void ClassHierarchyAnalysis::init() {
// Process all types implementing protocols.
SmallVector<Decl *, 32> Decls;
// TODO: It would be better if we could get all declarations
// from a given module, not only the top-level ones.
M->getSwiftModule()->getTopLevelDecls(Decls);
NominalTypeWalker Walker(ProtocolImplementationsCache);
for (auto *D: Decls) {
D->walk(Walker);
}
// For each class declaration in our V-table list:
for (auto &VT : M->getVTableList()) {
ClassDecl *C = VT.getClass();
// Ignore classes that are at the top of the class hierarchy:
if (!C->hasSuperclass())
continue;
// Add the superclass to the list of inherited classes.
ClassDecl *Super = C->getSuperclass()->getClassOrBoundGenericClass();
auto &K = DirectSubclassesCache[Super];
assert(std::find(K.begin(), K.end(), C) == K.end() &&
"Class vector must be unique");
K.push_back(C);
}
}
// Analyzing the body of this class destructor is valid because the object is
// dead. This means that the object is never passed to objc_setAssociatedObject,
// so its destructor cannot be extended at runtime.
static SILFunction *getDestructor(AllocRefInst *ARI) {
// We only support classes.
ClassDecl *ClsDecl = ARI->getType().getClassOrBoundGenericClass();
if (!ClsDecl)
return nullptr;
// Look up the destructor of ClsDecl.
DestructorDecl *Destructor = ClsDecl->getDestructor();
assert(Destructor && "getDestructor() should never return a nullptr.");
// Find the destructor name via SILDeclRef.
// FIXME: When destructors get moved into vtables, update this to use the
// vtable for the class.
SILDeclRef Ref(Destructor);
SILFunction *Fn = ARI->getModule().lookUpFunction(Ref);
if (!Fn || Fn->empty()) {
DEBUG(llvm::dbgs() << " Could not find destructor.\n");
return nullptr;
}
DEBUG(llvm::dbgs() << " Found destructor!\n");
// If the destructor has an objc_method calling convention, we cannot
// analyze it since it could be swapped out from under us at runtime.
if (Fn->getRepresentation() == SILFunctionTypeRepresentation::ObjCMethod) {
DEBUG(llvm::dbgs() << " Found objective-c destructor. Can't "
"analyze!\n");
return nullptr;
}
return Fn;
}
void SILGenFunction::emitDestroyingDestructor(DestructorDecl *dd) {
MagicFunctionName = DeclName(SGM.M.getASTContext().getIdentifier("deinit"));
RegularLocation Loc(dd);
if (dd->isImplicit())
Loc.markAutoGenerated();
auto cd = cast<ClassDecl>(dd->getDeclContext());
SILValue selfValue = emitSelfDecl(dd->getImplicitSelfDecl());
// Create a basic block to jump to for the implicit destruction behavior
// of releasing the elements and calling the superclass destructor.
// We won't actually emit the block until we finish with the destructor body.
prepareEpilog(Type(), false, CleanupLocation::get(Loc));
emitProfilerIncrement(dd->getBody());
// Emit the destructor body.
emitStmt(dd->getBody());
Optional<SILValue> maybeReturnValue;
SILLocation returnLoc(Loc);
std::tie(maybeReturnValue, returnLoc) = emitEpilogBB(Loc);
if (!maybeReturnValue)
return;
auto cleanupLoc = CleanupLocation::get(Loc);
// If we have a superclass, invoke its destructor.
SILValue resultSelfValue;
SILType objectPtrTy = SILType::getNativeObjectType(F.getASTContext());
if (cd->hasSuperclass()) {
Type superclassTy
= ArchetypeBuilder::mapTypeIntoContext(dd, cd->getSuperclass());
ClassDecl *superclass = superclassTy->getClassOrBoundGenericClass();
auto superclassDtorDecl = superclass->getDestructor();
SILDeclRef dtorConstant =
SILDeclRef(superclassDtorDecl, SILDeclRef::Kind::Destroyer);
SILType baseSILTy = getLoweredLoadableType(superclassTy);
SILValue baseSelf = B.createUpcast(cleanupLoc, selfValue, baseSILTy);
ManagedValue dtorValue;
SILType dtorTy;
ArrayRef<Substitution> subs
= superclassTy->gatherAllSubstitutions(SGM.M.getSwiftModule(), nullptr);
std::tie(dtorValue, dtorTy, subs)
= emitSiblingMethodRef(cleanupLoc, baseSelf, dtorConstant, subs);
resultSelfValue = B.createApply(cleanupLoc, dtorValue.forward(*this),
dtorTy, objectPtrTy, subs, baseSelf);
} else {
resultSelfValue = B.createUncheckedRefCast(cleanupLoc, selfValue,
objectPtrTy);
}
// Release our members.
emitClassMemberDestruction(selfValue, cd, cleanupLoc);
B.createReturn(returnLoc, resultSelfValue);
}
// Wrapper function to findSoleConformingType that checks for additional
// constraints for classes using ClassHierarchyAnalysis.
bool ProtocolConformanceAnalysis::getSoleConformingType(
ProtocolDecl *Protocol, ClassHierarchyAnalysis *CHA, CanType &ConcreteType) {
// Determine the sole conforming type.
auto *NTD = findSoleConformingType(Protocol);
if (!NTD)
return false;
// Sole conforming class should not be open access or have any derived class.
ClassDecl *CD;
if ((CD = dyn_cast<ClassDecl>(NTD)) &&
(CD->getEffectiveAccess() == AccessLevel::Open ||
CHA->hasKnownDirectSubclasses(CD))) {
return false;
}
// Save the concrete type.
ConcreteType = NTD->getDeclaredType()->getCanonicalType();
return true;
}
void addMethod(SILDeclRef method) {
assert(method.getDecl()->getDeclContext() == CD);
if (CD->hasResilientMetadata()) {
if (FirstTime) {
FirstTime = false;
// If the class is itself resilient and has at least one vtable entry,
// it has a method lookup function.
TBD.addSymbol(LinkEntity::forMethodLookupFunction(CD));
}
TBD.addDispatchThunk(method);
}
TBD.addMethodDescriptor(method);
}
void layout() override {
PrettyStackTraceDecl DebugStack("emitting superclass metadata",
Class);
auto *M = IGM.getSILModule().getSwiftModule();
addTypeRef(M, Class->getDeclaredType()->getCanonicalType());
auto anyObjectDecl = IGM.Context.getProtocol(KnownProtocolKind::AnyObject);
addTypeRef(M, anyObjectDecl->getDeclaredType()->getCanonicalType());
addConstantInt32(1);
addConstantInt32(AssociatedTypeRecordSize);
auto NameGlobal = IGM.getAddrOfStringForTypeRef("super");
addRelativeAddress(NameGlobal);
addTypeRef(M, Superclass);
}
void SILGenFunction::emitObjCDestructor(SILDeclRef dtor) {
auto dd = cast<DestructorDecl>(dtor.getDecl());
auto cd = cast<ClassDecl>(dd->getDeclContext());
MagicFunctionName = DeclName(SGM.M.getASTContext().getIdentifier("deinit"));
RegularLocation loc(dd);
if (dd->isImplicit())
loc.markAutoGenerated();
SILValue selfValue = emitSelfDecl(dd->getImplicitSelfDecl());
// Create a basic block to jump to for the implicit destruction behavior
// of releasing the elements and calling the superclass destructor.
// We won't actually emit the block until we finish with the destructor body.
prepareEpilog(Type(), false, CleanupLocation::get(loc));
// Emit the destructor body.
emitStmt(dd->getBody());
Optional<SILValue> maybeReturnValue;
SILLocation returnLoc(loc);
std::tie(maybeReturnValue, returnLoc) = emitEpilogBB(loc);
if (!maybeReturnValue)
return;
auto cleanupLoc = CleanupLocation::get(loc);
// Note: the ivar destroyer is responsible for destroying the
// instance variables before the object is actually deallocated.
// Form a reference to the superclass -dealloc.
Type superclassTy = dd->mapTypeIntoContext(cd->getSuperclass());
assert(superclassTy && "Emitting Objective-C -dealloc without superclass?");
ClassDecl *superclass = superclassTy->getClassOrBoundGenericClass();
auto superclassDtorDecl = superclass->getDestructor();
SILDeclRef superclassDtor(superclassDtorDecl,
SILDeclRef::Kind::Deallocator,
SILDeclRef::ConstructAtBestResilienceExpansion,
SILDeclRef::ConstructAtNaturalUncurryLevel,
/*isForeign=*/true);
auto superclassDtorType = SGM.getConstantType(superclassDtor);
SILValue superclassDtorValue = B.createSuperMethod(
cleanupLoc, selfValue, superclassDtor,
superclassDtorType);
// Call the superclass's -dealloc.
SILType superclassSILTy = getLoweredLoadableType(superclassTy);
SILValue superSelf = B.createUpcast(cleanupLoc, selfValue, superclassSILTy);
ArrayRef<Substitution> subs
= superclassTy->gatherAllSubstitutions(SGM.M.getSwiftModule(), nullptr);
auto substDtorType = superclassDtorType.castTo<SILFunctionType>()
->substGenericArgs(SGM.M, subs);
SILFunctionConventions dtorConv(substDtorType, SGM.M);
B.createApply(cleanupLoc, superclassDtorValue,
SILType::getPrimitiveObjectType(substDtorType),
dtorConv.getSILResultType(), subs, superSelf);
// Return.
B.createReturn(returnLoc, emitEmptyTuple(cleanupLoc));
}
static void lookupVisibleMemberDeclsImpl(
Type BaseTy, VisibleDeclConsumer &Consumer, const DeclContext *CurrDC,
LookupState LS, DeclVisibilityKind Reason, LazyResolver *TypeResolver,
VisitedSet &Visited) {
// Just look through l-valueness. It doesn't affect name lookup.
assert(BaseTy && "lookup into null type");
BaseTy = BaseTy->getRValueType();
// Handle metatype references, as in "some_type.some_member". These are
// special and can't have extensions.
if (auto MTT = BaseTy->getAs<AnyMetatypeType>()) {
// The metatype represents an arbitrary named type: dig through to the
// declared type to see what we're dealing with.
Type Ty = MTT->getInstanceType();
// Just perform normal dot lookup on the type see if we find extensions or
// anything else. For example, type SomeTy.SomeMember can look up static
// functions, and can even look up non-static functions as well (thus
// getting the address of the member).
lookupVisibleMemberDeclsImpl(Ty, Consumer, CurrDC,
LookupState::makeQualified().withOnMetatype(),
Reason, TypeResolver, Visited);
return;
}
// Lookup module references, as on some_module.some_member. These are
// special and can't have extensions.
if (ModuleType *MT = BaseTy->getAs<ModuleType>()) {
AccessFilteringDeclConsumer FilteringConsumer(CurrDC, Consumer,
TypeResolver);
MT->getModule()->lookupVisibleDecls(Module::AccessPathTy(),
FilteringConsumer,
NLKind::QualifiedLookup);
return;
}
// If the base is a protocol, enumerate its members.
if (ProtocolType *PT = BaseTy->getAs<ProtocolType>()) {
lookupVisibleProtocolMemberDecls(BaseTy, PT, Consumer, CurrDC, LS, Reason,
TypeResolver, Visited);
return;
}
// If the base is a protocol composition, enumerate members of the protocols.
if (auto PC = BaseTy->getAs<ProtocolCompositionType>()) {
for (auto Proto : PC->getProtocols())
lookupVisibleMemberDeclsImpl(Proto, Consumer, CurrDC, LS, Reason,
TypeResolver, Visited);
return;
}
// Enumerate members of archetype's requirements.
if (ArchetypeType *Archetype = BaseTy->getAs<ArchetypeType>()) {
for (auto Proto : Archetype->getConformsTo())
lookupVisibleProtocolMemberDecls(
BaseTy, Proto->getDeclaredType(), Consumer, CurrDC, LS,
getReasonForSuper(Reason), TypeResolver, Visited);
if (auto superclass = Archetype->getSuperclass())
lookupVisibleMemberDeclsImpl(superclass, Consumer, CurrDC, LS,
getReasonForSuper(Reason), TypeResolver,
Visited);
return;
}
do {
NominalTypeDecl *CurNominal = BaseTy->getAnyNominal();
if (!CurNominal)
break;
// Look in for members of a nominal type.
lookupTypeMembers(BaseTy, BaseTy, Consumer, CurrDC, LS, Reason,
TypeResolver);
lookupDeclsFromProtocolsBeingConformedTo(BaseTy, Consumer, LS, CurrDC,
Reason, TypeResolver, Visited);
// If we have a class type, look into its superclass.
ClassDecl *CurClass = dyn_cast<ClassDecl>(CurNominal);
if (CurClass && CurClass->hasSuperclass()) {
assert(BaseTy.getPointer() != CurClass->getSuperclass().getPointer() &&
"type is its own superclass");
BaseTy = CurClass->getSuperclass();
Reason = getReasonForSuper(Reason);
bool InheritsSuperclassInitializers =
CurClass->inheritsSuperclassInitializers(TypeResolver);
if (LS.isOnSuperclass() && !InheritsSuperclassInitializers)
LS = LS.withoutInheritsSuperclassInitializers();
else if (!LS.isOnSuperclass()) {
LS = LS.withOnSuperclass();
if (InheritsSuperclassInitializers)
LS = LS.withInheritsSuperclassInitializers();
}
} else {
break;
}
} while (1);
}
/// \brief Try to speculate the call target for the call \p AI. This function
/// returns true if a change was made.
static bool tryToSpeculateTarget(FullApplySite AI,
ClassHierarchyAnalysis *CHA) {
ClassMethodInst *CMI = cast<ClassMethodInst>(AI.getCallee());
// We cannot devirtualize in cases where dynamic calls are
// semantically required.
if (CMI->isVolatile())
return false;
// Strip any upcasts off of our 'self' value, potentially leaving us
// with a value whose type is closer (in the class hierarchy) to the
// actual dynamic type.
auto SubTypeValue = CMI->getOperand().stripUpCasts();
SILType SubType = SubTypeValue.getType();
// Bail if any generic types parameters of the class instance type are
// unbound.
// We cannot devirtualize unbound generic calls yet.
if (isNominalTypeWithUnboundGenericParameters(SubType, AI.getModule()))
return false;
auto &M = CMI->getModule();
auto ClassType = SubType;
if (SubType.is<MetatypeType>())
ClassType = SubType.getMetatypeInstanceType(M);
CheckedCastBranchInst *LastCCBI = nullptr;
ClassDecl *CD = ClassType.getClassOrBoundGenericClass();
assert(CD && "Expected decl for class type!");
if (!CHA->hasKnownDirectSubclasses(CD)) {
// If there is only one possible alternative for this method,
// try to devirtualize it completely.
ClassHierarchyAnalysis::ClassList Subs;
if (isDefaultCaseKnown(CHA, AI, CD, Subs)) {
auto NewInstPair = tryDevirtualizeClassMethod(AI, SubTypeValue);
if (NewInstPair.first)
replaceDeadApply(AI, NewInstPair.first);
return NewInstPair.second.getInstruction() != nullptr;
}
DEBUG(llvm::dbgs() << "Inserting monomorphic speculative call for class " <<
CD->getName() << "\n");
return !!speculateMonomorphicTarget(AI, SubType, LastCCBI);
}
// True if any instructions were changed or generated.
bool Changed = false;
// Collect the direct and indirect subclasses for the class.
// Sort these subclasses in the order they should be tested by the
// speculative devirtualization. Different strategies could be used,
// E.g. breadth-first, depth-first, etc.
// Currently, let's use the breadth-first strategy.
// The exact static type of the instance should be tested first.
auto &DirectSubs = CHA->getDirectSubClasses(CD);
auto &IndirectSubs = CHA->getIndirectSubClasses(CD);
SmallVector<ClassDecl *, 8> Subs(DirectSubs);
Subs.append(IndirectSubs.begin(), IndirectSubs.end());
if (isa<BoundGenericClassType>(ClassType.getSwiftRValueType())) {
// Filter out any subclassses that do not inherit from this
// specific bound class.
auto RemovedIt = std::remove_if(Subs.begin(),
Subs.end(),
[&ClassType, &M](ClassDecl *Sub){
auto SubCanTy = Sub->getDeclaredType()->getCanonicalType();
// Unbound generic type can override a method from
// a bound generic class, but this unbound generic
// class is not considered to be a subclass of a
// bound generic class in a general case.
if (isa<UnboundGenericType>(SubCanTy))
return false;
// Handle the usual case here: the class in question
// should be a real subclass of a bound generic class.
return !ClassType.isSuperclassOf(
SILType::getPrimitiveObjectType(SubCanTy));
});
Subs.erase(RemovedIt, Subs.end());
}
// Number of subclasses which cannot be handled by checked_cast_br checks.
int NotHandledSubsNum = 0;
if (Subs.size() > MaxNumSpeculativeTargets) {
DEBUG(llvm::dbgs() << "Class " << CD->getName() << " has too many ("
<< Subs.size() << ") subclasses. Performing speculative "
"devirtualization only for the first "
<< MaxNumSpeculativeTargets << " of them.\n");
NotHandledSubsNum += (Subs.size() - MaxNumSpeculativeTargets);
Subs.erase(&Subs[MaxNumSpeculativeTargets], Subs.end());
}
DEBUG(llvm::dbgs() << "Class " << CD->getName() << " is a superclass. "
"Inserting polymorphic speculative call.\n");
// Try to devirtualize the static class of instance
// if it is possible.
auto FirstAI = speculateMonomorphicTarget(AI, SubType, LastCCBI);
if (FirstAI) {
Changed = true;
AI = FirstAI;
}
// Perform a speculative devirtualization of a method invocation.
// It replaces an indirect class_method-based call by a code to perform
// a direct call of the method implementation based on the dynamic class
// of the instance.
//
// The code is generated according to the following principles:
//
// - For each direct subclass, a dedicated checked_cast_br instruction
// is generated to check if a dynamic class of the instance is exactly
// this subclass.
//
// - If this check succeeds, then it jumps to the code which performs a
// direct call of a method implementation specific to this subclass.
//
// - If this check fails, then a different subclass is checked by means of
// checked_cast_br in a similar way.
//
// - Finally, if the instance does not exactly match any of the direct
// subclasses, the "default" case code is generated, which should handle
// all remaining alternatives, i.e. it should be able to dispatch to any
// possible remaining method implementations. Typically this is achieved by
// using a class_method instruction, which performs an indirect invocation.
// But if it can be proven that only one specific implementation of
// a method will be always invoked by this code, then a class_method-based
// call can be devirtualized and replaced by a more efficient direct
// invocation of this specific method implementation.
//
// Remark: With the current implementation of a speculative devirtualization,
// if devirtualization of the "default" case is possible, then it would
// by construction directly invoke the implementation of the method
// corresponding to the static type of the instance. This may change
// in the future, if we start using PGO for ordering of checked_cast_br
// checks.
// TODO: The ordering of checks may benefit from using a PGO, because
// the most probable alternatives could be checked first.
for (auto S : Subs) {
DEBUG(llvm::dbgs() << "Inserting a speculative call for class "
<< CD->getName() << " and subclass " << S->getName() << "\n");
CanType CanClassType = S->getDeclaredType()->getCanonicalType();
SILType ClassType = SILType::getPrimitiveObjectType(CanClassType);
if (!ClassType.getClassOrBoundGenericClass()) {
// This subclass cannot be handled. This happens e.g. if it is
// a generic class.
NotHandledSubsNum++;
continue;
}
auto ClassOrMetatypeType = ClassType;
if (auto EMT = SubType.getAs<AnyMetatypeType>()) {
auto InstTy = ClassType.getSwiftRValueType();
auto *MetaTy = MetatypeType::get(InstTy, EMT->getRepresentation());
auto CanMetaTy = CanMetatypeType::CanTypeWrapper(MetaTy);
ClassOrMetatypeType = SILType::getPrimitiveObjectType(CanMetaTy);
}
// Pass the metatype of the subclass.
auto NewAI = speculateMonomorphicTarget(AI, ClassOrMetatypeType, LastCCBI);
if (!NewAI) {
NotHandledSubsNum++;
continue;
}
AI = NewAI;
Changed = true;
}
// Check if there is only a single statically known implementation
// of the method which can be called by the default case handler.
if (NotHandledSubsNum || !isDefaultCaseKnown(CHA, AI, CD, Subs)) {
// Devirtualization of remaining cases is not possible,
// because more than one implementation of the method
// needs to be handled here. Thus, an indirect call through
// the class_method cannot be eliminated completely.
//
return Changed;
}
// At this point it is known that there is only one remaining method
// implementation which is not covered by checked_cast_br checks yet.
// So, it is safe to replace a class_method invocation by
// a direct call of this remaining implementation.
if (LastCCBI && SubTypeValue == LastCCBI->getOperand()) {
// Remove last checked_cast_br, because it will always succeed.
SILBuilderWithScope B(LastCCBI);
auto CastedValue = B.createUncheckedBitCast(LastCCBI->getLoc(),
LastCCBI->getOperand(),
LastCCBI->getCastType());
B.createBranch(LastCCBI->getLoc(), LastCCBI->getSuccessBB(), {CastedValue});
LastCCBI->eraseFromParent();
return true;
}
auto NewInstPair = tryDevirtualizeClassMethod(AI, SubTypeValue);
assert(NewInstPair.first && "Expected to be able to devirtualize apply!");
replaceDeadApply(AI, NewInstPair.first);
return true;
}
void SILGenFunction::emitObjCDestructor(SILDeclRef dtor) {
auto dd = cast<DestructorDecl>(dtor.getDecl());
auto cd = cast<ClassDecl>(dd->getDeclContext());
MagicFunctionName = DeclName(SGM.M.getASTContext().getIdentifier("deinit"));
RegularLocation loc(dd);
if (dd->isImplicit())
loc.markAutoGenerated();
SILValue selfValue = emitSelfDecl(dd->getImplicitSelfDecl());
// Create a basic block to jump to for the implicit destruction behavior
// of releasing the elements and calling the superclass destructor.
// We won't actually emit the block until we finish with the destructor body.
prepareEpilog(Type(), false, CleanupLocation::get(loc));
emitProfilerIncrement(dd->getBody());
// Emit the destructor body.
emitStmt(dd->getBody());
Optional<SILValue> maybeReturnValue;
SILLocation returnLoc(loc);
std::tie(maybeReturnValue, returnLoc) = emitEpilogBB(loc);
if (!maybeReturnValue)
return;
auto cleanupLoc = CleanupLocation::get(loc);
// Note: the ivar destroyer is responsible for destroying the
// instance variables before the object is actually deallocated.
// Form a reference to the superclass -dealloc.
Type superclassTy = dd->mapTypeIntoContext(cd->getSuperclass());
assert(superclassTy && "Emitting Objective-C -dealloc without superclass?");
ClassDecl *superclass = superclassTy->getClassOrBoundGenericClass();
auto superclassDtorDecl = superclass->getDestructor();
auto superclassDtor = SILDeclRef(superclassDtorDecl,
SILDeclRef::Kind::Deallocator)
.asForeign();
auto superclassDtorType = SGM.Types.getConstantType(superclassDtor);
SILValue superclassDtorValue = B.createObjCSuperMethod(
cleanupLoc, selfValue, superclassDtor,
superclassDtorType);
// Call the superclass's -dealloc.
SILType superclassSILTy = getLoweredLoadableType(superclassTy);
SILValue superSelf = B.createUpcast(cleanupLoc, selfValue, superclassSILTy);
assert(superSelf.getOwnershipKind() == ValueOwnershipKind::Owned);
auto subMap
= superclassTy->getContextSubstitutionMap(SGM.M.getSwiftModule(),
superclass);
auto substDtorType = superclassDtorType.substGenericArgs(SGM.M, subMap);
CanSILFunctionType substFnType = substDtorType.castTo<SILFunctionType>();
SILFunctionConventions dtorConv(substFnType, SGM.M);
assert(substFnType->getSelfParameter().getConvention() ==
ParameterConvention::Direct_Unowned &&
"Objective C deinitializing destructor takes self as unowned");
B.createApply(cleanupLoc, superclassDtorValue, substDtorType,
dtorConv.getSILResultType(), subMap, superSelf);
// We know that the givne value came in at +1, but we pass the relevant value
// as unowned to the destructor. Create a fake balance for the verifier to be
// happy.
B.createEndLifetime(cleanupLoc, superSelf);
// Return.
B.createReturn(returnLoc, emitEmptyTuple(cleanupLoc));
}
/// Emit a checked unconditional downcast of a class value.
llvm::Value *irgen::emitClassDowncast(IRGenFunction &IGF, llvm::Value *from,
SILType toType, CheckedCastMode mode) {
// Emit the value we're casting from.
if (from->getType() != IGF.IGM.Int8PtrTy)
from = IGF.Builder.CreateBitOrPointerCast(from, IGF.IGM.Int8PtrTy);
// Emit a reference to the metadata and figure out what cast
// function to use.
llvm::Value *metadataRef;
llvm::Constant *castFn;
// Get the best known type information about the destination type.
ClassDecl *destClass = nullptr;
if (auto archetypeTy = toType.getAs<ArchetypeType>()) {
if (auto superclassTy = archetypeTy->getSuperclass())
destClass = superclassTy->getClassOrBoundGenericClass();
} else {
destClass = toType.getClassOrBoundGenericClass();
assert(destClass != nullptr);
}
// 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.getSwiftRValueType());
switch (mode) {
case CheckedCastMode::Unconditional:
castFn = IGF.IGM.getDynamicCastClassUnconditionalFn();
break;
case CheckedCastMode::Conditional:
castFn = IGF.IGM.getDynamicCastClassFn();
break;
}
// 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>() ||
destClass->getForeignClassKind()==ClassDecl::ForeignKind::CFType) {
metadataRef = IGF.emitTypeMetadataRef(toType.getSwiftRValueType());
switch (mode) {
case CheckedCastMode::Unconditional:
castFn = IGF.IGM.getDynamicCastUnknownClassUnconditionalFn();
break;
case CheckedCastMode::Conditional:
castFn = IGF.IGM.getDynamicCastUnknownClassFn();
break;
}
// Otherwise, use the ObjC-specific entrypoint.
} else {
metadataRef = emitObjCHeapMetadataRef(IGF, destClass);
switch (mode) {
case CheckedCastMode::Unconditional:
castFn = IGF.IGM.getDynamicCastObjCClassUnconditionalFn();
break;
case CheckedCastMode::Conditional:
castFn = IGF.IGM.getDynamicCastObjCClassFn();
break;
}
}
if (metadataRef->getType() != IGF.IGM.Int8PtrTy)
metadataRef = IGF.Builder.CreateBitCast(metadataRef, IGF.IGM.Int8PtrTy);
// Call the (unconditional) dynamic cast.
auto cc = IGF.IGM.DefaultCC;
if (auto fun = dyn_cast<llvm::Function>(castFn))
cc = fun->getCallingConv();
auto call
= IGF.Builder.CreateCall(castFn, {from, metadataRef});
// FIXME: Eventually, we may want to throw.
call->setCallingConv(cc);
call->setDoesNotThrow();
llvm::Type *subTy = IGF.getTypeInfo(toType).getStorageType();
return IGF.Builder.CreateBitCast(call, subTy);
}