/// Emit a checked cast to a protocol or protocol composition.
void irgen::emitScalarExistentialDowncast(IRGenFunction &IGF,
llvm::Value *value,
SILType srcType,
SILType destType,
CheckedCastMode mode,
Optional<MetatypeRepresentation> metatypeKind,
Explosion &ex) {
SmallVector<ProtocolDecl*, 4> allProtos;
destType.getSwiftRValueType().getAnyExistentialTypeProtocols(allProtos);
// Look up witness tables for the protocols that need them and get
// references to the ObjC Protocol* values for the objc protocols.
SmallVector<llvm::Value*, 4> objcProtos;
SmallVector<llvm::Value*, 4> witnessTableProtos;
bool hasClassConstraint = false;
bool hasClassConstraintByProtocol = false;
for (auto proto : allProtos) {
// If the protocol introduces a class constraint, track whether we need
// to check for it independent of protocol witnesses.
if (proto->requiresClass()) {
hasClassConstraint = true;
if (proto->getKnownProtocolKind()
&& *proto->getKnownProtocolKind() == KnownProtocolKind::AnyObject) {
// AnyObject only requires that the type be a class.
continue;
}
// If this protocol is class-constrained but not AnyObject, checking its
// conformance will check the class constraint too.
hasClassConstraintByProtocol = true;
}
if (Lowering::TypeConverter::protocolRequiresWitnessTable(proto)) {
auto descriptor = emitProtocolDescriptorRef(IGF, proto);
witnessTableProtos.push_back(descriptor);
}
if (!proto->isObjC())
continue;
objcProtos.push_back(emitReferenceToObjCProtocol(IGF, proto));
}
llvm::Type *resultType;
if (metatypeKind) {
switch (*metatypeKind) {
case MetatypeRepresentation::Thin:
llvm_unreachable("can't cast to thin metatype");
case MetatypeRepresentation::Thick:
resultType = IGF.IGM.TypeMetadataPtrTy;
break;
case MetatypeRepresentation::ObjC:
resultType = IGF.IGM.ObjCClassPtrTy;
break;
}
} else {
auto schema = IGF.getTypeInfo(destType).getSchema();
resultType = schema[0].getScalarType();
}
// We only need to check the class constraint for metatype casts where
// no protocol conformance indirectly requires the constraint for us.
bool checkClassConstraint =
(bool)metatypeKind && hasClassConstraint && !hasClassConstraintByProtocol;
llvm::Value *resultValue = value;
// If we don't have anything we really need to check, then trivially succeed.
if (objcProtos.empty() && witnessTableProtos.empty() &&
!checkClassConstraint) {
resultValue = IGF.Builder.CreateBitCast(value, resultType);
ex.add(resultValue);
return;
}
// Check the ObjC protocol conformances if there were any.
llvm::Value *objcCast = nullptr;
if (!objcProtos.empty()) {
// Get the ObjC instance or class object to check for these conformances.
llvm::Value *objcObject;
if (metatypeKind) {
switch (*metatypeKind) {
case MetatypeRepresentation::Thin:
llvm_unreachable("can't cast to thin metatype");
case MetatypeRepresentation::Thick: {
// The metadata might be for a non-class type, which wouldn't have
// an ObjC class object.
objcObject = nullptr;
break;
}
case MetatypeRepresentation::ObjC:
// Metatype is already an ObjC object.
objcObject = value;
break;
}
} else {
// Class instance is already an ObjC object.
objcObject = value;
}
if (objcObject)
objcObject = IGF.Builder.CreateBitCast(objcObject,
IGF.IGM.UnknownRefCountedPtrTy);
// Pick the cast function based on the cast mode and on whether we're
// casting a Swift metatype or ObjC object.
llvm::Value *castFn;
switch (mode) {
case CheckedCastMode::Unconditional:
castFn = objcObject
? IGF.IGM.getDynamicCastObjCProtocolUnconditionalFn()
: IGF.IGM.getDynamicCastTypeToObjCProtocolUnconditionalFn();
break;
case CheckedCastMode::Conditional:
castFn = objcObject
? IGF.IGM.getDynamicCastObjCProtocolConditionalFn()
: IGF.IGM.getDynamicCastTypeToObjCProtocolConditionalFn();
break;
}
llvm::Value *objcCastObject = objcObject ? objcObject : value;
Address protoRefsBuf = IGF.createAlloca(
llvm::ArrayType::get(IGF.IGM.Int8PtrTy,
objcProtos.size()),
IGF.IGM.getPointerAlignment(),
"objc_protocols");
protoRefsBuf = IGF.Builder.CreateBitCast(protoRefsBuf,
IGF.IGM.Int8PtrPtrTy);
for (unsigned index : indices(objcProtos)) {
Address protoRefSlot = IGF.Builder.CreateConstArrayGEP(
protoRefsBuf, index,
IGF.IGM.getPointerSize());
IGF.Builder.CreateStore(objcProtos[index], protoRefSlot);
++index;
}
objcCast = IGF.Builder.CreateCall(
castFn,
{objcCastObject, IGF.IGM.getSize(Size(objcProtos.size())),
protoRefsBuf.getAddress()});
resultValue = IGF.Builder.CreateBitCast(objcCast, resultType);
}
// If we don't need to look up any witness tables, we're done.
if (witnessTableProtos.empty() && !checkClassConstraint) {
ex.add(resultValue);
return;
}
// If we're doing a conditional cast, and the ObjC protocol checks failed,
// then the cast is done.
Optional<ConditionalDominanceScope> condition;
llvm::BasicBlock *origBB = nullptr, *successBB = nullptr, *contBB = nullptr;
if (!objcProtos.empty()) {
switch (mode) {
case CheckedCastMode::Unconditional:
break;
case CheckedCastMode::Conditional: {
origBB = IGF.Builder.GetInsertBlock();
successBB = IGF.createBasicBlock("success");
contBB = IGF.createBasicBlock("cont");
auto isNull = IGF.Builder.CreateICmpEQ(objcCast,
llvm::ConstantPointerNull::get(
cast<llvm::PointerType>(objcCast->getType())));
IGF.Builder.CreateCondBr(isNull, contBB, successBB);
IGF.Builder.emitBlock(successBB);
condition.emplace(IGF);
}
}
}
// Get the Swift type metadata for the type.
llvm::Value *metadataValue;
if (metatypeKind) {
switch (*metatypeKind) {
case MetatypeRepresentation::Thin:
llvm_unreachable("can't cast to thin metatype");
case MetatypeRepresentation::Thick:
// The value is already a native metatype.
metadataValue = value;
break;
case MetatypeRepresentation::ObjC:
// Get the type metadata from the ObjC class, which may be a wrapper.
metadataValue = emitObjCMetadataRefForMetadata(IGF, value);
}
} else {
// Get the type metadata for the instance.
metadataValue = emitDynamicTypeOfHeapObject(IGF, value, srcType);
}
// Look up witness tables for the protocols that need them.
auto fn = emitExistentialScalarCastFn(IGF.IGM, witnessTableProtos.size(),
mode, checkClassConstraint);
llvm::SmallVector<llvm::Value *, 4> args;
if (resultValue->getType() != IGF.IGM.Int8PtrTy)
resultValue = IGF.Builder.CreateBitCast(resultValue, IGF.IGM.Int8PtrTy);
args.push_back(resultValue);
args.push_back(metadataValue);
for (auto proto : witnessTableProtos)
args.push_back(proto);
auto valueAndWitnessTables = IGF.Builder.CreateCall(fn, args);
resultValue = IGF.Builder.CreateExtractValue(valueAndWitnessTables, 0);
if (resultValue->getType() != resultType)
resultValue = IGF.Builder.CreateBitCast(resultValue, resultType);
ex.add(resultValue);
for (unsigned i = 0, e = witnessTableProtos.size(); i < e; ++i) {
auto wt = IGF.Builder.CreateExtractValue(valueAndWitnessTables, i + 1);
ex.add(wt);
}
// If we had conditional ObjC checks, join the failure paths.
if (contBB) {
condition.reset();
IGF.Builder.CreateBr(contBB);
IGF.Builder.emitBlock(contBB);
// Return null on the failure path.
Explosion successEx = std::move(ex);
ex.reset();
while (!successEx.empty()) {
auto successVal = successEx.claimNext();
auto failureVal = llvm::Constant::getNullValue(successVal->getType());
auto phi = IGF.Builder.CreatePHI(successVal->getType(), 2);
phi->addIncoming(successVal, successBB);
phi->addIncoming(failureVal, origBB);
ex.add(phi);
}
}
}
/// Emit a checked cast to a protocol or protocol composition.
void irgen::emitScalarExistentialDowncast(IRGenFunction &IGF,
llvm::Value *value,
SILType srcType,
SILType destType,
CheckedCastMode mode,
Optional<MetatypeRepresentation> metatypeKind,
Explosion &ex) {
auto srcInstanceType = srcType.getSwiftRValueType();
auto destInstanceType = destType.getSwiftRValueType();
while (auto metatypeType = dyn_cast<ExistentialMetatypeType>(
destInstanceType)) {
destInstanceType = metatypeType.getInstanceType();
srcInstanceType = cast<AnyMetatypeType>(srcInstanceType).getInstanceType();
}
auto layout = destInstanceType.getExistentialLayout();
// Look up witness tables for the protocols that need them and get
// references to the ObjC Protocol* values for the objc protocols.
SmallVector<llvm::Value*, 4> objcProtos;
SmallVector<llvm::Value*, 4> witnessTableProtos;
bool hasClassConstraint = layout.requiresClass();
bool hasClassConstraintByProtocol = false;
bool hasSuperclassConstraint = bool(layout.superclass);
for (auto protoTy : layout.getProtocols()) {
auto *protoDecl = protoTy->getDecl();
// If the protocol introduces a class constraint, track whether we need
// to check for it independent of protocol witnesses.
if (protoDecl->requiresClass()) {
assert(hasClassConstraint);
hasClassConstraintByProtocol = true;
}
if (Lowering::TypeConverter::protocolRequiresWitnessTable(protoDecl)) {
auto descriptor = emitProtocolDescriptorRef(IGF, protoDecl);
witnessTableProtos.push_back(descriptor);
}
if (protoDecl->isObjC())
objcProtos.push_back(emitReferenceToObjCProtocol(IGF, protoDecl));
}
llvm::Type *resultType;
if (metatypeKind) {
switch (*metatypeKind) {
case MetatypeRepresentation::Thin:
llvm_unreachable("can't cast to thin metatype");
case MetatypeRepresentation::Thick:
resultType = IGF.IGM.TypeMetadataPtrTy;
break;
case MetatypeRepresentation::ObjC:
resultType = IGF.IGM.ObjCClassPtrTy;
break;
}
} else {
auto schema = IGF.getTypeInfo(destType).getSchema();
resultType = schema[0].getScalarType();
}
// The source of a scalar cast is statically known to be a class or a
// metatype, so we only have to check the class constraint in two cases:
//
// 1) The destination type has an explicit superclass constraint that is
// more derived than what the source type is known to be.
//
// 2) We are casting between metatypes, in which case the source might
// be a non-class metatype.
bool checkClassConstraint = false;
if ((bool)metatypeKind &&
hasClassConstraint &&
!hasClassConstraintByProtocol &&
!srcInstanceType->mayHaveSuperclass())
checkClassConstraint = true;
// If the source has an equal or more derived superclass constraint than
// the destination, we can elide the superclass check.
//
// Note that destInstanceType is always an existential type, so calling
// getSuperclass() returns the superclass constraint of the existential,
// not the superclass of some concrete class.
bool checkSuperclassConstraint =
hasSuperclassConstraint &&
!destInstanceType->getSuperclass()->isExactSuperclassOf(srcInstanceType);
if (checkSuperclassConstraint)
checkClassConstraint = true;
llvm::Value *resultValue = value;
// If we don't have anything we really need to check, then trivially succeed.
if (objcProtos.empty() && witnessTableProtos.empty() &&
!checkClassConstraint) {
resultValue = IGF.Builder.CreateBitCast(value, resultType);
ex.add(resultValue);
return;
}
// Check the ObjC protocol conformances if there were any.
llvm::Value *objcCast = nullptr;
if (!objcProtos.empty()) {
// Get the ObjC instance or class object to check for these conformances.
llvm::Value *objcObject;
if (metatypeKind) {
switch (*metatypeKind) {
case MetatypeRepresentation::Thin:
llvm_unreachable("can't cast to thin metatype");
case MetatypeRepresentation::Thick: {
// The metadata might be for a non-class type, which wouldn't have
// an ObjC class object.
objcObject = nullptr;
break;
}
case MetatypeRepresentation::ObjC:
// Metatype is already an ObjC object.
objcObject = value;
break;
}
} else {
// Class instance is already an ObjC object.
objcObject = value;
}
if (objcObject)
objcObject = IGF.Builder.CreateBitCast(objcObject,
IGF.IGM.UnknownRefCountedPtrTy);
// Pick the cast function based on the cast mode and on whether we're
// casting a Swift metatype or ObjC object.
llvm::Constant *castFn;
switch (mode) {
case CheckedCastMode::Unconditional:
castFn = objcObject
? IGF.IGM.getDynamicCastObjCProtocolUnconditionalFn()
: IGF.IGM.getDynamicCastTypeToObjCProtocolUnconditionalFn();
break;
case CheckedCastMode::Conditional:
castFn = objcObject
? IGF.IGM.getDynamicCastObjCProtocolConditionalFn()
: IGF.IGM.getDynamicCastTypeToObjCProtocolConditionalFn();
break;
}
llvm::Value *objcCastObject = objcObject ? objcObject : value;
Address protoRefsBuf = IGF.createAlloca(
llvm::ArrayType::get(IGF.IGM.Int8PtrTy,
objcProtos.size()),
IGF.IGM.getPointerAlignment(),
"objc_protocols");
protoRefsBuf = IGF.Builder.CreateBitCast(protoRefsBuf,
IGF.IGM.Int8PtrPtrTy);
for (unsigned index : indices(objcProtos)) {
Address protoRefSlot = IGF.Builder.CreateConstArrayGEP(
protoRefsBuf, index,
IGF.IGM.getPointerSize());
IGF.Builder.CreateStore(objcProtos[index], protoRefSlot);
++index;
}
auto cc = IGF.IGM.DefaultCC;
if (auto fun = dyn_cast<llvm::Function>(castFn))
cc = fun->getCallingConv();
auto call = IGF.Builder.CreateCall(
castFn,
{objcCastObject, IGF.IGM.getSize(Size(objcProtos.size())),
protoRefsBuf.getAddress()});
call->setCallingConv(cc);
objcCast = call;
resultValue = IGF.Builder.CreateBitCast(objcCast, resultType);
}
// If we don't need to look up any witness tables, we're done.
if (witnessTableProtos.empty() && !checkClassConstraint) {
ex.add(resultValue);
return;
}
// If we're doing a conditional cast, and the ObjC protocol checks failed,
// then the cast is done.
Optional<ConditionalDominanceScope> condition;
llvm::BasicBlock *origBB = nullptr, *successBB = nullptr, *contBB = nullptr;
if (!objcProtos.empty()) {
switch (mode) {
case CheckedCastMode::Unconditional:
break;
case CheckedCastMode::Conditional: {
origBB = IGF.Builder.GetInsertBlock();
successBB = IGF.createBasicBlock("success");
contBB = IGF.createBasicBlock("cont");
auto isNull = IGF.Builder.CreateICmpEQ(objcCast,
llvm::ConstantPointerNull::get(
cast<llvm::PointerType>(objcCast->getType())));
IGF.Builder.CreateCondBr(isNull, contBB, successBB);
IGF.Builder.emitBlock(successBB);
condition.emplace(IGF);
}
}
}
// Get the Swift type metadata for the type.
llvm::Value *metadataValue;
if (metatypeKind) {
switch (*metatypeKind) {
case MetatypeRepresentation::Thin:
llvm_unreachable("can't cast to thin metatype");
case MetatypeRepresentation::Thick:
// The value is already a native metatype.
metadataValue = value;
break;
case MetatypeRepresentation::ObjC:
// Get the type metadata from the ObjC class, which may be a wrapper.
metadataValue = emitObjCMetadataRefForMetadata(IGF, value);
}
} else {
// Get the type metadata for the instance.
metadataValue = emitDynamicTypeOfHeapObject(IGF, value, srcType);
}
// Look up witness tables for the protocols that need them.
auto fn = emitExistentialScalarCastFn(IGF.IGM,
witnessTableProtos.size(),
mode,
checkClassConstraint,
checkSuperclassConstraint);
llvm::SmallVector<llvm::Value *, 4> args;
if (resultValue->getType() != IGF.IGM.Int8PtrTy)
resultValue = IGF.Builder.CreateBitCast(resultValue, IGF.IGM.Int8PtrTy);
args.push_back(resultValue);
args.push_back(metadataValue);
if (checkSuperclassConstraint)
args.push_back(IGF.emitTypeMetadataRef(CanType(layout.superclass)));
for (auto proto : witnessTableProtos)
args.push_back(proto);
auto valueAndWitnessTables = IGF.Builder.CreateCall(fn, args);
resultValue = IGF.Builder.CreateExtractValue(valueAndWitnessTables, 0);
if (resultValue->getType() != resultType)
resultValue = IGF.Builder.CreateBitCast(resultValue, resultType);
ex.add(resultValue);
for (unsigned i = 0, e = witnessTableProtos.size(); i < e; ++i) {
auto wt = IGF.Builder.CreateExtractValue(valueAndWitnessTables, i + 1);
ex.add(wt);
}
// If we had conditional ObjC checks, join the failure paths.
if (contBB) {
condition.reset();
IGF.Builder.CreateBr(contBB);
IGF.Builder.emitBlock(contBB);
// Return null on the failure path.
Explosion successEx = std::move(ex);
ex.reset();
while (!successEx.empty()) {
auto successVal = successEx.claimNext();
auto failureVal = llvm::Constant::getNullValue(successVal->getType());
auto phi = IGF.Builder.CreatePHI(successVal->getType(), 2);
phi->addIncoming(successVal, successBB);
phi->addIncoming(failureVal, origBB);
ex.add(phi);
}
}
}
