//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This contains code to emit Constant Expr nodes as LLVM code. // //===----------------------------------------------------------------------===// #include "CodeGenFunction.h" #include "CGCXXABI.h" #include "CGObjCRuntime.h" #include "CGRecordLayout.h" #include "CodeGenModule.h" #include "clang/AST/APValue.h" #include "clang/AST/ASTContext.h" #include "clang/AST/RecordLayout.h" #include "clang/AST/StmtVisitor.h" #include "clang/Basic/Builtins.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/Function.h" #include "llvm/IR/GlobalVariable.h" using namespace clang; using namespace CodeGen; //===----------------------------------------------------------------------===// // ConstStructBuilder //===----------------------------------------------------------------------===// namespace { class ConstStructBuilder { CodeGenModule &CGM; CodeGenFunction *CGF; bool Packed; CharUnits NextFieldOffsetInChars; CharUnits LLVMStructAlignment; SmallVector Elements; public: static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE); static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, const APValue &Value, QualType ValTy); private: ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF) : CGM(CGM), CGF(CGF), Packed(false), NextFieldOffsetInChars(CharUnits::Zero()), LLVMStructAlignment(CharUnits::One()) { } void AppendVTablePointer(BaseSubobject Base, llvm::Constant *VTable, const CXXRecordDecl *VTableClass); void AppendField(const FieldDecl *Field, uint64_t FieldOffset, llvm::Constant *InitExpr); void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst); void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, llvm::ConstantInt *InitExpr); void AppendPadding(CharUnits PadSize); void AppendTailPadding(CharUnits RecordSize); void ConvertStructToPacked(); bool Build(InitListExpr *ILE); void Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase, llvm::Constant *VTable, const CXXRecordDecl *VTableClass, CharUnits BaseOffset); llvm::Constant *Finalize(QualType Ty); CharUnits getAlignment(const llvm::Constant *C) const { if (Packed) return CharUnits::One(); return CharUnits::fromQuantity( CGM.getDataLayout().getABITypeAlignment(C->getType())); } CharUnits getSizeInChars(const llvm::Constant *C) const { return CharUnits::fromQuantity( CGM.getDataLayout().getTypeAllocSize(C->getType())); } }; void ConstStructBuilder::AppendVTablePointer(BaseSubobject Base, llvm::Constant *VTable, const CXXRecordDecl *VTableClass) { // Find the appropriate vtable within the vtable group. uint64_t AddressPoint = CGM.getVTableContext().getVTableLayout(VTableClass).getAddressPoint(Base); llvm::Value *Indices[] = { llvm::ConstantInt::get(CGM.Int64Ty, 0), llvm::ConstantInt::get(CGM.Int64Ty, AddressPoint) }; llvm::Constant *VTableAddressPoint = llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Indices); // Add the vtable at the start of the object. AppendBytes(Base.getBaseOffset(), VTableAddressPoint); } void ConstStructBuilder:: AppendField(const FieldDecl *Field, uint64_t FieldOffset, llvm::Constant *InitCst) { const ASTContext &Context = CGM.getContext(); CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset); AppendBytes(FieldOffsetInChars, InitCst); } void ConstStructBuilder:: AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) { assert(NextFieldOffsetInChars <= FieldOffsetInChars && "Field offset mismatch!"); CharUnits FieldAlignment = getAlignment(InitCst); // Round up the field offset to the alignment of the field type. CharUnits AlignedNextFieldOffsetInChars = NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment); if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) { assert(!Packed && "Alignment is wrong even with a packed struct!"); // Convert the struct to a packed struct. ConvertStructToPacked(); AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; } if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) { // We need to append padding. AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars); assert(NextFieldOffsetInChars == FieldOffsetInChars && "Did not add enough padding!"); AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; } // Add the field. Elements.push_back(InitCst); NextFieldOffsetInChars = AlignedNextFieldOffsetInChars + getSizeInChars(InitCst); if (Packed) assert(LLVMStructAlignment == CharUnits::One() && "Packed struct not byte-aligned!"); else LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); } void ConstStructBuilder::AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, llvm::ConstantInt *CI) { const ASTContext &Context = CGM.getContext(); const uint64_t CharWidth = Context.getCharWidth(); uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); if (FieldOffset > NextFieldOffsetInBits) { // We need to add padding. CharUnits PadSize = Context.toCharUnitsFromBits( llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits, Context.getTargetInfo().getCharAlign())); AppendPadding(PadSize); } uint64_t FieldSize = Field->getBitWidthValue(Context); llvm::APInt FieldValue = CI->getValue(); // Promote the size of FieldValue if necessary // FIXME: This should never occur, but currently it can because initializer // constants are cast to bool, and because clang is not enforcing bitfield // width limits. if (FieldSize > FieldValue.getBitWidth()) FieldValue = FieldValue.zext(FieldSize); // Truncate the size of FieldValue to the bit field size. if (FieldSize < FieldValue.getBitWidth()) FieldValue = FieldValue.trunc(FieldSize); NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); if (FieldOffset < NextFieldOffsetInBits) { // Either part of the field or the entire field can go into the previous // byte. assert(!Elements.empty() && "Elements can't be empty!"); unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; bool FitsCompletelyInPreviousByte = BitsInPreviousByte >= FieldValue.getBitWidth(); llvm::APInt Tmp = FieldValue; if (!FitsCompletelyInPreviousByte) { unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; if (CGM.getDataLayout().isBigEndian()) { Tmp = Tmp.lshr(NewFieldWidth); Tmp = Tmp.trunc(BitsInPreviousByte); // We want the remaining high bits. FieldValue = FieldValue.trunc(NewFieldWidth); } else { Tmp = Tmp.trunc(BitsInPreviousByte); // We want the remaining low bits. FieldValue = FieldValue.lshr(BitsInPreviousByte); FieldValue = FieldValue.trunc(NewFieldWidth); } } Tmp = Tmp.zext(CharWidth); if (CGM.getDataLayout().isBigEndian()) { if (FitsCompletelyInPreviousByte) Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); } else { Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); } // 'or' in the bits that go into the previous byte. llvm::Value *LastElt = Elements.back(); if (llvm::ConstantInt *Val = dyn_cast(LastElt)) Tmp |= Val->getValue(); else { assert(isa(LastElt)); // If there is an undef field that we're adding to, it can either be a // scalar undef (in which case, we just replace it with our field) or it // is an array. If it is an array, we have to pull one byte off the // array so that the other undef bytes stay around. if (!isa(LastElt->getType())) { // The undef padding will be a multibyte array, create a new smaller // padding and then an hole for our i8 to get plopped into. assert(isa(LastElt->getType()) && "Expected array padding of undefs"); llvm::ArrayType *AT = cast(LastElt->getType()); assert(AT->getElementType()->isIntegerTy(CharWidth) && AT->getNumElements() != 0 && "Expected non-empty array padding of undefs"); // Remove the padding array. NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); Elements.pop_back(); // Add the padding back in two chunks. AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); AppendPadding(CharUnits::One()); assert(isa(Elements.back()) && Elements.back()->getType()->isIntegerTy(CharWidth) && "Padding addition didn't work right"); } } Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); if (FitsCompletelyInPreviousByte) return; } while (FieldValue.getBitWidth() > CharWidth) { llvm::APInt Tmp; if (CGM.getDataLayout().isBigEndian()) { // We want the high bits. Tmp = FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); } else { // We want the low bits. Tmp = FieldValue.trunc(CharWidth); FieldValue = FieldValue.lshr(CharWidth); } Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); ++NextFieldOffsetInChars; FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); } assert(FieldValue.getBitWidth() > 0 && "Should have at least one bit left!"); assert(FieldValue.getBitWidth() <= CharWidth && "Should not have more than a byte left!"); if (FieldValue.getBitWidth() < CharWidth) { if (CGM.getDataLayout().isBigEndian()) { unsigned BitWidth = FieldValue.getBitWidth(); FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); } else FieldValue = FieldValue.zext(CharWidth); } // Append the last element. Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), FieldValue)); ++NextFieldOffsetInChars; } void ConstStructBuilder::AppendPadding(CharUnits PadSize) { if (PadSize.isZero()) return; llvm::Type *Ty = CGM.Int8Ty; if (PadSize > CharUnits::One()) Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); llvm::Constant *C = llvm::UndefValue::get(Ty); Elements.push_back(C); assert(getAlignment(C) == CharUnits::One() && "Padding must have 1 byte alignment!"); NextFieldOffsetInChars += getSizeInChars(C); } void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { assert(NextFieldOffsetInChars <= RecordSize && "Size mismatch!"); AppendPadding(RecordSize - NextFieldOffsetInChars); } void ConstStructBuilder::ConvertStructToPacked() { SmallVector PackedElements; CharUnits ElementOffsetInChars = CharUnits::Zero(); for (unsigned i = 0, e = Elements.size(); i != e; ++i) { llvm::Constant *C = Elements[i]; CharUnits ElementAlign = CharUnits::fromQuantity( CGM.getDataLayout().getABITypeAlignment(C->getType())); CharUnits AlignedElementOffsetInChars = ElementOffsetInChars.RoundUpToAlignment(ElementAlign); if (AlignedElementOffsetInChars > ElementOffsetInChars) { // We need some padding. CharUnits NumChars = AlignedElementOffsetInChars - ElementOffsetInChars; llvm::Type *Ty = CGM.Int8Ty; if (NumChars > CharUnits::One()) Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity()); llvm::Constant *Padding = llvm::UndefValue::get(Ty); PackedElements.push_back(Padding); ElementOffsetInChars += getSizeInChars(Padding); } PackedElements.push_back(C); ElementOffsetInChars += getSizeInChars(C); } assert(ElementOffsetInChars == NextFieldOffsetInChars && "Packing the struct changed its size!"); Elements.swap(PackedElements); LLVMStructAlignment = CharUnits::One(); Packed = true; } bool ConstStructBuilder::Build(InitListExpr *ILE) { if (ILE->initializesStdInitializerList()) { //CGM.ErrorUnsupported(ILE, "global std::initializer_list"); return false; } RecordDecl *RD = ILE->getType()->getAs()->getDecl(); const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); unsigned FieldNo = 0; unsigned ElementNo = 0; const FieldDecl *LastFD = 0; bool IsMsStruct = RD->isMsStruct(CGM.getContext()); for (RecordDecl::field_iterator Field = RD->field_begin(), FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { if (IsMsStruct) { // Zero-length bitfields following non-bitfield members are // ignored: if (CGM.getContext().ZeroBitfieldFollowsNonBitfield(*Field, LastFD)) { --FieldNo; continue; } LastFD = *Field; } // If this is a union, skip all the fields that aren't being initialized. if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) continue; // Don't emit anonymous bitfields, they just affect layout. if (Field->isUnnamedBitfield()) { LastFD = *Field; continue; } // Get the initializer. A struct can include fields without initializers, // we just use explicit null values for them. llvm::Constant *EltInit; if (ElementNo < ILE->getNumInits()) EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), Field->getType(), CGF); else EltInit = CGM.EmitNullConstant(Field->getType()); if (!EltInit) return false; if (!Field->isBitField()) { // Handle non-bitfield members. AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit); } else { // Otherwise we have a bitfield. AppendBitField(*Field, Layout.getFieldOffset(FieldNo), cast(EltInit)); } } return true; } namespace { struct BaseInfo { BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index) : Decl(Decl), Offset(Offset), Index(Index) { } const CXXRecordDecl *Decl; CharUnits Offset; unsigned Index; bool operator<(const BaseInfo &O) const { return Offset < O.Offset; } }; } void ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase, llvm::Constant *VTable, const CXXRecordDecl *VTableClass, CharUnits Offset) { const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); if (const CXXRecordDecl *CD = dyn_cast(RD)) { // Add a vtable pointer, if we need one and it hasn't already been added. if (CD->isDynamicClass() && !IsPrimaryBase) AppendVTablePointer(BaseSubobject(CD, Offset), VTable, VTableClass); // Accumulate and sort bases, in order to visit them in address order, which // may not be the same as declaration order. SmallVector Bases; Bases.reserve(CD->getNumBases()); unsigned BaseNo = 0; for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(), BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) { assert(!Base->isVirtual() && "should not have virtual bases here"); const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl(); CharUnits BaseOffset = Layout.getBaseClassOffset(BD); Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo)); } std::stable_sort(Bases.begin(), Bases.end()); for (unsigned I = 0, N = Bases.size(); I != N; ++I) { BaseInfo &Base = Bases[I]; bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl; Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase, VTable, VTableClass, Offset + Base.Offset); } } unsigned FieldNo = 0; const FieldDecl *LastFD = 0; bool IsMsStruct = RD->isMsStruct(CGM.getContext()); uint64_t OffsetBits = CGM.getContext().toBits(Offset); for (RecordDecl::field_iterator Field = RD->field_begin(), FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { if (IsMsStruct) { // Zero-length bitfields following non-bitfield members are // ignored: if (CGM.getContext().ZeroBitfieldFollowsNonBitfield(*Field, LastFD)) { --FieldNo; continue; } LastFD = *Field; } // If this is a union, skip all the fields that aren't being initialized. if (RD->isUnion() && Val.getUnionField() != *Field) continue; // Don't emit anonymous bitfields, they just affect layout. if (Field->isUnnamedBitfield()) { LastFD = *Field; continue; } // Emit the value of the initializer. const APValue &FieldValue = RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo); llvm::Constant *EltInit = CGM.EmitConstantValueForMemory(FieldValue, Field->getType(), CGF); assert(EltInit && "EmitConstantValue can't fail"); if (!Field->isBitField()) { // Handle non-bitfield members. AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit); } else { // Otherwise we have a bitfield. AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, cast(EltInit)); } } } llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) { RecordDecl *RD = Ty->getAs()->getDecl(); const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); CharUnits LayoutSizeInChars = Layout.getSize(); if (NextFieldOffsetInChars > LayoutSizeInChars) { // If the struct is bigger than the size of the record type, // we must have a flexible array member at the end. assert(RD->hasFlexibleArrayMember() && "Must have flexible array member if struct is bigger than type!"); // No tail padding is necessary. } else { // Append tail padding if necessary. AppendTailPadding(LayoutSizeInChars); CharUnits LLVMSizeInChars = NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment); // Check if we need to convert the struct to a packed struct. if (NextFieldOffsetInChars <= LayoutSizeInChars && LLVMSizeInChars > LayoutSizeInChars) { assert(!Packed && "Size mismatch!"); ConvertStructToPacked(); assert(NextFieldOffsetInChars <= LayoutSizeInChars && "Converting to packed did not help!"); } assert(LayoutSizeInChars == NextFieldOffsetInChars && "Tail padding mismatch!"); } // Pick the type to use. If the type is layout identical to the ConvertType // type then use it, otherwise use whatever the builder produced for us. llvm::StructType *STy = llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), Elements, Packed); llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty); if (llvm::StructType *ValSTy = dyn_cast(ValTy)) { if (ValSTy->isLayoutIdentical(STy)) STy = ValSTy; } llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements); assert(NextFieldOffsetInChars.RoundUpToAlignment(getAlignment(Result)) == getSizeInChars(Result) && "Size mismatch!"); return Result; } llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) { ConstStructBuilder Builder(CGM, CGF); if (!Builder.Build(ILE)) return 0; return Builder.Finalize(ILE->getType()); } llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, const APValue &Val, QualType ValTy) { ConstStructBuilder Builder(CGM, CGF); const RecordDecl *RD = ValTy->castAs()->getDecl(); const CXXRecordDecl *CD = dyn_cast(RD); llvm::Constant *VTable = 0; if (CD && CD->isDynamicClass()) VTable = CGM.getVTables().GetAddrOfVTable(CD); Builder.Build(Val, RD, false, VTable, CD, CharUnits::Zero()); return Builder.Finalize(ValTy); } //===----------------------------------------------------------------------===// // ConstExprEmitter //===----------------------------------------------------------------------===// /// This class only needs to handle two cases: /// 1) Literals (this is used by APValue emission to emit literals). /// 2) Arrays, structs and unions (outside C++11 mode, we don't currently /// constant fold these types). class ConstExprEmitter : public StmtVisitor { CodeGenModule &CGM; CodeGenFunction *CGF; llvm::LLVMContext &VMContext; public: ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { } //===--------------------------------------------------------------------===// // Visitor Methods //===--------------------------------------------------------------------===// llvm::Constant *VisitStmt(Stmt *S) { return 0; } llvm::Constant *VisitParenExpr(ParenExpr *PE) { return Visit(PE->getSubExpr()); } llvm::Constant * VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) { return Visit(PE->getReplacement()); } llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { return Visit(GE->getResultExpr()); } llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { return Visit(E->getInitializer()); } llvm::Constant *VisitCastExpr(CastExpr* E) { Expr *subExpr = E->getSubExpr(); llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); if (!C) return 0; llvm::Type *destType = ConvertType(E->getType()); switch (E->getCastKind()) { case CK_ToUnion: { // GCC cast to union extension assert(E->getType()->isUnionType() && "Destination type is not union type!"); // Build a struct with the union sub-element as the first member, // and padded to the appropriate size SmallVector Elts; SmallVector Types; Elts.push_back(C); Types.push_back(C->getType()); unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType()); unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destType); assert(CurSize <= TotalSize && "Union size mismatch!"); if (unsigned NumPadBytes = TotalSize - CurSize) { llvm::Type *Ty = CGM.Int8Ty; if (NumPadBytes > 1) Ty = llvm::ArrayType::get(Ty, NumPadBytes); Elts.push_back(llvm::UndefValue::get(Ty)); Types.push_back(Ty); } llvm::StructType* STy = llvm::StructType::get(C->getType()->getContext(), Types, false); return llvm::ConstantStruct::get(STy, Elts); } case CK_LValueToRValue: case CK_AtomicToNonAtomic: case CK_NonAtomicToAtomic: case CK_NoOp: return C; case CK_Dependent: llvm_unreachable("saw dependent cast!"); case CK_BuiltinFnToFnPtr: llvm_unreachable("builtin functions are handled elsewhere"); case CK_ReinterpretMemberPointer: case CK_DerivedToBaseMemberPointer: case CK_BaseToDerivedMemberPointer: return CGM.getCXXABI().EmitMemberPointerConversion(E, C); // These will never be supported. case CK_ObjCObjectLValueCast: case CK_ARCProduceObject: case CK_ARCConsumeObject: case CK_ARCReclaimReturnedObject: case CK_ARCExtendBlockObject: case CK_CopyAndAutoreleaseBlockObject: return 0; // These don't need to be handled here because Evaluate knows how to // evaluate them in the cases where they can be folded. case CK_BitCast: case CK_ToVoid: case CK_Dynamic: case CK_LValueBitCast: case CK_NullToMemberPointer: case CK_UserDefinedConversion: case CK_ConstructorConversion: case CK_CPointerToObjCPointerCast: case CK_BlockPointerToObjCPointerCast: case CK_AnyPointerToBlockPointerCast: case CK_ArrayToPointerDecay: case CK_FunctionToPointerDecay: case CK_BaseToDerived: case CK_DerivedToBase: case CK_UncheckedDerivedToBase: case CK_MemberPointerToBoolean: case CK_VectorSplat: case CK_FloatingRealToComplex: case CK_FloatingComplexToReal: case CK_FloatingComplexToBoolean: case CK_FloatingComplexCast: case CK_FloatingComplexToIntegralComplex: case CK_IntegralRealToComplex: case CK_IntegralComplexToReal: case CK_IntegralComplexToBoolean: case CK_IntegralComplexCast: case CK_IntegralComplexToFloatingComplex: case CK_PointerToIntegral: case CK_PointerToBoolean: case CK_NullToPointer: case CK_IntegralCast: case CK_IntegralToPointer: case CK_IntegralToBoolean: case CK_IntegralToFloating: case CK_FloatingToIntegral: case CK_FloatingToBoolean: case CK_FloatingCast: case CK_ZeroToOCLEvent: return 0; } llvm_unreachable("Invalid CastKind"); } llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { return Visit(DAE->getExpr()); } llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) { // No need for a DefaultInitExprScope: we don't handle 'this' in a // constant expression. return Visit(DIE->getExpr()); } llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) { return Visit(E->GetTemporaryExpr()); } llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { if (ILE->isStringLiteralInit()) return Visit(ILE->getInit(0)); llvm::ArrayType *AType = cast(ConvertType(ILE->getType())); llvm::Type *ElemTy = AType->getElementType(); unsigned NumInitElements = ILE->getNumInits(); unsigned NumElements = AType->getNumElements(); // Initialising an array requires us to automatically // initialise any elements that have not been initialised explicitly unsigned NumInitableElts = std::min(NumInitElements, NumElements); // Copy initializer elements. std::vector Elts; Elts.reserve(NumInitableElts + NumElements); bool RewriteType = false; for (unsigned i = 0; i < NumInitableElts; ++i) { Expr *Init = ILE->getInit(i); llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); if (!C) return 0; RewriteType |= (C->getType() != ElemTy); Elts.push_back(C); } // Initialize remaining array elements. // FIXME: This doesn't handle member pointers correctly! llvm::Constant *fillC; if (Expr *filler = ILE->getArrayFiller()) fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF); else fillC = llvm::Constant::getNullValue(ElemTy); if (!fillC) return 0; RewriteType |= (fillC->getType() != ElemTy); Elts.resize(NumElements, fillC); if (RewriteType) { // FIXME: Try to avoid packing the array std::vector Types; Types.reserve(NumInitableElts + NumElements); for (unsigned i = 0, e = Elts.size(); i < e; ++i) Types.push_back(Elts[i]->getType()); llvm::StructType *SType = llvm::StructType::get(AType->getContext(), Types, true); return llvm::ConstantStruct::get(SType, Elts); } return llvm::ConstantArray::get(AType, Elts); } llvm::Constant *EmitRecordInitialization(InitListExpr *ILE) { return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); } llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { return CGM.EmitNullConstant(E->getType()); } llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { if (ILE->getType()->isArrayType()) return EmitArrayInitialization(ILE); if (ILE->getType()->isRecordType()) return EmitRecordInitialization(ILE); return 0; } llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { if (!E->getConstructor()->isTrivial()) return 0; QualType Ty = E->getType(); // FIXME: We should not have to call getBaseElementType here. const RecordType *RT = CGM.getContext().getBaseElementType(Ty)->getAs(); const CXXRecordDecl *RD = cast(RT->getDecl()); // If the class doesn't have a trivial destructor, we can't emit it as a // constant expr. if (!RD->hasTrivialDestructor()) return 0; // Only copy and default constructors can be trivial. if (E->getNumArgs()) { assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); assert(E->getConstructor()->isCopyOrMoveConstructor() && "trivial ctor has argument but isn't a copy/move ctor"); Expr *Arg = E->getArg(0); assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && "argument to copy ctor is of wrong type"); return Visit(Arg); } return CGM.EmitNullConstant(Ty); } llvm::Constant *VisitStringLiteral(StringLiteral *E) { return CGM.GetConstantArrayFromStringLiteral(E); } llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { // This must be an @encode initializing an array in a static initializer. // Don't emit it as the address of the string, emit the string data itself // as an inline array. std::string Str; CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); const ConstantArrayType *CAT = cast(E->getType()); // Resize the string to the right size, adding zeros at the end, or // truncating as needed. Str.resize(CAT->getSize().getZExtValue(), '\0'); return llvm::ConstantDataArray::getString(VMContext, Str, false); } llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { return Visit(E->getSubExpr()); } // Utility methods llvm::Type *ConvertType(QualType T) { return CGM.getTypes().ConvertType(T); } public: llvm::Constant *EmitLValue(APValue::LValueBase LVBase) { if (const ValueDecl *Decl = LVBase.dyn_cast()) { if (Decl->hasAttr()) return CGM.GetWeakRefReference(Decl); if (const FunctionDecl *FD = dyn_cast(Decl)) return CGM.GetAddrOfFunction(FD); if (const VarDecl* VD = dyn_cast(Decl)) { // We can never refer to a variable with local storage. if (!VD->hasLocalStorage()) { if (VD->isFileVarDecl() || VD->hasExternalStorage()) return CGM.GetAddrOfGlobalVar(VD); else if (VD->isLocalVarDecl()) return CGM.getStaticLocalDeclAddress(VD); } } return 0; } Expr *E = const_cast(LVBase.get()); switch (E->getStmtClass()) { default: break; case Expr::CompoundLiteralExprClass: { // Note that due to the nature of compound literals, this is guaranteed // to be the only use of the variable, so we just generate it here. CompoundLiteralExpr *CLE = cast(E); llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(), CLE->getType(), CGF); // FIXME: "Leaked" on failure. if (C) C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), E->getType().isConstant(CGM.getContext()), llvm::GlobalValue::InternalLinkage, C, ".compoundliteral", 0, llvm::GlobalVariable::NotThreadLocal, CGM.getContext().getTargetAddressSpace(E->getType())); return C; } case Expr::StringLiteralClass: return CGM.GetAddrOfConstantStringFromLiteral(cast(E)); case Expr::ObjCEncodeExprClass: return CGM.GetAddrOfConstantStringFromObjCEncode(cast(E)); case Expr::ObjCStringLiteralClass: { ObjCStringLiteral* SL = cast(E); llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(SL->getString()); return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); } case Expr::PredefinedExprClass: { unsigned Type = cast(E)->getIdentType(); if (CGF) { LValue Res = CGF->EmitPredefinedLValue(cast(E)); return cast(Res.getAddress()); } else if (Type == PredefinedExpr::PrettyFunction) { return CGM.GetAddrOfConstantCString("top level", ".tmp"); } return CGM.GetAddrOfConstantCString("", ".tmp"); } case Expr::AddrLabelExprClass: { assert(CGF && "Invalid address of label expression outside function."); llvm::Constant *Ptr = CGF->GetAddrOfLabel(cast(E)->getLabel()); return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); } case Expr::CallExprClass: { CallExpr* CE = cast(E); unsigned builtin = CE->isBuiltinCall(); if (builtin != Builtin::BI__builtin___CFStringMakeConstantString && builtin != Builtin::BI__builtin___NSStringMakeConstantString) break; const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); const StringLiteral *Literal = cast(Arg); if (builtin == Builtin::BI__builtin___NSStringMakeConstantString) { return CGM.getObjCRuntime().GenerateConstantString(Literal); } // FIXME: need to deal with UCN conversion issues. return CGM.GetAddrOfConstantCFString(Literal); } case Expr::BlockExprClass: { std::string FunctionName; if (CGF) FunctionName = CGF->CurFn->getName(); else FunctionName = "global"; return CGM.GetAddrOfGlobalBlock(cast(E), FunctionName.c_str()); } case Expr::CXXTypeidExprClass: { CXXTypeidExpr *Typeid = cast(E); QualType T; if (Typeid->isTypeOperand()) T = Typeid->getTypeOperand(); else T = Typeid->getExprOperand()->getType(); return CGM.GetAddrOfRTTIDescriptor(T); } case Expr::CXXUuidofExprClass: { return CGM.GetAddrOfUuidDescriptor(cast(E)); } } return 0; } }; } // end anonymous namespace. llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D, CodeGenFunction *CGF) { // Make a quick check if variable can be default NULL initialized // and avoid going through rest of code which may do, for c++11, // initialization of memory to all NULLs. if (!D.hasLocalStorage()) { QualType Ty = D.getType(); if (Ty->isArrayType()) Ty = Context.getBaseElementType(Ty); if (Ty->isRecordType()) if (const CXXConstructExpr *E = dyn_cast_or_null(D.getInit())) { const CXXConstructorDecl *CD = E->getConstructor(); if (CD->isTrivial() && CD->isDefaultConstructor()) return EmitNullConstant(D.getType()); } } if (const APValue *Value = D.evaluateValue()) return EmitConstantValueForMemory(*Value, D.getType(), CGF); // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a // reference is a constant expression, and the reference binds to a temporary, // then constant initialization is performed. ConstExprEmitter will // incorrectly emit a prvalue constant in this case, and the calling code // interprets that as the (pointer) value of the reference, rather than the // desired value of the referee. if (D.getType()->isReferenceType()) return 0; const Expr *E = D.getInit(); assert(E && "No initializer to emit"); llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast(E)); if (C && C->getType()->isIntegerTy(1)) { llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); C = llvm::ConstantExpr::getZExt(C, BoolTy); } return C; } llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, QualType DestType, CodeGenFunction *CGF) { Expr::EvalResult Result; bool Success = false; if (DestType->isReferenceType()) Success = E->EvaluateAsLValue(Result, Context); else Success = E->EvaluateAsRValue(Result, Context); llvm::Constant *C = 0; if (Success && !Result.HasSideEffects) C = EmitConstantValue(Result.Val, DestType, CGF); else C = ConstExprEmitter(*this, CGF).Visit(const_cast(E)); if (C && C->getType()->isIntegerTy(1)) { llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); C = llvm::ConstantExpr::getZExt(C, BoolTy); } return C; } llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value, QualType DestType, CodeGenFunction *CGF) { switch (Value.getKind()) { case APValue::Uninitialized: llvm_unreachable("Constant expressions should be initialized."); case APValue::LValue: { llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); llvm::Constant *Offset = llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity()); llvm::Constant *C; if (APValue::LValueBase LVBase = Value.getLValueBase()) { // An array can be represented as an lvalue referring to the base. if (isa(DestTy)) { assert(Offset->isNullValue() && "offset on array initializer"); return ConstExprEmitter(*this, CGF).Visit( const_cast(LVBase.get())); } C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase); // Apply offset if necessary. if (!Offset->isNullValue()) { llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Int8PtrTy); Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset); C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); } // Convert to the appropriate type; this could be an lvalue for // an integer. if (isa(DestTy)) return llvm::ConstantExpr::getBitCast(C, DestTy); return llvm::ConstantExpr::getPtrToInt(C, DestTy); } else { C = Offset; // Convert to the appropriate type; this could be an lvalue for // an integer. if (isa(DestTy)) return llvm::ConstantExpr::getIntToPtr(C, DestTy); // If the types don't match this should only be a truncate. if (C->getType() != DestTy) return llvm::ConstantExpr::getTrunc(C, DestTy); return C; } } case APValue::Int: return llvm::ConstantInt::get(VMContext, Value.getInt()); case APValue::ComplexInt: { llvm::Constant *Complex[2]; Complex[0] = llvm::ConstantInt::get(VMContext, Value.getComplexIntReal()); Complex[1] = llvm::ConstantInt::get(VMContext, Value.getComplexIntImag()); // FIXME: the target may want to specify that this is packed. llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), Complex[1]->getType(), NULL); return llvm::ConstantStruct::get(STy, Complex); } case APValue::Float: { const llvm::APFloat &Init = Value.getFloat(); if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf && !Context.getLangOpts().NativeHalfType) return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt()); else return llvm::ConstantFP::get(VMContext, Init); } case APValue::ComplexFloat: { llvm::Constant *Complex[2]; Complex[0] = llvm::ConstantFP::get(VMContext, Value.getComplexFloatReal()); Complex[1] = llvm::ConstantFP::get(VMContext, Value.getComplexFloatImag()); // FIXME: the target may want to specify that this is packed. llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), Complex[1]->getType(), NULL); return llvm::ConstantStruct::get(STy, Complex); } case APValue::Vector: { SmallVector Inits; unsigned NumElts = Value.getVectorLength(); for (unsigned i = 0; i != NumElts; ++i) { const APValue &Elt = Value.getVectorElt(i); if (Elt.isInt()) Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); else Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); } return llvm::ConstantVector::get(Inits); } case APValue::AddrLabelDiff: { const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS(); const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS(); llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF); llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF); // Compute difference llvm::Type *ResultType = getTypes().ConvertType(DestType); LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy); RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy); llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS); // LLVM is a bit sensitive about the exact format of the // address-of-label difference; make sure to truncate after // the subtraction. return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType); } case APValue::Struct: case APValue::Union: return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType); case APValue::Array: { const ArrayType *CAT = Context.getAsArrayType(DestType); unsigned NumElements = Value.getArraySize(); unsigned NumInitElts = Value.getArrayInitializedElts(); std::vector Elts; Elts.reserve(NumElements); // Emit array filler, if there is one. llvm::Constant *Filler = 0; if (Value.hasArrayFiller()) Filler = EmitConstantValueForMemory(Value.getArrayFiller(), CAT->getElementType(), CGF); // Emit initializer elements. llvm::Type *CommonElementType = 0; for (unsigned I = 0; I < NumElements; ++I) { llvm::Constant *C = Filler; if (I < NumInitElts) C = EmitConstantValueForMemory(Value.getArrayInitializedElt(I), CAT->getElementType(), CGF); else assert(Filler && "Missing filler for implicit elements of initializer"); if (I == 0) CommonElementType = C->getType(); else if (C->getType() != CommonElementType) CommonElementType = 0; Elts.push_back(C); } if (!CommonElementType) { // FIXME: Try to avoid packing the array std::vector Types; Types.reserve(NumElements); for (unsigned i = 0, e = Elts.size(); i < e; ++i) Types.push_back(Elts[i]->getType()); llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true); return llvm::ConstantStruct::get(SType, Elts); } llvm::ArrayType *AType = llvm::ArrayType::get(CommonElementType, NumElements); return llvm::ConstantArray::get(AType, Elts); } case APValue::MemberPointer: return getCXXABI().EmitMemberPointer(Value, DestType); } llvm_unreachable("Unknown APValue kind"); } llvm::Constant * CodeGenModule::EmitConstantValueForMemory(const APValue &Value, QualType DestType, CodeGenFunction *CGF) { llvm::Constant *C = EmitConstantValue(Value, DestType, CGF); if (C->getType()->isIntegerTy(1)) { llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType); C = llvm::ConstantExpr::getZExt(C, BoolTy); } return C; } llvm::Constant * CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) { assert(E->isFileScope() && "not a file-scope compound literal expr"); return ConstExprEmitter(*this, 0).EmitLValue(E); } llvm::Constant * CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { // Member pointer constants always have a very particular form. const MemberPointerType *type = cast(uo->getType()); const ValueDecl *decl = cast(uo->getSubExpr())->getDecl(); // A member function pointer. if (const CXXMethodDecl *method = dyn_cast(decl)) return getCXXABI().EmitMemberPointer(method); // Otherwise, a member data pointer. uint64_t fieldOffset = getContext().getFieldOffset(decl); CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); return getCXXABI().EmitMemberDataPointer(type, chars); } static void FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, SmallVectorImpl &Elements, uint64_t StartOffset) { assert(StartOffset % CGM.getContext().getCharWidth() == 0 && "StartOffset not byte aligned!"); if (CGM.getTypes().isZeroInitializable(T)) return; if (const ConstantArrayType *CAT = CGM.getContext().getAsConstantArrayType(T)) { QualType ElementTy = CAT->getElementType(); uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { FillInNullDataMemberPointers(CGM, ElementTy, Elements, StartOffset + I * ElementSize); } } else if (const RecordType *RT = T->getAs()) { const CXXRecordDecl *RD = cast(RT->getDecl()); const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); // Go through all bases and fill in any null pointer to data members. for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), E = RD->bases_end(); I != E; ++I) { if (I->isVirtual()) { // Ignore virtual bases. continue; } const CXXRecordDecl *BaseDecl = cast(I->getType()->getAs()->getDecl()); // Ignore empty bases. if (BaseDecl->isEmpty()) continue; // Ignore bases that don't have any pointer to data members. if (CGM.getTypes().isZeroInitializable(BaseDecl)) continue; uint64_t BaseOffset = CGM.getContext().toBits(Layout.getBaseClassOffset(BaseDecl)); FillInNullDataMemberPointers(CGM, I->getType(), Elements, StartOffset + BaseOffset); } // Visit all fields. unsigned FieldNo = 0; for (RecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end(); I != E; ++I, ++FieldNo) { QualType FieldType = I->getType(); if (CGM.getTypes().isZeroInitializable(FieldType)) continue; uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); } } else { assert(T->isMemberPointerType() && "Should only see member pointers here!"); assert(!T->getAs()->getPointeeType()->isFunctionType() && "Should only see pointers to data members here!"); CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); // FIXME: hardcodes Itanium member pointer representation! llvm::Constant *NegativeOne = llvm::ConstantInt::get(CGM.Int8Ty, -1ULL, /*isSigned*/true); // Fill in the null data member pointer. for (CharUnits I = StartIndex; I != EndIndex; ++I) Elements[I.getQuantity()] = NegativeOne; } } static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, llvm::Type *baseType, const CXXRecordDecl *base); static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, const CXXRecordDecl *record, bool asCompleteObject) { const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); llvm::StructType *structure = (asCompleteObject ? layout.getLLVMType() : layout.getBaseSubobjectLLVMType()); unsigned numElements = structure->getNumElements(); std::vector elements(numElements); // Fill in all the bases. for (CXXRecordDecl::base_class_const_iterator I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { if (I->isVirtual()) { // Ignore virtual bases; if we're laying out for a complete // object, we'll lay these out later. continue; } const CXXRecordDecl *base = cast(I->getType()->castAs()->getDecl()); // Ignore empty bases. if (base->isEmpty()) continue; unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); llvm::Type *baseType = structure->getElementType(fieldIndex); elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); } // Fill in all the fields. for (RecordDecl::field_iterator I = record->field_begin(), E = record->field_end(); I != E; ++I) { const FieldDecl *field = *I; // Fill in non-bitfields. (Bitfields always use a zero pattern, which we // will fill in later.) if (!field->isBitField()) { unsigned fieldIndex = layout.getLLVMFieldNo(field); elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); } // For unions, stop after the first named field. if (record->isUnion() && field->getDeclName()) break; } // Fill in the virtual bases, if we're working with the complete object. if (asCompleteObject) { for (CXXRecordDecl::base_class_const_iterator I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { const CXXRecordDecl *base = cast(I->getType()->castAs()->getDecl()); // Ignore empty bases. if (base->isEmpty()) continue; unsigned fieldIndex = layout.getVirtualBaseIndex(base); // We might have already laid this field out. if (elements[fieldIndex]) continue; llvm::Type *baseType = structure->getElementType(fieldIndex); elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); } } // Now go through all other fields and zero them out. for (unsigned i = 0; i != numElements; ++i) { if (!elements[i]) elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); } return llvm::ConstantStruct::get(structure, elements); } /// Emit the null constant for a base subobject. static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, llvm::Type *baseType, const CXXRecordDecl *base) { const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); // Just zero out bases that don't have any pointer to data members. if (baseLayout.isZeroInitializableAsBase()) return llvm::Constant::getNullValue(baseType); // If the base type is a struct, we can just use its null constant. if (isa(baseType)) { return EmitNullConstant(CGM, base, /*complete*/ false); } // Otherwise, some bases are represented as arrays of i8 if the size // of the base is smaller than its corresponding LLVM type. Figure // out how many elements this base array has. llvm::ArrayType *baseArrayType = cast(baseType); unsigned numBaseElements = baseArrayType->getNumElements(); // Fill in null data member pointers. SmallVector baseElements(numBaseElements); FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), baseElements, 0); // Now go through all other elements and zero them out. if (numBaseElements) { llvm::Constant *i8_zero = llvm::Constant::getNullValue(CGM.Int8Ty); for (unsigned i = 0; i != numBaseElements; ++i) { if (!baseElements[i]) baseElements[i] = i8_zero; } } return llvm::ConstantArray::get(baseArrayType, baseElements); } llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { if (getTypes().isZeroInitializable(T)) return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { llvm::ArrayType *ATy = cast(getTypes().ConvertTypeForMem(T)); QualType ElementTy = CAT->getElementType(); llvm::Constant *Element = EmitNullConstant(ElementTy); unsigned NumElements = CAT->getSize().getZExtValue(); if (Element->isNullValue()) return llvm::ConstantAggregateZero::get(ATy); SmallVector Array(NumElements, Element); return llvm::ConstantArray::get(ATy, Array); } if (const RecordType *RT = T->getAs()) { const CXXRecordDecl *RD = cast(RT->getDecl()); return ::EmitNullConstant(*this, RD, /*complete object*/ true); } assert(T->isMemberPointerType() && "Should only see member pointers here!"); assert(!T->getAs()->getPointeeType()->isFunctionType() && "Should only see pointers to data members here!"); // Itanium C++ ABI 2.3: // A NULL pointer is represented as -1. return getCXXABI().EmitNullMemberPointer(T->castAs()); } llvm::Constant * CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { return ::EmitNullConstant(*this, Record, false); }