// returns true if bit is a useful condition for testing as sufficient
// (no loop-modified terms, preserves reachability of assert, etc.)
// regardless of whether it is actually sufficient.
bool TestBit(Bit *bit)
{
Vector<Bit*> &tested_list = propagate->m_sufficient_tested_list;
Vector<Bit*> &possible_list = propagate->m_sufficient_possible_list;
Vector<Bit*> &sufficient_list = propagate->m_sufficient_list;
Solver *solver = state->GetSolver();
if (tested_list.Contains(bit)) {
if (possible_list.Contains(bit))
return true;
return false;
}
if (verbose)
logout << "SUFFICIENT: " << frame
<< ": Testing " << bit << " [" << bit->Hash() << "]" << endl;
tested_list.PushBack(bit);
// don't test for sufficient conditions if a timeout has occurred.
if (TimerAlarm::ActiveExpired()) {
if (verbose)
logout << "SUFFICIENT: " << frame << ": Alarm expired" << endl;
return false;
}
// check that the sufficient condition does not render the point
// of the assertion unreachable: the solver is still satisfiable after
// asserting the sufficient condition. this also takes care of
// unsatisfiable sufficient conditions.
state->PushContext();
// ignore bits we can't do any propagation from.
CheckerPropagate *test_propagate =
new CheckerPropagate(frame, propagate->m_point,
propagate->m_allow_point);
test_propagate->SetTest(bit);
// propagations can trigger new solver side conditions. TODO: should figure
// out what's going on here.
if (!solver->IsSatisfiable()) {
state->PopContext();
return false;
}
if (test_propagate->m_where->IsNone()) {
if (verbose)
logout << "SUFFICIENT: " << frame << ": Failed propagate: "
<< test_propagate->m_where << endl;
state->PopContext();
delete test_propagate;
return false;
}
// assert the tested sufficient holds in the frame.
frame->AddAssert(bit);
if (!solver->IsSatisfiable()) {
// the sufficient condition rendered the assertion point unreachable.
if (verbose)
logout << "SUFFICIENT: " << frame
<< ": Renders point unreachable" << endl;
state->PopContext();
delete test_propagate;
return false;
}
// this is a good potential sufficient condition, remember it.
possible_list.PushBack(bit);
// check whether the bit is actually a sufficient condition.
// just assert the original negated safe bit, and if it is unsatisfiable
// it cannot occur under this sufficient condition.
state->AssertBaseBits();
bool satisfiable = solver->IsSatisfiable();
if (verbose) {
if (satisfiable) {
logout << "SUFFICIENT: " << frame
<< ": Not a sufficient condition:" << endl;
solver->PinAssign();
solver->PrintRawAssignment();
solver->UnpinAssign();
}
else {
logout << "SUFFICIENT: " << frame << ": Success!" << endl;
}
}
if (!satisfiable) {
sufficient_list.PushBack(bit);
propagate_list->PushBack(test_propagate);
}
else {
delete test_propagate;
}
state->PopContext();
return true;
}
