widened_range.cpp

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/*******************************************************************\
 
 Module: helper for extending intervals during widening merges
 
 Author: Jez Higgins
 
\*******************************************************************/
 
#include "widened_range.h"
#include <util/simplify_expr.h>
 
static bool has_underflowed(const exprt &value)
{
  return constant_interval_exprt::greater_than(
    value, from_integer(0, value.type()));
}
static bool has_overflowed(const exprt &value, const exprt &initial_value)
{
  return constant_interval_exprt::less_than(value, initial_value);
}
 
exprt widened_ranget::widen_lower_bound() const
{
  if(!is_lower_widened)
    return lower_bound;
 
  auto new_lower_bound = simplify_expr(minus_exprt(lower_bound, range_), ns_);
 
  if(
    constant_interval_exprt::contains_extreme(new_lower_bound) ||
    has_underflowed(new_lower_bound))
    return min_value_exprt(lower_bound.type());
 
  return new_lower_bound;
}
 
exprt widened_ranget::widen_upper_bound() const
{
  if(!is_upper_widened)
    return upper_bound;
 
  auto new_upper_bound = simplify_expr(plus_exprt(upper_bound, range_), ns_);
 
  if(
    constant_interval_exprt::contains_extreme(new_upper_bound) ||
    has_overflowed(new_upper_bound, upper_bound))
    return max_value_exprt(upper_bound.type());
 
  return new_upper_bound;
}