interval_analysis.cpp

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/*******************************************************************\
 
Module: Interval Analysis
 
Author: Daniel Kroening, kroening@kroening.com
 
\*******************************************************************/
 
 
#include "interval_analysis.h"
 
#include <util/find_symbols.h>
 
#include "ai.h"
#include "interval_domain.h"
 
void instrument_intervals(
  const ait<interval_domaint> &interval_analysis,
  goto_functionst::goto_functiont &goto_function)
{
  std::set<symbol_exprt> symbols;
 
  for(const auto &i : goto_function.body.instructions)
    i.apply([&symbols](const exprt &e) { find_symbols(e, symbols); });
 
  Forall_goto_program_instructions(i_it, goto_function.body)
  {
    if(i_it==goto_function.body.instructions.begin())
    {
      // first instruction, we instrument
    }
    else
    {
      goto_programt::const_targett previous = std::prev(i_it);
 
      if(previous->is_goto() && !previous->condition().is_true())
      {
        // we follow a branch, instrument
      }
      else if(previous->is_function_call())
      {
        // we follow a function call, instrument
      }
      else if(i_it->is_target() || i_it->is_function_call())
      {
        // we are a target or a function call, instrument
      }
      else
        continue; // don't instrument
    }
 
    const interval_domaint &d=interval_analysis[i_it];
 
    exprt::operandst assertion;
 
    for(const auto &symbol_expr : symbols)
    {
      exprt tmp=d.make_expression(symbol_expr);
      if(!tmp.is_true())
        assertion.push_back(tmp);
    }
 
    if(!assertion.empty())
    {
      goto_programt::targett t=i_it;
      goto_function.body.insert_before_swap(i_it);
      i_it++; // goes to original instruction
      *t = goto_programt::make_assumption(
        conjunction(assertion), i_it->source_location());
    }
  }
}
 
void interval_analysis(goto_modelt &goto_model)
{
  ait<interval_domaint> interval_analysis;
 
  const namespacet ns(goto_model.symbol_table);
  interval_analysis(goto_model.goto_functions, ns);
 
  for(auto &gf_entry : goto_model.goto_functions.function_map)
    instrument_intervals(interval_analysis, gf_entry.second);
}