forked from OSchip/llvm-project
[MS-ABI] Implement dynamic_cast
This patch implements call lower from dynamic_cast to __RTDynamicCast and __RTCastToVoid. Test cases are included. A feature of note is that helper function getPolymorphicOffset is placed in such a way that it can be used by EmitTypeid (to be implemented in a later patch) without being moved. Details are included as comments directly in the code. llvm-svn: 210377
This commit is contained in:
Warren Hunt
parent
58f770ffa4
commit
b57b4b098c
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@ -1628,6 +1628,20 @@ static void EmitBadTypeidCall(CodeGenFunction &CGF) {
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CGF.Builder.CreateUnreachable();
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}
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/// \brief Gets the offset to the virtual base that contains the vfptr for
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/// MS-ABI polymorphic types.
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static llvm::Value *getPolymorphicOffset(CodeGenFunction &CGF,
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const CXXRecordDecl *RD,
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llvm::Value *Value) {
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const ASTContext &Context = RD->getASTContext();
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for (const CXXBaseSpecifier &Base : RD->vbases())
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if (Context.getASTRecordLayout(Base.getType()->getAsCXXRecordDecl())
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.hasExtendableVFPtr())
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return CGF.CGM.getCXXABI().GetVirtualBaseClassOffset(
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CGF, Value, RD, Base.getType()->getAsCXXRecordDecl());
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llvm_unreachable("One of our vbases should be polymorphic.");
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}
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static llvm::Value *EmitTypeidFromVTable(CodeGenFunction &CGF,
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const Expr *E,
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llvm::Type *StdTypeInfoPtrTy) {
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@ -1686,7 +1700,7 @@ llvm::Value *CodeGenFunction::EmitCXXTypeidExpr(const CXXTypeidExpr *E) {
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StdTypeInfoPtrTy);
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}
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static llvm::Constant *getDynamicCastFn(CodeGenFunction &CGF) {
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static llvm::Constant *getItaniumDynamicCastFn(CodeGenFunction &CGF) {
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// void *__dynamic_cast(const void *sub,
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// const abi::__class_type_info *src,
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// const abi::__class_type_info *dst,
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@ -1774,7 +1788,7 @@ static CharUnits computeOffsetHint(ASTContext &Context,
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}
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static llvm::Value *
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EmitDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value,
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EmitItaniumDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value,
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QualType SrcTy, QualType DestTy,
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llvm::BasicBlock *CastEnd) {
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llvm::Type *PtrDiffLTy =
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@ -1834,7 +1848,7 @@ EmitDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value,
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Value = CGF.EmitCastToVoidPtr(Value);
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llvm::Value *args[] = { Value, SrcRTTI, DestRTTI, OffsetHint };
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Value = CGF.EmitNounwindRuntimeCall(getDynamicCastFn(CGF), args);
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Value = CGF.EmitNounwindRuntimeCall(getItaniumDynamicCastFn(CGF), args);
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Value = CGF.Builder.CreateBitCast(Value, DestLTy);
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/// C++ [expr.dynamic.cast]p9:
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@ -1867,8 +1881,125 @@ static llvm::Value *EmitDynamicCastToNull(CodeGenFunction &CGF,
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return llvm::UndefValue::get(DestLTy);
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}
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namespace {
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struct MSDynamicCastBuilder {
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MSDynamicCastBuilder(CodeGenFunction &CGF, const CXXDynamicCastExpr *DCE);
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llvm::Value *emitDynamicCastCall(llvm::Value *Value);
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llvm::Value *emitDynamicCast(llvm::Value *Value);
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CodeGenFunction &CGF;
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CGBuilderTy &Builder;
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llvm::PointerType *Int8PtrTy;
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QualType SrcTy, DstTy;
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const CXXRecordDecl *SrcDecl;
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bool IsPtrCast, IsCastToVoid, IsCastOfNull;
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};
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} // namespace
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MSDynamicCastBuilder::MSDynamicCastBuilder(CodeGenFunction &CGF,
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const CXXDynamicCastExpr *DCE)
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: CGF(CGF), Builder(CGF.Builder), Int8PtrTy(CGF.Int8PtrTy),
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SrcDecl(nullptr) {
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DstTy = DCE->getTypeAsWritten();
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IsPtrCast = DstTy->isPointerType();
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// Get the PointeeTypes. After this point the original types are not used.
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DstTy = IsPtrCast ? DstTy->castAs<PointerType>()->getPointeeType()
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: DstTy->castAs<ReferenceType>()->getPointeeType();
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IsCastToVoid = DstTy->isVoidType();
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IsCastOfNull = DCE->isAlwaysNull();
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if (IsCastOfNull)
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return;
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SrcTy = DCE->getSubExpr()->getType();
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SrcTy = IsPtrCast ? SrcTy->castAs<PointerType>()->getPointeeType() : SrcTy;
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SrcDecl = SrcTy->getAsCXXRecordDecl();
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// If we don't need a base adjustment, we don't need a SrcDecl so clear it
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// here. Later we use the existance of the SrcDecl to determine the need for
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// a base adjustment.
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if (CGF.getContext().getASTRecordLayout(SrcDecl).hasExtendableVFPtr())
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SrcDecl = nullptr;
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}
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llvm::Value *MSDynamicCastBuilder::emitDynamicCastCall(llvm::Value *Value) {
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llvm::IntegerType *Int32Ty = CGF.Int32Ty;
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llvm::Value *Offset = llvm::ConstantInt::get(Int32Ty, 0);
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Value = Builder.CreateBitCast(Value, Int8PtrTy);
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// If we need to perform a base adjustment, do it here.
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if (SrcDecl) {
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Offset = getPolymorphicOffset(CGF, SrcDecl, Value);
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Value = Builder.CreateInBoundsGEP(Value, Offset);
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Offset = Builder.CreateTrunc(Offset, Int32Ty);
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}
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if (IsCastToVoid) {
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// PVOID __RTCastToVoid(
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// PVOID inptr)
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llvm::Type *ArgTypes[] = {Int8PtrTy};
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llvm::Constant *Function = CGF.CGM.CreateRuntimeFunction(
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llvm::FunctionType::get(Int8PtrTy, ArgTypes, false), "__RTCastToVoid");
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llvm::Value *Args[] = {Value};
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return CGF.EmitRuntimeCall(Function, Args);
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}
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// PVOID __RTDynamicCast(
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// PVOID inptr,
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// LONG VfDelta,
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// PVOID SrcType,
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// PVOID TargetType,
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// BOOL isReference)
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llvm::Type *ArgTypes[] = {Int8PtrTy, Int32Ty, Int8PtrTy, Int8PtrTy, Int32Ty};
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llvm::Constant *Function = CGF.CGM.CreateRuntimeFunction(
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llvm::FunctionType::get(Int8PtrTy, ArgTypes, false), "__RTDynamicCast");
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llvm::Value *Args[] = {
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Value, Offset,
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CGF.CGM.GetAddrOfRTTIDescriptor(SrcTy.getUnqualifiedType()),
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CGF.CGM.GetAddrOfRTTIDescriptor(DstTy.getUnqualifiedType()),
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llvm::ConstantInt::get(Int32Ty, IsPtrCast ? 0 : 1)};
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return CGF.EmitRuntimeCall(Function, Args);
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}
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llvm::Value *MSDynamicCastBuilder::emitDynamicCast(llvm::Value *Value) {
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// Note about undefined behavior: If the dynamic cast is casting to a
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// reference type and the input is null, we hit a grey area in the standard.
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// Here we're interpreting the behavior as undefined. The effects are the
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// following: If the compiler determines that the argument is statically null
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// or if the argument is dynamically null but does not require base
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// adjustment, __RTDynamicCast will be called with a null argument and the
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// isreference bit set. In this case __RTDynamicCast will throw
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// std::bad_cast. If the argument is dynamically null and a base adjustment is
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// required the resulting code will produce an out of bounds memory reference
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// when trying to read VBTblPtr. In Itanium mode clang also emits a vtable
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// load that fails at run time.
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llvm::PointerType *DstLTy = CGF.ConvertType(DstTy)->getPointerTo();
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if (IsCastOfNull && IsPtrCast)
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return Builder.CreateBitCast(Value, DstLTy);
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if (IsCastOfNull || !IsPtrCast || !SrcDecl)
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return Builder.CreateBitCast(emitDynamicCastCall(Value), DstLTy);
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// !IsCastOfNull && IsPtrCast && SrcDecl
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// In this case we have a pointer that requires a base adjustment. An
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// adjustment is only required if the pointer is actually valid so here we
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// perform a null check before doing the base adjustment and calling
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// __RTDynamicCast. In the case that the argument is null we simply return
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// null without calling __RTDynamicCast.
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llvm::BasicBlock *EntryBlock = Builder.GetInsertBlock();
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llvm::BasicBlock *CallBlock = CGF.createBasicBlock("dynamic_cast.valid");
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llvm::BasicBlock *ExitBlock = CGF.createBasicBlock("dynamic_cast.call");
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Builder.CreateCondBr(Builder.CreateIsNull(Value), ExitBlock, CallBlock);
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// Emit the call block and code for it.
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CGF.EmitBlock(CallBlock);
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Value = emitDynamicCastCall(Value);
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// Emit the call block and the phi nodes for it.
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CGF.EmitBlock(ExitBlock);
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llvm::PHINode *ValuePHI = Builder.CreatePHI(Int8PtrTy, 2);
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ValuePHI->addIncoming(Value, CallBlock);
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ValuePHI->addIncoming(llvm::Constant::getNullValue(Int8PtrTy), EntryBlock);
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return Builder.CreateBitCast(ValuePHI, DstLTy);
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}
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llvm::Value *CodeGenFunction::EmitDynamicCast(llvm::Value *Value,
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const CXXDynamicCastExpr *DCE) {
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if (getTarget().getCXXABI().isMicrosoft()) {
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MSDynamicCastBuilder Builder(*this, DCE);
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return Builder.emitDynamicCast(Value);
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}
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QualType DestTy = DCE->getTypeAsWritten();
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if (DCE->isAlwaysNull())
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@ -1894,7 +2025,7 @@ llvm::Value *CodeGenFunction::EmitDynamicCast(llvm::Value *Value,
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EmitBlock(CastNotNull);
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}
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Value = EmitDynamicCastCall(*this, Value, SrcTy, DestTy, CastEnd);
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Value = EmitItaniumDynamicCastCall(*this, Value, SrcTy, DestTy, CastEnd);
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if (ShouldNullCheckSrcValue) {
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EmitBranch(CastEnd);
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@ -0,0 +1,157 @@
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// RUN: %clang_cc1 -emit-llvm -O2 -optzns -o - -triple=i386-pc-win32 2>/dev/null %s | FileCheck %s
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struct S { char a; };
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struct V { virtual void f(){} };
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struct A : virtual V {};
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struct B : S, virtual V {};
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struct T {};
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T* test0() { return dynamic_cast<T*>((B*)0); }
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// CHECK: define noalias %struct.T* @"\01?test0@@YAPAUT@@XZ"() #0 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: ret %struct.T* null
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// CHECK-NEXT: }
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T* test1(V* x) { return &dynamic_cast<T&>(*x); }
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// CHECK: define %struct.T* @"\01?test1@@YAPAUT@@PAUV@@@Z"(%struct.V* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = bitcast %struct.V* %x to i8*
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// CHECK-NEXT: %1 = tail call i8* @__RTDynamicCast(i8* %0, i32 0, i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUV@@@8" to i8*), i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUT@@@8" to i8*), i32 1) #2
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// CHECK-NEXT: %2 = bitcast i8* %1 to %struct.T*
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// CHECK-NEXT: ret %struct.T* %2
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// CHECK-NEXT: }
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T* test2(A* x) { return &dynamic_cast<T&>(*x); }
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// CHECK: define %struct.T* @"\01?test2@@YAPAUT@@PAUA@@@Z"(%struct.A* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = bitcast %struct.A* %x to i8*
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// CHECK-NEXT: %1 = bitcast %struct.A* %x to i8**
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// CHECK-NEXT: %vbtable = load i8** %1, align 4
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// CHECK-NEXT: %2 = getelementptr inbounds i8* %vbtable, i32 4
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// CHECK-NEXT: %3 = bitcast i8* %2 to i32*
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// CHECK-NEXT: %vbase_offs = load i32* %3, align 4
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// CHECK-NEXT: %4 = getelementptr inbounds i8* %0, i32 %vbase_offs
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// CHECK-NEXT: %5 = tail call i8* @__RTDynamicCast(i8* %4, i32 %vbase_offs, i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUA@@@8" to i8*), i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUT@@@8" to i8*), i32 1) #2
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// CHECK-NEXT: %6 = bitcast i8* %5 to %struct.T*
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// CHECK-NEXT: ret %struct.T* %6
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// CHECK-NEXT: }
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T* test3(B* x) { return &dynamic_cast<T&>(*x); }
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// CHECK: define %struct.T* @"\01?test3@@YAPAUT@@PAUB@@@Z"(%struct.B* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = getelementptr inbounds %struct.B* %x, i32 0, i32 0, i32 0
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// CHECK-NEXT: %vbptr = getelementptr inbounds i8* %0, i32 4
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// CHECK-NEXT: %1 = bitcast i8* %vbptr to i8**
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// CHECK-NEXT: %vbtable = load i8** %1, align 4
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// CHECK-NEXT: %2 = getelementptr inbounds i8* %vbtable, i32 4
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// CHECK-NEXT: %3 = bitcast i8* %2 to i32*
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// CHECK-NEXT: %vbase_offs = load i32* %3, align 4
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// CHECK-NEXT: %4 = add nsw i32 %vbase_offs, 4
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// CHECK-NEXT: %5 = getelementptr inbounds i8* %0, i32 %4
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// CHECK-NEXT: %6 = tail call i8* @__RTDynamicCast(i8* %5, i32 %4, i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUB@@@8" to i8*), i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUT@@@8" to i8*), i32 1) #2
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// CHECK-NEXT: %7 = bitcast i8* %6 to %struct.T*
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// CHECK-NEXT: ret %struct.T* %7
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// CHECK-NEXT: }
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T* test4(V* x) { return dynamic_cast<T*>(x); }
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// CHECK: define %struct.T* @"\01?test4@@YAPAUT@@PAUV@@@Z"(%struct.V* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = bitcast %struct.V* %x to i8*
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// CHECK-NEXT: %1 = tail call i8* @__RTDynamicCast(i8* %0, i32 0, i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUV@@@8" to i8*), i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUT@@@8" to i8*), i32 0) #2
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// CHECK-NEXT: %2 = bitcast i8* %1 to %struct.T*
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// CHECK-NEXT: ret %struct.T* %2
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// CHECK-NEXT: }
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T* test5(A* x) { return dynamic_cast<T*>(x); }
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// CHECK: define %struct.T* @"\01?test5@@YAPAUT@@PAUA@@@Z"(%struct.A* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = icmp eq %struct.A* %x, null
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// CHECK-NEXT: br i1 %0, label %dynamic_cast.call, label %dynamic_cast.valid
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// CHECK: dynamic_cast.valid: ; preds = %entry
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// CHECK-NEXT: %1 = bitcast %struct.A* %x to i8*
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// CHECK-NEXT: %2 = bitcast %struct.A* %x to i8**
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// CHECK-NEXT: %vbtable = load i8** %2, align 4
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// CHECK-NEXT: %3 = getelementptr inbounds i8* %vbtable, i32 4
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// CHECK-NEXT: %4 = bitcast i8* %3 to i32*
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// CHECK-NEXT: %vbase_offs = load i32* %4, align 4
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// CHECK-NEXT: %5 = getelementptr inbounds i8* %1, i32 %vbase_offs
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// CHECK-NEXT: %6 = tail call i8* @__RTDynamicCast(i8* %5, i32 %vbase_offs, i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUA@@@8" to i8*), i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUT@@@8" to i8*), i32 0) #2
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// CHECK-NEXT: %phitmp = bitcast i8* %6 to %struct.T*
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// CHECK-NEXT: br label %dynamic_cast.call
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// CHECK: dynamic_cast.call: ; preds = %dynamic_cast.valid, %entry
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// CHECK-NEXT: %7 = phi %struct.T* [ %phitmp, %dynamic_cast.valid ], [ null, %entry ]
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// CHECK-NEXT: ret %struct.T* %7
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// CHECK-NEXT: }
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T* test6(B* x) { return dynamic_cast<T*>(x); }
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// CHECK: define %struct.T* @"\01?test6@@YAPAUT@@PAUB@@@Z"(%struct.B* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = icmp eq %struct.B* %x, null
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// CHECK-NEXT: br i1 %0, label %dynamic_cast.call, label %dynamic_cast.valid
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// CHECK: dynamic_cast.valid: ; preds = %entry
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// CHECK-NEXT: %1 = getelementptr inbounds %struct.B* %x, i32 0, i32 0, i32 0
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// CHECK-NEXT: %vbptr = getelementptr inbounds i8* %1, i32 4
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// CHECK-NEXT: %2 = bitcast i8* %vbptr to i8**
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// CHECK-NEXT: %vbtable = load i8** %2, align 4
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// CHECK-NEXT: %3 = getelementptr inbounds i8* %vbtable, i32 4
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// CHECK-NEXT: %4 = bitcast i8* %3 to i32*
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// CHECK-NEXT: %vbase_offs = load i32* %4, align 4
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// CHECK-NEXT: %5 = add nsw i32 %vbase_offs, 4
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// CHECK-NEXT: %6 = getelementptr inbounds i8* %1, i32 %5
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// CHECK-NEXT: %7 = tail call i8* @__RTDynamicCast(i8* %6, i32 %5, i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUB@@@8" to i8*), i8* bitcast (%"MSRTTITypeDescriptor\07"* @"\01??_R0?AUT@@@8" to i8*), i32 0) #2
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// CHECK-NEXT: %phitmp = bitcast i8* %7 to %struct.T*
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// CHECK-NEXT: br label %dynamic_cast.call
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// CHECK: dynamic_cast.call: ; preds = %dynamic_cast.valid, %entry
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// CHECK-NEXT: %8 = phi %struct.T* [ %phitmp, %dynamic_cast.valid ], [ null, %entry ]
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// CHECK-NEXT: ret %struct.T* %8
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// CHECK-NEXT: }
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void* test7(V* x) { return dynamic_cast<void*>(x); }
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// CHECK: define i8* @"\01?test7@@YAPAXPAUV@@@Z"(%struct.V* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = bitcast %struct.V* %x to i8*
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// CHECK-NEXT: %1 = tail call i8* @__RTCastToVoid(i8* %0) #2
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// CHECK-NEXT: ret i8* %1
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// CHECK-NEXT: }
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void* test8(A* x) { return dynamic_cast<void*>(x); }
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// CHECK: define i8* @"\01?test8@@YAPAXPAUA@@@Z"(%struct.A* %x) #1 {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: %0 = icmp eq %struct.A* %x, null
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// CHECK-NEXT: br i1 %0, label %dynamic_cast.call, label %dynamic_cast.valid
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// CHECK: dynamic_cast.valid: ; preds = %entry
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// CHECK-NEXT: %1 = bitcast %struct.A* %x to i8*
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// CHECK-NEXT: %2 = bitcast %struct.A* %x to i8**
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// CHECK-NEXT: %vbtable = load i8** %2, align 4
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// CHECK-NEXT: %3 = getelementptr inbounds i8* %vbtable, i32 4
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// CHECK-NEXT: %4 = bitcast i8* %3 to i32*
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// CHECK-NEXT: %vbase_offs = load i32* %4, align 4
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// CHECK-NEXT: %5 = getelementptr inbounds i8* %1, i32 %vbase_offs
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// CHECK-NEXT: %6 = tail call i8* @__RTCastToVoid(i8* %5) #2
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// CHECK-NEXT: br label %dynamic_cast.call
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// CHECK: dynamic_cast.call: ; preds = %dynamic_cast.valid, %entry
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// CHECK-NEXT: %7 = phi i8* [ %6, %dynamic_cast.valid ], [ null, %entry ]
|
||||
// CHECK-NEXT: ret i8* %7
|
||||
// CHECK-NEXT: }
|
||||
|
||||
void* test9(B* x) { return dynamic_cast<void*>(x); }
|
||||
// CHECK: define i8* @"\01?test9@@YAPAXPAUB@@@Z"(%struct.B* %x) #1 {
|
||||
// CHECK-NEXT: entry:
|
||||
// CHECK-NEXT: %0 = icmp eq %struct.B* %x, null
|
||||
// CHECK-NEXT: br i1 %0, label %dynamic_cast.call, label %dynamic_cast.valid
|
||||
// CHECK: dynamic_cast.valid: ; preds = %entry
|
||||
// CHECK-NEXT: %1 = getelementptr inbounds %struct.B* %x, i32 0, i32 0, i32 0
|
||||
// CHECK-NEXT: %vbptr = getelementptr inbounds i8* %1, i32 4
|
||||
// CHECK-NEXT: %2 = bitcast i8* %vbptr to i8**
|
||||
// CHECK-NEXT: %vbtable = load i8** %2, align 4
|
||||
// CHECK-NEXT: %3 = getelementptr inbounds i8* %vbtable, i32 4
|
||||
// CHECK-NEXT: %4 = bitcast i8* %3 to i32*
|
||||
// CHECK-NEXT: %vbase_offs = load i32* %4, align 4
|
||||
// CHECK-NEXT: %5 = add nsw i32 %vbase_offs, 4
|
||||
// CHECK-NEXT: %6 = getelementptr inbounds i8* %1, i32 %5
|
||||
// CHECK-NEXT: %7 = tail call i8* @__RTCastToVoid(i8* %6) #2
|
||||
// CHECK-NEXT: br label %dynamic_cast.call
|
||||
// CHECK: dynamic_cast.call: ; preds = %dynamic_cast.valid, %entry
|
||||
// CHECK-NEXT: %8 = phi i8* [ %7, %dynamic_cast.valid ], [ null, %entry ]
|
||||
// CHECK-NEXT: ret i8* %8
|
||||
// CHECK-NEXT: }
|
||||
Loading…
Reference in New Issue