remove_unused_functions.cpp

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/*******************************************************************\
 
Module: Unused function removal
 
Author: CM Wintersteiger
 
\*******************************************************************/

 
#include "remove_unused_functions.h"
 
#include <util/message.h>
 
#include "goto_model.h"
 
void remove_unused_functions(
  goto_modelt &goto_model,
  message_handlert &message_handler)
{
  remove_unused_functions(goto_model.goto_functions, message_handler);
}
 
void remove_unused_functions(
  goto_functionst &functions,
  message_handlert &message_handler)
{
  std::set<irep_idt> used_functions;
  std::list<goto_functionst::function_mapt::iterator> unused_functions;
  find_used_functions(
    goto_functionst::entry_point(), functions, used_functions);
 
  for(goto_functionst::function_mapt::iterator it=
        functions.function_map.begin();
      it!=functions.function_map.end();
      it++)
  {
    if(used_functions.find(it->first)==used_functions.end())
      unused_functions.push_back(it);
  }
 
  messaget message(message_handler);
 
  if(!unused_functions.empty())
  {
    message.statistics()
      << "Dropping " << unused_functions.size() << " of " <<
      functions.function_map.size() << " functions (" <<
      used_functions.size() << " used)" << messaget::eom;
  }
 
  for(const auto &f : unused_functions)
    functions.function_map.erase(f);
}
 
void find_used_functions(
  const irep_idt &start,
  goto_functionst &functions,
  std::set<irep_idt> &seen)
{
  std::pair<std::set<irep_idt>::const_iterator, bool> res =
    seen.insert(start);
 
  if(!res.second)
    return;
  else
  {
    goto_functionst::function_mapt::const_iterator f_it =
      functions.function_map.find(start);
 
    if(f_it!=functions.function_map.end())
    {
      for(const auto &instruction : f_it->second.body.instructions)
      {
        if(instruction.is_function_call())
        {
          const auto &function = instruction.call_function();
 
          const irep_idt &identifier =
            to_symbol_expr(function).get_identifier();
 
          find_used_functions(identifier, functions, seen);
        }
      }
    }
  }
}