static bool hasUnsafeGuaranteedOperand(SILValue UnsafeGuaranteedValue,
SILValue UnsafeGuaranteedValueOperand,
RCIdentityFunctionInfo &RCII,
SILInstruction &Release) {
assert(isa<StrongReleaseInst>(Release) ||
isa<ReleaseValueInst>(Release) && "Expecting a release");
auto RCRoot = RCII.getRCIdentityRoot(Release.getOperand(0));
return RCRoot == UnsafeGuaranteedValue ||
RCRoot == UnsafeGuaranteedValueOperand;
}
/// Remove retain/release pairs around builtin "unsafeGuaranteed" instruction
/// sequences.
static bool removeGuaranteedRetainReleasePairs(SILFunction &F,
RCIdentityFunctionInfo &RCIA,
PostDominanceAnalysis *PDA) {
DEBUG(llvm::dbgs() << "Running on function " << F.getName() << "\n");
bool Changed = false;
// Lazily compute post-dominance info only when we really need it.
PostDominanceInfo *PDI = nullptr;
for (auto &BB : F) {
auto It = BB.begin(), End = BB.end();
llvm::DenseMap<SILValue, SILInstruction *> LastRetain;
while (It != End) {
auto *CurInst = &*It;
++It;
// Memorize the last retain.
if (isa<StrongRetainInst>(CurInst) || isa<RetainValueInst>(CurInst)) {
LastRetain[RCIA.getRCIdentityRoot(CurInst->getOperand(0))] = CurInst;
continue;
}
// Look for a builtin "unsafeGuaranteed" instruction.
auto *UnsafeGuaranteedI = dyn_cast<BuiltinInst>(CurInst);
if (!UnsafeGuaranteedI || !UnsafeGuaranteedI->getBuiltinKind() ||
*UnsafeGuaranteedI->getBuiltinKind() !=
BuiltinValueKind::UnsafeGuaranteed)
continue;
auto Opd = UnsafeGuaranteedI->getOperand(0);
auto RCIdOpd = RCIA.getRCIdentityRoot(UnsafeGuaranteedI->getOperand(0));
if (!LastRetain.count(RCIdOpd)) {
DEBUG(llvm::dbgs() << "LastRetain failed\n");
continue;
}
// This code is very conservative. Check that there is a matching retain
// before the unsafeGuaranteed builtin with only retains inbetween.
auto *LastRetainInst = LastRetain[RCIdOpd];
auto NextInstIter = std::next(SILBasicBlock::iterator(LastRetainInst));
while (NextInstIter != BB.end() && &*NextInstIter != CurInst &&
(isa<RetainValueInst>(*NextInstIter) ||
isa<StrongRetainInst>(*NextInstIter) ||
!NextInstIter->mayHaveSideEffects() ||
isa<DebugValueInst>(*NextInstIter) ||
isa<DebugValueAddrInst>(*NextInstIter)))
++NextInstIter;
if (&*NextInstIter != CurInst) {
DEBUG(llvm::dbgs() << "Last retain right before match failed\n");
continue;
}
DEBUG(llvm::dbgs() << "Saw " << *UnsafeGuaranteedI);
DEBUG(llvm::dbgs() << " with operand " << *Opd);
// Match the reference and token result.
// %4 = builtin "unsafeGuaranteed"<Foo>(%0 : $Foo)
// %5 = tuple_extract %4 : $(Foo, Builtin.Int8), 0
// %6 = tuple_extract %4 : $(Foo, Builtin.Int8), 1
SILInstruction *UnsafeGuaranteedValue;
SILInstruction *UnsafeGuaranteedToken;
std::tie(UnsafeGuaranteedValue, UnsafeGuaranteedToken) =
getSingleUnsafeGuaranteedValueResult(UnsafeGuaranteedI);
if (!UnsafeGuaranteedValue) {
DEBUG(llvm::dbgs() << " no single unsafeGuaranteed value use\n");
continue;
}
// Look for a builtin "unsafeGuaranteedEnd" instruction that uses the
// token.
// builtin "unsafeGuaranteedEnd"(%6 : $Builtin.Int8) : $()
auto *UnsafeGuaranteedEndI =
getUnsafeGuaranteedEndUser(UnsafeGuaranteedToken);
if (!UnsafeGuaranteedEndI) {
DEBUG(llvm::dbgs() << " no single unsafeGuaranteedEnd use found\n");
continue;
}
if (!PDI)
PDI = PDA->get(&F);
// It needs to post-dominated the end instruction, since we need to remove
// the release along all paths to exit.
if (!PDI->properlyDominates(UnsafeGuaranteedEndI, UnsafeGuaranteedI))
continue;
// Find the release to match with the unsafeGuaranteedValue.
auto &UnsafeGuaranteedEndBB = *UnsafeGuaranteedEndI->getParent();
auto LastRelease = findReleaseToMatchUnsafeGuaranteedValue(
UnsafeGuaranteedEndI, UnsafeGuaranteedI, UnsafeGuaranteedValue,
UnsafeGuaranteedEndBB, RCIA);
if (!LastRelease) {
DEBUG(llvm::dbgs() << " no release before/after unsafeGuaranteedEnd found\n");
continue;
}
// Restart iteration before the earliest instruction we remove.
bool RestartAtBeginningOfBlock = false;
auto LastRetainIt = SILBasicBlock::iterator(LastRetainInst);
if (LastRetainIt != BB.begin()) {
It = std::prev(LastRetainIt);
} else RestartAtBeginningOfBlock = true;
// Okay we found a post dominating release. Let's remove the
// retain/unsafeGuaranteed/release combo.
//
LastRetainInst->eraseFromParent();
LastRelease->eraseFromParent();
UnsafeGuaranteedEndI->eraseFromParent();
deleteAllDebugUses(UnsafeGuaranteedValue);
deleteAllDebugUses(UnsafeGuaranteedToken);
deleteAllDebugUses(UnsafeGuaranteedI);
UnsafeGuaranteedValue->replaceAllUsesWith(Opd);
UnsafeGuaranteedValue->eraseFromParent();
UnsafeGuaranteedToken->eraseFromParent();
UnsafeGuaranteedI->replaceAllUsesWith(Opd);
UnsafeGuaranteedI->eraseFromParent();
if (RestartAtBeginningOfBlock)
It = BB.begin();
Changed = true;
}
}
return Changed;
}
/// Return the rc-identity root of the SILValue.
SILValue getRCRoot(SILValue R) {
return RCFI->getRCIdentityRoot(R);
}
