void symex_target_equationt::convert_assertions(
prop_convt &prop_conv)
{
// we find out if there is only _one_ assertion,
// which allows for a simpler formula
unsigned number_of_assertions=count_assertions();
if(number_of_assertions==0)
return;
if(number_of_assertions==1)
{
for(SSA_stepst::iterator it=SSA_steps.begin();
it!=SSA_steps.end(); it++)
if(it->is_assert())
{
prop_conv.set_to_false(it->cond_expr);
it->cond_literal=const_literal(false);
return; // prevent further assumptions!
}
else if(it->is_assume())
prop_conv.set_to_true(it->cond_expr);
assert(false); // unreachable
}
bvt bv;
bv.reserve(number_of_assertions);
literalt assumption_literal=const_literal(true);
for(SSA_stepst::iterator it=SSA_steps.begin();
it!=SSA_steps.end(); it++)
if(it->is_assert())
{
// do the expression
literalt tmp_literal=prop_conv.convert(it->cond_expr);
it->cond_literal=prop_conv.prop.limplies(assumption_literal, tmp_literal);
bv.push_back(prop_conv.prop.lnot(it->cond_literal));
}
else if(it->is_assume())
assumption_literal=
prop_conv.prop.land(assumption_literal, it->cond_literal);
if(!bv.empty())
prop_conv.prop.lcnf(bv);
}
void symex_target_equationt::convert_assertions(
prop_convt &prop_conv)
{
// we find out if there is only _one_ assertion,
// which allows for a simpler formula
unsigned number_of_assertions=count_assertions();
if(number_of_assertions==0)
return;
if(number_of_assertions==1)
{
for(auto & it : SSA_steps)
{
if(it.is_assert())
{
prop_conv.set_to_false(it.cond_expr);
it.cond_literal=const_literal(false);
return; // prevent further assumptions!
}
else if(it.is_assume())
prop_conv.set_to_true(it.cond_expr);
}
assert(false); // unreachable
}
// We do (NOT a1) OR (NOT a2) ...
// where the a's are the assertions
or_exprt::operandst disjuncts;
disjuncts.reserve(number_of_assertions);
exprt assumption=true_exprt();
for(auto & it : SSA_steps)
{
if(it.is_assert())
{
implies_exprt implication(
assumption,
it.cond_expr);
// do the conversion
it.cond_literal=prop_conv.convert(implication);
// store disjunct
disjuncts.push_back(literal_exprt(!it.cond_literal));
}
else if(it.is_assume())
{
// the assumptions have been converted before
// avoid deep nesting of ID_and expressions
if(assumption.id()==ID_and)
assumption.copy_to_operands(literal_exprt(it.cond_literal));
else
assumption=
and_exprt(assumption, literal_exprt(it.cond_literal));
}
}
// the below is 'true' if there are no assertions
prop_conv.set_to_true(disjunction(disjuncts));
}
