-analysis/value_set_dereference.h
+++ b/src/pointer-analysis/value_set_dereference.h
@@ -71,7 +71,7 @@ class value_set_dereferencet final
   static bool should_ignore_value(
     const exprt &what,
     bool exclude_null_derefs,
-    const irep_idt &language_mode);
+    irep_idt language_mode);
 
   static valuet build_reference_to(
     const exprt &what,
diff --git a/src/pointer-analysis/value_set_domain.h b/src/pointer-analysis/value_set_domain.h
index b7de38763bc..afee42d3d17 100644
--- a/src/pointer-analysis/value_set_domain.h
+++ b/src/pointer-analysis/value_set_domain.h
@@ -80,9 +80,9 @@ class value_set_domain_templatet : public ai_domain_baset
   }
 
   void transform(
-    const irep_idt &function_from,
+    irep_idt function_from,
     trace_ptrt from,
-    const irep_idt &function_to,
+    irep_idt function_to,
     trace_ptrt to,
     ai_baset &ai,
     const namespacet &ns) override;
@@ -118,9 +118,9 @@ typedef value_set_domain_templatet<value_sett> value_set_domaint;
 
 template <class VST>
 void value_set_domain_templatet<VST>::transform(
-  const irep_idt &,
+  irep_idt,
   trace_ptrt from,
-  const irep_idt &function_to,
+  irep_idt function_to,
   trace_ptrt to,
   ai_baset &,
   const namespacet &ns)
diff --git a/src/pointer-analysis/value_set_domain_fi.cpp b/src/pointer-analysis/value_set_domain_fi.cpp
index 01c618d60c8..e42253904f0 100644
--- a/src/pointer-analysis/value_set_domain_fi.cpp
+++ b/src/pointer-analysis/value_set_domain_fi.cpp
@@ -14,9 +14,9 @@ Author: Daniel Kroening, kroening@kroening.com
 
 bool value_set_domain_fit::transform(
   const namespacet &ns,
-  const irep_idt &function_from,
+  irep_idt function_from,
   locationt from_l,
-  const irep_idt &function_to,
+  irep_idt function_to,
   locationt to_l)
 {
   value_set.changed = false;
diff --git a/src/pointer-analysis/value_set_domain_fi.h b/src/pointer-analysis/value_set_domain_fi.h
index f6412dfb7a9..b8078f6ac5a 100644
--- a/src/pointer-analysis/value_set_domain_fi.h
+++ b/src/pointer-analysis/value_set_domain_fi.h
@@ -41,9 +41,9 @@ class value_set_domain_fit:public flow_insensitive_abstract_domain_baset
 
   bool transform(
     const namespacet &ns,
-    const irep_idt &function_from,
+    irep_idt function_from,
     locationt from_l,
-    const irep_idt &function_to,
+    irep_idt function_to,
     locationt to_l) override;
 
   void get_reference_set(
diff --git a/src/pointer-analysis/value_set_fi.cpp b/src/pointer-analysis/value_set_fi.cpp
index 7a57fdad707..3a8b296bc51 100644
--- a/src/pointer-analysis/value_set_fi.cpp
+++ b/src/pointer-analysis/value_set_fi.cpp
@@ -1319,7 +1319,7 @@ void value_set_fit::assign_rec(
 }
 
 void value_set_fit::do_function_call(
-  const irep_idt &function,
+  irep_idt function,
   const exprt::operandst &arguments,
   const namespacet &ns)
 {
diff --git a/src/pointer-analysis/value_set_fi.h b/src/pointer-analysis/value_set_fi.h
index d07e01ead43..c6ac264beee 100644
--- a/src/pointer-analysis/value_set_fi.h
+++ b/src/pointer-analysis/value_set_fi.h
@@ -41,13 +41,13 @@ class value_set_fit
   static object_numberingt object_numbering;
   static numberingt<irep_idt> function_numbering;
 
-  void set_from(const irep_idt &function, unsigned inx)
+  void set_from(irep_idt function, unsigned inx)
   {
     from_function = function_numbering.number(function);
     from_target_index = inx;
   }
 
-  void set_to(const irep_idt &function, unsigned inx)
+  void set_to(irep_idt function, unsigned inx)
   {
     to_function = function_numbering.number(function);
     to_target_index = inx;
@@ -180,9 +180,8 @@ class value_set_fit
     {
     }
 
-    entryt(const idt &_identifier, const std::string _suffix):
-      identifier(_identifier),
-      suffix(_suffix)
+    entryt(idt _identifier, const std::string _suffix)
+      : identifier(_identifier), suffix(_suffix)
     {
     }
   };
@@ -200,16 +199,14 @@ class value_set_fit
   std::vector<exprt>
   get_value_set(const exprt &expr, const namespacet &ns) const;
 
-  expr_sett &get(
-    const idt &identifier,
-    const std::string &suffix);
+  expr_sett &get(idt identifier, const std::string &suffix);
 
   void clear()
   {
     values.clear();
   }
 
-  void add_var(const idt &id)
+  void add_var(idt id)
   {
     get_entry(id, "");
   }
@@ -219,7 +216,7 @@ class value_set_fit
     get_entry(e.identifier, e.suffix);
   }
 
-  entryt &get_entry(const idt &id, const std::string &suffix)
+  entryt &get_entry(idt id, const std::string &suffix)
   {
     return get_entry(entryt(id, suffix));
   }
@@ -271,7 +268,7 @@ class value_set_fit
     const namespacet &ns);
 
   void do_function_call(
-    const irep_idt &function,
+    irep_idt function,
     const exprt::operandst &arguments,
     const namespacet &ns);
 
diff --git a/src/pointer-analysis/value_sets.h b/src/pointer-analysis/value_sets.h
index 2b04626d5f4..1b548b14970 100644
--- a/src/pointer-analysis/value_sets.h
+++ b/src/pointer-analysis/value_sets.h
@@ -29,7 +29,7 @@ class value_setst
 
   // this is not const to allow a lazy evaluation
   virtual std::vector<exprt> get_values(
-    const irep_idt &function_id,
+    irep_idt function_id,
     goto_programt::const_targett l,
     const exprt &expr) = 0;
 
diff --git a/src/solvers/flattening/boolbv_map.cpp b/src/solvers/flattening/boolbv_map.cpp
index 9c1b2747948..543ed34181d 100644
--- a/src/solvers/flattening/boolbv_map.cpp
+++ b/src/solvers/flattening/boolbv_map.cpp
@@ -39,7 +39,7 @@ void boolbv_mapt::show(std::ostream &out) const
 }
 
 const bvt &boolbv_mapt::get_literals(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const typet &type,
   std::size_t width)
 {
@@ -73,7 +73,7 @@ const bvt &boolbv_mapt::get_literals(
 }
 
 void boolbv_mapt::set_literals(
-  const irep_idt &identifier,
+  irep_idt identifier,
   const typet &type,
   const bvt &literals)
 {
@@ -115,9 +115,7 @@ void boolbv_mapt::set_literals(
   }
 }
 
-void boolbv_mapt::erase_literals(
-  const irep_idt &identifier,
-  const typet &)
+void boolbv_mapt::erase_literals(irep_idt identifier, const typet &)
 {
   mapping.erase(identifier);
 }
diff --git a/src/solvers/flattening/boolbv_map.h b/src/solvers/flattening/boolbv_map.h
index a9ba3063079..381d78399b1 100644
--- a/src/solvers/flattening/boolbv_map.h
+++ b/src/solvers/flattening/boolbv_map.h
@@ -39,22 +39,16 @@ class boolbv_mapt
 
   void show(std::ostream &out) const;
 
-  const bvt &get_literals(
-    const irep_idt &identifier,
-    const typet &type,
-    std::size_t width);
+  const bvt &
+  get_literals(irep_idt identifier, const typet &type, std::size_t width);
 
-  void set_literals(
-    const irep_idt &identifier,
-    const typet &type,
-    const bvt &literals);
+  void
+  set_literals(irep_idt identifier, const typet &type, const bvt &literals);
 
-  void erase_literals(
-    const irep_idt &identifier,
-    const typet &type);
+  void erase_literals(irep_idt identifier, const typet &type);
 
   std::optional<std::reference_wrapper<const map_entryt>>
-  get_map_entry(const irep_idt &identifier) const
+  get_map_entry(irep_idt identifier) const
   {
     const auto entry = mapping.find(identifier);
     if(entry == mapping.end())
diff --git a/src/solvers/flattening/boolbv_width.cpp b/src/solvers/flattening/boolbv_width.cpp
index 998312fd37e..04fce2fe726 100644
--- a/src/solvers/flattening/boolbv_width.cpp
+++ b/src/solvers/flattening/boolbv_width.cpp
@@ -223,9 +223,8 @@ const boolbv_widtht::entryt &boolbv_widtht::get_entry(const typet &type) const
   return cache_entry;
 }
 
-const boolbv_widtht::membert &boolbv_widtht::get_member(
-  const struct_typet &type,
-  const irep_idt &member) const
+const boolbv_widtht::membert &
+boolbv_widtht::get_member(const struct_typet &type, irep_idt member) const
 {
   const auto &entry_opt = get_entry(type);
   CHECK_RETURN(entry_opt.has_value());
diff --git a/src/solvers/flattening/boolbv_width.h b/src/solvers/flattening/boolbv_width.h
index d6e66f75c09..c086b0db862 100644
--- a/src/solvers/flattening/boolbv_width.h
+++ b/src/solvers/flattening/boolbv_width.h
@@ -41,8 +41,7 @@ class boolbv_widtht
     std::size_t offset, width;
   };
 
-  const membert &
-  get_member(const struct_typet &type, const irep_idt &member) const;
+  const membert &get_member(const struct_typet &type, irep_idt member) const;
 
 protected:
   const namespacet &ns;
diff --git a/src/solvers/prop/prop.h b/src/solvers/prop/prop.h
index dda20bfef39..cc58a15c04a 100644
--- a/src/solvers/prop/prop.h
+++ b/src/solvers/prop/prop.h
@@ -92,7 +92,9 @@ class propt
 
   // variables
   virtual literalt new_variable()=0;
-  virtual void set_variable_name(literalt, const irep_idt &) { }
+  virtual void set_variable_name(literalt, irep_idt)
+  {
+  }
   virtual size_t no_variables() const=0;
   virtual bvt new_variables(std::size_t width);
 
diff --git a/src/solvers/prop/prop_conv_solver.cpp b/src/solvers/prop/prop_conv_solver.cpp
index 575fdfc6565..c1b2b222dc5 100644
--- a/src/solvers/prop/prop_conv_solver.cpp
+++ b/src/solvers/prop/prop_conv_solver.cpp
@@ -57,7 +57,7 @@ exprt prop_conv_solvert::handle(const exprt &expr)
   return literal_exprt(l);
 }
 
-literalt prop_conv_solvert::get_literal(const irep_idt &identifier)
+literalt prop_conv_solvert::get_literal(irep_idt identifier)
 {
   auto result =
     symbols.insert(std::pair<irep_idt, literalt>(identifier, literalt()));
diff --git a/src/solvers/prop/prop_conv_solver.h b/src/solvers/prop/prop_conv_solver.h
index f8bcb40fda1..e0905c4b53b 100644
--- a/src/solvers/prop/prop_conv_solver.h
+++ b/src/solvers/prop/prop_conv_solver.h
@@ -120,7 +120,7 @@ class prop_conv_solvert : public conflict_providert,
   // symbols
   symbolst symbols;
 
-  virtual literalt get_literal(const irep_idt &symbol);
+  virtual literalt get_literal(irep_idt symbol);
 
   // cache
   cachet cache;
diff --git a/src/solvers/smt2/smt2_conv.cpp b/src/solvers/smt2/smt2_conv.cpp
index d118a55ef32..c8c3357079f 100644
--- a/src/solvers/smt2/smt2_conv.cpp
+++ b/src/solvers/smt2/smt2_conv.cpp
@@ -275,9 +275,7 @@ static bool is_zero_width(const typet &type, const namespacet &ns)
     return false;
 }
 
-void smt2_convt::define_object_size(
-  const irep_idt &id,
-  const object_size_exprt &expr)
+void smt2_convt::define_object_size(irep_idt id, const object_size_exprt &expr)
 {
   const exprt &ptr = expr.pointer();
   std::size_t pointer_width = boolbv_width(ptr.type());
@@ -1094,7 +1092,7 @@ static bool is_smt2_simple_identifier(const std::string &identifier)
   return true;
 }
 
-std::string smt2_convt::convert_identifier(const irep_idt &identifier)
+std::string smt2_convt::convert_identifier(irep_idt identifier)
 {
   // Is this a "simple identifier"?
   if(is_smt2_simple_identifier(id2string(identifier)))
diff --git a/src/solvers/smt2/smt2_conv.h b/src/solvers/smt2/smt2_conv.h
index ca94493a6be..7f381cea9aa 100644
--- a/src/solvers/smt2/smt2_conv.h
+++ b/src/solvers/smt2/smt2_conv.h
@@ -88,7 +88,7 @@ class smt2_convt : public stack_decision_proceduret
 
   std::size_t get_number_of_solver_calls() const override;
 
-  static std::string convert_identifier(const irep_idt &identifier);
+  static std::string convert_identifier(irep_idt identifier);
 
   void set_converter(irep_idt id, std::function<void(const exprt &)> converter)
   {
@@ -212,7 +212,7 @@ class smt2_convt : public stack_decision_proceduret
   class smt2_symbolt : public nullary_exprt
   {
   public:
-    smt2_symbolt(const irep_idt &_identifier, const typet &_type)
+    smt2_symbolt(irep_idt _identifier, const typet &_type)
       : nullary_exprt(ID_smt2_symbol, _type)
     { set(ID_identifier, _identifier); }
 
@@ -241,7 +241,7 @@ class smt2_convt : public stack_decision_proceduret
   void convert_address_of_rec(
     const exprt &expr, const pointer_typet &result_type);
 
-  void define_object_size(const irep_idt &id, const object_size_exprt &expr);
+  void define_object_size(irep_idt id, const object_size_exprt &expr);
 
   // keeps track of all non-Boolean symbols and their value
   struct identifiert
diff --git a/src/solvers/smt2/smt2_parser.cpp b/src/solvers/smt2/smt2_parser.cpp
index 94ceb8b3306..7dd29a67640 100644
--- a/src/solvers/smt2/smt2_parser.cpp
+++ b/src/solvers/smt2/smt2_parser.cpp
@@ -423,7 +423,7 @@ exprt smt2_parsert::function_application_ieee_float_eq(
 }
 
 exprt smt2_parsert::function_application_ieee_float_op(
-  const irep_idt &id,
+  irep_idt id,
   const exprt::operandst &op)
 {
   if(op.size() != 3)
diff --git a/src/solvers/smt2/smt2_parser.h b/src/solvers/smt2/smt2_parser.h
index cc923e6b67e..6b561966317 100644
--- a/src/solvers/smt2/smt2_parser.h
+++ b/src/solvers/smt2/smt2_parser.h
@@ -150,9 +150,7 @@ class smt2_parsert
   void setup_expressions();
   exprt expression();
   exprt function_application();
-  exprt function_application_ieee_float_op(
-    const irep_idt &,
-    const exprt::operandst &);
+  exprt function_application_ieee_float_op(irep_idt, const exprt::operandst &);
   exprt function_application_ieee_float_eq(const exprt::operandst &);
   exprt function_application_fp(const exprt::operandst &);
   exprt::operandst operands();
diff --git a/src/solvers/smt2_incremental/ast/smt_commands.cpp b/src/solvers/smt2_incremental/ast/smt_commands.cpp
index ca16b6a3311..be40df29707 100644
--- a/src/solvers/smt2_incremental/ast/smt_commands.cpp
+++ b/src/solvers/smt2_incremental/ast/smt_commands.cpp
@@ -179,7 +179,7 @@ const smt_optiont &smt_set_option_commandt::option() const
 }
 
 template <typename visitort>
-void accept(const smt_commandt &command, const irep_idt &id, visitort &&visitor)
+void accept(const smt_commandt &command, irep_idt id, visitort &&visitor)
 {
 #define COMMAND_ID(the_id)                                                     \
   if(id == ID_smt_##the_id##_command)                                          \
diff --git a/src/solvers/smt2_incremental/ast/smt_logics.cpp b/src/solvers/smt2_incremental/ast/smt_logics.cpp
index 8412c5c8c8c..eb7a5fc85ab 100644
--- a/src/solvers/smt2_incremental/ast/smt_logics.cpp
+++ b/src/solvers/smt2_incremental/ast/smt_logics.cpp
@@ -20,7 +20,7 @@ bool smt_logict::operator!=(const smt_logict &other) const
 }
 
 template <typename visitort>
-void accept(const smt_logict &logic, const irep_idt &id, visitort &&visitor)
+void accept(const smt_logict &logic, irep_idt id, visitort &&visitor)
 {
 #define LOGIC_ID(the_id, the_name)                                             \
   if(id == ID_smt_logic_##the_id)                                              \
diff --git a/src/solvers/smt2_incremental/ast/smt_options.cpp b/src/solvers/smt2_incremental/ast/smt_options.cpp
index ab573690948..3ebe00e4147 100644
--- a/src/solvers/smt2_incremental/ast/smt_options.cpp
+++ b/src/solvers/smt2_incremental/ast/smt_options.cpp
@@ -35,7 +35,7 @@ bool smt_option_produce_modelst::setting() const
 }
 
 template <typename visitort>
-void accept(const smt_optiont &option, const irep_idt &id, visitort &&visitor)
+void accept(const smt_optiont &option, irep_idt id, visitort &&visitor)
 {
 #define OPTION_ID(the_id)                                                      \
   if(id == ID_smt_option_##the_id)                                             \
diff --git a/src/solvers/smt2_incremental/ast/smt_sorts.cpp b/src/solvers/smt2_incremental/ast/smt_sorts.cpp
index 589a21df8c9..a83c4f295db 100644
--- a/src/solvers/smt2_incremental/ast/smt_sorts.cpp
+++ b/src/solvers/smt2_incremental/ast/smt_sorts.cpp
@@ -84,7 +84,7 @@ const smt_sortt &smt_array_sortt::element_sort() const
 }
 
 template <typename visitort>
-void accept(const smt_sortt &sort, const irep_idt &id, visitort &&visitor)
+void accept(const smt_sortt &sort, irep_idt id, visitort &&visitor)
 {
 #define SORT_ID(the_id)                                                        \
   if(id == ID_smt_##the_id##_sort)                                             \
diff --git a/src/solvers/smt2_incremental/ast/smt_terms.cpp b/src/solvers/smt2_incremental/ast/smt_terms.cpp
index f679217e1c4..02be309f701 100644
--- a/src/solvers/smt2_incremental/ast/smt_terms.cpp
+++ b/src/solvers/smt2_incremental/ast/smt_terms.cpp
@@ -221,7 +221,7 @@ smt_exists_termt::bound_variables() const
 }
 
 template <typename visitort>
-void accept(const smt_termt &term, const irep_idt &id, visitort &&visitor)
+void accept(const smt_termt &term, irep_idt id, visitort &&visitor)
 {
 #define TERM_ID(the_id)                                                        \
   if(id == ID_smt_##the_id##_term)                                             \
diff --git a/src/solvers/smt2_incremental/smt2_incremental_decision_procedure.cpp b/src/solvers/smt2_incremental/smt2_incremental_decision_procedure.cpp
index 2817ba012fe..b90632d5749 100644
--- a/src/solvers/smt2_incremental/smt2_incremental_decision_procedure.cpp
+++ b/src/solvers/smt2_incremental/smt2_incremental_decision_procedure.cpp
@@ -165,7 +165,7 @@ void smt2_incremental_decision_proceduret::define_array_function(
 
 void send_function_definition(
   const exprt &expr,
-  const irep_idt &symbol_identifier,
+  irep_idt symbol_identifier,
   const std::unique_ptr<smt_base_solver_processt> &solver_process,
   std::unordered_map<exprt, smt_identifier_termt, irep_hash>
     &expression_identifiers,
diff --git a/src/solvers/smt2_incremental/smt_to_smt2_string.cpp b/src/solvers/smt2_incremental/smt_to_smt2_string.cpp
index 4d3558af3cc..f848357818f 100644
--- a/src/solvers/smt2_incremental/smt_to_smt2_string.cpp
+++ b/src/solvers/smt2_incremental/smt_to_smt2_string.cpp
@@ -16,7 +16,7 @@
 #include <stack>
 #include <string>
 
-static std::string escape_identifier(const irep_idt &identifier)
+static std::string escape_identifier(irep_idt identifier)
 {
   return smt2_convt::convert_identifier(identifier);
 }
diff --git a/src/solvers/strings/array_pool.cpp b/src/solvers/strings/array_pool.cpp
index 4b88e8fad56..1b276ba1644 100644
--- a/src/solvers/strings/array_pool.cpp
+++ b/src/solvers/strings/array_pool.cpp
@@ -10,8 +10,7 @@ Author: Romain Brenguier, romain.brenguier@diffblue.com
 
 #include <util/pointer_expr.h>
 
-symbol_exprt symbol_generatort::
-operator()(const irep_idt &prefix, const typet &type)
+symbol_exprt symbol_generatort::operator()(irep_idt prefix, const typet &type)
 {
   std::ostringstream buf;
   buf << "string_refinement#" << prefix << "#" << ++symbol_count;
diff --git a/src/solvers/strings/array_pool.h b/src/solvers/strings/array_pool.h
index fc210f76f5f..07412a2489f 100644
--- a/src/solvers/strings/array_pool.h
+++ b/src/solvers/strings/array_pool.h
@@ -24,8 +24,7 @@ class symbol_generatort final
   /// Generate a new symbol expression of the given \p type with some \p prefix
   /// \return a symbol of type \p type whose name starts with
   ///   "string_refinement#" followed by \p prefix
-  symbol_exprt
-  operator()(const irep_idt &prefix, const typet &type = bool_typet());
+  symbol_exprt operator()(irep_idt prefix, const typet &type = bool_typet());
 
 private:
   unsigned symbol_count = 0;
diff --git a/src/solvers/strings/string_format_builtin_function.cpp b/src/solvers/strings/string_format_builtin_function.cpp
index 14e32a86e8c..48cbf46e4df 100644
--- a/src/solvers/strings/string_format_builtin_function.cpp
+++ b/src/solvers/strings/string_format_builtin_function.cpp
@@ -23,7 +23,7 @@ Author: Romain Brenguier, Joel Allred
 
 static exprt format_arg_from_string(
   const array_string_exprt &string,
-  const irep_idt &id,
+  irep_idt id,
   array_poolt &array_pool);
 
 string_format_builtin_functiont::string_format_builtin_functiont(
@@ -242,7 +242,7 @@ add_axioms_for_format_specifier(
 /// The characters of `string` must be of type `unsignedbv_typet(16)`.
 static exprt format_arg_from_string(
   const array_string_exprt &string,
-  const irep_idt &id,
+  irep_idt id,
   array_poolt &array_pool)
 {
   PRECONDITION(
diff --git a/src/statement-list/converters/expr2statement_list.cpp b/src/statement-list/converters/expr2statement_list.cpp
index 6c0dae703fe..ec4791ffc0f 100644
--- a/src/statement-list/converters/expr2statement_list.cpp
+++ b/src/statement-list/converters/expr2statement_list.cpp
@@ -288,7 +288,7 @@ void expr2stlt::convert_first_non_trivial_operand(std::vector<exprt> &operands)
   inside_bit_string = true;
 }
 
-irep_idt expr2stlt::id_shorthand(const irep_idt &identifier)
+irep_idt expr2stlt::id_shorthand(irep_idt identifier)
 {
   const symbolt *symbol;
   std::string shorthand = id2string(identifier);
diff --git a/src/statement-list/converters/expr2statement_list.h b/src/statement-list/converters/expr2statement_list.h
index 2071c92c934..3d1a9013ab5 100644
--- a/src/statement-list/converters/expr2statement_list.h
+++ b/src/statement-list/converters/expr2statement_list.h
@@ -148,7 +148,7 @@ class expr2stlt
   /// looking up the symbol or cutting the scope when needed.
   /// \param identifier: Identifier that should be converted.
   /// \return Converted identifier.
-  irep_idt id_shorthand(const irep_idt &identifier);
+  irep_idt id_shorthand(irep_idt identifier);
 };
 
 #endif // CPROVER_STATEMENT_LIST_CONVERTERS_EXPR2STATEMENT_LIST_H
diff --git a/src/statement-list/statement_list_entry_point.cpp b/src/statement-list/statement_list_entry_point.cpp
index 97a2323297a..231e9adecac 100644
--- a/src/statement-list/statement_list_entry_point.cpp
+++ b/src/statement-list/statement_list_entry_point.cpp
@@ -41,7 +41,7 @@ Author: Matthias Weiss, matthias.weiss@diffblue.com
 static bool is_main_symbol_invalid(
   const symbol_table_baset &symbol_table,
   message_handlert &message_handler,
-  const irep_idt &main_symbol_name)
+  irep_idt main_symbol_name)
 {
   bool found = false;
 
diff --git a/src/statement-list/statement_list_parse_tree.cpp b/src/statement-list/statement_list_parse_tree.cpp
index 16ddf744136..857c1c740df 100644
--- a/src/statement-list/statement_list_parse_tree.cpp
+++ b/src/statement-list/statement_list_parse_tree.cpp
@@ -72,14 +72,14 @@ void statement_list_parse_treet::networkt::add_instruction(
 }
 
 statement_list_parse_treet::tia_modulet::tia_modulet(
-  const irep_idt &name,
+  irep_idt name,
   const std::string &version)
   : name(name), version(version)
 {
 }
 
 statement_list_parse_treet::function_blockt::function_blockt(
-  const irep_idt &name,
+  irep_idt name,
   const std::string &version)
   : tia_modulet(name, version)
 {
@@ -110,7 +110,7 @@ void statement_list_parse_treet::swap(statement_list_parse_treet &other)
 }
 
 statement_list_parse_treet::functiont::functiont(
-  const irep_idt &name,
+  irep_idt name,
   const std::string &version,
   const typet &return_type)
   : tia_modulet(name, version), return_type(return_type)
diff --git a/src/statement-list/statement_list_parse_tree.h b/src/statement-list/statement_list_parse_tree.h
index e7fa7aa50e0..cb25c125a04 100644
--- a/src/statement-list/statement_list_parse_tree.h
+++ b/src/statement-list/statement_list_parse_tree.h
@@ -122,7 +122,7 @@ class statement_list_parse_treet
     /// Create the module \p name with a specific \p version.
     /// \param name: Name of the module.
     /// \param version: Version of the module.
-    tia_modulet(const irep_idt &name, const std::string &version);
+    tia_modulet(irep_idt name, const std::string &version);
   };
 
   /// Structure for a simple function in Statement List. Includes fields for
@@ -138,7 +138,7 @@ class statement_list_parse_treet
     /// \param version: Version of the function.
     /// \param return_type: Type of the function's return value.
     functiont(
-      const irep_idt &name,
+      irep_idt name,
       const std::string &version,
       const typet &return_type);
   };
@@ -154,7 +154,7 @@ class statement_list_parse_treet
     /// Create the function block \p name with a specific \p version.
     /// \param name: Name of the function block.
     /// \param version: Version of the function block.
-    function_blockt(const irep_idt &name, const std::string &version);
+    function_blockt(irep_idt name, const std::string &version);
 
     /// Adds a variable declaration to the list of static variables.
     /// \param declaration: Variable declaration to be added.
diff --git a/src/statement-list/statement_list_typecheck.cpp b/src/statement-list/statement_list_typecheck.cpp
index f8ecf3a3fe2..10a5b0f1f09 100644
--- a/src/statement-list/statement_list_typecheck.cpp
+++ b/src/statement-list/statement_list_typecheck.cpp
@@ -69,7 +69,7 @@ static const std::vector<irep_idt> logic_sequence_terminators = {
 /// \return Parameter of the data block.
 static code_typet::parametert create_data_block_parameter(
   const struct_typet &data_block_type,
-  const irep_idt &function_block_name)
+  irep_idt function_block_name)
 {
   const pointer_typet db_ptr{data_block_type, STATEMENT_LIST_PTR_WIDTH};
   code_typet::parametert param{db_ptr};
@@ -264,7 +264,7 @@ struct_typet statement_list_typecheckt::create_instance_data_block_type(
 void statement_list_typecheckt::typecheck_function_block_var_decls(
   const statement_list_parse_treet::var_declarationst &var_decls,
   struct_union_typet::componentst &components,
-  const irep_idt &var_property)
+  irep_idt var_property)
 {
   for(const statement_list_parse_treet::var_declarationt &declaration :
       var_decls)
@@ -280,8 +280,8 @@ void statement_list_typecheckt::typecheck_function_block_var_decls(
 void statement_list_typecheckt::typecheck_function_var_decls(
   const statement_list_parse_treet::var_declarationst &var_decls,
   code_typet::parameterst &params,
-  const irep_idt &function_name,
-  const irep_idt &var_property)
+  irep_idt function_name,
+  irep_idt var_property)
 {
   for(const statement_list_parse_treet::var_declarationt &declaration :
       var_decls)
@@ -1401,7 +1401,7 @@ void statement_list_typecheckt::typecheck_statement_list_accu_real_arith(
 }
 
 void statement_list_typecheckt::typecheck_accumulator_compare_instruction(
-  const irep_idt &comparison)
+  irep_idt comparison)
 {
   const exprt &accu1{accumulator.back()};
   const exprt &accu2{accumulator.at(accumulator.size() - 2)};
@@ -1411,7 +1411,7 @@ void statement_list_typecheckt::typecheck_accumulator_compare_instruction(
 }
 
 void statement_list_typecheckt::typecheck_label_reference(
-  const irep_idt &label,
+  irep_idt label,
   bool sets_fc_false)
 {
   // If the label is already present in the list, check if it matches the
@@ -1520,7 +1520,7 @@ exprt statement_list_typecheckt::typecheck_simple_boolean_instruction_operand(
 
 exprt statement_list_typecheckt::typecheck_identifier(
   const symbolt &tia_element,
-  const irep_idt &identifier)
+  irep_idt identifier)
 {
   const code_typet &element_type{to_code_type(tia_element.type)};
 
diff --git a/src/statement-list/statement_list_typecheck.h b/src/statement-list/statement_list_typecheck.h
index c37fc401a58..796e81b348e 100644
--- a/src/statement-list/statement_list_typecheck.h
+++ b/src/statement-list/statement_list_typecheck.h
@@ -215,7 +215,7 @@ class statement_list_typecheckt : public typecheckt
   void typecheck_function_block_var_decls(
     const statement_list_parse_treet::var_declarationst &var_decls,
     struct_union_typet::componentst &components,
-    const irep_idt &var_property);
+    irep_idt var_property);
 
   /// Performs a typecheck on a variable declaration list and saves the result
   /// to the given component element.
@@ -228,8 +228,8 @@ class statement_list_typecheckt : public typecheckt
   void typecheck_function_var_decls(
     const statement_list_parse_treet::var_declarationst &var_decls,
     code_typet::parameterst &params,
-    const irep_idt &function_name,
-    const irep_idt &var_property);
+    irep_idt function_name,
+    irep_idt var_property);
 
   /// Performs a typecheck on the temp variables of a TIA module and saves the
   /// result to the given symbol value.
@@ -667,7 +667,7 @@ class statement_list_typecheckt : public typecheckt
   /// Performs a typecheck on an STL comparison instruction. Modifies the RLO.
   /// \param comparison: ID of the compare expression that should be pushed to
   ///   the RLO.
-  void typecheck_accumulator_compare_instruction(const irep_idt &comparison);
+  void typecheck_accumulator_compare_instruction(irep_idt comparison);
 
   /// Checks if the given label is already present and compares the current
   /// state with it. If there is no entry for the label, a new jump location
@@ -675,14 +675,13 @@ class statement_list_typecheckt : public typecheckt
   /// \param label: Label to check.
   /// \param sets_fc_false: Whether the encountered jump instruction sets the
   ///   /FC bit to false.
-  void typecheck_label_reference(const irep_idt &label, bool sets_fc_false);
+  void typecheck_label_reference(irep_idt label, bool sets_fc_false);
 
   /// Performs a typecheck on the given identifier and returns its symbol.
   /// \param identifier: Identifier that should be checked.
   /// \param tia_element: Symbol representation of the current TIA module.
   /// \return Expression including the symbol's name and type.
-  exprt
-  typecheck_identifier(const symbolt &tia_element, const irep_idt &identifier);
+  exprt typecheck_identifier(const symbolt &tia_element, irep_idt identifier);
 
   /// Performs a typecheck on a call of __CPOVER_ASSERT and saves the result
   /// to the given symbol.
diff --git a/src/util/arith_tools.cpp b/src/util/arith_tools.cpp
index f0c1c2793ba..a20a8e8264d 100644
--- a/src/util/arith_tools.cpp
+++ b/src/util/arith_tools.cpp
@@ -283,10 +283,7 @@ void mp_max(mp_integer &a, const mp_integer &b)
 /// \param src: the bitvector representation
 /// \param width: the number of bits in the bitvector
 /// \param bit_index: index (0 is the least significant)
-bool get_bvrep_bit(
-  const irep_idt &src,
-  std::size_t width,
-  std::size_t bit_index)
+bool get_bvrep_bit(irep_idt src, std::size_t width, std::size_t bit_index)
 {
   PRECONDITION(bit_index < width);
 
@@ -372,8 +369,8 @@ make_bvrep(const std::size_t width, const std::function<bool(std::size_t)> f)
 /// \param f: the functor
 /// \return new bitvector representation
 irep_idt bvrep_bitwise_op(
-  const irep_idt &a,
-  const irep_idt &b,
+  irep_idt a,
+  irep_idt b,
   const std::size_t width,
   const std::function<bool(bool, bool)> f)
 {
@@ -389,7 +386,7 @@ irep_idt bvrep_bitwise_op(
 /// \param f: the functor
 /// \return new bitvector representation
 irep_idt bvrep_bitwise_op(
-  const irep_idt &a,
+  irep_idt a,
   const std::size_t width,
   const std::function<bool(bool)> f)
 {
@@ -423,7 +420,7 @@ irep_idt integer2bvrep(const mp_integer &src, std::size_t width)
 }
 
 /// convert a bit-vector representation (possibly signed) to integer
-mp_integer bvrep2integer(const irep_idt &src, std::size_t width, bool is_signed)
+mp_integer bvrep2integer(irep_idt src, std::size_t width, bool is_signed)
 {
   if(is_signed)
   {
diff --git a/src/util/arith_tools.h b/src/util/arith_tools.h
index 92aaf3686f8..ed054cfac2d 100644
--- a/src/util/arith_tools.h
+++ b/src/util/arith_tools.h
@@ -168,15 +168,12 @@ bool is_power_of_two(const mp_integer &);
 void mp_min(mp_integer &a, const mp_integer &b);
 void mp_max(mp_integer &a, const mp_integer &b);
 
-bool get_bvrep_bit(
-  const irep_idt &src,
-  std::size_t width,
-  std::size_t bit_index);
+bool get_bvrep_bit(irep_idt src, std::size_t width, std::size_t bit_index);
 
 irep_idt
 make_bvrep(const std::size_t width, const std::function<bool(std::size_t)> f);
 
 irep_idt integer2bvrep(const mp_integer &, std::size_t width);
-mp_integer bvrep2integer(const irep_idt &, std::size_t width, bool is_signed);
+mp_integer bvrep2integer(irep_idt, std::size_t width, bool is_signed);
 
 #endif // CPROVER_UTIL_ARITH_TOOLS_H
diff --git a/src/util/bitvector_expr.cpp b/src/util/bitvector_expr.cpp
index e578f52b6ea..69a29a87f2a 100644
--- a/src/util/bitvector_expr.cpp
+++ b/src/util/bitvector_expr.cpp
@@ -12,10 +12,7 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "bitvector_types.h"
 #include "mathematical_types.h"
 
-shift_exprt::shift_exprt(
-  exprt _src,
-  const irep_idt &_id,
-  const std::size_t _distance)
+shift_exprt::shift_exprt(exprt _src, irep_idt _id, const std::size_t _distance)
   : binary_exprt(std::move(_src), _id, from_integer(_distance, integer_typet()))
 {
 }
diff --git a/src/util/bitvector_expr.h b/src/util/bitvector_expr.h
index b3dcb793602..19941af960f 100644
--- a/src/util/bitvector_expr.h
+++ b/src/util/bitvector_expr.h
@@ -421,12 +421,12 @@ inline bitnand_exprt &to_bitnand_expr(exprt &expr)
 class shift_exprt : public binary_exprt
 {
 public:
-  shift_exprt(exprt _src, const irep_idt &_id, exprt _distance)
+  shift_exprt(exprt _src, irep_idt _id, exprt _distance)
     : binary_exprt(std::move(_src), _id, std::move(_distance))
   {
   }
 
-  shift_exprt(exprt _src, const irep_idt &_id, const std::size_t _distance);
+  shift_exprt(exprt _src, irep_idt _id, const std::size_t _distance);
 
   exprt &op()
   {
@@ -1056,7 +1056,7 @@ inline popcount_exprt &to_popcount_expr(exprt &expr)
 class binary_overflow_exprt : public binary_predicate_exprt
 {
 public:
-  binary_overflow_exprt(exprt _lhs, const irep_idt &kind, exprt _rhs)
+  binary_overflow_exprt(exprt _lhs, irep_idt kind, exprt _rhs)
     : binary_predicate_exprt(std::move(_lhs), make_id(kind), std::move(_rhs))
   {
     INVARIANT(
@@ -1090,14 +1090,14 @@ class binary_overflow_exprt : public binary_predicate_exprt
   }
 
   /// Returns true iff \p id is a valid identifier of a `binary_overflow_exprt`.
-  static bool valid_id(const irep_idt &id)
+  static bool valid_id(irep_idt id)
   {
     return id == ID_overflow_plus || id == ID_overflow_mult ||
            id == ID_overflow_minus || id == ID_overflow_shl;
   }
 
 private:
-  static irep_idt make_id(const irep_idt &kind)
+  static irep_idt make_id(irep_idt kind)
   {
     if(valid_id(kind))
       return kind;
@@ -1223,7 +1223,7 @@ inline bool can_cast_expr<shl_overflow_exprt>(const exprt &base)
 class unary_overflow_exprt : public unary_predicate_exprt
 {
 public:
-  unary_overflow_exprt(const irep_idt &kind, exprt _op)
+  unary_overflow_exprt(irep_idt kind, exprt _op)
     : unary_predicate_exprt("overflow-" + id2string(kind), std::move(_op))
   {
   }
@@ -1656,7 +1656,7 @@ inline saturating_minus_exprt &to_saturating_minus_expr(exprt &expr)
 class overflow_result_exprt : public expr_protectedt
 {
 public:
-  overflow_result_exprt(exprt _lhs, const irep_idt &kind, exprt _rhs)
+  overflow_result_exprt(exprt _lhs, irep_idt kind, exprt _rhs)
     : expr_protectedt(
         make_id(kind),
         struct_typet{
@@ -1670,7 +1670,7 @@ class overflow_result_exprt : public expr_protectedt
       "of expected valid kinds.");
   }
 
-  overflow_result_exprt(exprt _op, const irep_idt &kind)
+  overflow_result_exprt(exprt _op, irep_idt kind)
     : expr_protectedt(
         make_id(kind),
         struct_typet{
@@ -1721,7 +1721,7 @@ class overflow_result_exprt : public expr_protectedt
   }
 
   /// Returns true iff \p id is a valid identifier of an `overflow_exprt`.
-  static bool valid_id(const irep_idt &id)
+  static bool valid_id(irep_idt id)
   {
     return id == ID_overflow_result_plus || id == ID_overflow_result_mult ||
            id == ID_overflow_result_minus || id == ID_overflow_result_shl ||
@@ -1729,7 +1729,7 @@ class overflow_result_exprt : public expr_protectedt
   }
 
 private:
-  static irep_idt make_id(const irep_idt &kind)
+  static irep_idt make_id(irep_idt kind)
   {
     return "overflow_result-" + id2string(kind);
   }
diff --git a/src/util/bitvector_types.h b/src/util/bitvector_types.h
index f3db88296f1..3cb72e41e01 100644
--- a/src/util/bitvector_types.h
+++ b/src/util/bitvector_types.h
@@ -26,16 +26,16 @@ class constant_exprt;
 class bitvector_typet : public typet
 {
 public:
-  explicit bitvector_typet(const irep_idt &_id) : typet(_id)
+  explicit bitvector_typet(irep_idt _id) : typet(_id)
   {
   }
 
-  bitvector_typet(const irep_idt &_id, std::size_t width) : typet(_id)
+  bitvector_typet(irep_idt _id, std::size_t width) : typet(_id)
   {
     set_width(width);
   }
 
-  bitvector_typet(const irep_idt &_id, mp_integer _width) : typet(_id)
+  bitvector_typet(irep_idt _id, mp_integer _width) : typet(_id)
   {
     width(_width);
   }
@@ -165,12 +165,12 @@ inline bv_typet &to_bv_type(typet &type)
 class integer_bitvector_typet : public bitvector_typet
 {
 public:
-  integer_bitvector_typet(const irep_idt &id, std::size_t width)
+  integer_bitvector_typet(irep_idt id, std::size_t width)
     : bitvector_typet(id, width)
   {
   }
 
-  integer_bitvector_typet(const irep_idt &id, const mp_integer &width)
+  integer_bitvector_typet(irep_idt id, const mp_integer &width)
     : bitvector_typet(id, width)
   {
   }
diff --git a/src/util/c_types.cpp b/src/util/c_types.cpp
index 2b18e322f59..2c52b33c161 100644
--- a/src/util/c_types.cpp
+++ b/src/util/c_types.cpp
@@ -248,7 +248,7 @@ empty_typet void_type()
   return result;
 }
 
-std::string c_type_as_string(const irep_idt &c_type)
+std::string c_type_as_string(irep_idt c_type)
 {
   if(c_type==ID_signed_int)
     return "signed int";
diff --git a/src/util/c_types.h b/src/util/c_types.h
index a16151d17d8..d5d1b4780b8 100644
--- a/src/util/c_types.h
+++ b/src/util/c_types.h
@@ -198,7 +198,7 @@ inline union_typet &to_union_type(typet &type)
 class union_tag_typet : public struct_or_union_tag_typet
 {
 public:
-  explicit union_tag_typet(const irep_idt &identifier)
+  explicit union_tag_typet(irep_idt identifier)
     : struct_or_union_tag_typet(ID_union_tag, identifier)
   {
   }
@@ -250,7 +250,7 @@ class c_enum_typet : public type_with_subtypet
     {
       return get(ID_value);
     }
-    void set_value(const irep_idt &value)
+    void set_value(irep_idt value)
     {
       set(ID_value, value);
     }
@@ -258,7 +258,7 @@ class c_enum_typet : public type_with_subtypet
     {
       return get(ID_identifier);
     }
-    void set_identifier(const irep_idt &identifier)
+    void set_identifier(irep_idt identifier)
     {
       set(ID_identifier, identifier);
     }
@@ -266,7 +266,7 @@ class c_enum_typet : public type_with_subtypet
     {
       return get(ID_base_name);
     }
-    void set_base_name(const irep_idt &base_name)
+    void set_base_name(irep_idt base_name)
     {
       set(ID_base_name, base_name);
     }
@@ -351,7 +351,7 @@ inline c_enum_typet &to_c_enum_type(typet &type)
 class c_enum_tag_typet : public tag_typet
 {
 public:
-  explicit c_enum_tag_typet(const irep_idt &identifier)
+  explicit c_enum_tag_typet(irep_idt identifier)
     : tag_typet(ID_c_enum_tag, identifier)
   {
   }
@@ -509,6 +509,6 @@ reference_typet reference_type(const typet &);
 
 // Turns an ID_C_c_type into a string, e.g.,
 // ID_signed_int gets "signed int".
-std::string c_type_as_string(const irep_idt &);
+std::string c_type_as_string(irep_idt);
 
 #endif // CPROVER_UTIL_C_TYPES_H
diff --git a/src/util/c_types_util.h b/src/util/c_types_util.h
index bc943f914e3..a0ddf59246d 100644
--- a/src/util/c_types_util.h
+++ b/src/util/c_types_util.h
@@ -83,7 +83,7 @@ inline bool is_c_enum_type(const typet &type)
 /// \return constant, that could be assigned as the value of an expression with
 ///   type c_enum.
 inline constant_exprt convert_member_name_to_enum_value(
-  const irep_idt &member_name,
+  irep_idt member_name,
   const c_enum_typet &c_enum)
 {
   for(const auto &enum_value : c_enum.members())
diff --git a/src/util/config.cpp b/src/util/config.cpp
index da70a3b9888..7e93ae4b8a6 100644
--- a/src/util/config.cpp
+++ b/src/util/config.cpp
@@ -217,7 +217,7 @@ void configt::ansi_ct::set_arch_spec_x86_64()
   }
 }
 
-void configt::ansi_ct::set_arch_spec_power(const irep_idt &subarch)
+void configt::ansi_ct::set_arch_spec_power(irep_idt subarch)
 {
   if(subarch=="powerpc")
     set_ILP32();
@@ -278,7 +278,7 @@ void configt::ansi_ct::set_arch_spec_power(const irep_idt &subarch)
   }
 }
 
-void configt::ansi_ct::set_arch_spec_arm(const irep_idt &subarch)
+void configt::ansi_ct::set_arch_spec_arm(irep_idt subarch)
 {
   if(subarch=="arm64")
   {
@@ -353,7 +353,7 @@ void configt::ansi_ct::set_arch_spec_alpha()
   }
 }
 
-void configt::ansi_ct::set_arch_spec_mips(const irep_idt &subarch)
+void configt::ansi_ct::set_arch_spec_mips(irep_idt subarch)
 {
   if(subarch=="mipsel" ||
      subarch=="mips" ||
@@ -486,7 +486,7 @@ void configt::ansi_ct::set_arch_spec_s390x()
   }
 }
 
-void configt::ansi_ct::set_arch_spec_sparc(const irep_idt &subarch)
+void configt::ansi_ct::set_arch_spec_sparc(irep_idt subarch)
 {
   if(subarch=="sparc64")
   {
@@ -760,7 +760,7 @@ configt::cppt::cpp_standardt configt::cppt::default_cpp_standard()
   #endif
 }
 
-void configt::set_arch(const irep_idt &arch)
+void configt::set_arch(irep_idt arch)
 {
   ansi_c.arch=arch;
 
diff --git a/src/util/config.h b/src/util/config.h
index e1cdc3eb99c..49bf5c65ee8 100644
--- a/src/util/config.h
+++ b/src/util/config.h
@@ -251,14 +251,14 @@ class configt
 
     void set_arch_spec_i386();
     void set_arch_spec_x86_64();
-    void set_arch_spec_power(const irep_idt &subarch);
-    void set_arch_spec_arm(const irep_idt &subarch);
+    void set_arch_spec_power(irep_idt subarch);
+    void set_arch_spec_arm(irep_idt subarch);
     void set_arch_spec_alpha();
-    void set_arch_spec_mips(const irep_idt &subarch);
+    void set_arch_spec_mips(irep_idt subarch);
     void set_arch_spec_riscv64();
     void set_arch_spec_s390();
     void set_arch_spec_s390x();
-    void set_arch_spec_sparc(const irep_idt &subarch);
+    void set_arch_spec_sparc(irep_idt subarch);
     void set_arch_spec_ia64();
     void set_arch_spec_x32();
     void set_arch_spec_v850();
@@ -389,7 +389,7 @@ class configt
   // this is the function to start executing
   std::optional<std::string> main;
 
-  void set_arch(const irep_idt &);
+  void set_arch(irep_idt);
 
   void set_from_symbol_table(const symbol_table_baset &);
 
diff --git a/src/util/dstring.h b/src/util/dstring.h
index 38926cb754e..48d57727486 100644
--- a/src/util/dstring.h
+++ b/src/util/dstring.h
@@ -125,14 +125,17 @@ class dstringt final
 
   // ordering -- not the same as lexicographical ordering
 
-  bool operator< (const dstringt &b) const { return no<b.no; }
+  bool operator<(dstringt b) const
+  {
+    return no < b.no;
+  }
 
   // comparison with same type
 
-  bool operator==(const dstringt &b) const
+  bool operator==(dstringt b) const
   { return no==b.no; } // really fast equality testing
 
-  bool operator!=(const dstringt &b) const
+  bool operator!=(dstringt b) const
   { return no!=b.no; } // really fast equality testing
 
   // comparison with other types
@@ -147,7 +150,7 @@ class dstringt final
   bool operator<=(const std::string &b) const { return as_string()<=b; }
   bool operator>=(const std::string &b) const { return as_string()>=b; }
 
-  int compare(const dstringt &b) const
+  int compare(dstringt b) const
   {
     if(no==b.no)
       return 0; // equal
@@ -216,21 +219,24 @@ class dstringt final
 };
 
 // the reference returned is guaranteed to be stable
-inline const std::string &as_string(const dstringt &s)
+inline const std::string &as_string(dstringt s)
 { return get_string_container().get_string(s.get_no()); }
 
 // NOLINTNEXTLINE(readability/identifiers)
 struct dstring_hash
 {
-  size_t operator()(const dstringt &s) const { return s.hash(); }
+  size_t operator()(dstringt s) const
+  {
+    return s.hash();
+  }
 };
 
-inline size_t hash_string(const dstringt &s)
+inline size_t hash_string(dstringt s)
 {
   return s.hash();
 }
 
-inline std::ostream &operator<<(std::ostream &out, const dstringt &a)
+inline std::ostream &operator<<(std::ostream &out, dstringt a)
 {
   return a.operator<<(out);
 }
diff --git a/src/util/expr.h b/src/util/expr.h
index b5bbfecce09..346a07b2c51 100644
--- a/src/util/expr.h
+++ b/src/util/expr.h
@@ -60,7 +60,9 @@ class exprt:public irept
 
   // constructors
   exprt() { }
-  explicit exprt(const irep_idt &_id):irept(_id) { }
+  explicit exprt(irep_idt _id) : irept(_id)
+  {
+  }
 
   exprt(irep_idt _id, typet _type)
     : irept(std::move(_id), {{ID_type, std::move(_type)}}, {})
@@ -75,7 +77,7 @@ class exprt:public irept
   {
   }
 
-  exprt(const irep_idt &id, typet type, source_locationt loc)
+  exprt(irep_idt id, typet type, source_locationt loc)
     : exprt(id, std::move(type))
   {
     add_source_location() = std::move(loc);
@@ -305,12 +307,12 @@ class exprt:public irept
   }
 
 protected:
-  exprt &add_expr(const irep_idt &name)
+  exprt &add_expr(irep_idt name)
   {
     return static_cast<exprt &>(add(name));
   }
 
-  const exprt &find_expr(const irep_idt &name) const
+  const exprt &find_expr(irep_idt name) const
   {
     return static_cast<const exprt &>(find(name));
   }
diff --git a/src/util/expr_util.cpp b/src/util/expr_util.cpp
index 6e20238e988..05c9e7a7942 100644
--- a/src/util/expr_util.cpp
+++ b/src/util/expr_util.cpp
@@ -115,7 +115,7 @@ bool has_subexpr(
   return it != expr.depth_end();
 }
 
-bool has_subexpr(const exprt &src, const irep_idt &id)
+bool has_subexpr(const exprt &src, irep_idt id)
 {
   return has_subexpr(
     src, [&](const exprt &subexpr) { return subexpr.id() == id; });
@@ -163,7 +163,7 @@ bool has_subtype(
   return false;
 }
 
-bool has_subtype(const typet &type, const irep_idt &id, const namespacet &ns)
+bool has_subtype(const typet &type, irep_idt id, const namespacet &ns)
 {
   return has_subtype(
     type, [&](const typet &subtype) { return subtype.id() == id; }, ns);
diff --git a/src/util/expr_util.h b/src/util/expr_util.h
index 3b4d1dfa9e4..438aecaff2f 100644
--- a/src/util/expr_util.h
+++ b/src/util/expr_util.h
@@ -51,7 +51,7 @@ exprt boolean_negate(const exprt &);
 bool has_subexpr(const exprt &, const std::function<bool(const exprt &)> &pred);
 
 /// returns true if the expression has a subexpression with given ID
-bool has_subexpr(const exprt &, const irep_idt &);
+bool has_subexpr(const exprt &, irep_idt);
 
 /// returns true if any of the contained types satisfies pred
 /// \param type: a type
@@ -70,7 +70,7 @@ bool has_subtype(
   const namespacet &ns);
 
 /// returns true if any of the contained types is id
-bool has_subtype(const typet &, const irep_idt &id, const namespacet &);
+bool has_subtype(const typet &, irep_idt id, const namespacet &);
 
 /// lift up an if_exprt one level
 if_exprt lift_if(const exprt &, std::size_t operand_number);
diff --git a/src/util/find_symbols.cpp b/src/util/find_symbols.cpp
index 4b15498c771..5187951d15d 100644
--- a/src/util/find_symbols.cpp
+++ b/src/util/find_symbols.cpp
@@ -266,7 +266,7 @@ void find_symbols(const exprt &src, std::set<symbol_exprt> &dest)
 
 bool has_symbol_expr(
   const exprt &src,
-  const irep_idt &identifier,
+  irep_idt identifier,
   bool include_bound_symbols)
 {
   return !find_symbols(
diff --git a/src/util/find_symbols.h b/src/util/find_symbols.h
index c699ebd7380..711a7fb52cf 100644
--- a/src/util/find_symbols.h
+++ b/src/util/find_symbols.h
@@ -26,7 +26,7 @@ typedef std::unordered_set<irep_idt> find_symbols_sett;
 /// \p include_bound_symbols is true, then bindings are included in the search.
 bool has_symbol_expr(
   const exprt &src,
-  const irep_idt &identifier,
+  irep_idt identifier,
   bool include_bound_symbols);
 
 /// Add to the set \p dest the sub-expressions of \p src with id ID_symbol, for
diff --git a/src/util/floatbv_expr.h b/src/util/floatbv_expr.h
index e11fda2a02e..b9f211493cc 100644
--- a/src/util/floatbv_expr.h
+++ b/src/util/floatbv_expr.h
@@ -427,11 +427,7 @@ inline ieee_float_notequal_exprt &to_ieee_float_notequal_expr(exprt &expr)
 class ieee_float_op_exprt : public ternary_exprt
 {
 public:
-  ieee_float_op_exprt(
-    const exprt &_lhs,
-    const irep_idt &_id,
-    exprt _rhs,
-    exprt _rm)
+  ieee_float_op_exprt(const exprt &_lhs, irep_idt _id, exprt _rhs, exprt _rm)
     : ternary_exprt(_id, _lhs, std::move(_rhs), std::move(_rm), _lhs.type())
   {
   }
diff --git a/src/util/fresh_symbol.cpp b/src/util/fresh_symbol.cpp
index 8a3738b56c9..09c4fa5dd62 100644
--- a/src/util/fresh_symbol.cpp
+++ b/src/util/fresh_symbol.cpp
@@ -34,7 +34,7 @@ symbolt &get_fresh_aux_symbol(
   const std::string &name_prefix,
   const std::string &basename_prefix,
   const source_locationt &source_location,
-  const irep_idt &symbol_mode,
+  irep_idt symbol_mode,
   const namespacet &ns,
   symbol_table_baset &symbol_table)
 {
@@ -73,7 +73,7 @@ symbolt &get_fresh_aux_symbol(
   const std::string &name_prefix,
   const std::string &basename_prefix,
   const source_locationt &source_location,
-  const irep_idt &symbol_mode,
+  irep_idt symbol_mode,
   symbol_table_baset &symbol_table)
 {
   return get_fresh_aux_symbol(
diff --git a/src/util/fresh_symbol.h b/src/util/fresh_symbol.h
index 72d2ca22ac7..d15cad4c995 100644
--- a/src/util/fresh_symbol.h
+++ b/src/util/fresh_symbol.h
@@ -31,7 +31,7 @@ get_fresh_aux_symbol(
   const std::string &name_prefix,
   const std::string &basename_prefix,
   const source_locationt &source_location,
-  const irep_idt &symbol_mode,
+  irep_idt symbol_mode,
   symbol_table_baset &symbol_table);
 
 #if defined(__GNUC__) && __GNUC__ >= 14
@@ -43,7 +43,7 @@ get_fresh_aux_symbol(
   const std::string &name_prefix,
   const std::string &basename_prefix,
   const source_locationt &source_location,
-  const irep_idt &symbol_mode,
+  irep_idt symbol_mode,
   const namespacet &ns,
   symbol_table_baset &symbol_table);
 
diff --git a/src/util/interval.cpp b/src/util/interval.cpp
index 8236240a1cf..cb109ab2dbd 100644
--- a/src/util/interval.cpp
+++ b/src/util/interval.cpp
@@ -471,7 +471,7 @@ constant_interval_exprt constant_interval_exprt::decrement() const
 constant_interval_exprt constant_interval_exprt::get_extremes(
   const constant_interval_exprt &a,
   const constant_interval_exprt &b,
-  const irep_idt &operation)
+  irep_idt operation)
 {
   std::vector<exprt> results;
 
@@ -572,7 +572,7 @@ exprt constant_interval_exprt::get_extreme(
 void constant_interval_exprt::generate_expression(
   const exprt &lhs,
   const exprt &rhs,
-  const irep_idt &operation,
+  irep_idt operation,
   std::vector<exprt> &collection)
 {
   if(operation == ID_mult)
@@ -790,7 +790,7 @@ exprt constant_interval_exprt::generate_modulo_expression(
   return simplified_expr(modulo_expr);
 }
 
-constant_interval_exprt constant_interval_exprt::eval(const irep_idt &id) const
+constant_interval_exprt constant_interval_exprt::eval(irep_idt id) const
 {
   if(id == ID_unary_plus)
   {
@@ -813,7 +813,7 @@ constant_interval_exprt constant_interval_exprt::eval(const irep_idt &id) const
 }
 
 constant_interval_exprt constant_interval_exprt::eval(
-  const irep_idt &binary_operator,
+  irep_idt binary_operator,
   const constant_interval_exprt &other) const
 {
   if(binary_operator == ID_plus)
@@ -899,7 +899,7 @@ constant_interval_exprt constant_interval_exprt::eval(
 exprt constant_interval_exprt::generate_shift_expression(
   const exprt &lhs,
   const exprt &rhs,
-  const irep_idt &operation)
+  irep_idt operation)
 {
   PRECONDITION(operation == ID_shl || operation == ID_ashr);
 
@@ -936,8 +936,7 @@ exprt constant_interval_exprt::generate_shift_expression(
 }
 
 constant_interval_exprt
-constant_interval_exprt::handle_constant_unary_expression(
-  const irep_idt &op) const
+constant_interval_exprt::handle_constant_unary_expression(irep_idt op) const
 {
   if(is_single_value_interval())
   {
@@ -950,7 +949,7 @@ constant_interval_exprt::handle_constant_unary_expression(
 constant_interval_exprt
 constant_interval_exprt::handle_constant_binary_expression(
   const constant_interval_exprt &other,
-  const irep_idt &op) const
+  irep_idt op) const
 {
   PRECONDITION(is_single_value_interval() && other.is_single_value_interval());
   auto expr = binary_exprt(get_lower(), op, other.get_lower());
diff --git a/src/util/interval.h b/src/util/interval.h
index 9e70d2a637f..4d0f07a9fba 100644
--- a/src/util/interval.h
+++ b/src/util/interval.h
@@ -131,15 +131,14 @@ class constant_interval_exprt : public binary_exprt
   const exprt &get_upper() const;
 
   /** SET OF ARITHMETIC OPERATORS */
-  constant_interval_exprt
-  handle_constant_unary_expression(const irep_idt &op) const;
+  constant_interval_exprt handle_constant_unary_expression(irep_idt op) const;
   constant_interval_exprt handle_constant_binary_expression(
     const constant_interval_exprt &other,
-    const irep_idt &) const;
+    irep_idt) const;
 
-  constant_interval_exprt eval(const irep_idt &unary_operator) const;
+  constant_interval_exprt eval(irep_idt unary_operator) const;
   constant_interval_exprt
-  eval(const irep_idt &binary_operator, const constant_interval_exprt &o) const;
+  eval(irep_idt binary_operator, const constant_interval_exprt &o) const;
 
   /* Unary arithmetic */
   constant_interval_exprt unary_plus() const;
@@ -366,7 +365,7 @@ class constant_interval_exprt : public binary_exprt
   static constant_interval_exprt get_extremes(
     const constant_interval_exprt &lhs,
     const constant_interval_exprt &rhs,
-    const irep_idt &operation);
+    irep_idt operation);
   static exprt get_extreme(std::vector<exprt> values, bool min = true);
   static exprt get_max(const exprt &a, const exprt &b);
   static exprt get_min(const exprt &a, const exprt &b);
@@ -437,7 +436,7 @@ class constant_interval_exprt : public binary_exprt
   static void generate_expression(
     const exprt &lhs,
     const exprt &rhs,
-    const irep_idt &operation,
+    irep_idt operation,
     std::vector<exprt> &collection);
   static void append_multiply_expression(
     const exprt &lower,
@@ -455,7 +454,7 @@ class constant_interval_exprt : public binary_exprt
   static exprt generate_shift_expression(
     const exprt &lhs,
     const exprt &rhs,
-    const irep_idt &operation);
+    irep_idt operation);
 };
 
 inline const constant_interval_exprt &
diff --git a/src/util/irep.cpp b/src/util/irep.cpp
index 36e103ea8ff..fa670164c81 100644
--- a/src/util/irep.cpp
+++ b/src/util/irep.cpp
@@ -23,7 +23,7 @@ const irept &get_nil_irep()
   return nil_rep_storage;
 }
 
-void irept::move_to_named_sub(const irep_idt &name, irept &irep)
+void irept::move_to_named_sub(irep_idt name, irept &irep)
 {
   #ifdef SHARING
   detach();
@@ -41,7 +41,7 @@ void irept::move_to_sub(irept &irep)
   get_sub().back().swap(irep);
 }
 
-const irep_idt &irept::get(const irep_idt &name) const
+const irep_idt &irept::get(irep_idt name) const
 {
   const named_subt &s = get_named_sub();
   named_subt::const_iterator it=s.find(name);
@@ -54,43 +54,43 @@ const irep_idt &irept::get(const irep_idt &name) const
   return it->second.id();
 }
 
-bool irept::get_bool(const irep_idt &name) const
+bool irept::get_bool(irep_idt name) const
 {
   return get(name)==ID_1;
 }
 
-int irept::get_int(const irep_idt &name) const
+int irept::get_int(irep_idt name) const
 {
   return unsafe_string2int(get_string(name));
 }
 
-std::size_t irept::get_size_t(const irep_idt &name) const
+std::size_t irept::get_size_t(irep_idt name) const
 {
   return unsafe_string2size_t(get_string(name));
 }
 
-long long irept::get_long_long(const irep_idt &name) const
+long long irept::get_long_long(irep_idt name) const
 {
   return unsafe_string2signedlonglong(get_string(name));
 }
 
-void irept::set(const irep_idt &name, const long long value)
+void irept::set(irep_idt name, const long long value)
 {
   add(name).id(to_dstring(value));
 }
 
-void irept::set_size_t(const irep_idt &name, const std::size_t value)
+void irept::set_size_t(irep_idt name, const std::size_t value)
 {
   add(name).id(to_dstring(value));
 }
 
-void irept::remove(const irep_idt &name)
+void irept::remove(irep_idt name)
 {
   named_subt &s = get_named_sub();
   s.erase(name);
 }
 
-const irept &irept::find(const irep_idt &name) const
+const irept &irept::find(irep_idt name) const
 {
   const named_subt &s = get_named_sub();
   auto it = s.find(name);
@@ -100,13 +100,13 @@ const irept &irept::find(const irep_idt &name) const
   return it->second;
 }
 
-irept &irept::add(const irep_idt &name)
+irept &irept::add(irep_idt name)
 {
   named_subt &s = get_named_sub();
   return s[name];
 }
 
-irept &irept::add(const irep_idt &name, irept irep)
+irept &irept::add(irep_idt name, irept irep)
 {
   named_subt &s = get_named_sub();
 
diff --git a/src/util/irep.h b/src/util/irep.h
index 28f87062c48..770d037544a 100644
--- a/src/util/irep.h
+++ b/src/util/irep.h
@@ -41,7 +41,7 @@ typedef dstring_hash irep_id_hash;
 [[gnu::no_dangling]]
 #endif
 inline const std::string &
-id2string(const irep_idt &d)
+id2string(irep_idt d)
 {
   return as_string(d);
 }
@@ -374,11 +374,11 @@ class irept
     return id() != ID_nil;
   }
 
-  explicit irept(const irep_idt &_id) : baset(_id)
+  explicit irept(irep_idt _id) : baset(_id)
   {
   }
 
-  irept(const irep_idt &_id, const named_subt &_named_sub, const subt &_sub)
+  irept(irep_idt _id, const named_subt &_named_sub, const subt &_sub)
     : baset(_id, _named_sub, _sub)
   {
   }
@@ -391,38 +391,38 @@ class irept
   const std::string &id_string() const
   { return id2string(read().data); }
 
-  void id(const irep_idt &_data)
+  void id(irep_idt _data)
   { write().data=_data; }
 
-  const irept &find(const irep_idt &name) const;
-  irept &add(const irep_idt &name);
-  irept &add(const irep_idt &name, irept irep);
+  const irept &find(irep_idt name) const;
+  irept &add(irep_idt name);
+  irept &add(irep_idt name, irept irep);
 
-  const std::string &get_string(const irep_idt &name) const
+  const std::string &get_string(irep_idt name) const
   {
     return id2string(get(name));
   }
 
-  const irep_idt &get(const irep_idt &name) const;
-  bool get_bool(const irep_idt &name) const;
-  signed int get_int(const irep_idt &name) const;
-  std::size_t get_size_t(const irep_idt &name) const;
-  long long get_long_long(const irep_idt &name) const;
+  const irep_idt &get(irep_idt name) const;
+  bool get_bool(irep_idt name) const;
+  signed int get_int(irep_idt name) const;
+  std::size_t get_size_t(irep_idt name) const;
+  long long get_long_long(irep_idt name) const;
 
-  void set(const irep_idt &name, const irep_idt &value)
+  void set(irep_idt name, irep_idt value)
   {
     add(name, irept(value));
   }
-  void set(const irep_idt &name, irept irep)
+  void set(irep_idt name, irept irep)
   {
     add(name, std::move(irep));
   }
-  void set(const irep_idt &name, const long long value);
-  void set_size_t(const irep_idt &name, const std::size_t value);
+  void set(irep_idt name, const long long value);
+  void set_size_t(irep_idt name, const std::size_t value);
 
-  void remove(const irep_idt &name);
+  void remove(irep_idt name);
   void move_to_sub(irept &irep);
-  void move_to_named_sub(const irep_idt &name, irept &irep);
+  void move_to_named_sub(irep_idt name, irept &irep);
 
   bool operator==(const irept &other) const;
 
@@ -457,7 +457,7 @@ class irept
 
   std::string pretty(unsigned indent=0, unsigned max_indent=0) const;
 
-  static bool is_comment(const irep_idt &name)
+  static bool is_comment(irep_idt name)
   { return !name.empty() && name[0]=='#'; }
 
   /// count the number of named_sub elements that are not comments
diff --git a/src/util/irep_serialization.cpp b/src/util/irep_serialization.cpp
index 20f37d8a194..6ba85f2702b 100644
--- a/src/util/irep_serialization.cpp
+++ b/src/util/irep_serialization.cpp
@@ -208,9 +208,7 @@ irep_idt irep_serializationt::read_gb_string(std::istream &in)
 /// Output a string and maintain a reference to it
 /// \param out: output stream
 /// \param s: string to output
-void irep_serializationt::write_string_ref(
-  std::ostream &out,
-  const irep_idt &s)
+void irep_serializationt::write_string_ref(std::ostream &out, irep_idt s)
 {
   size_t id = s.get_no();
   if(id>=ireps_container.string_map.size())
diff --git a/src/util/irep_serialization.h b/src/util/irep_serialization.h
index 275e9268ff5..2a8a4fe2c9f 100644
--- a/src/util/irep_serialization.h
+++ b/src/util/irep_serialization.h
@@ -65,7 +65,7 @@ class irep_serializationt
   void reference_convert(const irept &irep, std::ostream &);
 
   irep_idt read_string_ref(std::istream &);
-  void write_string_ref(std::ostream &, const irep_idt &);
+  void write_string_ref(std::ostream &, irep_idt);
 
   void clear() { ireps_container.clear(); }
 
diff --git a/src/util/journalling_symbol_table.h b/src/util/journalling_symbol_table.h
index a1f9643d048..bf33ab48118 100644
--- a/src/util/journalling_symbol_table.h
+++ b/src/util/journalling_symbol_table.h
@@ -73,7 +73,7 @@ class journalling_symbol_tablet : public symbol_table_baset
   {
   }
 
-  virtual const symbol_tablet &get_symbol_table() const override
+  const symbol_tablet &get_symbol_table() const override
   {
     return base_symbol_table.get_symbol_table();
   }
@@ -83,7 +83,7 @@ class journalling_symbol_tablet : public symbol_table_baset
     return journalling_symbol_tablet(base_symbol_table);
   }
 
-  virtual bool move(symbolt &symbol, symbolt *&new_symbol) override
+  bool move(symbolt &symbol, symbolt *&new_symbol) override
   {
     bool ret = base_symbol_table.move(symbol, new_symbol);
     if(!ret)
@@ -93,7 +93,7 @@ class journalling_symbol_tablet : public symbol_table_baset
     return ret;
   }
 
-  virtual symbolt *get_writeable(const irep_idt &identifier) override
+  symbolt *get_writeable(irep_idt identifier) override
   {
     symbolt *result = base_symbol_table.get_writeable(identifier);
     if(result)
@@ -106,7 +106,7 @@ class journalling_symbol_tablet : public symbol_table_baset
     return base_symbol_table.next_unused_suffix(prefix);
   }
 
-  virtual std::pair<symbolt &, bool> insert(symbolt symbol) override
+  std::pair<symbolt &, bool> insert(symbolt symbol) override
   {
     std::pair<symbolt &, bool> result =
       base_symbol_table.insert(std::move(symbol));
@@ -115,30 +115,29 @@ class journalling_symbol_tablet : public symbol_table_baset
     return result;
   }
 
-  virtual void
-  erase(const symbol_table_baset::symbolst::const_iterator &entry) override
+  void erase(const symbol_table_baset::symbolst::const_iterator &entry) override
   {
     const irep_idt entry_name = entry->first;
     base_symbol_table.erase(entry);
     on_remove(entry_name);
   }
 
-  virtual void clear() override
+  void clear() override
   {
     for(const auto &named_symbol : base_symbol_table.symbols)
       on_remove(named_symbol.first);
     base_symbol_table.clear();
   }
 
-  virtual iteratort begin() override
+  iteratort begin() override
   {
     return iteratort(
-      base_symbol_table.begin(), [this](const irep_idt &id) { on_update(id); });
+      base_symbol_table.begin(), [this](irep_idt id) { on_update(id); });
   }
-  virtual iteratort end() override
+  iteratort end() override
   {
     return iteratort(
-      base_symbol_table.end(), [this](const irep_idt &id) { on_update(id); });
+      base_symbol_table.end(), [this](irep_idt id) { on_update(id); });
   }
 
   using symbol_table_baset::begin;
@@ -164,19 +163,19 @@ class journalling_symbol_tablet : public symbol_table_baset
   }
 
 private:
-  void on_insert(const irep_idt &id)
+  void on_insert(irep_idt id)
   {
     if(removed.erase(id) == 0)
       inserted.insert(id);
     updated.insert(id);
   }
 
-  void on_update(const irep_idt &id)
+  void on_update(irep_idt id)
   {
     updated.insert(id);
   }
 
-  void on_remove(const irep_idt &id)
+  void on_remove(irep_idt id)
   {
     if(inserted.erase(id) == 0)
       removed.insert(id);
diff --git a/src/util/json.h b/src/util/json.h
index 2ef36d85f07..cec99d23617 100644
--- a/src/util/json.h
+++ b/src/util/json.h
@@ -274,7 +274,7 @@ class json_stringt:public jsont
   {
   }
 
-  explicit json_stringt(const irep_idt &_value)
+  explicit json_stringt(irep_idt _value)
     : jsont(kindt::J_STRING, id2string(_value))
   {
   }
diff --git a/src/util/mathematical_expr.h b/src/util/mathematical_expr.h
index b8c0eb76a6c..6f10c8d47be 100644
--- a/src/util/mathematical_expr.h
+++ b/src/util/mathematical_expr.h
@@ -21,7 +21,7 @@ class transt : public ternary_exprt
 {
 public:
   transt(
-    const irep_idt &_id,
+    irep_idt _id,
     const exprt &_op0,
     const exprt &_op1,
     const exprt &_op2,
diff --git a/src/util/namespace.cpp b/src/util/namespace.cpp
index 82c80725071..f959898fe9f 100644
--- a/src/util/namespace.cpp
+++ b/src/util/namespace.cpp
@@ -131,9 +131,7 @@ std::size_t namespacet::smallest_unused_suffix(const std::string &prefix) const
 /// \param symbol: The const pointer to the reference of the symbol
 ///   if it's found during lookup.
 /// \return False if the symbol was found, True otherwise.
-bool namespacet::lookup(
-  const irep_idt &name,
-  const symbolt *&symbol) const
+bool namespacet::lookup(irep_idt name, const symbolt *&symbol) const
 {
   symbol_table_baset::symbolst::const_iterator it;
 
@@ -182,9 +180,7 @@ multi_namespacet::smallest_unused_suffix(const std::string &prefix) const
 /// \param symbol: The const pointer to the reference of the symbol
 ///   if it's found during lookup.
 /// \return False if the symbol was found, True otherwise.
-bool multi_namespacet::lookup(
-  const irep_idt &name,
-  const symbolt *&symbol) const
+bool multi_namespacet::lookup(irep_idt name, const symbolt *&symbol) const
 {
   symbol_table_baset::symbolst::const_iterator s_it;
 
diff --git a/src/util/namespace.h b/src/util/namespace.h
index 1594fea198d..cab07f4e5c5 100644
--- a/src/util/namespace.h
+++ b/src/util/namespace.h
@@ -42,7 +42,7 @@ class namespace_baset
   /// \return A reference to the symbol found.
   /// \remarks: It is a PRECONDITION that the symbol name exists
   ///   in the namespace.
-  const symbolt &lookup(const irep_idt &name) const
+  const symbolt &lookup(irep_idt name) const
   {
     const symbolt *symbol;
     bool not_found = lookup(name, symbol);
@@ -79,7 +79,7 @@ class namespace_baset
   /// and then symbol_table2.
   /// \return False iff the requested symbol is found in at least one of the
   ///   tables.
-  virtual bool lookup(const irep_idt &name, const symbolt *&symbol) const=0;
+  virtual bool lookup(irep_idt name, const symbolt *&symbol) const = 0;
 };
 
 /// A namespacet is essentially one or two symbol tables bound
@@ -114,7 +114,7 @@ class namespacet:public namespace_baset
 
   /// See documentation for namespace_baset::lookup(). Note that
   /// \ref namespacet has two symbol tables.
-  bool lookup(const irep_idt &name, const symbolt *&symbol) const override;
+  bool lookup(irep_idt name, const symbolt *&symbol) const override;
 
   /// See documentation for namespace_baset::smallest_unused_suffix().
   std::size_t smallest_unused_suffix(const std::string &prefix) const override;
@@ -151,7 +151,7 @@ class multi_namespacet:public namespacet
   using namespace_baset::lookup;
 
   /// See documentation for namespace_baset::lookup().
-  bool lookup(const irep_idt &name, const symbolt *&symbol) const override;
+  bool lookup(irep_idt name, const symbolt *&symbol) const override;
   /// See documentation for namespace_baset::smallest_unused_suffix().
   std::size_t smallest_unused_suffix(const std::string &prefix) const override;
 
diff --git a/src/util/parser.h b/src/util/parser.h
index eeec3b469a0..be9b8dbb503 100644
--- a/src/util/parser.h
+++ b/src/util/parser.h
@@ -81,7 +81,7 @@ class parsert
     line_no=_line_no;
   }
 
-  void set_file(const irep_idt &file)
+  void set_file(irep_idt file)
   {
     _source_location.set_file(file);
     _source_location.set_working_directory(
@@ -130,7 +130,7 @@ class parsert
     e.add_source_location() = source_location();
   }
 
-  void set_function(const irep_idt &function)
+  void set_function(irep_idt function)
   {
     _source_location.set_function(function);
   }
diff --git a/src/util/pointer_expr.cpp b/src/util/pointer_expr.cpp
index 7de79c38a1c..99cbb025561 100644
--- a/src/util/pointer_expr.cpp
+++ b/src/util/pointer_expr.cpp
@@ -148,7 +148,7 @@ symbol_exprt object_address_exprt::object_expr() const
 
 field_address_exprt::field_address_exprt(
   exprt compound_ptr,
-  const irep_idt &component_name,
+  irep_idt component_name,
   pointer_typet _type)
   : unary_exprt(ID_field_address, std::move(compound_ptr), std::move(_type))
 {
diff --git a/src/util/pointer_expr.h b/src/util/pointer_expr.h
index d3130b3110c..95ecce00ba0 100644
--- a/src/util/pointer_expr.h
+++ b/src/util/pointer_expr.h
@@ -665,10 +665,7 @@ class field_address_exprt : public unary_exprt
 public:
   /// constructor for field addresses.
   /// The base address must be a pointer to a compound type.
-  field_address_exprt(
-    exprt base,
-    const irep_idt &component_name,
-    pointer_typet type);
+  field_address_exprt(exprt base, irep_idt component_name, pointer_typet type);
 
   exprt &base()
   {
@@ -1209,9 +1206,7 @@ inline const prophecy_w_ok_exprt &to_prophecy_w_ok_expr(const exprt &expr)
 class annotated_pointer_constant_exprt : public unary_exprt
 {
 public:
-  annotated_pointer_constant_exprt(
-    const irep_idt &_value,
-    const exprt &_pointer)
+  annotated_pointer_constant_exprt(irep_idt _value, const exprt &_pointer)
     : unary_exprt(ID_annotated_pointer_constant, _pointer, _pointer.type())
   {
     set_value(_value);
@@ -1222,7 +1217,7 @@ class annotated_pointer_constant_exprt : public unary_exprt
     return get(ID_value);
   }
 
-  void set_value(const irep_idt &value)
+  void set_value(irep_idt value)
   {
     set(ID_value, value);
   }
diff --git a/src/util/pointer_offset_size.cpp b/src/util/pointer_offset_size.cpp
index cdc1b87c9c8..f050efa3d45 100644
--- a/src/util/pointer_offset_size.cpp
+++ b/src/util/pointer_offset_size.cpp
@@ -22,10 +22,8 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "ssa_expr.h"
 #include "std_expr.h"
 
-std::optional<mp_integer> member_offset(
-  const struct_typet &type,
-  const irep_idt &member,
-  const namespacet &ns)
+std::optional<mp_integer>
+member_offset(const struct_typet &type, irep_idt member, const namespacet &ns)
 {
   mp_integer result = 0;
   std::size_t bit_field_bits = 0;
@@ -65,7 +63,7 @@ std::optional<mp_integer> member_offset(
 
 std::optional<mp_integer> member_offset_bits(
   const struct_typet &type,
-  const irep_idt &member,
+  irep_idt member,
   const namespacet &ns)
 {
   mp_integer offset=0;
@@ -240,7 +238,7 @@ member_offset_expr(const member_exprt &member_expr, const namespacet &ns)
 
 std::optional<exprt> member_offset_expr(
   const struct_typet &type,
-  const irep_idt &member,
+  irep_idt member,
   const namespacet &ns)
 {
   PRECONDITION(size_type().get_width() != 0);
diff --git a/src/util/pointer_offset_size.h b/src/util/pointer_offset_size.h
index 97107b11b87..f0c7b1d803d 100644
--- a/src/util/pointer_offset_size.h
+++ b/src/util/pointer_offset_size.h
@@ -23,14 +23,12 @@ class struct_typet;
 class typet;
 class member_exprt;
 
-std::optional<mp_integer> member_offset(
-  const struct_typet &type,
-  const irep_idt &member,
-  const namespacet &ns);
+std::optional<mp_integer>
+member_offset(const struct_typet &type, irep_idt member, const namespacet &ns);
 
 std::optional<mp_integer> member_offset_bits(
   const struct_typet &type,
-  const irep_idt &member,
+  irep_idt member,
   const namespacet &ns);
 
 std::optional<mp_integer>
@@ -47,7 +45,7 @@ member_offset_expr(const member_exprt &, const namespacet &ns);
 
 std::optional<exprt> member_offset_expr(
   const struct_typet &type,
-  const irep_idt &member,
+  irep_idt member,
   const namespacet &ns);
 
 std::optional<exprt> size_of_expr(const typet &type, const namespacet &ns);
diff --git a/src/util/rename.cpp b/src/util/rename.cpp
index 2b622b96874..10635a96763 100644
--- a/src/util/rename.cpp
+++ b/src/util/rename.cpp
@@ -12,8 +12,7 @@ Author: Daniel Kroening, kroening@kroening.com
 
 #include "namespace.h"
 
-irep_idt
-get_new_name(const irep_idt &name, const namespacet &ns, char delimiter)
+irep_idt get_new_name(irep_idt name, const namespacet &ns, char delimiter)
 {
   const symbolt *symbol;
   if(ns.lookup(name, symbol))
diff --git a/src/util/rename.h b/src/util/rename.h
index b60f472ca74..7c2e9ee4b82 100644
--- a/src/util/rename.h
+++ b/src/util/rename.h
@@ -26,6 +26,6 @@ class namespacet;
 ///   suffix
 /// \return Identifier that is not yet part of the namespace.
 [[nodiscard]] irep_idt
-get_new_name(const irep_idt &name, const namespacet &ns, char delimiter = '_');
+get_new_name(irep_idt name, const namespacet &ns, char delimiter = '_');
 
 #endif // CPROVER_UTIL_RENAME_H
diff --git a/src/util/rename_symbol.h b/src/util/rename_symbol.h
index 8fcd4538cb3..a4b923af8df 100644
--- a/src/util/rename_symbol.h
+++ b/src/util/rename_symbol.h
@@ -28,8 +28,7 @@ class rename_symbolt
   typedef std::unordered_map<irep_idt, irep_idt> expr_mapt;
   typedef std::unordered_map<irep_idt, irep_idt> type_mapt;
 
-  void insert_expr(const irep_idt &old_id,
-                   const irep_idt &new_id)
+  void insert_expr(irep_idt old_id, irep_idt new_id)
   {
     expr_map.insert(std::pair<irep_idt, irep_idt>(old_id, new_id));
   }
@@ -37,8 +36,7 @@ class rename_symbolt
   void insert(const class symbol_exprt &old_expr,
               const class symbol_exprt &new_expr);
 
-  void insert_type(const irep_idt &old_id,
-                   const irep_idt &new_id)
+  void insert_type(irep_idt old_id, irep_idt new_id)
   {
     type_map.insert(std::pair<irep_idt, irep_idt>(old_id, new_id));
   }
diff --git a/src/util/replace_symbol.h b/src/util/replace_symbol.h
index 15fecca5181..c6f3232b9f5 100644
--- a/src/util/replace_symbol.h
+++ b/src/util/replace_symbol.h
@@ -61,7 +61,7 @@ class replace_symbolt
     return expr_map.empty();
   }
 
-  std::size_t erase(const irep_idt &id)
+  std::size_t erase(irep_idt id)
   {
     return expr_map.erase(id);
   }
@@ -71,7 +71,7 @@ class replace_symbolt
     return expr_map.erase(it);
   }
 
-  bool replaces_symbol(const irep_idt &id) const
+  bool replaces_symbol(irep_idt id) const
   {
     return expr_map.find(id) != expr_map.end();
   }
diff --git a/src/util/simplify_utils.cpp b/src/util/simplify_utils.cpp
index ce2b5f8f4a3..ebd10d55823 100644
--- a/src/util/simplify_utils.cpp
+++ b/src/util/simplify_utils.cpp
@@ -108,7 +108,7 @@ struct saj_tablet
 
 static bool is_associative_and_commutative_for_type(
   const struct saj_tablet &saj_entry,
-  const irep_idt &type_id)
+  irep_idt type_id)
 {
   for(unsigned i=0; !saj_entry.type_ids[i].empty(); i++)
     if(type_id==saj_entry.type_ids[i])
@@ -118,7 +118,7 @@ static bool is_associative_and_commutative_for_type(
 }
 
 static const struct saj_tablet &
-get_sort_and_join_table_entry(const irep_idt &id, const irep_idt &type_id)
+get_sort_and_join_table_entry(irep_idt id, irep_idt type_id)
 {
   unsigned i=0;
 
@@ -140,7 +140,7 @@ static bool sort_and_join(exprt &expr, bool do_sort)
   if(!expr.has_operands())
     return true;
 
-  const struct saj_tablet &saj_entry =
+  const struct saj_tablet saj_entry =
     get_sort_and_join_table_entry(expr.id(), as_const(expr).type().id());
   if(saj_entry.id.empty())
     return true;
diff --git a/src/util/source_location.h b/src/util/source_location.h
index d2dc44f6d7b..2996fbd003a 100644
--- a/src/util/source_location.h
+++ b/src/util/source_location.h
@@ -101,17 +101,17 @@ class source_locationt:public irept
     return get_bool(ID_property_fatal);
   }
 
-  void set_file(const irep_idt &file)
+  void set_file(irep_idt file)
   {
     set(ID_file, file);
   }
 
-  void set_working_directory(const irep_idt &cwd)
+  void set_working_directory(irep_idt cwd)
   {
     set(ID_working_directory, cwd);
   }
 
-  void set_line(const irep_idt &line)
+  void set_line(irep_idt line)
   {
     set(ID_line, line);
   }
@@ -121,7 +121,7 @@ class source_locationt:public irept
     set(ID_line, line);
   }
 
-  void set_column(const irep_idt &column)
+  void set_column(irep_idt column)
   {
     set(ID_column, column);
   }
@@ -132,7 +132,7 @@ class source_locationt:public irept
   }
 
   DEPRECATED(SINCE(2022, 10, 13, "use identifier of containing function"))
-  void set_function(const irep_idt &function)
+  void set_function(irep_idt function)
   {
     PRECONDITION(!function.empty());
     set(ID_function, function);
@@ -143,28 +143,28 @@ class source_locationt:public irept
     remove(ID_function);
   }
 
-  void set_property_id(const irep_idt &property_id)
+  void set_property_id(irep_idt property_id)
   {
     set(ID_property_id, property_id);
   }
 
-  void set_property_class(const irep_idt &property_class)
+  void set_property_class(irep_idt property_class)
   {
     set(ID_property_class, property_class);
   }
 
-  void set_comment(const irep_idt &comment)
+  void set_comment(irep_idt comment)
   {
     set(ID_comment, comment);
   }
 
   // for switch case number
-  void set_case_number(const irep_idt &number)
+  void set_case_number(irep_idt number)
   {
     set(ID_switch_case_number, number);
   }
 
-  void set_java_bytecode_index(const irep_idt &index)
+  void set_java_bytecode_index(irep_idt index)
   {
     set(ID_java_bytecode_index, index);
   }
@@ -210,7 +210,7 @@ class source_locationt:public irept
 
   std::optional<std::string> full_path() const;
 
-  void add_pragma(const irep_idt &pragma)
+  void add_pragma(irep_idt pragma)
   {
     add(ID_pragma).add(pragma);
   }
diff --git a/src/util/ssa_expr.cpp b/src/util/ssa_expr.cpp
index 2edb9ef296a..072beb029f7 100644
--- a/src/util/ssa_expr.cpp
+++ b/src/util/ssa_expr.cpp
@@ -55,9 +55,9 @@ ssa_exprt::ssa_exprt(const exprt &expr) : symbol_exprt(expr.type())
 /// and add "..component_name" or "[[index]]" to \p os.
 static void build_ssa_identifier_rec(
   const exprt &expr,
-  const irep_idt &l0,
-  const irep_idt &l1,
-  const irep_idt &l2,
+  irep_idt l0,
+  irep_idt l1,
+  irep_idt l2,
   std::ostream &os,
   std::ostream &l1_object_os)
 {
@@ -110,11 +110,8 @@ static void build_ssa_identifier_rec(
     UNREACHABLE;
 }
 
-static std::pair<irep_idt, irep_idt> build_identifier(
-  const exprt &expr,
-  const irep_idt &l0,
-  const irep_idt &l1,
-  const irep_idt &l2)
+static std::pair<irep_idt, irep_idt>
+build_identifier(const exprt &expr, irep_idt l0, irep_idt l1, irep_idt l2)
 {
   std::ostringstream oss;
   std::ostringstream l1_object_oss;
diff --git a/src/util/std_code.h b/src/util/std_code.h
index 41f137b3dcf..9eb8382946f 100644
--- a/src/util/std_code.h
+++ b/src/util/std_code.h
@@ -840,12 +840,12 @@ inline code_fort &to_code_for(codet &code)
 class code_gotot:public codet
 {
 public:
-  explicit code_gotot(const irep_idt &label):codet(ID_goto)
+  explicit code_gotot(irep_idt label) : codet(ID_goto)
   {
     set_destination(label);
   }
 
-  void set_destination(const irep_idt &label)
+  void set_destination(irep_idt label)
   {
     set(ID_destination, label);
   }
@@ -958,7 +958,7 @@ inline code_frontend_returnt &to_code_frontend_return(codet &code)
 class code_labelt:public codet
 {
 public:
-  code_labelt(const irep_idt &_label, codet _code)
+  code_labelt(irep_idt _label, codet _code)
     : codet(ID_label, {std::move(_code)})
   {
     set_label(_label);
@@ -969,7 +969,7 @@ class code_labelt:public codet
     return get(ID_label);
   }
 
-  void set_label(const irep_idt &label)
+  void set_label(irep_idt label)
   {
     set(ID_label, label);
   }
@@ -1265,7 +1265,7 @@ class code_asmt:public codet
     return get(ID_flavor);
   }
 
-  void set_flavor(const irep_idt &f)
+  void set_flavor(irep_idt f)
   {
     set(ID_flavor, f);
   }
@@ -1450,7 +1450,7 @@ class side_effect_exprt : public exprt
 {
 public:
   side_effect_exprt(
-    const irep_idt &statement,
+    irep_idt statement,
     operandst _operands,
     typet _type,
     source_locationt loc)
@@ -1460,10 +1460,7 @@ class side_effect_exprt : public exprt
     operands() = std::move(_operands);
   }
 
-  side_effect_exprt(
-    const irep_idt &statement,
-    typet _type,
-    source_locationt loc)
+  side_effect_exprt(irep_idt statement, typet _type, source_locationt loc)
     : exprt(ID_side_effect, std::move(_type), std::move(loc))
   {
     set_statement(statement);
@@ -1474,7 +1471,7 @@ class side_effect_exprt : public exprt
     return get(ID_statement);
   }
 
-  void set_statement(const irep_idt &statement)
+  void set_statement(irep_idt statement)
   {
     return set(ID_statement, statement);
   }
@@ -1816,18 +1813,18 @@ class code_push_catcht:public codet
     {
     }
 
-    explicit exception_list_entryt(const irep_idt &tag)
+    explicit exception_list_entryt(irep_idt tag)
     {
       set(ID_tag, tag);
     }
 
-    exception_list_entryt(const irep_idt &tag, const irep_idt &label)
+    exception_list_entryt(irep_idt tag, irep_idt label)
     {
       set(ID_tag, tag);
       set(ID_label, label);
     }
 
-    void set_tag(const irep_idt &tag)
+    void set_tag(irep_idt tag)
     {
       set(ID_tag, tag);
     }
@@ -1836,7 +1833,7 @@ class code_push_catcht:public codet
       return get(ID_tag);
     }
 
-    void set_label(const irep_idt &label)
+    void set_label(irep_idt label)
     {
       set(ID_label, label);
     }
@@ -1848,10 +1845,7 @@ class code_push_catcht:public codet
 
   typedef std::vector<exception_list_entryt> exception_listt;
 
-  code_push_catcht(
-    const irep_idt &tag,
-    const irep_idt &label):
-    codet(ID_push_catch)
+  code_push_catcht(irep_idt tag, irep_idt label) : codet(ID_push_catch)
   {
     set(ID_exception_list, irept(ID_exception_list));
     exception_list().push_back(exception_list_entryt(tag, label));
diff --git a/src/util/std_code_base.h b/src/util/std_code_base.h
index 9c50cf0f1ad..dc38d35a794 100644
--- a/src/util/std_code_base.h
+++ b/src/util/std_code_base.h
@@ -31,12 +31,12 @@ class codet : public exprt
   /// \param statement: Specifies the type of the `codet` to be constructed,
   ///   e.g. `ID_block` for a \ref code_blockt or `ID_assign` for a
   ///   \ref code_frontend_assignt.
-  explicit codet(const irep_idt &statement) : exprt(ID_code, empty_typet())
+  explicit codet(irep_idt statement) : exprt(ID_code, empty_typet())
   {
     set_statement(statement);
   }
 
-  codet(const irep_idt &statement, source_locationt loc)
+  codet(irep_idt statement, source_locationt loc)
     : exprt(ID_code, empty_typet(), std::move(loc))
   {
     set_statement(statement);
@@ -46,18 +46,18 @@ class codet : public exprt
   ///   e.g. `ID_block` for a \ref code_blockt or `ID_assign` for a
   ///   \ref code_frontend_assignt.
   /// \param _op: any operands to be added
-  explicit codet(const irep_idt &statement, operandst _op) : codet(statement)
+  explicit codet(irep_idt statement, operandst _op) : codet(statement)
   {
     operands() = std::move(_op);
   }
 
-  codet(const irep_idt &statement, operandst op, source_locationt loc)
+  codet(irep_idt statement, operandst op, source_locationt loc)
     : codet(statement, std::move(loc))
   {
     operands() = std::move(op);
   }
 
-  void set_statement(const irep_idt &statement)
+  void set_statement(irep_idt statement)
   {
     set(ID_statement, statement);
   }
diff --git a/src/util/std_expr.cpp b/src/util/std_expr.cpp
index fe99bb30a0e..d62dca90693 100644
--- a/src/util/std_expr.cpp
+++ b/src/util/std_expr.cpp
@@ -288,7 +288,7 @@ exprt conjunction(const exprt::operandst &op)
 
 // Implementation of struct_exprt::component for const / non const overloads.
 template <typename T>
-auto component(T &struct_expr, const irep_idt &name, const namespacet &ns)
+auto component(T &struct_expr, irep_idt name, const namespacet &ns)
   -> decltype(struct_expr.op0())
 {
   static_assert(
@@ -305,14 +305,13 @@ auto component(T &struct_expr, const irep_idt &name, const namespacet &ns)
 }
 
 /// \return The expression for a named component of this struct.
-exprt &struct_exprt::component(const irep_idt &name, const namespacet &ns)
+exprt &struct_exprt::component(irep_idt name, const namespacet &ns)
 {
   return ::component(*this, name, ns);
 }
 
 /// \return The expression for a named component of this struct.
-const exprt &
-struct_exprt::component(const irep_idt &name, const namespacet &ns) const
+const exprt &struct_exprt::component(irep_idt name, const namespacet &ns) const
 {
   return ::component(*this, name, ns);
 }
diff --git a/src/util/std_expr.h b/src/util/std_expr.h
index 1c1ee58fd42..18d125f6b6c 100644
--- a/src/util/std_expr.h
+++ b/src/util/std_expr.h
@@ -22,7 +22,7 @@ Author: Daniel Kroening, kroening@kroening.com
 class nullary_exprt : public expr_protectedt
 {
 public:
-  nullary_exprt(const irep_idt &_id, typet _type)
+  nullary_exprt(irep_idt _id, typet _type)
     : expr_protectedt(_id, std::move(_type))
   {
   }
@@ -68,12 +68,7 @@ class ternary_exprt : public expr_protectedt
 {
 public:
   // constructor
-  ternary_exprt(
-    const irep_idt &_id,
-    exprt _op0,
-    exprt _op1,
-    exprt _op2,
-    typet _type)
+  ternary_exprt(irep_idt _id, exprt _op0, exprt _op1, exprt _op2, typet _type)
     : expr_protectedt(
         _id,
         std::move(_type),
@@ -138,7 +133,7 @@ class symbol_exprt : public nullary_exprt
 
   /// \param identifier: Name of symbol
   /// \param type: Type of symbol
-  symbol_exprt(const irep_idt &identifier, typet type)
+  symbol_exprt(irep_idt identifier, typet type)
     : nullary_exprt{ID_symbol, std::move(type)}
   {
     this->identifier(identifier);
@@ -146,18 +141,18 @@ class symbol_exprt : public nullary_exprt
 
   /// Generate a symbol_exprt without a proper type. Use if, and only if, the
   /// type either cannot be determined just yet (such as before type checking).
-  static symbol_exprt typeless(const irep_idt &id)
+  static symbol_exprt typeless(irep_idt id)
   {
     return symbol_exprt{id, typet{}};
   }
 
   DEPRECATED(SINCE(2026, 1, 18, "use identifier(...) instead"))
-  void set_identifier(const irep_idt &identifier)
+  void set_identifier(irep_idt identifier)
   {
     this->identifier(identifier);
   }
 
-  void identifier(const irep_idt &identifier)
+  void identifier(irep_idt identifier)
   {
     set(ID_identifier, identifier);
   }
@@ -254,7 +249,7 @@ class decorated_symbol_exprt:public symbol_exprt
 public:
   /// \param identifier: Name of symbol
   /// \param type: Type of symbol
-  decorated_symbol_exprt(const irep_idt &identifier, typet type)
+  decorated_symbol_exprt(irep_idt identifier, typet type)
     : symbol_exprt(identifier, std::move(type))
   {
   }
@@ -296,7 +291,7 @@ class nondet_symbol_exprt : public nullary_exprt
 public:
   /// \param identifier: Name of symbol
   /// \param type: Type of symbol
-  nondet_symbol_exprt(const irep_idt &identifier, typet type)
+  nondet_symbol_exprt(irep_idt identifier, typet type)
     : nullary_exprt(ID_nondet_symbol, std::move(type))
   {
     set_identifier(identifier);
@@ -315,7 +310,7 @@ class nondet_symbol_exprt : public nullary_exprt
     add_source_location() = std::move(location);
   }
 
-  void set_identifier(const irep_idt &identifier)
+  void set_identifier(irep_idt identifier)
   {
     set(ID_identifier, identifier);
   }
@@ -363,12 +358,12 @@ inline nondet_symbol_exprt &to_nondet_symbol_expr(exprt &expr)
 class unary_exprt : public expr_protectedt
 {
 public:
-  unary_exprt(const irep_idt &_id, const exprt &_op)
+  unary_exprt(irep_idt _id, const exprt &_op)
     : expr_protectedt(_id, _op.type(), {_op})
   {
   }
 
-  unary_exprt(const irep_idt &_id, exprt _op, typet _type)
+  unary_exprt(irep_idt _id, exprt _op, typet _type)
     : expr_protectedt(_id, std::move(_type), {std::move(_op)})
   {
   }
@@ -556,8 +551,7 @@ inline unary_plus_exprt &to_unary_plus_expr(exprt &expr)
 class predicate_exprt : public expr_protectedt
 {
 public:
-  explicit predicate_exprt(const irep_idt &_id)
-    : expr_protectedt(_id, bool_typet())
+  explicit predicate_exprt(irep_idt _id) : expr_protectedt(_id, bool_typet())
   {
   }
 
@@ -573,7 +567,7 @@ class predicate_exprt : public expr_protectedt
 class unary_predicate_exprt:public unary_exprt
 {
 public:
-  unary_predicate_exprt(const irep_idt &_id, exprt _op)
+  unary_predicate_exprt(irep_idt _id, exprt _op)
     : unary_exprt(_id, std::move(_op), bool_typet())
   {
   }
@@ -648,12 +642,12 @@ inline sign_exprt &to_sign_expr(exprt &expr)
 class binary_exprt : public expr_protectedt
 {
 public:
-  binary_exprt(const exprt &_lhs, const irep_idt &_id, exprt _rhs)
+  binary_exprt(const exprt &_lhs, irep_idt _id, exprt _rhs)
     : expr_protectedt(_id, _lhs.type(), {_lhs, std::move(_rhs)})
   {
   }
 
-  binary_exprt(exprt _lhs, const irep_idt &_id, exprt _rhs, typet _type)
+  binary_exprt(exprt _lhs, irep_idt _id, exprt _rhs, typet _type)
     : expr_protectedt(_id, std::move(_type), {std::move(_lhs), std::move(_rhs)})
   {
   }
@@ -736,7 +730,7 @@ inline binary_exprt &to_binary_expr(exprt &expr)
 class binary_predicate_exprt:public binary_exprt
 {
 public:
-  binary_predicate_exprt(exprt _op0, const irep_idt &_id, exprt _op1)
+  binary_predicate_exprt(exprt _op0, irep_idt _id, exprt _op1)
     : binary_exprt(std::move(_op0), _id, std::move(_op1), bool_typet())
   {
   }
@@ -783,7 +777,7 @@ inline binary_predicate_exprt &to_binary_predicate_expr(exprt &expr)
 class binary_relation_exprt:public binary_predicate_exprt
 {
 public:
-  binary_relation_exprt(exprt _lhs, const irep_idt &_id, exprt _rhs)
+  binary_relation_exprt(exprt _lhs, irep_idt _id, exprt _rhs)
     : binary_predicate_exprt(std::move(_lhs), _id, std::move(_rhs))
   {
   }
@@ -907,13 +901,13 @@ inline bool can_cast_expr<less_than_or_equal_exprt>(const exprt &base)
 class multi_ary_exprt : public expr_protectedt
 {
 public:
-  multi_ary_exprt(const irep_idt &_id, operandst _operands, typet _type)
+  multi_ary_exprt(irep_idt _id, operandst _operands, typet _type)
     : expr_protectedt(_id, std::move(_type))
   {
     operands() = std::move(_operands);
   }
 
-  multi_ary_exprt(const irep_idt &_id, operandst _operands)
+  multi_ary_exprt(irep_idt _id, operandst _operands)
     : expr_protectedt(_id, typet{})
   {
     PRECONDITION(!_operands.empty());
@@ -921,12 +915,12 @@ class multi_ary_exprt : public expr_protectedt
     operands() = std::move(_operands);
   }
 
-  multi_ary_exprt(const exprt &_lhs, const irep_idt &_id, exprt _rhs)
+  multi_ary_exprt(const exprt &_lhs, irep_idt _id, exprt _rhs)
     : expr_protectedt(_id, _lhs.type(), {_lhs, std::move(_rhs)})
   {
   }
 
-  multi_ary_exprt(exprt _lhs, const irep_idt &_id, exprt _rhs, typet _type)
+  multi_ary_exprt(exprt _lhs, irep_idt _id, exprt _rhs, typet _type)
     : expr_protectedt(_id, std::move(_type), {std::move(_lhs), std::move(_rhs)})
   {
   }
@@ -1723,7 +1717,7 @@ inline vector_exprt &to_vector_expr(exprt &expr)
 class union_exprt:public unary_exprt
 {
 public:
-  union_exprt(const irep_idt &_component_name, exprt _value, typet _type)
+  union_exprt(irep_idt _component_name, exprt _value, typet _type)
     : unary_exprt(ID_union, std::move(_value), std::move(_type))
   {
     set_component_name(_component_name);
@@ -1734,7 +1728,7 @@ class union_exprt:public unary_exprt
     return get(ID_component_name);
   }
 
-  void set_component_name(const irep_idt &component_name)
+  void set_component_name(irep_idt component_name)
   {
     set(ID_component_name, component_name);
   }
@@ -1824,8 +1818,8 @@ class struct_exprt : public multi_ary_exprt
   {
   }
 
-  exprt &component(const irep_idt &name, const namespacet &ns);
-  const exprt &component(const irep_idt &name, const namespacet &ns) const;
+  exprt &component(irep_idt name, const namespacet &ns);
+  const exprt &component(irep_idt name, const namespacet &ns) const;
 };
 
 template <>
@@ -2634,7 +2628,7 @@ inline index_designatort &to_index_designator(exprt &expr)
 class member_designatort : public expr_protectedt
 {
 public:
-  explicit member_designatort(const irep_idt &_component_name)
+  explicit member_designatort(irep_idt _component_name)
     : expr_protectedt(ID_member_designator, typet())
   {
     set(ID_component_name, _component_name);
@@ -2865,7 +2859,7 @@ inline array_update_exprt &to_array_update_expr(exprt &expr)
 class member_exprt:public unary_exprt
 {
 public:
-  member_exprt(exprt op, const irep_idt &component_name, typet _type)
+  member_exprt(exprt op, irep_idt component_name, typet _type)
     : unary_exprt(ID_member, std::move(op), std::move(_type))
   {
     const auto &compound_type_id = compound().type().id();
@@ -2890,7 +2884,7 @@ class member_exprt:public unary_exprt
     return get(ID_component_name);
   }
 
-  void set_component_name(const irep_idt &component_name)
+  void set_component_name(irep_idt component_name)
   {
     set(ID_component_name, component_name);
   }
@@ -3006,7 +3000,7 @@ inline type_exprt &to_type_expr(exprt &expr)
 class constant_exprt : public nullary_exprt
 {
 public:
-  constant_exprt(const irep_idt &_value, typet _type)
+  constant_exprt(irep_idt _value, typet _type)
     : nullary_exprt(ID_constant, std::move(_type))
   {
     set_value(_value);
@@ -3017,7 +3011,7 @@ class constant_exprt : public nullary_exprt
     return get(ID_value);
   }
 
-  void set_value(const irep_idt &value)
+  void set_value(irep_idt value)
   {
     set(ID_value, value);
   }
diff --git a/src/util/std_types.cpp b/src/util/std_types.cpp
index 34deb1776ef..6db1e4a1843 100644
--- a/src/util/std_types.cpp
+++ b/src/util/std_types.cpp
@@ -44,8 +44,7 @@ typet array_typet::index_type() const
 }
 
 /// Return the sequence number of the component with given name.
-std::size_t struct_union_typet::component_number(
-  const irep_idt &component_name) const
+std::size_t struct_union_typet::component_number(irep_idt component_name) const
 {
   std::size_t number=0;
 
@@ -61,8 +60,8 @@ std::size_t struct_union_typet::component_number(
 }
 
 /// Get the reference to a component with given name.
-const struct_union_typet::componentt &struct_union_typet::get_component(
-  const irep_idt &component_name) const
+const struct_union_typet::componentt &
+struct_union_typet::get_component(irep_idt component_name) const
 {
   for(const auto &c : components())
   {
@@ -73,8 +72,7 @@ const struct_union_typet::componentt &struct_union_typet::get_component(
   return static_cast<const componentt &>(get_nil_irep());
 }
 
-const typet &
-struct_union_typet::component_type(const irep_idt &component_name) const
+const typet &struct_union_typet::component_type(irep_idt component_name) const
 {
   const auto &c = get_component(component_name);
   CHECK_RETURN(c.is_not_nil());
@@ -101,8 +99,7 @@ void struct_typet::add_base(const struct_tag_typet &base)
   bases().push_back(baset(base));
 }
 
-std::optional<struct_typet::baset>
-struct_typet::get_base(const irep_idt &id) const
+std::optional<struct_typet::baset> struct_typet::get_base(irep_idt id) const
 {
   for(const auto &b : bases())
   {
diff --git a/src/util/std_types.h b/src/util/std_types.h
index 1ab4dc069ba..6ebbe218900 100644
--- a/src/util/std_types.h
+++ b/src/util/std_types.h
@@ -60,7 +60,7 @@ class empty_typet:public typet
 class struct_union_typet:public typet
 {
 public:
-  explicit struct_union_typet(const irep_idt &_id):typet(_id)
+  explicit struct_union_typet(irep_idt _id) : typet(_id)
   {
   }
 
@@ -69,7 +69,7 @@ class struct_union_typet:public typet
   public:
     componentt() = default;
 
-    componentt(const irep_idt &_name, typet _type)
+    componentt(irep_idt _name, typet _type)
     {
       set_name(_name);
       type().swap(_type);
@@ -80,7 +80,7 @@ class struct_union_typet:public typet
       return get(ID_name);
     }
 
-    void set_name(const irep_idt &name)
+    void set_name(irep_idt name)
     {
       return set(ID_name, name);
     }
@@ -90,7 +90,7 @@ class struct_union_typet:public typet
       return get(ID_C_base_name);
     }
 
-    void set_base_name(const irep_idt &base_name)
+    void set_base_name(irep_idt base_name)
     {
       return set(ID_C_base_name, base_name);
     }
@@ -100,7 +100,7 @@ class struct_union_typet:public typet
       return get(ID_access);
     }
 
-    void set_access(const irep_idt &access)
+    void set_access(irep_idt access)
     {
       return set(ID_access, access);
     }
@@ -110,7 +110,7 @@ class struct_union_typet:public typet
       return get(ID_C_pretty_name);
     }
 
-    void set_pretty_name(const irep_idt &name)
+    void set_pretty_name(irep_idt name)
     {
       return set(ID_C_pretty_name, name);
     }
@@ -138,7 +138,7 @@ class struct_union_typet:public typet
 
   typedef std::vector<componentt> componentst;
 
-  struct_union_typet(const irep_idt &_id, componentst _components) : typet(_id)
+  struct_union_typet(irep_idt _id, componentst _components) : typet(_id)
   {
     components() = std::move(_components);
   }
@@ -153,19 +153,21 @@ class struct_union_typet:public typet
     return (componentst &)(add(ID_components).get_sub());
   }
 
-  bool has_component(const irep_idt &component_name) const
+  bool has_component(irep_idt component_name) const
   {
     return get_component(component_name).is_not_nil();
   }
 
-  const componentt &get_component(
-    const irep_idt &component_name) const;
+  const componentt &get_component(irep_idt component_name) const;
 
-  std::size_t component_number(const irep_idt &component_name) const;
-  const typet &component_type(const irep_idt &component_name) const;
+  std::size_t component_number(irep_idt component_name) const;
+  const typet &component_type(irep_idt component_name) const;
 
   irep_idt get_tag() const { return get(ID_tag); }
-  void set_tag(const irep_idt &tag) { set(ID_tag, tag); }
+  void set_tag(irep_idt tag)
+  {
+    set(ID_tag, tag);
+  }
 
   /// A struct may be a class, where members may have access restrictions.
   bool is_class() const
@@ -276,12 +278,12 @@ class struct_typet:public struct_union_typet
   /// Return the base with the given name, if exists.
   /// \param id: The name of the base we are looking for.
   /// \return The base if exists.
-  std::optional<baset> get_base(const irep_idt &id) const;
+  std::optional<baset> get_base(irep_idt id) const;
 
   /// Test whether `id` is a base class/struct.
   /// \param id: symbol type name
   /// \return True if, and only if, the symbol type `id` is a base class/struct.
-  bool has_base(const irep_idt &id) const
+  bool has_base(irep_idt id) const
   {
     return get_base(id).has_value();
   }
@@ -394,14 +396,12 @@ inline class_typet &to_class_type(typet &type)
 class tag_typet:public typet
 {
 public:
-  explicit tag_typet(
-    const irep_idt &_id,
-    const irep_idt &identifier):typet(_id)
+  explicit tag_typet(irep_idt _id, irep_idt identifier) : typet(_id)
   {
     set_identifier(identifier);
   }
 
-  void set_identifier(const irep_idt &identifier)
+  void set_identifier(irep_idt identifier)
   {
     set(ID_identifier, identifier);
   }
@@ -449,7 +449,7 @@ inline tag_typet &to_tag_type(typet &type)
 class struct_or_union_tag_typet : public tag_typet
 {
 protected:
-  struct_or_union_tag_typet(const irep_idt &id, const irep_idt &identifier)
+  struct_or_union_tag_typet(irep_idt id, irep_idt identifier)
     : tag_typet(id, identifier)
   {
     PRECONDITION(id == ID_struct_tag || id == ID_union_tag);
@@ -491,7 +491,7 @@ inline struct_or_union_tag_typet &to_struct_or_union_tag_type(typet &type)
 class struct_tag_typet : public struct_or_union_tag_typet
 {
 public:
-  explicit struct_tag_typet(const irep_idt &identifier)
+  explicit struct_tag_typet(irep_idt identifier)
     : struct_or_union_tag_typet(ID_struct_tag, identifier)
   {
   }
@@ -620,12 +620,12 @@ class code_typet:public typet
     // The following for methods will go away;
     // these should not be part of the signature of a function,
     // but rather part of the body.
-    void set_identifier(const irep_idt &identifier)
+    void set_identifier(irep_idt identifier)
     {
       set(ID_C_identifier, identifier);
     }
 
-    void set_base_name(const irep_idt &name)
+    void set_base_name(irep_idt name)
     {
       set(ID_C_base_name, name);
     }
@@ -720,7 +720,7 @@ class code_typet:public typet
     return get(ID_access);
   }
 
-  void set_access(const irep_idt &access)
+  void set_access(irep_idt access)
   {
     return set(ID_access, access);
   }
diff --git a/src/util/string_constant.cpp b/src/util/string_constant.cpp
index 6f26c62a4c6..b894858f303 100644
--- a/src/util/string_constant.cpp
+++ b/src/util/string_constant.cpp
@@ -12,19 +12,19 @@ Author: Daniel Kroening, kroening@kroening.com
 #include "c_types.h"
 #include "std_expr.h"
 
-static array_typet make_type(const irep_idt &value)
+static array_typet make_type(irep_idt value)
 {
   exprt size_expr = from_integer(value.size() + 1, c_index_type());
   return array_typet(char_type(), size_expr);
 }
 
-string_constantt::string_constantt(const irep_idt &_value)
+string_constantt::string_constantt(irep_idt _value)
   : nullary_exprt(ID_string_constant, make_type(_value))
 {
   value(_value);
 }
 
-void string_constantt::value(const irep_idt &_value)
+void string_constantt::value(irep_idt _value)
 {
   exprt::type() = make_type(_value);
   set(ID_value, _value);
diff --git a/src/util/string_constant.h b/src/util/string_constant.h
index 05d8ee7b9c9..2bf914feabf 100644
--- a/src/util/string_constant.h
+++ b/src/util/string_constant.h
@@ -14,9 +14,9 @@ Author: Daniel Kroening, kroening@kroening.com
 class string_constantt : public nullary_exprt
 {
 public:
-  explicit string_constantt(const irep_idt &);
+  explicit string_constantt(irep_idt);
 
-  void value(const irep_idt &);
+  void value(irep_idt);
 
   const irep_idt &value() const
   {
diff --git a/src/util/symbol.h b/src/util/symbol.h
index 1a7121234e8..10530645a25 100644
--- a/src/util/symbol.h
+++ b/src/util/symbol.h
@@ -84,7 +84,7 @@ class symbolt
   {
   }
 
-  symbolt(const irep_idt &_name, typet _type, const irep_idt &_mode)
+  symbolt(irep_idt _name, typet _type, irep_idt _mode)
     : type(std::move(_type)),
       value(static_cast<const exprt &>(get_nil_irep())),
       location(source_locationt::nil()),
@@ -138,7 +138,7 @@ std::ostream &operator<<(std::ostream &out, const symbolt &symbol);
 class type_symbolt:public symbolt
 {
 public:
-  type_symbolt(const irep_idt &_name, typet _type, const irep_idt &_mode)
+  type_symbolt(irep_idt _name, typet _type, irep_idt _mode)
     : symbolt(_name, _type, _mode)
   {
     is_type = true;
@@ -161,7 +161,7 @@ class auxiliary_symbolt:public symbolt
     is_auxiliary=true;
   }
 
-  auxiliary_symbolt(const irep_idt &name, typet type, const irep_idt &mode)
+  auxiliary_symbolt(irep_idt name, typet type, irep_idt mode)
     : symbolt(name, type, mode)
   {
     is_lvalue = true;
diff --git a/src/util/symbol_table.h b/src/util/symbol_table.h
index a6fa8b798fe..d7664c26a47 100644
--- a/src/util/symbol_table.h
+++ b/src/util/symbol_table.h
@@ -79,7 +79,7 @@ class symbol_tablet : public symbol_table_baset
   }
 
 public:
-  virtual const symbol_tablet &get_symbol_table() const override
+  const symbol_tablet &get_symbol_table() const override
   {
     return *this;
   }
@@ -87,29 +87,29 @@ class symbol_tablet : public symbol_table_baset
   /// Find a symbol in the symbol table for read-write access.
   /// \param name: The name of the symbol to look for
   /// \return A pointer to the found symbol if it exists, nullptr otherwise.
-  virtual symbolt *get_writeable(const irep_idt &name) override
+  symbolt *get_writeable(irep_idt name) override
   {
     symbolst::iterator it = internal_symbols.find(name);
     return it != internal_symbols.end() ? &it->second : nullptr;
   }
 
-  virtual std::pair<symbolt &, bool> insert(symbolt symbol) override;
-  virtual bool move(symbolt &symbol, symbolt *&new_symbol) override;
+  std::pair<symbolt &, bool> insert(symbolt symbol) override;
+  bool move(symbolt &symbol, symbolt *&new_symbol) override;
 
-  virtual void erase(const symbolst::const_iterator &entry) override;
+  void erase(const symbolst::const_iterator &entry) override;
   /// Wipe internal state of the symbol table.
-  virtual void clear() override
+  void clear() override
   {
     internal_symbols.clear();
     internal_symbol_base_map.clear();
     internal_symbol_module_map.clear();
   }
 
-  virtual iteratort begin() override
+  iteratort begin() override
   {
     return iteratort(internal_symbols.begin());
   }
-  virtual iteratort end() override
+  iteratort end() override
   {
     return iteratort(internal_symbols.end());
   }
diff --git a/src/util/symbol_table_base.cpp b/src/util/symbol_table_base.cpp
index c97ff46d059..3d493120475 100644
--- a/src/util/symbol_table_base.cpp
+++ b/src/util/symbol_table_base.cpp
@@ -24,7 +24,7 @@ bool symbol_table_baset::add(const symbolt &symbol)
 /// \param name: The name of the symbol to remove
 /// \return Returns a boolean indicating whether the process failed
 ///   i.e. false if the symbol was removed, or true if it didn't exist.
-bool symbol_table_baset::remove(const irep_idt &name)
+bool symbol_table_baset::remove(irep_idt name)
 {
   symbolst::const_iterator entry = symbols.find(name);
   if(entry == symbols.end())
@@ -44,7 +44,7 @@ std::vector<irep_idt> symbol_table_baset::sorted_symbol_names() const
   std::sort(
     sorted_names.begin(),
     sorted_names.end(),
-    [](const irep_idt &a, const irep_idt &b) { return a.compare(b) < 0; });
+    [](irep_idt a, irep_idt b) { return a.compare(b) < 0; });
 
   return sorted_names;
 }
diff --git a/src/util/symbol_table_base.h b/src/util/symbol_table_base.h
index 976d108f4b7..c3c353fb02c 100644
--- a/src/util/symbol_table_base.h
+++ b/src/util/symbol_table_base.h
@@ -85,7 +85,7 @@ class symbol_table_baset
   /// Check whether a symbol exists in the symbol table
   /// \param name: The name of the symbol to look for
   /// \return True if the symbol exists
-  bool has_symbol(const irep_idt &name) const
+  bool has_symbol(irep_idt name) const
   {
     return symbols.find(name) != symbols.end();
   }
@@ -93,7 +93,7 @@ class symbol_table_baset
   /// Find a symbol in the symbol table for read-only access.
   /// \param name: The name of the symbol to look for
   /// \return A pointer to the found symbol if it exists, nullptr otherwise.
-  const symbolt *lookup(const irep_idt &name) const
+  const symbolt *lookup(irep_idt name) const
   {
     symbolst::const_iterator it = symbols.find(name);
     return it != symbols.end() ? &it->second : nullptr;
@@ -102,7 +102,7 @@ class symbol_table_baset
   /// Find a symbol in the symbol table for read-only access.
   /// \param name: The name of the symbol to look for
   /// \return A reference to the symbol
-  const symbolt &lookup_ref(const irep_idt &name) const
+  const symbolt &lookup_ref(irep_idt name) const
   {
     const symbolt *const symbol = lookup(name);
     INVARIANT(
@@ -112,8 +112,7 @@ class symbol_table_baset
 
   /// Collect all symbols the name of which matches \p id or the base name of
   /// which matches \p id.
-  std::list<symbolst::const_iterator>
-  match_name_or_base_name(const irep_idt &id) const
+  std::list<symbolst::const_iterator> match_name_or_base_name(irep_idt id) const
   {
     std::list<symbolst::const_iterator> results;
 
@@ -140,13 +139,13 @@ class symbol_table_baset
   /// Find a symbol in the symbol table for read-write access.
   /// \param name: The name of the symbol to look for
   /// \return A pointer to the found symbol if it exists, nullptr otherwise.
-  virtual symbolt *get_writeable(const irep_idt &name) = 0;
+  virtual symbolt *get_writeable(irep_idt name) = 0;
 
   /// Find a symbol in the symbol table for read-write access.
   /// \param name: The name of the symbol to look for.
   /// \return A reference to the symbol.
   /// \throw `std::out_of_range` if no such symbol exists
-  symbolt &get_writeable_ref(const irep_idt &name)
+  symbolt &get_writeable_ref(irep_idt name)
   {
     symbolt *symbol = get_writeable(name);
     if(symbol == nullptr)
@@ -167,7 +166,7 @@ class symbol_table_baset
   virtual std::pair<symbolt &, bool> insert(symbolt symbol) = 0;
   virtual bool move(symbolt &symbol, symbolt *&new_symbol) = 0;
 
-  bool remove(const irep_idt &name);
+  bool remove(irep_idt name);
   /// Remove a symbol from the symbol table
   /// \param entry: an iterator pointing at the symbol to remove
   virtual void erase(const symbolst::const_iterator &entry) = 0;
@@ -183,7 +182,7 @@ class symbol_table_baset
   {
   private:
     symbolst::iterator it;
-    std::function<void(const irep_idt &id)> on_get_writeable;
+    std::function<void(irep_idt id)> on_get_writeable;
 
   public:
     explicit iteratort(symbolst::iterator it) : it(std::move(it))
@@ -191,8 +190,8 @@ class symbol_table_baset
     }
 
     iteratort(
-        const iteratort &it,
-        std::function<void(const irep_idt &id)> on_get_writeable)
+      const iteratort &it,
+      std::function<void(irep_idt id)> on_get_writeable)
       : it(it.it), on_get_writeable(std::move(on_get_writeable))
     {
     }
diff --git a/src/util/symbol_table_builder.h b/src/util/symbol_table_builder.h
index 28046919de6..90ca0bf4aec 100644
--- a/src/util/symbol_table_builder.h
+++ b/src/util/symbol_table_builder.h
@@ -65,7 +65,7 @@ class symbol_table_buildert : public symbol_table_baset
     return base_symbol_table.move(symbol, new_symbol);
   }
 
-  symbolt *get_writeable(const irep_idt &identifier) override
+  symbolt *get_writeable(irep_idt identifier) override
   {
     return base_symbol_table.get_writeable(identifier);
   }
diff --git a/src/util/type.h b/src/util/type.h
index 94170e003db..a23346772e1 100644
--- a/src/util/type.h
+++ b/src/util/type.h
@@ -30,7 +30,9 @@ class typet:public irept
 public:
   typet() { }
 
-  explicit typet(const irep_idt &_id):irept(_id) { }
+  explicit typet(irep_idt _id) : irept(_id)
+  {
+  }
 
   // the STL implementation shipped with GCC 5 is broken
 #if !defined(__GLIBCXX__) || __GLIBCXX__ >= 20181026
@@ -112,12 +114,12 @@ class typet:public irept
     return *this;
   }
 
-  typet &add_type(const irep_idt &name)
+  typet &add_type(irep_idt name)
   {
     return static_cast<typet &>(add(name));
   }
 
-  const typet &find_type(const irep_idt &name) const
+  const typet &find_type(irep_idt name) const
   {
     return static_cast<const typet &>(find(name));
   }
@@ -223,13 +225,12 @@ class type_with_subtypest:public typet
 public:
   typedef std::vector<typet> subtypest;
 
-  type_with_subtypest(const irep_idt &_id, const subtypest &_subtypes)
-    : typet(_id)
+  type_with_subtypest(irep_idt _id, const subtypest &_subtypes) : typet(_id)
   {
     subtypes() = _subtypes;
   }
 
-  type_with_subtypest(const irep_idt &_id, subtypest &&_subtypes) : typet(_id)
+  type_with_subtypest(irep_idt _id, subtypest &&_subtypes) : typet(_id)
   {
     subtypes() = std::move(_subtypes);
   }
diff --git a/unit/analyses/ai/ai.cpp b/unit/analyses/ai/ai.cpp
index aa888cc33f3..314bea3777c 100644
--- a/unit/analyses/ai/ai.cpp
+++ b/unit/analyses/ai/ai.cpp
@@ -31,9 +31,9 @@ class instruction_counter_domaint : public ai_domain_baset
   std::optional<unsigned> path_length;
 
   void transform(
-    const irep_idt &,
+    irep_idt,
     trace_ptrt,
-    const irep_idt &,
+    irep_idt,
     trace_ptrt,
     ai_baset &,
     const namespacet &) override
diff --git a/unit/analyses/ai/ai_simplify_lhs.cpp b/unit/analyses/ai/ai_simplify_lhs.cpp
index 7e38f26f392..918ce433403 100644
--- a/unit/analyses/ai/ai_simplify_lhs.cpp
+++ b/unit/analyses/ai/ai_simplify_lhs.cpp
@@ -28,9 +28,9 @@ class constant_simplification_mockt:public ai_domain_baset
 {
 public:
   void transform(
-    const irep_idt &,
+    irep_idt,
     trace_ptrt,
-    const irep_idt &,
+    irep_idt,
     trace_ptrt,
     ai_baset &,
     const namespacet &) override
diff --git a/unit/analyses/variable-sensitivity/eval.cpp b/unit/analyses/variable-sensitivity/eval.cpp
index 15f50e48a36..3ae53f8751a 100644
--- a/unit/analyses/variable-sensitivity/eval.cpp
+++ b/unit/analyses/variable-sensitivity/eval.cpp
@@ -12,7 +12,7 @@
 #include <analyses/variable-sensitivity/variable_sensitivity_object_factory.h>
 #include <testing-utils/use_catch.h>
 
-static symbolt simple_symbol(const irep_idt &identifier, const typet &type)
+static symbolt simple_symbol(irep_idt identifier, const typet &type)
 {
   symbolt b1{identifier, type, irep_idt{}};
   b1.base_name = b1.pretty_name = identifier;
diff --git a/unit/analyses/variable-sensitivity/value_expression_evaluation/assume.cpp b/unit/analyses/variable-sensitivity/value_expression_evaluation/assume.cpp
index f26e0da09b5..0657d85c35d 100644
--- a/unit/analyses/variable-sensitivity/value_expression_evaluation/assume.cpp
+++ b/unit/analyses/variable-sensitivity/value_expression_evaluation/assume.cpp
@@ -24,7 +24,7 @@
 #include <testing-utils/use_catch.h>
 
 exprt binary_expression(
-  const irep_idt &exprId,
+  irep_idt exprId,
   const abstract_object_pointert &op1,
   const abstract_object_pointert &op2,
   abstract_environmentt &environment,
@@ -83,7 +83,7 @@ class assume_testert
   }
 
   void test_fn(
-    const irep_idt &exprId,
+    irep_idt exprId,
     bool is_true,
     std::string const &test,
     std::string const &delimiter)
diff --git a/unit/analyses/variable-sensitivity/value_expression_evaluation/assume_prune.cpp b/unit/analyses/variable-sensitivity/value_expression_evaluation/assume_prune.cpp
index 18c7e0b86ca..3b5f37b6c84 100644
--- a/unit/analyses/variable-sensitivity/value_expression_evaluation/assume_prune.cpp
+++ b/unit/analyses/variable-sensitivity/value_expression_evaluation/assume_prune.cpp
@@ -25,7 +25,7 @@
 
 static void ASSUME_TRUE(
   symbol_exprt const &x,
-  const irep_idt &id,
+  irep_idt id,
   symbol_exprt const &y,
   abstract_environmentt &env,
   const namespacet &ns)
diff --git a/unit/goto-checker/report_util/is_property_less_than.cpp b/unit/goto-checker/report_util/is_property_less_than.cpp
index fca7802da02..ab1bfbc032f 100644
--- a/unit/goto-checker/report_util/is_property_less_than.cpp
+++ b/unit/goto-checker/report_util/is_property_less_than.cpp
@@ -3,10 +3,8 @@
 #include <goto-checker/report_util.cpp>
 #include <testing-utils/use_catch.h>
 
-static goto_programt::instructiont instruction_for_location(
-  const irep_idt &file,
-  const irep_idt &function,
-  size_t line_no)
+static goto_programt::instructiont
+instruction_for_location(irep_idt file, irep_idt function, size_t line_no)
 {
   source_locationt location;
   location.set_file(file);
@@ -26,8 +24,7 @@ static property_infot test_info(const goto_programt::const_targett &target)
   return property_infot(target, "ignored", property_statust::UNKNOWN);
 }
 
-static propertyt
-property(const irep_idt &identifier, const property_infot &info)
+static propertyt property(irep_idt identifier, const property_infot &info)
 {
   return std::make_pair(identifier, info);
 }
diff --git a/unit/goto-instrument/cover/cover_only.cpp b/unit/goto-instrument/cover/cover_only.cpp
index 68c413f7253..6132ec31826 100644
--- a/unit/goto-instrument/cover/cover_only.cpp
+++ b/unit/goto-instrument/cover/cover_only.cpp
@@ -15,7 +15,7 @@ Author: Diffblue Ltd
 
 namespace
 {
-symbolt create_new_symbol(const irep_idt &name, const irep_idt &file_name)
+symbolt create_new_symbol(irep_idt name, irep_idt file_name)
 {
   symbolt symbol;
   symbol.name = name;
diff --git a/unit/goto-symex/apply_condition.cpp b/unit/goto-symex/apply_condition.cpp
index 9702a683c53..7b28db43637 100644
--- a/unit/goto-symex/apply_condition.cpp
+++ b/unit/goto-symex/apply_condition.cpp
@@ -41,7 +41,7 @@ SCENARIO(
   symex_targett::sourcet source{"fun", target.begin()};
   guard_managert guard_manager;
   std::size_t count = 0;
-  auto fresh_name = [&count](const irep_idt &) { return count++; };
+  auto fresh_name = [&count](irep_idt) { return count++; };
   goto_symex_statet state{
     source,
     DEFAULT_MAX_FIELD_SENSITIVITY_ARRAY_SIZE,
diff --git a/unit/goto-symex/goto_symex_state.cpp b/unit/goto-symex/goto_symex_state.cpp
index e84340e6709..3771a881baf 100644
--- a/unit/goto-symex/goto_symex_state.cpp
+++ b/unit/goto-symex/goto_symex_state.cpp
@@ -35,9 +35,8 @@ SCENARIO(
   symex_targett::sourcet source{"fun", target.begin()};
   guard_managert manager;
   std::size_t fresh_name_count = 1;
-  auto fresh_name = [&fresh_name_count](const irep_idt &) {
-    return fresh_name_count++;
-  };
+  auto fresh_name = [&fresh_name_count](irep_idt)
+  { return fresh_name_count++; };
   goto_symex_statet state{
     source,
     DEFAULT_MAX_FIELD_SENSITIVITY_ARRAY_SIZE,
diff --git a/unit/goto-symex/symex_assign.cpp b/unit/goto-symex/symex_assign.cpp
index 934138fe490..55fc9d81846 100644
--- a/unit/goto-symex/symex_assign.cpp
+++ b/unit/goto-symex/symex_assign.cpp
@@ -45,9 +45,8 @@ SCENARIO(
   symex_targett::sourcet source{"fun", target.begin()};
   guard_managert manager;
   std::size_t fresh_name_count = 1;
-  auto fresh_name = [&fresh_name_count](const irep_idt &) {
-    return fresh_name_count++;
-  };
+  auto fresh_name = [&fresh_name_count](irep_idt)
+  { return fresh_name_count++; };
   goto_symex_statet state{
     source,
     DEFAULT_MAX_FIELD_SENSITIVITY_ARRAY_SIZE,
diff --git a/unit/goto-symex/try_evaluate_pointer_comparisons.cpp b/unit/goto-symex/try_evaluate_pointer_comparisons.cpp
index f2dff4a284d..9c03a150802 100644
--- a/unit/goto-symex/try_evaluate_pointer_comparisons.cpp
+++ b/unit/goto-symex/try_evaluate_pointer_comparisons.cpp
@@ -57,7 +57,7 @@ SCENARIO(
   symex_targett::sourcet source{"fun", target.begin()};
   guard_managert guard_manager;
   std::size_t count = 0;
-  auto fresh_name = [&count](const irep_idt &) { return count++; };
+  auto fresh_name = [&count](irep_idt) { return count++; };
   goto_symex_statet state{
     source,
     DEFAULT_MAX_FIELD_SENSITIVITY_ARRAY_SIZE,
diff --git a/unit/testing-utils/call_graph_test_utils.cpp b/unit/testing-utils/call_graph_test_utils.cpp
index 167deaecfc7..ac24335a77a 100644
--- a/unit/testing-utils/call_graph_test_utils.cpp
+++ b/unit/testing-utils/call_graph_test_utils.cpp
@@ -10,8 +10,7 @@ Author: Chris Smowton, chris.smowton@diffblue.com
 
 #include <util/std_code_base.h>
 
-symbolt
-create_void_function_symbol(const irep_idt &name, const codet &code)
+symbolt create_void_function_symbol(irep_idt name, const codet &code)
 {
   const code_typet void_function_type({}, empty_typet());
   symbolt function{name, void_function_type, ID_java};
@@ -21,7 +20,7 @@ create_void_function_symbol(const irep_idt &name, const codet &code)
 
 bool multimap_key_matches(
   const std::multimap<irep_idt, irep_idt> &map,
-  const irep_idt &key,
+  irep_idt key,
   const std::set<irep_idt> &values)
 {
   auto matching_values = map.equal_range(key);
diff --git a/unit/testing-utils/call_graph_test_utils.h b/unit/testing-utils/call_graph_test_utils.h
index ec37b7449e1..fe81b612e95 100644
--- a/unit/testing-utils/call_graph_test_utils.h
+++ b/unit/testing-utils/call_graph_test_utils.h
@@ -16,12 +16,11 @@ Author: Chris Smowton, chris.smowton@diffblue.com
 
 class codet;
 
-symbolt
-create_void_function_symbol(const irep_idt &name, const codet &code);
+symbolt create_void_function_symbol(irep_idt name, const codet &code);
 
 bool multimap_key_matches(
   const std::multimap<irep_idt, irep_idt> &map,
-  const irep_idt &key,
+  irep_idt key,
   const std::set<irep_idt> &values);
 
 #endif /* CPROVER_TESTING_UTILS_CALL_GRAPH_TEST_UTILS_HT */
diff --git a/unit/testing-utils/require_expr.cpp b/unit/testing-utils/require_expr.cpp
index f5fc7d32dc8..36c0a16b695 100644
--- a/unit/testing-utils/require_expr.cpp
+++ b/unit/testing-utils/require_expr.cpp
@@ -52,8 +52,8 @@ index_exprt require_expr::require_top_index(const exprt &expr)
 /// \param component_identifier: The name of the component that should be being
 ///   accessed.
 /// \return The expr cast to a member_exprt.
-member_exprt require_expr::require_member(
-  const exprt &expr, const irep_idt &component_identifier)
+member_exprt
+require_expr::require_member(const exprt &expr, irep_idt component_identifier)
 {
   REQUIRE(expr.id()==ID_member);
   const member_exprt &member_expr=to_member_expr(expr);
@@ -66,8 +66,8 @@ member_exprt require_expr::require_member(
 /// \param expr: The expression.
 /// \param symbol_name: The intended identifier of the symbol
 /// \return The expr cast to a symbol_exprt
-symbol_exprt require_expr::require_symbol(
-  const exprt &expr, const irep_idt &symbol_name)
+symbol_exprt
+require_expr::require_symbol(const exprt &expr, irep_idt symbol_name)
 {
   const symbol_exprt &symbol_expr = require_symbol(expr);
   REQUIRE(symbol_expr.identifier() == symbol_name);
@@ -98,7 +98,7 @@ typecast_exprt require_expr::require_typecast(const exprt &expr)
 /// \return The expr cast to a side_effect_exprt
 side_effect_exprt require_expr::require_side_effect_expr(
   const exprt &expr,
-  const irep_idt &side_effect_statement)
+  irep_idt side_effect_statement)
 {
   REQUIRE(expr.id() == ID_side_effect);
   const side_effect_exprt &side_effect_expr = to_side_effect_expr(expr);
diff --git a/unit/testing-utils/require_expr.h b/unit/testing-utils/require_expr.h
index c2e28295428..62e55660435 100644
--- a/unit/testing-utils/require_expr.h
+++ b/unit/testing-utils/require_expr.h
@@ -23,19 +23,16 @@ namespace require_expr
   index_exprt require_index(const exprt &expr, int expected_index);
   index_exprt require_top_index(const exprt &expr);
 
-  member_exprt require_member(
-    const exprt &expr, const irep_idt &component_identifier);
+  member_exprt require_member(const exprt &expr, irep_idt component_identifier);
 
-  symbol_exprt require_symbol(
-    const exprt &expr, const irep_idt &symbol_name);
+  symbol_exprt require_symbol(const exprt &expr, irep_idt symbol_name);
 
   symbol_exprt require_symbol(const exprt &expr);
 
   typecast_exprt require_typecast(const exprt &expr);
 
-  side_effect_exprt require_side_effect_expr(
-    const exprt &expr,
-    const irep_idt &side_effect_statement);
+  side_effect_exprt
+  require_side_effect_expr(const exprt &expr, irep_idt side_effect_statement);
 }
 
 #endif // CPROVER_TESTING_UTILS_REQUIRE_EXPR_H
diff --git a/unit/testing-utils/require_symbol.cpp b/unit/testing-utils/require_symbol.cpp
index 4e3289ff32f..234648326b3 100644
--- a/unit/testing-utils/require_symbol.cpp
+++ b/unit/testing-utils/require_symbol.cpp
@@ -17,7 +17,7 @@ Author: Diffblue Limited.
 /// \param symbol_identifier: The name of the symbol
 const symbolt &require_symbol::require_symbol_exists(
   const symbol_tablet &symbol_table,
-  const irep_idt &symbol_identifier)
+  irep_idt symbol_identifier)
 {
   const symbolt *found_symbol = symbol_table.lookup(symbol_identifier);
   INFO("Looking for symbol: " + id2string(symbol_identifier));
diff --git a/unit/testing-utils/require_symbol.h b/unit/testing-utils/require_symbol.h
index 846b17d10df..ddc4c8e4d61 100644
--- a/unit/testing-utils/require_symbol.h
+++ b/unit/testing-utils/require_symbol.h
@@ -26,7 +26,7 @@ namespace require_symbol
 const symbolt &
 require_symbol_exists(
   const symbol_tablet &symbol_table,
-  const irep_idt &symbol_identifier);
+  irep_idt symbol_identifier);
 }
 
 #endif // CPROVER_TESTING_UTILS_REQUIRE_SYMBOL_H
diff --git a/unit/util/sharing_map.cpp b/unit/util/sharing_map.cpp
index 8b4640405e2..ef265e6cacd 100644
--- a/unit/util/sharing_map.cpp
+++ b/unit/util/sharing_map.cpp
@@ -534,16 +534,17 @@ TEST_CASE("Sharing map views and iteration", "[core][util]")
   {
     sharing_map_standardt sm;
 
-    sm.iterate([](const irep_idt &key, const std::string &value) {});
+    sm.iterate([](irep_idt key, const std::string &value) {});
 
     fill(sm);
 
     typedef std::pair<std::string, std::string> pt;
     std::vector<pt> pairs;
 
-    sm.iterate([&pairs](const irep_idt &key, const std::string &value) {
-      pairs.push_back({id2string(key), value});
-    });
+    sm.iterate(
+      [&pairs](irep_idt key, const std::string &value) {
+        pairs.push_back({id2string(key), value});
+      });
 
     std::sort(pairs.begin(), pairs.end());
     REQUIRE(pairs.size() == 3);