From f0cb4a6ac7ffcba25309a5d1ad1a4bf869b13a33 Mon Sep 17 00:00:00 2001 From: Anders Carlsson Date: Mon, 11 Apr 2011 00:46:40 +0000 Subject: [PATCH] Clean up CodeGenFunction::EmitDynamicCast. No functionality change. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129262 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/CGExprCXX.cpp | 245 ++++++++++++++++++++++---------------- 1 file changed, 141 insertions(+), 104 deletions(-) diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp index f6043e5f3f..ff7b7112ca 100644 --- a/lib/CodeGen/CGExprCXX.cpp +++ b/lib/CodeGen/CGExprCXX.cpp @@ -1388,120 +1388,157 @@ llvm::Value *CodeGenFunction::EmitCXXTypeidExpr(const CXXTypeidExpr *E) { return Builder.CreateBitCast(CGM.GetAddrOfRTTIDescriptor(Ty), LTy); } -llvm::Value *CodeGenFunction::EmitDynamicCast(llvm::Value *V, - const CXXDynamicCastExpr *DCE) { - QualType SrcTy = DCE->getSubExpr()->getType(); - QualType DestTy = DCE->getTypeAsWritten(); - QualType InnerType = DestTy->getPointeeType(); +static llvm::Constant *getDynamicCastFn(CodeGenFunction &CGF) { + // void *__dynamic_cast(const void *sub, + // const abi::__class_type_info *src, + // const abi::__class_type_info *dst, + // std::ptrdiff_t src2dst_offset); + + const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); + const llvm::Type *PtrDiffTy = + CGF.ConvertType(CGF.getContext().getPointerDiffType()); + + const llvm::Type *Args[4] = { Int8PtrTy, Int8PtrTy, Int8PtrTy, PtrDiffTy }; + + const llvm::FunctionType *FTy = + llvm::FunctionType::get(Int8PtrTy, Args, false); + + return CGF.CGM.CreateRuntimeFunction(FTy, "__dynamic_cast"); +} + +static llvm::Constant *getBadCastFn(CodeGenFunction &CGF) { + // void __cxa_bad_cast(); + + const llvm::Type *VoidTy = llvm::Type::getVoidTy(CGF.getLLVMContext()); + const llvm::FunctionType *FTy = + llvm::FunctionType::get(VoidTy, false); - const llvm::Type *LTy = ConvertType(DCE->getType()); - - bool CanBeZero = false; - bool ToVoid = false; - bool ThrowOnBad = false; - if (DestTy->isPointerType()) { - // FIXME: if PointerType->hasAttr(), we don't set this - CanBeZero = true; - if (InnerType->isVoidType()) - ToVoid = true; + return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_bad_cast"); +} + +static llvm::Value * +EmitDynamicCastCall(CodeGenFunction &CGF, llvm::Value *Value, + QualType SrcTy, QualType DestTy, + llvm::BasicBlock *CastEnd) { + const llvm::Type *PtrDiffLTy = + CGF.ConvertType(CGF.getContext().getPointerDiffType()); + const llvm::Type *DestLTy = CGF.ConvertType(DestTy); + + if (const PointerType *PTy = DestTy->getAs()) { + if (PTy->getPointeeType()->isVoidType()) { + // C++ [expr.dynamic.cast]p7: + // If T is "pointer to cv void," then the result is a pointer to the + // most derived object pointed to by v. + + // Get the vtable pointer. + llvm::Value *VTable = CGF.GetVTablePtr(Value, PtrDiffLTy->getPointerTo()); + + // Get the offset-to-top from the vtable. + llvm::Value *OffsetToTop = + CGF.Builder.CreateConstInBoundsGEP1_64(VTable, -2ULL); + OffsetToTop = CGF.Builder.CreateLoad(OffsetToTop, "offset.to.top"); + + // Finally, add the offset to the pointer. + Value = CGF.EmitCastToVoidPtr(Value); + Value = CGF.Builder.CreateInBoundsGEP(Value, OffsetToTop); + + return CGF.Builder.CreateBitCast(Value, DestLTy); + } + } + + QualType SrcRecordTy; + QualType DestRecordTy; + + if (const PointerType *DestPTy = DestTy->getAs()) { + SrcRecordTy = SrcTy->castAs()->getPointeeType(); + DestRecordTy = DestPTy->getPointeeType(); } else { - LTy = LTy->getPointerTo(); - - // FIXME: What if exceptions are disabled? - ThrowOnBad = true; + SrcRecordTy = SrcTy; + DestRecordTy = DestTy->castAs()->getPointeeType(); } - if (SrcTy->isPointerType() || SrcTy->isReferenceType()) - SrcTy = SrcTy->getPointeeType(); - SrcTy = SrcTy.getUnqualifiedType(); - - if (DestTy->isPointerType() || DestTy->isReferenceType()) - DestTy = DestTy->getPointeeType(); - DestTy = DestTy.getUnqualifiedType(); - - llvm::BasicBlock *ContBlock = createBasicBlock(); - llvm::BasicBlock *NullBlock = 0; - llvm::BasicBlock *NonZeroBlock = 0; - if (CanBeZero) { - NonZeroBlock = createBasicBlock(); - NullBlock = createBasicBlock(); - Builder.CreateCondBr(Builder.CreateIsNotNull(V), NonZeroBlock, NullBlock); - EmitBlock(NonZeroBlock); + assert(SrcRecordTy->isRecordType() && "source type must be a record type!"); + assert(DestRecordTy->isRecordType() && "dest type must be a record type!"); + + llvm::Value *SrcRTTI = + CGF.CGM.GetAddrOfRTTIDescriptor(SrcRecordTy.getUnqualifiedType()); + llvm::Value *DestRTTI = + CGF.CGM.GetAddrOfRTTIDescriptor(DestRecordTy.getUnqualifiedType()); + + // FIXME: Actually compute a hint here. + llvm::Value *OffsetHint = llvm::ConstantInt::get(PtrDiffLTy, -1ULL); + + // Emit the call to __dynamic_cast. + Value = CGF.EmitCastToVoidPtr(Value); + Value = CGF.Builder.CreateCall4(getDynamicCastFn(CGF), Value, + SrcRTTI, DestRTTI, OffsetHint); + Value = CGF.Builder.CreateBitCast(Value, DestLTy); + + /// C++ [expr.dynamic.cast]p9: + /// A failed cast to reference type throws std::bad_cast + if (DestTy->isReferenceType()) { + llvm::BasicBlock *BadCastBlock = + CGF.createBasicBlock("dynamic_cast.bad_cast"); + + llvm::Value *IsNull = CGF.Builder.CreateIsNull(Value); + CGF.Builder.CreateCondBr(IsNull, BadCastBlock, CastEnd); + + CGF.EmitBlock(BadCastBlock); + llvm::Value *F = getBadCastFn(CGF); + if (llvm::BasicBlock *InvokeDest = CGF.getInvokeDest()) { + llvm::BasicBlock *Cont = CGF.createBasicBlock("invoke.cont"); + CGF.Builder.CreateInvoke(F, Cont, InvokeDest)->setDoesNotReturn(); + CGF.EmitBlock(Cont); + } else + CGF.Builder.CreateCall(F)->setDoesNotReturn(); + + CGF.Builder.CreateUnreachable(); } - llvm::BasicBlock *BadCastBlock = 0; + return Value; +} + +llvm::Value *CodeGenFunction::EmitDynamicCast(llvm::Value *Value, + const CXXDynamicCastExpr *DCE) { + QualType SrcTy = DCE->getSubExpr()->getType(); + QualType DestTy = DCE->getTypeAsWritten(); - const llvm::Type *PtrDiffTy = ConvertType(getContext().getPointerDiffType()); + // C++ [expr.dynamic.cast]p4: + // If the value of v is a null pointer value in the pointer case, the result + // is the null pointer value of type T. + bool ShouldNullCheckSrcValue = SrcTy->isPointerType(); + + llvm::BasicBlock *CastNull = 0; + llvm::BasicBlock *CastNotNull = 0; + llvm::BasicBlock *CastEnd = createBasicBlock("dynamic_cast.end"); + + if (ShouldNullCheckSrcValue) { + CastNull = createBasicBlock("dynamic_cast.null"); + CastNotNull = createBasicBlock("dynamic_cast.notnull"); - // See if this is a dynamic_cast(void*) - if (ToVoid) { - llvm::Value *This = V; - V = GetVTablePtr(This, PtrDiffTy->getPointerTo()); - V = Builder.CreateConstInBoundsGEP1_64(V, -2ULL); - V = Builder.CreateLoad(V, "offset to top"); - This = EmitCastToVoidPtr(This); - V = Builder.CreateInBoundsGEP(This, V); - V = Builder.CreateBitCast(V, LTy); - } else { - /// Call __dynamic_cast - const llvm::Type *ResultType = Int8PtrTy; - const llvm::FunctionType *FTy; - std::vector ArgTys; - ArgTys.push_back(Int8PtrTy); - ArgTys.push_back(Int8PtrTy); - ArgTys.push_back(Int8PtrTy); - ArgTys.push_back(PtrDiffTy); - FTy = llvm::FunctionType::get(ResultType, ArgTys, false); - - // FIXME: Calculate better hint. - llvm::Value *hint = llvm::ConstantInt::get(PtrDiffTy, -1ULL); - - assert(SrcTy->isRecordType() && "Src type must be record type!"); - assert(DestTy->isRecordType() && "Dest type must be record type!"); - - llvm::Value *SrcArg - = CGM.GetAddrOfRTTIDescriptor(SrcTy.getUnqualifiedType()); - llvm::Value *DestArg - = CGM.GetAddrOfRTTIDescriptor(DestTy.getUnqualifiedType()); - - V = Builder.CreateBitCast(V, Int8PtrTy); - V = Builder.CreateCall4(CGM.CreateRuntimeFunction(FTy, "__dynamic_cast"), - V, SrcArg, DestArg, hint); - V = Builder.CreateBitCast(V, LTy); - - if (ThrowOnBad) { - BadCastBlock = createBasicBlock(); - Builder.CreateCondBr(Builder.CreateIsNotNull(V), ContBlock, BadCastBlock); - EmitBlock(BadCastBlock); - /// Invoke __cxa_bad_cast - ResultType = llvm::Type::getVoidTy(getLLVMContext()); - const llvm::FunctionType *FBadTy; - FBadTy = llvm::FunctionType::get(ResultType, false); - llvm::Value *F = CGM.CreateRuntimeFunction(FBadTy, "__cxa_bad_cast"); - if (llvm::BasicBlock *InvokeDest = getInvokeDest()) { - llvm::BasicBlock *Cont = createBasicBlock("invoke.cont"); - Builder.CreateInvoke(F, Cont, InvokeDest)->setDoesNotReturn(); - EmitBlock(Cont); - } else { - // FIXME: Does this ever make sense? - Builder.CreateCall(F)->setDoesNotReturn(); - } - Builder.CreateUnreachable(); - } + llvm::Value *IsNull = Builder.CreateIsNull(Value); + Builder.CreateCondBr(IsNull, CastNull, CastNotNull); + EmitBlock(CastNotNull); } - - if (CanBeZero) { - Builder.CreateBr(ContBlock); - EmitBlock(NullBlock); - Builder.CreateBr(ContBlock); + + Value = EmitDynamicCastCall(*this, Value, SrcTy, DestTy, CastEnd); + + if (ShouldNullCheckSrcValue) { + EmitBranch(CastEnd); + + EmitBlock(CastNull); + EmitBranch(CastEnd); } - EmitBlock(ContBlock); - if (CanBeZero) { - llvm::PHINode *PHI = Builder.CreatePHI(LTy, 2); - PHI->addIncoming(V, NonZeroBlock); - PHI->addIncoming(llvm::Constant::getNullValue(LTy), NullBlock); - V = PHI; + + EmitBlock(CastEnd); + + if (ShouldNullCheckSrcValue) { + llvm::PHINode *PHI = Builder.CreatePHI(Value->getType(), 2); + PHI->addIncoming(Value, CastNotNull); + PHI->addIncoming(llvm::Constant::getNullValue(Value->getType()), CastNull); + + Value = PHI; } - return V; + return Value; } -- 2.40.0