remove_unreachable.cpp

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/*******************************************************************\
 
Module: Program Transformation
 
Author: Daniel Kroening, kroening@kroening.com
 
\*******************************************************************/

 
#include "remove_unreachable.h"
 
#include <set>
#include <stack>
 
#include "goto_functions.h"

void remove_unreachable(goto_programt &goto_program)
{
  std::set<goto_programt::targett, goto_programt::target_less_than> reachable;
  std::stack<goto_programt::targett> working;
 
  working.push(goto_program.instructions.begin());
 
  while(!working.empty())
  {
    goto_programt::targett t=working.top();
    working.pop();
 
    if(reachable.find(t)==reachable.end() &&
       t!=goto_program.instructions.end())
    {
      reachable.insert(t);
 
      for(const auto &succ : goto_program.get_successors(t))
        working.push(succ);
    }
  }
 
  // make all unreachable code a skip
  // unless it's an 'end_function'
  bool did_something = false;
 
  Forall_goto_program_instructions(it, goto_program)
  {
    if(reachable.find(it)==reachable.end() &&
       !it->is_end_function())
    {
      it->turn_into_skip();
      did_something = true;
    }
  }
 
  if(did_something)
    goto_program.update();
}

void remove_unreachable(goto_functionst &goto_functions)
{
  for(auto &gf_entry : goto_functions.function_map)
    remove_unreachable(gf_entry.second.body);
}