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GOTO-symex: propagate notequal conditions for boolean types [TG-9390] #5089

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GOTO-symex: propagate notequal conditions for boolean types [TG-9390] #5089

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61 changes: 61 additions & 0 deletions src/goto-symex/goto_state.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,11 +46,72 @@ void goto_statet::apply_condition(
{
if(condition.id() == ID_and)
{
// A == B && C == D && E == F ...
// -->
// Apply each condition individually
for(const auto &op : condition.operands())
apply_condition(op, previous_state, ns);
}
else if(condition.id() == ID_notequal &&
to_notequal_expr(condition).lhs().type() == bool_typet())
{
// A != (true|false)
// -->
// A == (false|true)
exprt lhs = to_notequal_expr(condition).lhs();
exprt rhs = to_notequal_expr(condition).rhs();
if(is_ssa_expr(rhs))
std::swap(lhs, rhs);

if(rhs.is_true())
apply_condition(equal_exprt(lhs, false_exprt()), previous_state, ns);
else if(rhs.is_false())
apply_condition(equal_exprt(lhs, true_exprt()), previous_state, ns);
}
else if(condition.id() == ID_not &&
to_not_expr(condition).op().id() == ID_notequal)
{
// !(A != B)
// -->
// A == B
const auto &notequal_expr = to_notequal_expr(to_not_expr(condition).op());
apply_condition(
equal_exprt(notequal_expr.lhs(), notequal_expr.rhs()),
previous_state,
ns);
}
else if(condition.id() == ID_not &&
to_not_expr(condition).op().id() == ID_equal)
{
// !(A == B)
// -->
// A != B
const auto &equal_expr = to_equal_expr(to_not_expr(condition).op());
apply_condition(
notequal_exprt(equal_expr.lhs(), equal_expr.rhs()),
previous_state,
ns);
}
else if(condition.id() == ID_not)
{
// !A
// -->
// A == false
apply_condition(
equal_exprt(to_not_expr(condition).op(), false_exprt()),
previous_state,
ns);
}
else if(condition.id() == ID_symbol && condition.type() == bool_typet())
{
// A
// -->
// A == true
apply_condition(equal_exprt(condition, true_exprt()), previous_state, ns);
}
else if(condition.id() == ID_equal)
{
// Base case: try to apply a single equality constraint
exprt lhs = to_equal_expr(condition).lhs();
exprt rhs = to_equal_expr(condition).rhs();
if(is_ssa_expr(rhs))
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17 changes: 4 additions & 13 deletions src/goto-symex/symex_goto.cpp
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Expand Up @@ -55,21 +55,12 @@ void goto_symext::apply_goto_condition(

jump_taken_state.apply_condition(new_guard, current_state, ns);

// Try to find a negative condition that implies an equality constraint on
// the branch-not-taken path.
// Could use not_exprt + simplify, but let's avoid paying that cost on quite
// a hot path:
if(new_guard.id() == ID_not)
jump_not_taken_state.apply_condition(
to_not_expr(new_guard).op(), current_state, ns);
else if(new_guard.id() == ID_notequal)
{
auto &not_equal_expr = to_notequal_expr(new_guard);
jump_not_taken_state.apply_condition(
equal_exprt(not_equal_expr.lhs(), not_equal_expr.rhs()),
current_state,
ns);
}
exprt negated_new_guard = new_guard.id() ==
ID_not ? to_not_expr(new_guard).op() : not_exprt(new_guard);
jump_not_taken_state.apply_condition(
negated_new_guard, current_state, ns);
}

/// Try to evaluate a simple pointer comparison.
Expand Down