called_functions: use unordered_set

Instead of using an ordered set, use a faster unordered set. This way,
running the algorithms against larger code bases should result in
decreased run times, while on small programs the run time might slightly
increase.

As this function is used in function pointer removal, and in code that
computes unreachable functions, the type change had to be propagated to
the related classes as well.

Author: nmanthey

src/goto-analyzer/unreachable_instructions.cpp

@@ -167,7 +167,7 @@ void unreachable_instructions(
 {
   json_arrayt json_result;
 
-  std::set<irep_idt> called=
+  std::unordered_set<irep_idt> called=
     compute_called_functions(goto_model);
 
   const namespacet ns(goto_model.symbol_table);
@@ -289,9 +289,10 @@ static void xml_output_function(
   x.set_attribute("last line", id2string(last_location.get_line()));
 }
 
+template <class T>
 static void list_functions(
   const goto_modelt &goto_model,
-  const std::set<irep_idt> called,
+  const T called,
   const optionst &options,
   std::ostream &os,
   bool unreachable)
@@ -387,7 +388,7 @@ void unreachable_functions(
   else
     options.set_option("text", true);
 
-  std::set<irep_idt> called = compute_called_functions(goto_model);
+  std::unordered_set<irep_idt> called = compute_called_functions(goto_model);
 
   list_functions(goto_model, called, options, os, true);
 }
@@ -403,7 +404,7 @@ void reachable_functions(
   else
     options.set_option("text", true);
 
-  std::set<irep_idt> called = compute_called_functions(goto_model);
+  std::unordered_set<irep_idt> called = compute_called_functions(goto_model);
 
   list_functions(goto_model, called, options, os, false);
 }

src/goto-programs/compute_called_functions.cpp

@@ -16,7 +16,7 @@ Author: Daniel Kroening, [email protected]
 /// get all functions whose address is taken
 void compute_address_taken_functions(
   const exprt &src,
-  std::set<irep_idt> &address_taken)
+  std::unordered_set<irep_idt> &address_taken)
 {
   forall_operands(it, src)
     compute_address_taken_functions(*it, address_taken);
@@ -35,7 +35,7 @@ void compute_address_taken_functions(
 /// get all functions in the expression
 void compute_functions(
   const exprt &src,
-  std::set<irep_idt> &address_taken)
+  std::unordered_set<irep_idt> &address_taken)
 {
   forall_operands(it, src)
     compute_functions(*it, address_taken);
@@ -48,7 +48,7 @@ void compute_functions(
 /// get all functions whose address is taken
 void compute_address_taken_functions(
   const goto_programt &goto_program,
-  std::set<irep_idt> &address_taken)
+  std::unordered_set<irep_idt> &address_taken)
 {
   forall_goto_program_instructions(it, goto_program)
   {
@@ -60,27 +60,27 @@ void compute_address_taken_functions(
 /// get all functions whose address is taken
 void compute_address_taken_functions(
   const goto_functionst &goto_functions,
-  std::set<irep_idt> &address_taken)
+  std::unordered_set<irep_idt> &address_taken)
 {
   forall_goto_functions(it, goto_functions)
     compute_address_taken_functions(it->second.body, address_taken);
 }
 
 /// get all functions whose address is taken
-std::set<irep_idt> compute_address_taken_functions(
+std::unordered_set<irep_idt> compute_address_taken_functions(
   const goto_functionst &goto_functions)
 {
-  std::set<irep_idt> address_taken;
+  std::unordered_set<irep_idt> address_taken;
   compute_address_taken_functions(goto_functions, address_taken);
   return address_taken;
 }
 
 /// computes the functions that are (potentially) called
-std::set<irep_idt> compute_called_functions(
+std::unordered_set<irep_idt> compute_called_functions(
   const goto_functionst &goto_functions)
 {
-  std::set<irep_idt> working_queue;
-  std::set<irep_idt> functions;
+  std::unordered_set<irep_idt> working_queue;
+  std::unordered_set<irep_idt> functions;
 
   // start from entry point
   working_queue.insert(goto_functions.entry_point());
@@ -121,7 +121,7 @@ std::set<irep_idt> compute_called_functions(
 }
 
 /// computes the functions that are (potentially) called
-std::set<irep_idt> compute_called_functions(
+std::unordered_set<irep_idt> compute_called_functions(
   const goto_modelt &goto_model)
 {
   return compute_called_functions(goto_model.goto_functions);

src/goto-programs/compute_called_functions.h

@@ -18,18 +18,18 @@ Author: Daniel Kroening, [email protected]
 
 void compute_address_taken_functions(
   const exprt &,
-  std::set<irep_idt> &);
+  std::unordered_set<irep_idt> &);
 
 void compute_address_taken_functions(
   const goto_programt &,
-  std::set<irep_idt> &);
+  std::unordered_set<irep_idt> &);
 
 void compute_address_taken_functions(
   const goto_functionst &,
-  std::set<irep_idt> &);
+  std::unordered_set<irep_idt> &);
 
 // computes the functions that are (potentially) called
-std::set<irep_idt> compute_called_functions(const goto_functionst &);
-std::set<irep_idt> compute_called_functions(const goto_modelt &);
+std::unordered_set<irep_idt> compute_called_functions(const goto_functionst &);
+std::unordered_set<irep_idt> compute_called_functions(const goto_modelt &);
 
 #endif // CPROVER_GOTO_PROGRAMS_COMPUTE_CALLED_FUNCTIONS_H

src/goto-programs/link_to_library.cpp

@@ -45,7 +45,7 @@ void link_to_library(
 
   while(true)
   {
-    std::set<irep_idt> called_functions=
+    std::unordered_set<irep_idt> called_functions=
       compute_called_functions(goto_functions);
 
     // eliminate those for which we already have a body

src/goto-programs/remove_function_pointers.cpp

@@ -61,7 +61,7 @@ class remove_function_pointerst:public messaget
     goto_programt &goto_program,
     goto_programt::targett target);
 
-  std::set<irep_idt> address_taken;
+  std::unordered_set<irep_idt> address_taken;
 
   typedef std::map<irep_idt, code_typet> type_mapt;
   type_mapt type_map;
@@ -81,7 +81,7 @@ class remove_function_pointerst:public messaget
     goto_programt &dest);
 
   void compute_address_taken_in_symbols(
-    std::set<irep_idt> &address_taken)
+    std::unordered_set<irep_idt> &address_taken)
   {
     const symbol_tablet &symbol_table=ns.get_symbol_table();