bool AliasAnalysis::canApplyDecrementRefCount(FullApplySite FAS, SILValue Ptr) {
// Treat applications of no-return functions as decrementing ref counts. This
// causes the apply to become a sink barrier for ref count increments.
if (FAS.isCalleeNoReturn())
return true;
/// If the pointer cannot escape to the function we are done.
if (!EA->canEscapeTo(Ptr, FAS))
return false;
SideEffectAnalysis::FunctionEffects ApplyEffects;
SEA->getEffects(ApplyEffects, FAS);
auto &GlobalEffects = ApplyEffects.getGlobalEffects();
if (ApplyEffects.mayReadRC() || GlobalEffects.mayRelease())
return true;
/// The function has no unidentified releases, so let's look at the arguments
// in detail.
for (unsigned Idx = 0, End = FAS.getNumArguments(); Idx < End; ++Idx) {
auto &ArgEffect = ApplyEffects.getParameterEffects()[Idx];
if (ArgEffect.mayRelease()) {
// The function may release this argument, so check if the pointer can
// escape to it.
if (EA->canEscapeToValue(Ptr, FAS.getArgument(Idx)))
return true;
}
}
return false;
}
/// Returns true if this block ends in an unreachable or an apply of a
/// no-return apply or builtin.
bool SILBasicBlock::isNoReturn() const {
if (isa<UnreachableInst>(getTerminator()))
return true;
auto Iter = prev_or_begin(getTerminator()->getIterator(), begin());
FullApplySite FAS = FullApplySite::isa(const_cast<SILInstruction *>(&*Iter));
if (FAS && FAS.isCalleeNoReturn()) {
return true;
}
if (auto *BI = dyn_cast<BuiltinInst>(&*Iter)) {
return BI->getModule().isNoReturnBuiltinOrIntrinsic(BI->getName());
}
return false;
}