scratch_program.cpp

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/*******************************************************************\
 
Module: Loop Acceleration
 
Author: Matt Lewis
 
\*******************************************************************/
 
 
#include "scratch_program.h"
 
#include <solvers/decision_procedure.h>
 
#include <goto-symex/slice.h>
 
#include <goto-programs/remove_skip.h>
 
#ifdef DEBUG
#include <iostream>
#endif
 
bool scratch_programt::check_sat(bool do_slice, guard_managert &guard_manager)
{
  fix_types();
 
  add(goto_programt::make_end_function());
 
  remove_skip(*this);
 
#ifdef DEBUG
  std::cout << "Checking following program for satness:\n";
  output(ns, "scratch", std::cout);
#endif
 
  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 & {
    if(key == goto_functionst::entry_point())
      return this_goto_function;
    else
      return functions.function_map.at(key);
  };
 
  symex_state = symex.initialize_entry_point_state(get_goto_function);
 
  symex_symbol_table = symex.symex_with_state(*symex_state, get_goto_function);
 
  if(do_slice)
  {
    slice(equation);
  }
 
  if(equation.count_assertions()==0)
  {
    // Symex sliced away all our assertions.
#ifdef DEBUG
    std::cout << "Trivially unsat\n";
#endif
    return false;
  }
 
  equation.convert(*checker);
 
#ifdef DEBUG
  std::cout << "Finished symex, invoking decision procedure.\n";
#endif
 
  switch((*checker)())
  {
  case decision_proceduret::resultt::D_ERROR:
    throw "error running the SMT solver";
 
  case decision_proceduret::resultt::D_SATISFIABLE:
    return true;
 
  case decision_proceduret::resultt::D_UNSATISFIABLE:
    return false;
 
    UNREACHABLE;
  }
 
  UNREACHABLE;
}
 
exprt scratch_programt::eval(const exprt &e)
{
  return checker->get(symex_state->rename<L2>(e, ns).get());
}
 
void scratch_programt::append(goto_programt::instructionst &new_instructions)
{
  instructions.insert(
    instructions.end(),
    new_instructions.begin(),
    new_instructions.end());
}
 
goto_programt::targett scratch_programt::assign(
  const exprt &lhs,
  const exprt &rhs)
{
  return add(goto_programt::make_assignment(lhs, rhs));
}
 
goto_programt::targett scratch_programt::assume(const exprt &guard)
{
  return add(goto_programt::make_assumption(guard));
}
 
static void fix_types(exprt &expr)
{
  Forall_operands(it, expr)
  {
    fix_types(*it);
  }
 
  if(expr.id()==ID_equal ||
     expr.id()==ID_notequal ||
     expr.id()==ID_gt ||
     expr.id()==ID_lt ||
     expr.id()==ID_ge ||
     expr.id()==ID_le)
  {
    auto &rel_expr = to_binary_relation_expr(expr);
    exprt &lhs = rel_expr.lhs();
    exprt &rhs = rel_expr.rhs();
 
    if(lhs.type()!=rhs.type())
    {
      typecast_exprt typecast(rhs, lhs.type());
      rel_expr.rhs().swap(typecast);
    }
  }
}
 
void scratch_programt::fix_types()
{
  for(goto_programt::instructionst::iterator it=instructions.begin();
      it!=instructions.end();
      ++it)
  {
    if(it->is_assign())
    {
      if(it->assign_lhs().type() != it->assign_rhs().type())
      {
        typecast_exprt typecast{it->assign_rhs(), it->assign_lhs().type()};
        it->assign_rhs_nonconst() = typecast;
      }
    }
    else if(it->is_assume() || it->is_assert())
    {
      ::fix_types(it->condition_nonconst());
    }
  }
}
 
void scratch_programt::append_path(patht &path)
{
  for(patht::iterator it=path.begin();
      it!=path.end();
      ++it)
  {
    if(it->loc->is_assign() || it->loc->is_assume())
    {
      instructions.push_back(*it->loc);
    }
    else if(it->loc->is_goto())
    {
      if(it->guard.id()!=ID_nil)
      {
        add(goto_programt::make_assumption(it->guard));
      }
    }
    else if(it->loc->is_assert())
    {
      add(goto_programt::make_assumption(it->loc->condition()));
    }
  }
}
 
void scratch_programt::append(goto_programt &program)
{
  goto_programt scratch;
 
  scratch.copy_from(program);
  destructive_append(scratch);
}
 
void scratch_programt::append_loop(
  goto_programt &program,
  goto_programt::targett loop_header)
{
  append(program);
 
  // Update any back jumps to the loop header.
  (void)loop_header; // unused parameter
  assume(false_exprt());
 
  goto_programt::targett end = add(goto_programt::make_skip());
 
  update();
 
  for(goto_programt::targett t=instructions.begin();
      t!=instructions.end();
      ++t)
  {
    if(t->is_backwards_goto())
    {
      t->targets.clear();
      t->targets.push_back(end);
    }
  }
}
 
optionst scratch_programt::get_default_options()
{
  optionst ret;
  ret.set_option("simplify", true);
  return ret;
}