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Fix casts involving the 'Self' type #28401

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Merged
merged 2 commits into from
Dec 3, 2019
Merged

Fix casts involving the 'Self' type #28401

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efe4883
SILOptimizer: Fix to deal with casts involving dynamic Self
slavapestov Nov 21, 2019
c8da158
IRGen: Correctly use formal type for class downcasts
slavapestov Nov 21, 2019
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74 changes: 43 additions & 31 deletions lib/IRGen/GenCast.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -164,7 +164,7 @@ getDynamicCastArguments(IRGenFunction &IGF,

/// Emit a checked unconditional downcast of a class value.
llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,
SILType toType, CheckedCastMode mode) {
CanType toType, CheckedCastMode mode) {
// Emit the value we're casting from.
if (from->getType() != IGF.IGM.Int8PtrTy)
from = IGF.Builder.CreateBitOrPointerCast(from, IGF.IGM.Int8PtrTy);
Expand All @@ -174,11 +174,19 @@ llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,
llvm::Value *metadataRef;
llvm::Constant *castFn;

// If true, the target class is not known at compile time because it is a
// class-bounded archetype or the dynamic Self type.
bool nonSpecificClass = false;

// Get the best known type information about the destination type.
ClassDecl *destClass = nullptr;
if (auto archetypeTy = toType.getAs<ArchetypeType>()) {
if (auto archetypeTy = dyn_cast<ArchetypeType>(toType)) {
nonSpecificClass = true;
if (auto superclassTy = archetypeTy->getSuperclass())
destClass = superclassTy->getClassOrBoundGenericClass();
} else if (auto selfTy = dyn_cast<DynamicSelfType>(toType)) {
nonSpecificClass = true;
destClass = selfTy->getSelfType()->getClassOrBoundGenericClass();
} else {
destClass = toType.getClassOrBoundGenericClass();
assert(destClass != nullptr);
Expand All @@ -187,7 +195,7 @@ llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,
// If the destination type is known to have a Swift-compatible
// implementation, use the most specific entrypoint.
if (destClass && destClass->hasKnownSwiftImplementation()) {
metadataRef = IGF.emitTypeMetadataRef(toType.getASTType());
metadataRef = IGF.emitTypeMetadataRef(toType);

switch (mode) {
case CheckedCastMode::Unconditional:
Expand All @@ -200,9 +208,9 @@ llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,

// If the destination type is a CF type or a non-specific
// class-bounded archetype, use the most general cast entrypoint.
} else if (toType.is<ArchetypeType>() ||
} else if (nonSpecificClass ||
destClass->getForeignClassKind()==ClassDecl::ForeignKind::CFType) {
metadataRef = IGF.emitTypeMetadataRef(toType.getASTType());
metadataRef = IGF.emitTypeMetadataRef(toType);

switch (mode) {
case CheckedCastMode::Unconditional:
Expand Down Expand Up @@ -249,7 +257,7 @@ llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,
call->setCallingConv(cc);
call->setDoesNotThrow();

llvm::Type *subTy = IGF.getTypeInfo(toType).getStorageType();
llvm::Type *subTy = IGF.getTypeInfoForUnlowered(toType).getStorageType();
return IGF.Builder.CreateBitCast(call, subTy);
}

Expand Down Expand Up @@ -871,12 +879,14 @@ void irgen::emitScalarExistentialDowncast(IRGenFunction &IGF,
/// isn't exposed.
void irgen::emitScalarCheckedCast(IRGenFunction &IGF,
Explosion &value,
SILType sourceType,
SILType targetType,
SILType sourceLoweredType,
CanType sourceFormalType,
SILType targetLoweredType,
CanType targetFormalType,
CheckedCastMode mode,
Explosion &out) {
assert(sourceType.isObject());
assert(targetType.isObject());
assert(sourceLoweredType.isObject());
assert(targetLoweredType.isObject());

llvm::BasicBlock *nilCheckBB = nullptr;
llvm::BasicBlock *nilMergeBB = nullptr;
Expand Down Expand Up @@ -906,22 +916,23 @@ void irgen::emitScalarCheckedCast(IRGenFunction &IGF,
}
};

if (auto sourceOptObjectType = sourceType.getOptionalObjectType()) {
if (auto sourceOptObjectType = sourceLoweredType.getOptionalObjectType()) {
// Translate the value from an enum representation to a possibly-null
// representation. Note that we assume that this projection is safe
// for the particular case of an optional class-reference or metatype
// value.
Explosion optValue;
auto someDecl = IGF.IGM.Context.getOptionalSomeDecl();
emitProjectLoadableEnum(IGF, sourceType, value, someDecl, optValue);
emitProjectLoadableEnum(IGF, sourceLoweredType, value, someDecl, optValue);

assert(value.empty());
value = std::move(optValue);
sourceType = sourceOptObjectType;
sourceLoweredType = sourceOptObjectType;
sourceFormalType = sourceFormalType.getOptionalObjectType();

// We need a null-check because the runtime function can't handle null in
// some of the cases.
if (targetType.isExistentialType()) {
if (targetLoweredType.isExistentialType()) {
auto &Builder = IGF.Builder;
auto val = value.getAll()[0];
auto isNotNil = Builder.CreateICmpNE(
Expand All @@ -938,7 +949,7 @@ void irgen::emitScalarCheckedCast(IRGenFunction &IGF,

// If the source value is a metatype, either do a metatype-to-metatype
// cast or cast it to an object instance and continue.
if (auto sourceMetatype = sourceType.getAs<AnyMetatypeType>()) {
if (auto sourceMetatype = sourceLoweredType.getAs<AnyMetatypeType>()) {
llvm::Value *metatypeVal = nullptr;
if (sourceMetatype->getRepresentation() != MetatypeRepresentation::Thin)
metatypeVal = value.claimNext();
Expand All @@ -952,60 +963,61 @@ void irgen::emitScalarCheckedCast(IRGenFunction &IGF,
SmallVector<ProtocolDecl*, 1> protocols;

// Casts to existential metatypes.
if (auto existential = targetType.getAs<ExistentialMetatypeType>()) {
emitScalarExistentialDowncast(IGF, metatypeVal, sourceType, targetType,
mode, existential->getRepresentation(),
if (auto existential = targetLoweredType.getAs<ExistentialMetatypeType>()) {
emitScalarExistentialDowncast(IGF, metatypeVal, sourceLoweredType,
targetLoweredType, mode,
existential->getRepresentation(),
out);
return;

// Casts to concrete metatypes.
} else if (auto destMetaType = targetType.getAs<MetatypeType>()) {
} else if (auto destMetaType = targetLoweredType.getAs<MetatypeType>()) {
emitMetatypeDowncast(IGF, metatypeVal, destMetaType, mode, out);
return;
}

// Otherwise, this is a metatype-to-object cast.
assert(targetType.isAnyClassReferenceType());
assert(targetLoweredType.isAnyClassReferenceType());

// Convert the metatype value to AnyObject.
llvm::Value *object =
emitMetatypeToAnyObjectDowncast(IGF, metatypeVal, sourceMetatype, mode);

SILType anyObjectType =
SILType::getPrimitiveObjectType(
IGF.IGM.Context.getAnyObjectType());
sourceFormalType = IGF.IGM.Context.getAnyObjectType();
sourceLoweredType = SILType::getPrimitiveObjectType(sourceFormalType);

// Continue, pretending that the source value was an (optional) value.
Explosion newValue;
newValue.add(object);
value = std::move(newValue);
sourceType = anyObjectType;
}

assert(!targetType.is<AnyMetatypeType>() &&
assert(!targetLoweredType.is<AnyMetatypeType>() &&
"scalar cast of class reference to metatype is unimplemented");

// If the source type is existential, project out the class pointer.
//
// TODO: if we're casting to an existential type, don't throw away the
// protocol conformance information we already have.
llvm::Value *instance;
if (sourceType.isExistentialType()) {
instance = emitClassExistentialProjection(IGF, value, sourceType,
if (sourceLoweredType.isExistentialType()) {
instance = emitClassExistentialProjection(IGF, value, sourceLoweredType,
CanArchetypeType());
} else {
instance = value.claimNext();
}

if (targetType.isExistentialType()) {
if (targetFormalType.isExistentialType()) {
Explosion outRes;
emitScalarExistentialDowncast(IGF, instance, sourceType, targetType,
mode, /*not a metatype*/ None, outRes);
emitScalarExistentialDowncast(IGF, instance, sourceLoweredType,
targetLoweredType, mode,
/*not a metatype*/ None, outRes);
returnNilCheckedResult(IGF.Builder, outRes);
return;
}

Explosion outRes;
llvm::Value *result = emitClassDowncast(IGF, instance, targetType, mode);
llvm::Value *result = emitClassDowncast(IGF, instance, targetFormalType,
mode);
out.add(result);
}
9 changes: 5 additions & 4 deletions lib/IRGen/GenCast.h
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Original file line number Diff line number Diff line change
Expand Up @@ -48,16 +48,17 @@ namespace irgen {
CheckedCastMode mode);

void emitScalarCheckedCast(IRGenFunction &IGF, Explosion &value,
SILType valueType, SILType loweredTargetType,
SILType sourceLoweredType,
CanType sourceFormalType,
SILType targetLoweredType,
CanType targetFormalType,
CheckedCastMode mode, Explosion &out);

/// Convert a class object to the given destination type,
/// using a runtime-checked cast.
///
/// FIXME: toType should be an AST CanType.
llvm::Value *emitClassDowncast(IRGenFunction &IGF,
llvm::Value *from,
SILType toType,
CanType toType,
CheckedCastMode mode);

/// A result of a cast generation function.
Expand Down
13 changes: 9 additions & 4 deletions lib/IRGen/IRGenSIL.cpp
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Expand Up @@ -4834,7 +4834,11 @@ void IRGenSILFunction::visitUnconditionalCheckedCastInst(
swift::UnconditionalCheckedCastInst *i) {
Explosion value = getLoweredExplosion(i->getOperand());
Explosion ex;
emitScalarCheckedCast(*this, value, i->getOperand()->getType(), i->getType(),
emitScalarCheckedCast(*this, value,
i->getSourceLoweredType(),
i->getSourceFormalType(),
i->getTargetLoweredType(),
i->getTargetFormalType(),
CheckedCastMode::Unconditional, ex);
setLoweredExplosion(i, ex);
}
Expand Down Expand Up @@ -5038,20 +5042,21 @@ void IRGenSILFunction::visitCheckedCastValueBranchInst(

void IRGenSILFunction::visitCheckedCastBranchInst(
swift::CheckedCastBranchInst *i) {
SILType destTy = i->getTargetLoweredType();
FailableCastResult castResult;
Explosion ex;
if (i->isExact()) {
auto operand = i->getOperand();
Explosion source = getLoweredExplosion(operand);
castResult = emitClassIdenticalCast(*this, source.claimNext(),
i->getSourceLoweredType(),
destTy);
i->getTargetLoweredType());
} else {
Explosion value = getLoweredExplosion(i->getOperand());
emitScalarCheckedCast(*this, value,
i->getSourceLoweredType(),
i->getSourceFormalType(),
i->getTargetLoweredType(),
i->getTargetFormalType(),
CheckedCastMode::Conditional, ex);
auto val = ex.claimNext();
castResult.casted = val;
Expand All @@ -5065,7 +5070,7 @@ void IRGenSILFunction::visitCheckedCastBranchInst(


auto &successBB = getLoweredBB(i->getSuccessBB());
llvm::Type *toTy = IGM.getTypeInfo(destTy).getStorageType();
llvm::Type *toTy = IGM.getTypeInfo(i->getTargetLoweredType()).getStorageType();
if (toTy->isPointerTy())
castResult.casted = Builder.CreateBitCast(castResult.casted, toTy);

Expand Down
10 changes: 3 additions & 7 deletions lib/SILOptimizer/Transforms/DeadCodeElimination.cpp
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Expand Up @@ -400,22 +400,18 @@ void DCE::propagateLiveness(SILInstruction *I) {
case TermKind::SwitchEnumInst:
case TermKind::SwitchEnumAddrInst:
case TermKind::DynamicMethodBranchInst:
case TermKind::CheckedCastBranchInst:
case TermKind::CheckedCastValueBranchInst:
markValueLive(I->getOperand(0));
return;

case TermKind::CheckedCastBranchInst:
case TermKind::CheckedCastValueBranchInst:
case TermKind::CheckedCastAddrBranchInst:
case TermKind::TryApplyInst:
case TermKind::SwitchValueInst:
case TermKind::YieldInst:
for (auto &O : I->getAllOperands())
markValueLive(O.get());
return;

case TermKind::CheckedCastAddrBranchInst:
markValueLive(I->getOperand(0));
markValueLive(I->getOperand(1));
return;
}
llvm_unreachable("corrupt instruction!");
}
Expand Down
13 changes: 5 additions & 8 deletions lib/SILOptimizer/Utils/CastOptimizer.cpp
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Expand Up @@ -997,6 +997,9 @@ CastOptimizer::simplifyCheckedCastBranchInst(CheckedCastBranchInst *Inst) {
// Check if we can statically predict the outcome of the cast.
auto Feasibility =
dynamicCast.classifyFeasibility(false /*allow whole module*/);
if (Feasibility == DynamicCastFeasibility::MaySucceed) {
return nullptr;
}

SILBuilderWithScope Builder(Inst, builderContext);
if (Feasibility == DynamicCastFeasibility::WillFail) {
Expand All @@ -1009,6 +1012,8 @@ CastOptimizer::simplifyCheckedCastBranchInst(CheckedCastBranchInst *Inst) {
return NewI;
}

assert(Feasibility == DynamicCastFeasibility::WillSucceed);

bool ResultNotUsed = SuccessBB->getArgument(0)->use_empty();
SILValue CastedValue;
if (Op->getType() != TargetLoweredType) {
Expand All @@ -1022,14 +1027,6 @@ CastOptimizer::simplifyCheckedCastBranchInst(CheckedCastBranchInst *Inst) {
llvm_unreachable(
"Bridged casts cannot be expressed by checked_cast_br yet");
} else {
// If the cast may succeed or fail and can't be turned into a bridging
// call, then let it be.
if (Feasibility == DynamicCastFeasibility::MaySucceed) {
return nullptr;
}

assert(Feasibility == DynamicCastFeasibility::WillSucceed);

// Replace by unconditional_cast, followed by a branch.
// The unconditional_cast can be skipped, if the result of a cast
// is not used afterwards.
Expand Down
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