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[IRGen] Emit null check before swift_conformsToProtocol for nullable metatypes

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rdar://149882902

swift_conformsToProtocol does not properly handle nullptr values, which can currently be passed if the source type is an optional metatype. This change adds emission of a null check before calling the runtime function in these cases.
This commit is contained in:
Dario Rexin
2025-06-13 13:21:26 -07:00
parent 083cb114b3
commit 2a3999049f
3 changed files with 63 additions and 12 deletions
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49
lib/IRGen/GenCast.cpp
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@@ -544,8 +544,8 @@ llvm::Value *irgen::emitMetatypeToAnyObjectDowncast(IRGenFunction &IGF,
/// Emit a checked cast to a protocol or protocol composition.
void irgen::emitScalarExistentialDowncast(
IRGenFunction &IGF, llvm::Value *value, SILType srcType, SILType destType,
CheckedCastMode mode, std::optional<MetatypeRepresentation> metatypeKind,
Explosion &ex) {
CheckedCastMode mode, bool sourceWrappedInOptional,
std::optional<MetatypeRepresentation> metatypeKind, Explosion &ex) {
auto srcInstanceType = srcType.getASTType();
auto destInstanceType = destType.getASTType();
while (auto metatypeType = dyn_cast<ExistentialMetatypeType>(
@@ -800,7 +800,36 @@ void irgen::emitScalarExistentialDowncast(
for (auto proto : witnessTableProtos)
args.push_back(proto);
auto valueAndWitnessTables = IGF.Builder.CreateCall(fn, args);
llvm::BasicBlock *nilCheckedCont = nullptr;
llvm::BasicBlock *nilBB = nullptr;
llvm::BasicBlock *nonNilBB = nullptr;
if (sourceWrappedInOptional) {
nilBB = IGF.createBasicBlock("is-nil");
nonNilBB = IGF.createBasicBlock("is-non-nil");
nilCheckedCont = IGF.createBasicBlock("nil-checked-cont");
auto isNotNil = IGF.Builder.CreateICmpNE(
metadataValue, llvm::ConstantPointerNull::get(
cast<llvm::PointerType>(IGF.IGM.Int8PtrTy)));
IGF.Builder.CreateCondBr(isNotNil, nonNilBB, nilBB);
IGF.Builder.emitBlock(nilBB);
IGF.Builder.CreateBr(nilCheckedCont);
IGF.Builder.emitBlock(nonNilBB);
}
llvm::Value *valueAndWitnessTables = IGF.Builder.CreateCall(fn, args);
if (nilCheckedCont) {
IGF.Builder.CreateBr(nilCheckedCont);
IGF.Builder.emitBlock(nilCheckedCont);
auto *returnTy = valueAndWitnessTables->getType();
auto failureVal = llvm::Constant::getNullValue(returnTy);
auto phi = IGF.Builder.CreatePHI(returnTy, 2);
phi->addIncoming(valueAndWitnessTables, nonNilBB);
phi->addIncoming(failureVal, nilBB);
valueAndWitnessTables = phi;
}
resultValue = IGF.Builder.CreateExtractValue(valueAndWitnessTables, 0);
if (resultValue->getType() != resultType)
@@ -945,10 +974,9 @@ void irgen::emitScalarCheckedCast(IRGenFunction &IGF,
// Casts to existential metatypes.
if (auto existential = targetLoweredType.getAs<ExistentialMetatypeType>()) {
emitScalarExistentialDowncast(IGF, metatypeVal, sourceLoweredType,
targetLoweredType, mode,
existential->getRepresentation(),
out);
emitScalarExistentialDowncast(
IGF, metatypeVal, sourceLoweredType, targetLoweredType, mode,
sourceWrappedInOptional, existential->getRepresentation(), out);
return;
// Casts to concrete metatypes.
@@ -1023,9 +1051,10 @@ void irgen::emitScalarCheckedCast(IRGenFunction &IGF,
if (targetFormalType.isExistentialType()) {
Explosion outRes;
emitScalarExistentialDowncast(
IGF, instance, sourceLoweredType, targetLoweredType, mode,
/*not a metatype*/ std::nullopt, outRes);
emitScalarExistentialDowncast(IGF, instance, sourceLoweredType,
targetLoweredType, mode,
/*sourceWrappedInOptional*/ false,
/*not a metatype*/ std::nullopt, outRes);
returnNilCheckedResult(IGF.Builder, outRes);
return;
}