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Diffstat (limited to 'clang/lib/CodeGen/CGExprConstant.cpp')
| -rw-r--r-- | clang/lib/CodeGen/CGExprConstant.cpp | 1496 |
1 files changed, 1496 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp new file mode 100644 index 0000000..bc9f9ef --- /dev/null +++ b/clang/lib/CodeGen/CGExprConstant.cpp @@ -0,0 +1,1496 @@ +//===--- 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 "CodeGenModule.h" +#include "CGCXXABI.h" +#include "CGObjCRuntime.h" +#include "CGRecordLayout.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/Constants.h" +#include "llvm/Function.h" +#include "llvm/GlobalVariable.h" +#include "llvm/Target/TargetData.h" +using namespace clang; +using namespace CodeGen; + +//===----------------------------------------------------------------------===// +// ConstStructBuilder +//===----------------------------------------------------------------------===// + +namespace { +class ConstStructBuilder { + CodeGenModule &CGM; + CodeGenFunction *CGF; + + bool Packed; + CharUnits NextFieldOffsetInChars; + CharUnits LLVMStructAlignment; + SmallVector<llvm::Constant *, 32> 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.getTargetData().getABITypeAlignment(C->getType())); + } + + CharUnits getSizeInChars(const llvm::Constant *C) const { + return CharUnits::fromQuantity( + CGM.getTargetData().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.getTargetData().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.getTargetData().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<llvm::ConstantInt>(LastElt)) + Tmp |= Val->getValue(); + else { + assert(isa<llvm::UndefValue>(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<llvm::IntegerType>(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<llvm::ArrayType>(LastElt->getType()) && + "Expected array padding of undefs"); + llvm::ArrayType *AT = cast<llvm::ArrayType>(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<llvm::UndefValue>(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.getTargetData().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.getTargetData().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<llvm::Constant *, 16> 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.getTargetData().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<RecordType>()->getDecl(); + const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); + + unsigned FieldNo = 0; + unsigned ElementNo = 0; + const FieldDecl *LastFD = 0; + bool IsMsStruct = RD->hasAttr<MsStructAttr>(); + + 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<llvm::ConstantInt>(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<CXXRecordDecl>(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. + llvm::SmallVector<BaseInfo, 8> 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->hasAttr<MsStructAttr>(); + 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<llvm::ConstantInt>(EltInit)); + } + } +} + +llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) { + RecordDecl *RD = Ty->getAs<RecordType>()->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<llvm::StructType>(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<RecordType>()->getDecl(); + const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(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<ConstExprEmitter, llvm::Constant*> { + 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<llvm::Constant*, 2> Elts; + SmallVector<llvm::Type*, 2> Types; + Elts.push_back(C); + Types.push_back(C->getType()); + unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); + unsigned TotalSize = CGM.getTargetData().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_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: + return 0; + } + llvm_unreachable("Invalid CastKind"); + } + + llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { + return Visit(DAE->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<llvm::ArrayType>(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<llvm::Constant*> 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<llvm::Type*> 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 *EmitStructInitialization(InitListExpr *ILE) { + return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); + } + + llvm::Constant *EmitUnionInitialization(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 EmitStructInitialization(ILE); + + if (ILE->getType()->isUnionType()) + return EmitUnionInitialization(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<RecordType>(); + const CXXRecordDecl *RD = cast<CXXRecordDecl>(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<ConstantArrayType>(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<const ValueDecl*>()) { + if (Decl->hasAttr<WeakRefAttr>()) + return CGM.GetWeakRefReference(Decl); + if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) + return CGM.GetAddrOfFunction(FD); + if (const VarDecl* VD = dyn_cast<VarDecl>(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()) { + assert(CGF && "Can't access static local vars without CGF"); + return CGF->GetAddrOfStaticLocalVar(VD); + } + } + } + return 0; + } + + Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>()); + 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<CompoundLiteralExpr>(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, false, + CGM.getContext().getTargetAddressSpace(E->getType())); + return C; + } + case Expr::StringLiteralClass: + return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); + case Expr::ObjCEncodeExprClass: + return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); + case Expr::ObjCStringLiteralClass: { + ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); + llvm::Constant *C = + CGM.getObjCRuntime().GenerateConstantString(SL->getString()); + return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); + } + case Expr::PredefinedExprClass: { + unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); + if (CGF) { + LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); + return cast<llvm::Constant>(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<AddrLabelExpr>(E)->getLabel()); + return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); + } + case Expr::CallExprClass: { + CallExpr* CE = cast<CallExpr>(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<StringLiteral>(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<BlockExpr>(E), FunctionName.c_str()); + } + case Expr::CXXTypeidExprClass: { + CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E); + QualType T; + if (Typeid->isTypeOperand()) + T = Typeid->getTypeOperand(); + else + T = Typeid->getExprOperand()->getType(); + return CGM.GetAddrOfRTTIDescriptor(T); + } + } + + return 0; + } +}; + +} // end anonymous namespace. + +llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D, + CodeGenFunction *CGF) { + 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<Expr*>(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<Expr*>(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<llvm::ArrayType>(DestTy)) { + assert(Offset->isNullValue() && "offset on array initializer"); + return ConstExprEmitter(*this, CGF).Visit( + const_cast<Expr*>(LVBase.get<const Expr*>())); + } + + 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<llvm::PointerType>(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<llvm::PointerType>(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) + 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<llvm::Constant *, 4> 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<llvm::Constant*> 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); + 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<llvm::Type*> 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<MemberPointerType>(uo->getType()); + const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); + + // A member function pointer. + if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(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<llvm::Constant *> &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<RecordType>()) { + const CXXRecordDecl *RD = cast<CXXRecordDecl>(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<CXXRecordDecl>(I->getType()->getAs<RecordType>()->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 = Layout.getBaseClassOffsetInBits(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<MemberPointerType>()->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<llvm::Constant *> 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<CXXRecordDecl>(I->getType()->castAs<RecordType>()->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<CXXRecordDecl>(I->getType()->castAs<RecordType>()->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<llvm::StructType>(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<llvm::ArrayType>(baseType); + unsigned numBaseElements = baseArrayType->getNumElements(); + + // Fill in null data member pointers. + SmallVector<llvm::Constant *, 16> 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<llvm::ArrayType>(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<llvm::Constant *, 8> Array(NumElements, Element); + return llvm::ConstantArray::get(ATy, Array); + } + + if (const RecordType *RT = T->getAs<RecordType>()) { + const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); + return ::EmitNullConstant(*this, RD, /*complete object*/ true); + } + + assert(T->isMemberPointerType() && "Should only see member pointers here!"); + assert(!T->getAs<MemberPointerType>()->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<MemberPointerType>()); +} + +llvm::Constant * +CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { + return ::EmitNullConstant(*this, Record, false); +} |