//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This contains code to emit Constant Expr nodes as LLVM code. // //===----------------------------------------------------------------------===// #include "CGCXXABI.h" #include "CGObjCRuntime.h" #include "CGRecordLayout.h" #include "CodeGenFunction.h" #include "CodeGenModule.h" #include "ConstantEmitter.h" #include "TargetInfo.h" #include "clang/AST/APValue.h" #include "clang/AST/ASTContext.h" #include "clang/AST/Attr.h" #include "clang/AST/RecordLayout.h" #include "clang/AST/StmtVisitor.h" #include "clang/Basic/Builtins.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/Sequence.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; //===----------------------------------------------------------------------===// // ConstantAggregateBuilder //===----------------------------------------------------------------------===// namespace { class ConstExprEmitter; struct ConstantAggregateBuilderUtils { CodeGenModule &CGM; ConstantAggregateBuilderUtils(CodeGenModule &CGM) : CGM(CGM) {} CharUnits getAlignment(const llvm::Constant *C) const { return CharUnits::fromQuantity( CGM.getDataLayout().getABITypeAlignment(C->getType())); } CharUnits getSize(llvm::Type *Ty) const { return CharUnits::fromQuantity(CGM.getDataLayout().getTypeAllocSize(Ty)); } CharUnits getSize(const llvm::Constant *C) const { return getSize(C->getType()); } llvm::Constant *getPadding(CharUnits PadSize) const { llvm::Type *Ty = CGM.Int8Ty; if (PadSize > CharUnits::One()) Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); return llvm::UndefValue::get(Ty); } llvm::Constant *getZeroes(CharUnits ZeroSize) const { llvm::Type *Ty = llvm::ArrayType::get(CGM.Int8Ty, ZeroSize.getQuantity()); return llvm::ConstantAggregateZero::get(Ty); } }; /// Incremental builder for an llvm::Constant* holding a struct or array /// constant. class ConstantAggregateBuilder : private ConstantAggregateBuilderUtils { /// The elements of the constant. These two arrays must have the same size; /// Offsets[i] describes the offset of Elems[i] within the constant. The /// elements are kept in increasing offset order, and we ensure that there /// is no overlap: Offsets[i+1] >= Offsets[i] + getSize(Elemes[i]). /// /// This may contain explicit padding elements (in order to create a /// natural layout), but need not. Gaps between elements are implicitly /// considered to be filled with undef. llvm::SmallVector Elems; llvm::SmallVector Offsets; /// The size of the constant (the maximum end offset of any added element). /// May be larger than the end of Elems.back() if we split the last element /// and removed some trailing undefs. CharUnits Size = CharUnits::Zero(); /// This is true only if laying out Elems in order as the elements of a /// non-packed LLVM struct will give the correct layout. bool NaturalLayout = true; bool split(size_t Index, CharUnits Hint); Optional splitAt(CharUnits Pos); static llvm::Constant *buildFrom(CodeGenModule &CGM, ArrayRef Elems, ArrayRef Offsets, CharUnits StartOffset, CharUnits Size, bool NaturalLayout, llvm::Type *DesiredTy, bool AllowOversized); public: ConstantAggregateBuilder(CodeGenModule &CGM) : ConstantAggregateBuilderUtils(CGM) {} /// Update or overwrite the value starting at \p Offset with \c C. /// /// \param AllowOverwrite If \c true, this constant might overwrite (part of) /// a constant that has already been added. This flag is only used to /// detect bugs. bool add(llvm::Constant *C, CharUnits Offset, bool AllowOverwrite); /// Update or overwrite the bits starting at \p OffsetInBits with \p Bits. bool addBits(llvm::APInt Bits, uint64_t OffsetInBits, bool AllowOverwrite); /// Attempt to condense the value starting at \p Offset to a constant of type /// \p DesiredTy. void condense(CharUnits Offset, llvm::Type *DesiredTy); /// Produce a constant representing the entire accumulated value, ideally of /// the specified type. If \p AllowOversized, the constant might be larger /// than implied by \p DesiredTy (eg, if there is a flexible array member). /// Otherwise, the constant will be of exactly the same size as \p DesiredTy /// even if we can't represent it as that type. llvm::Constant *build(llvm::Type *DesiredTy, bool AllowOversized) const { return buildFrom(CGM, Elems, Offsets, CharUnits::Zero(), Size, NaturalLayout, DesiredTy, AllowOversized); } }; template> static void replace(Container &C, size_t BeginOff, size_t EndOff, Range Vals) { assert(BeginOff <= EndOff && "invalid replacement range"); llvm::replace(C, C.begin() + BeginOff, C.begin() + EndOff, Vals); } bool ConstantAggregateBuilder::add(llvm::Constant *C, CharUnits Offset, bool AllowOverwrite) { // Common case: appending to a layout. if (Offset >= Size) { CharUnits Align = getAlignment(C); CharUnits AlignedSize = Size.alignTo(Align); if (AlignedSize > Offset || Offset.alignTo(Align) != Offset) NaturalLayout = false; else if (AlignedSize < Offset) { Elems.push_back(getPadding(Offset - Size)); Offsets.push_back(Size); } Elems.push_back(C); Offsets.push_back(Offset); Size = Offset + getSize(C); return true; } // Uncommon case: constant overlaps what we've already created. llvm::Optional FirstElemToReplace = splitAt(Offset); if (!FirstElemToReplace) return false; CharUnits CSize = getSize(C); llvm::Optional LastElemToReplace = splitAt(Offset + CSize); if (!LastElemToReplace) return false; assert((FirstElemToReplace == LastElemToReplace || AllowOverwrite) && "unexpectedly overwriting field"); replace(Elems, *FirstElemToReplace, *LastElemToReplace, {C}); replace(Offsets, *FirstElemToReplace, *LastElemToReplace, {Offset}); Size = std::max(Size, Offset + CSize); NaturalLayout = false; return true; } bool ConstantAggregateBuilder::addBits(llvm::APInt Bits, uint64_t OffsetInBits, bool AllowOverwrite) { const ASTContext &Context = CGM.getContext(); const uint64_t CharWidth = CGM.getContext().getCharWidth(); // Offset of where we want the first bit to go within the bits of the // current char. unsigned OffsetWithinChar = OffsetInBits % CharWidth; // We split bit-fields up into individual bytes. Walk over the bytes and // update them. for (CharUnits OffsetInChars = Context.toCharUnitsFromBits(OffsetInBits - OffsetWithinChar); /**/; ++OffsetInChars) { // Number of bits we want to fill in this char. unsigned WantedBits = std::min((uint64_t)Bits.getBitWidth(), CharWidth - OffsetWithinChar); // Get a char containing the bits we want in the right places. The other // bits have unspecified values. llvm::APInt BitsThisChar = Bits; if (BitsThisChar.getBitWidth() < CharWidth) BitsThisChar = BitsThisChar.zext(CharWidth); if (CGM.getDataLayout().isBigEndian()) { // Figure out how much to shift by. We may need to left-shift if we have // less than one byte of Bits left. int Shift = Bits.getBitWidth() - CharWidth + OffsetWithinChar; if (Shift > 0) BitsThisChar.lshrInPlace(Shift); else if (Shift < 0) BitsThisChar = BitsThisChar.shl(-Shift); } else { BitsThisChar = BitsThisChar.shl(OffsetWithinChar); } if (BitsThisChar.getBitWidth() > CharWidth) BitsThisChar = BitsThisChar.trunc(CharWidth); if (WantedBits == CharWidth) { // Got a full byte: just add it directly. add(llvm::ConstantInt::get(CGM.getLLVMContext(), BitsThisChar), OffsetInChars, AllowOverwrite); } else { // Partial byte: update the existing integer if there is one. If we // can't split out a 1-CharUnit range to update, then we can't add // these bits and fail the entire constant emission. llvm::Optional FirstElemToUpdate = splitAt(OffsetInChars); if (!FirstElemToUpdate) return false; llvm::Optional LastElemToUpdate = splitAt(OffsetInChars + CharUnits::One()); if (!LastElemToUpdate) return false; assert(*LastElemToUpdate - *FirstElemToUpdate < 2 && "should have at most one element covering one byte"); // Figure out which bits we want and discard the rest. llvm::APInt UpdateMask(CharWidth, 0); if (CGM.getDataLayout().isBigEndian()) UpdateMask.setBits(CharWidth - OffsetWithinChar - WantedBits, CharWidth - OffsetWithinChar); else UpdateMask.setBits(OffsetWithinChar, OffsetWithinChar + WantedBits); BitsThisChar &= UpdateMask; if (*FirstElemToUpdate == *LastElemToUpdate || Elems[*FirstElemToUpdate]->isNullValue() || isa(Elems[*FirstElemToUpdate])) { // All existing bits are either zero or undef. add(llvm::ConstantInt::get(CGM.getLLVMContext(), BitsThisChar), OffsetInChars, /*AllowOverwrite*/ true); } else { llvm::Constant *&ToUpdate = Elems[*FirstElemToUpdate]; // In order to perform a partial update, we need the existing bitwise // value, which we can only extract for a constant int. auto *CI = dyn_cast(ToUpdate); if (!CI) return false; // Because this is a 1-CharUnit range, the constant occupying it must // be exactly one CharUnit wide. assert(CI->getBitWidth() == CharWidth && "splitAt failed"); assert((!(CI->getValue() & UpdateMask) || AllowOverwrite) && "unexpectedly overwriting bitfield"); BitsThisChar |= (CI->getValue() & ~UpdateMask); ToUpdate = llvm::ConstantInt::get(CGM.getLLVMContext(), BitsThisChar); } } // Stop if we've added all the bits. if (WantedBits == Bits.getBitWidth()) break; // Remove the consumed bits from Bits. if (!CGM.getDataLayout().isBigEndian()) Bits.lshrInPlace(WantedBits); Bits = Bits.trunc(Bits.getBitWidth() - WantedBits); // The remanining bits go at the start of the following bytes. OffsetWithinChar = 0; } return true; } /// Returns a position within Elems and Offsets such that all elements /// before the returned index end before Pos and all elements at or after /// the returned index begin at or after Pos. Splits elements as necessary /// to ensure this. Returns None if we find something we can't split. Optional ConstantAggregateBuilder::splitAt(CharUnits Pos) { if (Pos >= Size) return Offsets.size(); while (true) { auto FirstAfterPos = llvm::upper_bound(Offsets, Pos); if (FirstAfterPos == Offsets.begin()) return 0; // If we already have an element starting at Pos, we're done. size_t LastAtOrBeforePosIndex = FirstAfterPos - Offsets.begin() - 1; if (Offsets[LastAtOrBeforePosIndex] == Pos) return LastAtOrBeforePosIndex; // We found an element starting before Pos. Check for overlap. if (Offsets[LastAtOrBeforePosIndex] + getSize(Elems[LastAtOrBeforePosIndex]) <= Pos) return LastAtOrBeforePosIndex + 1; // Try to decompose it into smaller constants. if (!split(LastAtOrBeforePosIndex, Pos)) return None; } } /// Split the constant at index Index, if possible. Return true if we did. /// Hint indicates the location at which we'd like to split, but may be /// ignored. bool ConstantAggregateBuilder::split(size_t Index, CharUnits Hint) { NaturalLayout = false; llvm::Constant *C = Elems[Index]; CharUnits Offset = Offsets[Index]; if (auto *CA = dyn_cast(C)) { // Expand the sequence into its contained elements. // FIXME: This assumes vector elements are byte-sized. replace(Elems, Index, Index + 1, llvm::map_range(llvm::seq(0u, CA->getNumOperands()), [&](unsigned Op) { return CA->getOperand(Op); })); if (isa(CA->getType()) || isa(CA->getType())) { // Array or vector. llvm::Type *ElemTy = llvm::GetElementPtrInst::getTypeAtIndex(CA->getType(), (uint64_t)0); CharUnits ElemSize = getSize(ElemTy); replace( Offsets, Index, Index + 1, llvm::map_range(llvm::seq(0u, CA->getNumOperands()), [&](unsigned Op) { return Offset + Op * ElemSize; })); } else { // Must be a struct. auto *ST = cast(CA->getType()); const llvm::StructLayout *Layout = CGM.getDataLayout().getStructLayout(ST); replace(Offsets, Index, Index + 1, llvm::map_range( llvm::seq(0u, CA->getNumOperands()), [&](unsigned Op) { return Offset + CharUnits::fromQuantity( Layout->getElementOffset(Op)); })); } return true; } if (auto *CDS = dyn_cast(C)) { // Expand the sequence into its contained elements. // FIXME: This assumes vector elements are byte-sized. // FIXME: If possible, split into two ConstantDataSequentials at Hint. CharUnits ElemSize = getSize(CDS->getElementType()); replace(Elems, Index, Index + 1, llvm::map_range(llvm::seq(0u, CDS->getNumElements()), [&](unsigned Elem) { return CDS->getElementAsConstant(Elem); })); replace(Offsets, Index, Index + 1, llvm::map_range( llvm::seq(0u, CDS->getNumElements()), [&](unsigned Elem) { return Offset + Elem * ElemSize; })); return true; } if (isa(C)) { // Split into two zeros at the hinted offset. CharUnits ElemSize = getSize(C); assert(Hint > Offset && Hint < Offset + ElemSize && "nothing to split"); replace(Elems, Index, Index + 1, {getZeroes(Hint - Offset), getZeroes(Offset + ElemSize - Hint)}); replace(Offsets, Index, Index + 1, {Offset, Hint}); return true; } if (isa(C)) { // Drop undef; it doesn't contribute to the final layout. replace(Elems, Index, Index + 1, {}); replace(Offsets, Index, Index + 1, {}); return true; } // FIXME: We could split a ConstantInt if the need ever arose. // We don't need to do this to handle bit-fields because we always eagerly // split them into 1-byte chunks. return false; } static llvm::Constant * EmitArrayConstant(CodeGenModule &CGM, llvm::ArrayType *DesiredType, llvm::Type *CommonElementType, unsigned ArrayBound, SmallVectorImpl &Elements, llvm::Constant *Filler); llvm::Constant *ConstantAggregateBuilder::buildFrom( CodeGenModule &CGM, ArrayRef Elems, ArrayRef Offsets, CharUnits StartOffset, CharUnits Size, bool NaturalLayout, llvm::Type *DesiredTy, bool AllowOversized) { ConstantAggregateBuilderUtils Utils(CGM); if (Elems.empty()) return llvm::UndefValue::get(DesiredTy); auto Offset = [&](size_t I) { return Offsets[I] - StartOffset; }; // If we want an array type, see if all the elements are the same type and // appropriately spaced. if (llvm::ArrayType *ATy = dyn_cast(DesiredTy)) { assert(!AllowOversized && "oversized array emission not supported"); bool CanEmitArray = true; llvm::Type *CommonType = Elems[0]->getType(); llvm::Constant *Filler = llvm::Constant::getNullValue(CommonType); CharUnits ElemSize = Utils.getSize(ATy->getElementType()); SmallVector ArrayElements; for (size_t I = 0; I != Elems.size(); ++I) { // Skip zeroes; we'll use a zero value as our array filler. if (Elems[I]->isNullValue()) continue; // All remaining elements must be the same type. if (Elems[I]->getType() != CommonType || Offset(I) % ElemSize != 0) { CanEmitArray = false; break; } ArrayElements.resize(Offset(I) / ElemSize + 1, Filler); ArrayElements.back() = Elems[I]; } if (CanEmitArray) { return EmitArrayConstant(CGM, ATy, CommonType, ATy->getNumElements(), ArrayElements, Filler); } // Can't emit as an array, carry on to emit as a struct. } CharUnits DesiredSize = Utils.getSize(DesiredTy); CharUnits Align = CharUnits::One(); for (llvm::Constant *C : Elems) Align = std::max(Align, Utils.getAlignment(C)); CharUnits AlignedSize = Size.alignTo(Align); bool Packed = false; ArrayRef UnpackedElems = Elems; llvm::SmallVector UnpackedElemStorage; if ((DesiredSize < AlignedSize && !AllowOversized) || DesiredSize.alignTo(Align) != DesiredSize) { // The natural layout would be the wrong size; force use of a packed layout. NaturalLayout = false; Packed = true; } else if (DesiredSize > AlignedSize) { // The constant would be too small. Add padding to fix it. UnpackedElemStorage.assign(Elems.begin(), Elems.end()); UnpackedElemStorage.push_back(Utils.getPadding(DesiredSize - Size)); UnpackedElems = UnpackedElemStorage; } // If we don't have a natural layout, insert padding as necessary. // As we go, double-check to see if we can actually just emit Elems // as a non-packed struct and do so opportunistically if possible. llvm::SmallVector PackedElems; if (!NaturalLayout) { CharUnits SizeSoFar = CharUnits::Zero(); for (size_t I = 0; I != Elems.size(); ++I) { CharUnits Align = Utils.getAlignment(Elems[I]); CharUnits NaturalOffset = SizeSoFar.alignTo(Align); CharUnits DesiredOffset = Offset(I); assert(DesiredOffset >= SizeSoFar && "elements out of order"); if (DesiredOffset != NaturalOffset) Packed = true; if (DesiredOffset != SizeSoFar) PackedElems.push_back(Utils.getPadding(DesiredOffset - SizeSoFar)); PackedElems.push_back(Elems[I]); SizeSoFar = DesiredOffset + Utils.getSize(Elems[I]); } // If we're using the packed layout, pad it out to the desired size if // necessary. if (Packed) { assert((SizeSoFar <= DesiredSize || AllowOversized) && "requested size is too small for contents"); if (SizeSoFar < DesiredSize) PackedElems.push_back(Utils.getPadding(DesiredSize - SizeSoFar)); } } llvm::StructType *STy = llvm::ConstantStruct::getTypeForElements( CGM.getLLVMContext(), Packed ? PackedElems : UnpackedElems, Packed); // Pick the type to use. If the type is layout identical to the desired // type then use it, otherwise use whatever the builder produced for us. if (llvm::StructType *DesiredSTy = dyn_cast(DesiredTy)) { if (DesiredSTy->isLayoutIdentical(STy)) STy = DesiredSTy; } return llvm::ConstantStruct::get(STy, Packed ? PackedElems : UnpackedElems); } void ConstantAggregateBuilder::condense(CharUnits Offset, llvm::Type *DesiredTy) { CharUnits Size = getSize(DesiredTy); llvm::Optional FirstElemToReplace = splitAt(Offset); if (!FirstElemToReplace) return; size_t First = *FirstElemToReplace; llvm::Optional LastElemToReplace = splitAt(Offset + Size); if (!LastElemToReplace) return; size_t Last = *LastElemToReplace; size_t Length = Last - First; if (Length == 0) return; if (Length == 1 && Offsets[First] == Offset && getSize(Elems[First]) == Size) { // Re-wrap single element structs if necessary. Otherwise, leave any single // element constant of the right size alone even if it has the wrong type. auto *STy = dyn_cast(DesiredTy); if (STy && STy->getNumElements() == 1 && STy->getElementType(0) == Elems[First]->getType()) Elems[First] = llvm::ConstantStruct::get(STy, Elems[First]); return; } llvm::Constant *Replacement = buildFrom( CGM, makeArrayRef(Elems).slice(First, Length), makeArrayRef(Offsets).slice(First, Length), Offset, getSize(DesiredTy), /*known to have natural layout=*/false, DesiredTy, false); replace(Elems, First, Last, {Replacement}); replace(Offsets, First, Last, {Offset}); } //===----------------------------------------------------------------------===// // ConstStructBuilder //===----------------------------------------------------------------------===// class ConstStructBuilder { CodeGenModule &CGM; ConstantEmitter &Emitter; ConstantAggregateBuilder &Builder; CharUnits StartOffset; public: static llvm::Constant *BuildStruct(ConstantEmitter &Emitter, InitListExpr *ILE, QualType StructTy); static llvm::Constant *BuildStruct(ConstantEmitter &Emitter, const APValue &Value, QualType ValTy); static bool UpdateStruct(ConstantEmitter &Emitter, ConstantAggregateBuilder &Const, CharUnits Offset, InitListExpr *Updater); private: ConstStructBuilder(ConstantEmitter &Emitter, ConstantAggregateBuilder &Builder, CharUnits StartOffset) : CGM(Emitter.CGM), Emitter(Emitter), Builder(Builder), StartOffset(StartOffset) {} bool AppendField(const FieldDecl *Field, uint64_t FieldOffset, llvm::Constant *InitExpr, bool AllowOverwrite = false); bool AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst, bool AllowOverwrite = false); bool AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, llvm::ConstantInt *InitExpr, bool AllowOverwrite = false); bool Build(InitListExpr *ILE, bool AllowOverwrite); bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase, const CXXRecordDecl *VTableClass, CharUnits BaseOffset); llvm::Constant *Finalize(QualType Ty); }; bool ConstStructBuilder::AppendField( const FieldDecl *Field, uint64_t FieldOffset, llvm::Constant *InitCst, bool AllowOverwrite) { const ASTContext &Context = CGM.getContext(); CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset); return AppendBytes(FieldOffsetInChars, InitCst, AllowOverwrite); } bool ConstStructBuilder::AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst, bool AllowOverwrite) { return Builder.add(InitCst, StartOffset + FieldOffsetInChars, AllowOverwrite); } bool ConstStructBuilder::AppendBitField( const FieldDecl *Field, uint64_t FieldOffset, llvm::ConstantInt *CI, bool AllowOverwrite) { const CGRecordLayout &RL = CGM.getTypes().getCGRecordLayout(Field->getParent()); const CGBitFieldInfo &Info = RL.getBitFieldInfo(Field); 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 (Info.Size > FieldValue.getBitWidth()) FieldValue = FieldValue.zext(Info.Size); // Truncate the size of FieldValue to the bit field size. if (Info.Size < FieldValue.getBitWidth()) FieldValue = FieldValue.trunc(Info.Size); return Builder.addBits(FieldValue, CGM.getContext().toBits(StartOffset) + FieldOffset, AllowOverwrite); } static bool EmitDesignatedInitUpdater(ConstantEmitter &Emitter, ConstantAggregateBuilder &Const, CharUnits Offset, QualType Type, InitListExpr *Updater) { if (Type->isRecordType()) return ConstStructBuilder::UpdateStruct(Emitter, Const, Offset, Updater); auto CAT = Emitter.CGM.getContext().getAsConstantArrayType(Type); if (!CAT) return false; QualType ElemType = CAT->getElementType(); CharUnits ElemSize = Emitter.CGM.getContext().getTypeSizeInChars(ElemType); llvm::Type *ElemTy = Emitter.CGM.getTypes().ConvertTypeForMem(ElemType); llvm::Constant *FillC = nullptr; if (Expr *Filler = Updater->getArrayFiller()) { if (!isa(Filler)) { FillC = Emitter.tryEmitAbstractForMemory(Filler, ElemType); if (!FillC) return false; } } unsigned NumElementsToUpdate = FillC ? CAT->getSize().getZExtValue() : Updater->getNumInits(); for (unsigned I = 0; I != NumElementsToUpdate; ++I, Offset += ElemSize) { Expr *Init = nullptr; if (I < Updater->getNumInits()) Init = Updater->getInit(I); if (!Init && FillC) { if (!Const.add(FillC, Offset, true)) return false; } else if (!Init || isa(Init)) { continue; } else if (InitListExpr *ChildILE = dyn_cast(Init)) { if (!EmitDesignatedInitUpdater(Emitter, Const, Offset, ElemType, ChildILE)) return false; // Attempt to reduce the array element to a single constant if necessary. Const.condense(Offset, ElemTy); } else { llvm::Constant *Val = Emitter.tryEmitPrivateForMemory(Init, ElemType); if (!Const.add(Val, Offset, true)) return false; } } return true; } bool ConstStructBuilder::Build(InitListExpr *ILE, bool AllowOverwrite) { RecordDecl *RD = ILE->getType()->castAs()->getDecl(); const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); unsigned FieldNo = -1; unsigned ElementNo = 0; // Bail out if we have base classes. We could support these, but they only // arise in C++1z where we will have already constant folded most interesting // cases. FIXME: There are still a few more cases we can handle this way. if (auto *CXXRD = dyn_cast(RD)) if (CXXRD->getNumBases()) return false; for (FieldDecl *Field : RD->fields()) { ++FieldNo; // If this is a union, skip all the fields that aren't being initialized. if (RD->isUnion() && !declaresSameEntity(ILE->getInitializedFieldInUnion(), Field)) continue; // Don't emit anonymous bitfields or zero-sized fields. if (Field->isUnnamedBitfield() || Field->isZeroSize(CGM.getContext())) continue; // Get the initializer. A struct can include fields without initializers, // we just use explicit null values for them. Expr *Init = nullptr; if (ElementNo < ILE->getNumInits()) Init = ILE->getInit(ElementNo++); if (Init && isa(Init)) continue; // When emitting a DesignatedInitUpdateExpr, a nested InitListExpr // represents additional overwriting of our current constant value, and not // a new constant to emit independently. if (AllowOverwrite && (Field->getType()->isArrayType() || Field->getType()->isRecordType())) { if (auto *SubILE = dyn_cast(Init)) { CharUnits Offset = CGM.getContext().toCharUnitsFromBits( Layout.getFieldOffset(FieldNo)); if (!EmitDesignatedInitUpdater(Emitter, Builder, StartOffset + Offset, Field->getType(), SubILE)) return false; // If we split apart the field's value, try to collapse it down to a // single value now. Builder.condense(StartOffset + Offset, CGM.getTypes().ConvertTypeForMem(Field->getType())); continue; } } llvm::Constant *EltInit = Init ? Emitter.tryEmitPrivateForMemory(Init, Field->getType()) : Emitter.emitNullForMemory(Field->getType()); if (!EltInit) return false; if (!Field->isBitField()) { // Handle non-bitfield members. if (!AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit, AllowOverwrite)) return false; // After emitting a non-empty field with [[no_unique_address]], we may // need to overwrite its tail padding. if (Field->hasAttr()) AllowOverwrite = true; } else { // Otherwise we have a bitfield. if (auto *CI = dyn_cast(EltInit)) { if (!AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI, AllowOverwrite)) return false; } else { // We are trying to initialize a bitfield with a non-trivial constant, // this must require run-time code. return false; } } } 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; } }; } bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase, 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 (Layout.hasOwnVFPtr()) { llvm::Constant *VTableAddressPoint = CGM.getCXXABI().getVTableAddressPointForConstExpr( BaseSubobject(CD, Offset), VTableClass); if (!AppendBytes(Offset, VTableAddressPoint)) return false; } // 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)); } llvm::stable_sort(Bases); 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, VTableClass, Offset + Base.Offset); } } unsigned FieldNo = 0; uint64_t OffsetBits = CGM.getContext().toBits(Offset); bool AllowOverwrite = false; for (RecordDecl::field_iterator Field = RD->field_begin(), FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { // If this is a union, skip all the fields that aren't being initialized. if (RD->isUnion() && !declaresSameEntity(Val.getUnionField(), *Field)) continue; // Don't emit anonymous bitfields or zero-sized fields. if (Field->isUnnamedBitfield() || Field->isZeroSize(CGM.getContext())) continue; // Emit the value of the initializer. const APValue &FieldValue = RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo); llvm::Constant *EltInit = Emitter.tryEmitPrivateForMemory(FieldValue, Field->getType()); if (!EltInit) return false; if (!Field->isBitField()) { // Handle non-bitfield members. if (!AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit, AllowOverwrite)) return false; // After emitting a non-empty field with [[no_unique_address]], we may // need to overwrite its tail padding. if (Field->hasAttr()) AllowOverwrite = true; } else { // Otherwise we have a bitfield. if (!AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, cast(EltInit), AllowOverwrite)) return false; } } return true; } llvm::Constant *ConstStructBuilder::Finalize(QualType Type) { RecordDecl *RD = Type->castAs()->getDecl(); llvm::Type *ValTy = CGM.getTypes().ConvertType(Type); return Builder.build(ValTy, RD->hasFlexibleArrayMember()); } llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter, InitListExpr *ILE, QualType ValTy) { ConstantAggregateBuilder Const(Emitter.CGM); ConstStructBuilder Builder(Emitter, Const, CharUnits::Zero()); if (!Builder.Build(ILE, /*AllowOverwrite*/false)) return nullptr; return Builder.Finalize(ValTy); } llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter, const APValue &Val, QualType ValTy) { ConstantAggregateBuilder Const(Emitter.CGM); ConstStructBuilder Builder(Emitter, Const, CharUnits::Zero()); const RecordDecl *RD = ValTy->castAs()->getDecl(); const CXXRecordDecl *CD = dyn_cast(RD); if (!Builder.Build(Val, RD, false, CD, CharUnits::Zero())) return nullptr; return Builder.Finalize(ValTy); } bool ConstStructBuilder::UpdateStruct(ConstantEmitter &Emitter, ConstantAggregateBuilder &Const, CharUnits Offset, InitListExpr *Updater) { return ConstStructBuilder(Emitter, Const, Offset) .Build(Updater, /*AllowOverwrite*/ true); } //===----------------------------------------------------------------------===// // ConstExprEmitter //===----------------------------------------------------------------------===// static ConstantAddress tryEmitGlobalCompoundLiteral(CodeGenModule &CGM, CodeGenFunction *CGF, const CompoundLiteralExpr *E) { CharUnits Align = CGM.getContext().getTypeAlignInChars(E->getType()); if (llvm::GlobalVariable *Addr = CGM.getAddrOfConstantCompoundLiteralIfEmitted(E)) return ConstantAddress(Addr, Align); LangAS addressSpace = E->getType().getAddressSpace(); ConstantEmitter emitter(CGM, CGF); llvm::Constant *C = emitter.tryEmitForInitializer(E->getInitializer(), addressSpace, E->getType()); if (!C) { assert(!E->isFileScope() && "file-scope compound literal did not have constant initializer!"); return ConstantAddress::invalid(); } auto GV = new llvm::GlobalVariable(CGM.getModule(), C->getType(), CGM.isTypeConstant(E->getType(), true), llvm::GlobalValue::InternalLinkage, C, ".compoundliteral", nullptr, llvm::GlobalVariable::NotThreadLocal, CGM.getContext().getTargetAddressSpace(addressSpace)); emitter.finalize(GV); GV->setAlignment(Align.getAsAlign()); CGM.setAddrOfConstantCompoundLiteral(E, GV); return ConstantAddress(GV, Align); } static llvm::Constant * EmitArrayConstant(CodeGenModule &CGM, llvm::ArrayType *DesiredType, llvm::Type *CommonElementType, unsigned ArrayBound, SmallVectorImpl &Elements, llvm::Constant *Filler) { // Figure out how long the initial prefix of non-zero elements is. unsigned NonzeroLength = ArrayBound; if (Elements.size() < NonzeroLength && Filler->isNullValue()) NonzeroLength = Elements.size(); if (NonzeroLength == Elements.size()) { while (NonzeroLength > 0 && Elements[NonzeroLength - 1]->isNullValue()) --NonzeroLength; } if (NonzeroLength == 0) return llvm::ConstantAggregateZero::get(DesiredType); // Add a zeroinitializer array filler if we have lots of trailing zeroes. unsigned TrailingZeroes = ArrayBound - NonzeroLength; if (TrailingZeroes >= 8) { assert(Elements.size() >= NonzeroLength && "missing initializer for non-zero element"); // If all the elements had the same type up to the trailing zeroes, emit a // struct of two arrays (the nonzero data and the zeroinitializer). if (CommonElementType && NonzeroLength >= 8) { llvm::Constant *Initial = llvm::ConstantArray::get( llvm::ArrayType::get(CommonElementType, NonzeroLength), makeArrayRef(Elements).take_front(NonzeroLength)); Elements.resize(2); Elements[0] = Initial; } else { Elements.resize(NonzeroLength + 1); } auto *FillerType = CommonElementType ? CommonElementType : DesiredType->getElementType(); FillerType = llvm::ArrayType::get(FillerType, TrailingZeroes); Elements.back() = llvm::ConstantAggregateZero::get(FillerType); CommonElementType = nullptr; } else if (Elements.size() != ArrayBound) { // Otherwise pad to the right size with the filler if necessary. Elements.resize(ArrayBound, Filler); if (Filler->getType() != CommonElementType) CommonElementType = nullptr; } // If all elements have the same type, just emit an array constant. if (CommonElementType) return llvm::ConstantArray::get( llvm::ArrayType::get(CommonElementType, ArrayBound), Elements); // We have mixed types. Use a packed struct. llvm::SmallVector Types; Types.reserve(Elements.size()); for (llvm::Constant *Elt : Elements) Types.push_back(Elt->getType()); llvm::StructType *SType = llvm::StructType::get(CGM.getLLVMContext(), Types, true); return llvm::ConstantStruct::get(SType, Elements); } // This class only needs to handle arrays, structs and unions. Outside C++11 // mode, we don't currently constant fold those types. All other types are // handled by constant folding. // // Constant folding is currently missing support for a few features supported // here: CK_ToUnion, CK_ReinterpretMemberPointer, and DesignatedInitUpdateExpr. class ConstExprEmitter : public StmtVisitor { CodeGenModule &CGM; ConstantEmitter &Emitter; llvm::LLVMContext &VMContext; public: ConstExprEmitter(ConstantEmitter &emitter) : CGM(emitter.CGM), Emitter(emitter), VMContext(CGM.getLLVMContext()) { } //===--------------------------------------------------------------------===// // Visitor Methods //===--------------------------------------------------------------------===// llvm::Constant *VisitStmt(Stmt *S, QualType T) { return nullptr; } llvm::Constant *VisitConstantExpr(ConstantExpr *CE, QualType T) { if (llvm::Constant *Result = Emitter.tryEmitConstantExpr(CE)) return Result; return Visit(CE->getSubExpr(), T); } llvm::Constant *VisitParenExpr(ParenExpr *PE, QualType T) { return Visit(PE->getSubExpr(), T); } llvm::Constant * VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE, QualType T) { return Visit(PE->getReplacement(), T); } llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE, QualType T) { return Visit(GE->getResultExpr(), T); } llvm::Constant *VisitChooseExpr(ChooseExpr *CE, QualType T) { return Visit(CE->getChosenSubExpr(), T); } llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E, QualType T) { return Visit(E->getInitializer(), T); } llvm::Constant *VisitCastExpr(CastExpr *E, QualType destType) { if (const auto *ECE = dyn_cast(E)) CGM.EmitExplicitCastExprType(ECE, Emitter.CGF); Expr *subExpr = E->getSubExpr(); switch (E->getCastKind()) { case CK_ToUnion: { // GCC cast to union extension assert(E->getType()->isUnionType() && "Destination type is not union type!"); auto field = E->getTargetUnionField(); auto C = Emitter.tryEmitPrivateForMemory(subExpr, field->getType()); if (!C) return nullptr; auto destTy = ConvertType(destType); if (C->getType() == destTy) return C; // 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(destTy); 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(VMContext, Types, false); return llvm::ConstantStruct::get(STy, Elts); } case CK_AddressSpaceConversion: { auto C = Emitter.tryEmitPrivate(subExpr, subExpr->getType()); if (!C) return nullptr; LangAS destAS = E->getType()->getPointeeType().getAddressSpace(); LangAS srcAS = subExpr->getType()->getPointeeType().getAddressSpace(); llvm::Type *destTy = ConvertType(E->getType()); return CGM.getTargetCodeGenInfo().performAddrSpaceCast(CGM, C, srcAS, destAS, destTy); } case CK_LValueToRValue: case CK_AtomicToNonAtomic: case CK_NonAtomicToAtomic: case CK_NoOp: case CK_ConstructorConversion: return Visit(subExpr, destType); case CK_IntToOCLSampler: llvm_unreachable("global sampler variables are not generated"); 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: { auto C = Emitter.tryEmitPrivate(subExpr, subExpr->getType()); if (!C) return nullptr; 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 nullptr; // 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_LValueToRValueBitCast: case CK_NullToMemberPointer: case CK_UserDefinedConversion: 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_BooleanToSignedIntegral: case CK_IntegralToPointer: case CK_IntegralToBoolean: case CK_IntegralToFloating: case CK_FloatingToIntegral: case CK_FloatingToBoolean: case CK_FloatingCast: case CK_FixedPointCast: case CK_FixedPointToBoolean: case CK_FixedPointToIntegral: case CK_IntegralToFixedPoint: case CK_ZeroToOCLOpaqueType: return nullptr; } llvm_unreachable("Invalid CastKind"); } llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE, QualType T) { // No need for a DefaultInitExprScope: we don't handle 'this' in a // constant expression. return Visit(DIE->getExpr(), T); } llvm::Constant *VisitExprWithCleanups(ExprWithCleanups *E, QualType T) { return Visit(E->getSubExpr(), T); } llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E, QualType T) { return Visit(E->getSubExpr(), T); } llvm::Constant *EmitArrayInitialization(InitListExpr *ILE, QualType T) { auto *CAT = CGM.getContext().getAsConstantArrayType(ILE->getType()); assert(CAT && "can't emit array init for non-constant-bound array"); unsigned NumInitElements = ILE->getNumInits(); unsigned NumElements = CAT->getSize().getZExtValue(); // Initialising an array requires us to automatically // initialise any elements that have not been initialised explicitly unsigned NumInitableElts = std::min(NumInitElements, NumElements); QualType EltType = CAT->getElementType(); // Initialize remaining array elements. llvm::Constant *fillC = nullptr; if (Expr *filler = ILE->getArrayFiller()) { fillC = Emitter.tryEmitAbstractForMemory(filler, EltType); if (!fillC) return nullptr; } // Copy initializer elements. SmallVector Elts; if (fillC && fillC->isNullValue()) Elts.reserve(NumInitableElts + 1); else Elts.reserve(NumElements); llvm::Type *CommonElementType = nullptr; for (unsigned i = 0; i < NumInitableElts; ++i) { Expr *Init = ILE->getInit(i); llvm::Constant *C = Emitter.tryEmitPrivateForMemory(Init, EltType); if (!C) return nullptr; if (i == 0) CommonElementType = C->getType(); else if (C->getType() != CommonElementType) CommonElementType = nullptr; Elts.push_back(C); } llvm::ArrayType *Desired = cast(CGM.getTypes().ConvertType(ILE->getType())); return EmitArrayConstant(CGM, Desired, CommonElementType, NumElements, Elts, fillC); } llvm::Constant *EmitRecordInitialization(InitListExpr *ILE, QualType T) { return ConstStructBuilder::BuildStruct(Emitter, ILE, T); } llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E, QualType T) { return CGM.EmitNullConstant(T); } llvm::Constant *VisitInitListExpr(InitListExpr *ILE, QualType T) { if (ILE->isTransparent()) return Visit(ILE->getInit(0), T); if (ILE->getType()->isArrayType()) return EmitArrayInitialization(ILE, T); if (ILE->getType()->isRecordType()) return EmitRecordInitialization(ILE, T); return nullptr; } llvm::Constant *VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E, QualType destType) { auto C = Visit(E->getBase(), destType); if (!C) return nullptr; ConstantAggregateBuilder Const(CGM); Const.add(C, CharUnits::Zero(), false); if (!EmitDesignatedInitUpdater(Emitter, Const, CharUnits::Zero(), destType, E->getUpdater())) return nullptr; llvm::Type *ValTy = CGM.getTypes().ConvertType(destType); bool HasFlexibleArray = false; if (auto *RT = destType->getAs()) HasFlexibleArray = RT->getDecl()->hasFlexibleArrayMember(); return Const.build(ValTy, HasFlexibleArray); } llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E, QualType Ty) { if (!E->getConstructor()->isTrivial()) return nullptr; // Only default and copy/move 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, Ty); } return CGM.EmitNullConstant(Ty); } llvm::Constant *VisitStringLiteral(StringLiteral *E, QualType T) { // This is a string literal initializing an array in an initializer. return CGM.GetConstantArrayFromStringLiteral(E); } llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E, QualType T) { // 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 = CGM.getContext().getAsConstantArrayType(T); // 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, QualType T) { return Visit(E->getSubExpr(), T); } // Utility methods llvm::Type *ConvertType(QualType T) { return CGM.getTypes().ConvertType(T); } }; } // end anonymous namespace. llvm::Constant *ConstantEmitter::validateAndPopAbstract(llvm::Constant *C, AbstractState saved) { Abstract = saved.OldValue; assert(saved.OldPlaceholdersSize == PlaceholderAddresses.size() && "created a placeholder while doing an abstract emission?"); // No validation necessary for now. // No cleanup to do for now. return C; } llvm::Constant * ConstantEmitter::tryEmitAbstractForInitializer(const VarDecl &D) { auto state = pushAbstract(); auto C = tryEmitPrivateForVarInit(D); return validateAndPopAbstract(C, state); } llvm::Constant * ConstantEmitter::tryEmitAbstract(const Expr *E, QualType destType) { auto state = pushAbstract(); auto C = tryEmitPrivate(E, destType); return validateAndPopAbstract(C, state); } llvm::Constant * ConstantEmitter::tryEmitAbstract(const APValue &value, QualType destType) { auto state = pushAbstract(); auto C = tryEmitPrivate(value, destType); return validateAndPopAbstract(C, state); } llvm::Constant *ConstantEmitter::tryEmitConstantExpr(const ConstantExpr *CE) { if (!CE->hasAPValueResult()) return nullptr; const Expr *Inner = CE->getSubExpr()->IgnoreImplicit(); QualType RetType; if (auto *Call = dyn_cast(Inner)) RetType = Call->getCallReturnType(CGF->getContext()); else if (auto *Ctor = dyn_cast(Inner)) RetType = Ctor->getType(); llvm::Constant *Res = emitAbstract(CE->getBeginLoc(), CE->getAPValueResult(), RetType); return Res; } llvm::Constant * ConstantEmitter::emitAbstract(const Expr *E, QualType destType) { auto state = pushAbstract(); auto C = tryEmitPrivate(E, destType); C = validateAndPopAbstract(C, state); if (!C) { CGM.Error(E->getExprLoc(), "internal error: could not emit constant value \"abstractly\""); C = CGM.EmitNullConstant(destType); } return C; } llvm::Constant * ConstantEmitter::emitAbstract(SourceLocation loc, const APValue &value, QualType destType) { auto state = pushAbstract(); auto C = tryEmitPrivate(value, destType); C = validateAndPopAbstract(C, state); if (!C) { CGM.Error(loc, "internal error: could not emit constant value \"abstractly\""); C = CGM.EmitNullConstant(destType); } return C; } llvm::Constant *ConstantEmitter::tryEmitForInitializer(const VarDecl &D) { initializeNonAbstract(D.getType().getAddressSpace()); return markIfFailed(tryEmitPrivateForVarInit(D)); } llvm::Constant *ConstantEmitter::tryEmitForInitializer(const Expr *E, LangAS destAddrSpace, QualType destType) { initializeNonAbstract(destAddrSpace); return markIfFailed(tryEmitPrivateForMemory(E, destType)); } llvm::Constant *ConstantEmitter::emitForInitializer(const APValue &value, LangAS destAddrSpace, QualType destType) { initializeNonAbstract(destAddrSpace); auto C = tryEmitPrivateForMemory(value, destType); assert(C && "couldn't emit constant value non-abstractly?"); return C; } llvm::GlobalValue *ConstantEmitter::getCurrentAddrPrivate() { assert(!Abstract && "cannot get current address for abstract constant"); // Make an obviously ill-formed global that should blow up compilation // if it survives. auto global = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty, true, llvm::GlobalValue::PrivateLinkage, /*init*/ nullptr, /*name*/ "", /*before*/ nullptr, llvm::GlobalVariable::NotThreadLocal, CGM.getContext().getTargetAddressSpace(DestAddressSpace)); PlaceholderAddresses.push_back(std::make_pair(nullptr, global)); return global; } void ConstantEmitter::registerCurrentAddrPrivate(llvm::Constant *signal, llvm::GlobalValue *placeholder) { assert(!PlaceholderAddresses.empty()); assert(PlaceholderAddresses.back().first == nullptr); assert(PlaceholderAddresses.back().second == placeholder); PlaceholderAddresses.back().first = signal; } namespace { struct ReplacePlaceholders { CodeGenModule &CGM; /// The base address of the global. llvm::Constant *Base; llvm::Type *BaseValueTy = nullptr; /// The placeholder addresses that were registered during emission. llvm::DenseMap PlaceholderAddresses; /// The locations of the placeholder signals. llvm::DenseMap Locations; /// The current index stack. We use a simple unsigned stack because /// we assume that placeholders will be relatively sparse in the /// initializer, but we cache the index values we find just in case. llvm::SmallVector Indices; llvm::SmallVector IndexValues; ReplacePlaceholders(CodeGenModule &CGM, llvm::Constant *base, ArrayRef> addresses) : CGM(CGM), Base(base), PlaceholderAddresses(addresses.begin(), addresses.end()) { } void replaceInInitializer(llvm::Constant *init) { // Remember the type of the top-most initializer. BaseValueTy = init->getType(); // Initialize the stack. Indices.push_back(0); IndexValues.push_back(nullptr); // Recurse into the initializer. findLocations(init); // Check invariants. assert(IndexValues.size() == Indices.size() && "mismatch"); assert(Indices.size() == 1 && "didn't pop all indices"); // Do the replacement; this basically invalidates 'init'. assert(Locations.size() == PlaceholderAddresses.size() && "missed a placeholder?"); // We're iterating over a hashtable, so this would be a source of // non-determinism in compiler output *except* that we're just // messing around with llvm::Constant structures, which never itself // does anything that should be visible in compiler output. for (auto &entry : Locations) { assert(entry.first->getParent() == nullptr && "not a placeholder!"); entry.first->replaceAllUsesWith(entry.second); entry.first->eraseFromParent(); } } private: void findLocations(llvm::Constant *init) { // Recurse into aggregates. if (auto agg = dyn_cast(init)) { for (unsigned i = 0, e = agg->getNumOperands(); i != e; ++i) { Indices.push_back(i); IndexValues.push_back(nullptr); findLocations(agg->getOperand(i)); IndexValues.pop_back(); Indices.pop_back(); } return; } // Otherwise, check for registered constants. while (true) { auto it = PlaceholderAddresses.find(init); if (it != PlaceholderAddresses.end()) { setLocation(it->second); break; } // Look through bitcasts or other expressions. if (auto expr = dyn_cast(init)) { init = expr->getOperand(0); } else { break; } } } void setLocation(llvm::GlobalVariable *placeholder) { assert(Locations.find(placeholder) == Locations.end() && "already found location for placeholder!"); // Lazily fill in IndexValues with the values from Indices. // We do this in reverse because we should always have a strict // prefix of indices from the start. assert(Indices.size() == IndexValues.size()); for (size_t i = Indices.size() - 1; i != size_t(-1); --i) { if (IndexValues[i]) { #ifndef NDEBUG for (size_t j = 0; j != i + 1; ++j) { assert(IndexValues[j] && isa(IndexValues[j]) && cast(IndexValues[j])->getZExtValue() == Indices[j]); } #endif break; } IndexValues[i] = llvm::ConstantInt::get(CGM.Int32Ty, Indices[i]); } // Form a GEP and then bitcast to the placeholder type so that the // replacement will succeed. llvm::Constant *location = llvm::ConstantExpr::getInBoundsGetElementPtr(BaseValueTy, Base, IndexValues); location = llvm::ConstantExpr::getBitCast(location, placeholder->getType()); Locations.insert({placeholder, location}); } }; } void ConstantEmitter::finalize(llvm::GlobalVariable *global) { assert(InitializedNonAbstract && "finalizing emitter that was used for abstract emission?"); assert(!Finalized && "finalizing emitter multiple times"); assert(global->getInitializer()); // Note that we might also be Failed. Finalized = true; if (!PlaceholderAddresses.empty()) { ReplacePlaceholders(CGM, global, PlaceholderAddresses) .replaceInInitializer(global->getInitializer()); PlaceholderAddresses.clear(); // satisfy } } ConstantEmitter::~ConstantEmitter() { assert((!InitializedNonAbstract || Finalized || Failed) && "not finalized after being initialized for non-abstract emission"); assert(PlaceholderAddresses.empty() && "unhandled placeholders"); } static QualType getNonMemoryType(CodeGenModule &CGM, QualType type) { if (auto AT = type->getAs()) { return CGM.getContext().getQualifiedType(AT->getValueType(), type.getQualifiers()); } return type; } llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) { // 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 = CGM.getContext().getBaseElementType(D.getType()); if (Ty->isRecordType()) if (const CXXConstructExpr *E = dyn_cast_or_null(D.getInit())) { const CXXConstructorDecl *CD = E->getConstructor(); if (CD->isTrivial() && CD->isDefaultConstructor()) return CGM.EmitNullConstant(D.getType()); } InConstantContext = true; } QualType destType = D.getType(); // Try to emit the initializer. Note that this can allow some things that // are not allowed by tryEmitPrivateForMemory alone. if (auto value = D.evaluateValue()) { return tryEmitPrivateForMemory(*value, destType); } // 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 (destType->isReferenceType()) return nullptr; const Expr *E = D.getInit(); assert(E && "No initializer to emit"); auto nonMemoryDestType = getNonMemoryType(CGM, destType); auto C = ConstExprEmitter(*this).Visit(const_cast(E), nonMemoryDestType); return (C ? emitForMemory(C, destType) : nullptr); } llvm::Constant * ConstantEmitter::tryEmitAbstractForMemory(const Expr *E, QualType destType) { auto nonMemoryDestType = getNonMemoryType(CGM, destType); auto C = tryEmitAbstract(E, nonMemoryDestType); return (C ? emitForMemory(C, destType) : nullptr); } llvm::Constant * ConstantEmitter::tryEmitAbstractForMemory(const APValue &value, QualType destType) { auto nonMemoryDestType = getNonMemoryType(CGM, destType); auto C = tryEmitAbstract(value, nonMemoryDestType); return (C ? emitForMemory(C, destType) : nullptr); } llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const Expr *E, QualType destType) { auto nonMemoryDestType = getNonMemoryType(CGM, destType); llvm::Constant *C = tryEmitPrivate(E, nonMemoryDestType); return (C ? emitForMemory(C, destType) : nullptr); } llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const APValue &value, QualType destType) { auto nonMemoryDestType = getNonMemoryType(CGM, destType); auto C = tryEmitPrivate(value, nonMemoryDestType); return (C ? emitForMemory(C, destType) : nullptr); } llvm::Constant *ConstantEmitter::emitForMemory(CodeGenModule &CGM, llvm::Constant *C, QualType destType) { // For an _Atomic-qualified constant, we may need to add tail padding. if (auto AT = destType->getAs()) { QualType destValueType = AT->getValueType(); C = emitForMemory(CGM, C, destValueType); uint64_t innerSize = CGM.getContext().getTypeSize(destValueType); uint64_t outerSize = CGM.getContext().getTypeSize(destType); if (innerSize == outerSize) return C; assert(innerSize < outerSize && "emitted over-large constant for atomic"); llvm::Constant *elts[] = { C, llvm::ConstantAggregateZero::get( llvm::ArrayType::get(CGM.Int8Ty, (outerSize - innerSize) / 8)) }; return llvm::ConstantStruct::getAnon(elts); } // Zero-extend bool. if (C->getType()->isIntegerTy(1)) { llvm::Type *boolTy = CGM.getTypes().ConvertTypeForMem(destType); return llvm::ConstantExpr::getZExt(C, boolTy); } return C; } llvm::Constant *ConstantEmitter::tryEmitPrivate(const Expr *E, QualType destType) { Expr::EvalResult Result; bool Success = false; if (destType->isReferenceType()) Success = E->EvaluateAsLValue(Result, CGM.getContext()); else Success = E->EvaluateAsRValue(Result, CGM.getContext(), InConstantContext); llvm::Constant *C; if (Success && !Result.HasSideEffects) C = tryEmitPrivate(Result.Val, destType); else C = ConstExprEmitter(*this).Visit(const_cast(E), destType); return C; } llvm::Constant *CodeGenModule::getNullPointer(llvm::PointerType *T, QualType QT) { return getTargetCodeGenInfo().getNullPointer(*this, T, QT); } namespace { /// A struct which can be used to peephole certain kinds of finalization /// that normally happen during l-value emission. struct ConstantLValue { llvm::Constant *Value; bool HasOffsetApplied; /*implicit*/ ConstantLValue(llvm::Constant *value, bool hasOffsetApplied = false) : Value(value), HasOffsetApplied(hasOffsetApplied) {} /*implicit*/ ConstantLValue(ConstantAddress address) : ConstantLValue(address.getPointer()) {} }; /// A helper class for emitting constant l-values. class ConstantLValueEmitter : public ConstStmtVisitor { CodeGenModule &CGM; ConstantEmitter &Emitter; const APValue &Value; QualType DestType; // Befriend StmtVisitorBase so that we don't have to expose Visit*. friend StmtVisitorBase; public: ConstantLValueEmitter(ConstantEmitter &emitter, const APValue &value, QualType destType) : CGM(emitter.CGM), Emitter(emitter), Value(value), DestType(destType) {} llvm::Constant *tryEmit(); private: llvm::Constant *tryEmitAbsolute(llvm::Type *destTy); ConstantLValue tryEmitBase(const APValue::LValueBase &base); ConstantLValue VisitStmt(const Stmt *S) { return nullptr; } ConstantLValue VisitConstantExpr(const ConstantExpr *E); ConstantLValue VisitCompoundLiteralExpr(const CompoundLiteralExpr *E); ConstantLValue VisitStringLiteral(const StringLiteral *E); ConstantLValue VisitObjCBoxedExpr(const ObjCBoxedExpr *E); ConstantLValue VisitObjCEncodeExpr(const ObjCEncodeExpr *E); ConstantLValue VisitObjCStringLiteral(const ObjCStringLiteral *E); ConstantLValue VisitPredefinedExpr(const PredefinedExpr *E); ConstantLValue VisitAddrLabelExpr(const AddrLabelExpr *E); ConstantLValue VisitCallExpr(const CallExpr *E); ConstantLValue VisitBlockExpr(const BlockExpr *E); ConstantLValue VisitCXXTypeidExpr(const CXXTypeidExpr *E); ConstantLValue VisitMaterializeTemporaryExpr( const MaterializeTemporaryExpr *E); bool hasNonZeroOffset() const { return !Value.getLValueOffset().isZero(); } /// Return the value offset. llvm::Constant *getOffset() { return llvm::ConstantInt::get(CGM.Int64Ty, Value.getLValueOffset().getQuantity()); } /// Apply the value offset to the given constant. llvm::Constant *applyOffset(llvm::Constant *C) { if (!hasNonZeroOffset()) return C; llvm::Type *origPtrTy = C->getType(); unsigned AS = origPtrTy->getPointerAddressSpace(); llvm::Type *charPtrTy = CGM.Int8Ty->getPointerTo(AS); C = llvm::ConstantExpr::getBitCast(C, charPtrTy); C = llvm::ConstantExpr::getGetElementPtr(CGM.Int8Ty, C, getOffset()); C = llvm::ConstantExpr::getPointerCast(C, origPtrTy); return C; } }; } llvm::Constant *ConstantLValueEmitter::tryEmit() { const APValue::LValueBase &base = Value.getLValueBase(); // The destination type should be a pointer or reference // type, but it might also be a cast thereof. // // FIXME: the chain of casts required should be reflected in the APValue. // We need this in order to correctly handle things like a ptrtoint of a // non-zero null pointer and addrspace casts that aren't trivially // represented in LLVM IR. auto destTy = CGM.getTypes().ConvertTypeForMem(DestType); assert(isa(destTy) || isa(destTy)); // If there's no base at all, this is a null or absolute pointer, // possibly cast back to an integer type. if (!base) { return tryEmitAbsolute(destTy); } // Otherwise, try to emit the base. ConstantLValue result = tryEmitBase(base); // If that failed, we're done. llvm::Constant *value = result.Value; if (!value) return nullptr; // Apply the offset if necessary and not already done. if (!result.HasOffsetApplied) { value = applyOffset(value); } // Convert to the appropriate type; this could be an lvalue for // an integer. FIXME: performAddrSpaceCast if (isa(destTy)) return llvm::ConstantExpr::getPointerCast(value, destTy); return llvm::ConstantExpr::getPtrToInt(value, destTy); } /// Try to emit an absolute l-value, such as a null pointer or an integer /// bitcast to pointer type. llvm::Constant * ConstantLValueEmitter::tryEmitAbsolute(llvm::Type *destTy) { // If we're producing a pointer, this is easy. auto destPtrTy = cast(destTy); if (Value.isNullPointer()) { // FIXME: integer offsets from non-zero null pointers. return CGM.getNullPointer(destPtrTy, DestType); } // Convert the integer to a pointer-sized integer before converting it // to a pointer. // FIXME: signedness depends on the original integer type. auto intptrTy = CGM.getDataLayout().getIntPtrType(destPtrTy); llvm::Constant *C; C = llvm::ConstantExpr::getIntegerCast(getOffset(), intptrTy, /*isSigned*/ false); C = llvm::ConstantExpr::getIntToPtr(C, destPtrTy); return C; } ConstantLValue ConstantLValueEmitter::tryEmitBase(const APValue::LValueBase &base) { // Handle values. if (const ValueDecl *D = base.dyn_cast()) { if (D->hasAttr()) return CGM.GetWeakRefReference(D).getPointer(); if (auto FD = dyn_cast(D)) return CGM.GetAddrOfFunction(FD); if (auto VD = dyn_cast(D)) { // We can never refer to a variable with local storage. if (!VD->hasLocalStorage()) { if (VD->isFileVarDecl() || VD->hasExternalStorage()) return CGM.GetAddrOfGlobalVar(VD); if (VD->isLocalVarDecl()) { return CGM.getOrCreateStaticVarDecl( *VD, CGM.getLLVMLinkageVarDefinition(VD, /*IsConstant=*/false)); } } } if (auto *GD = dyn_cast(D)) return CGM.GetAddrOfMSGuidDecl(GD); return nullptr; } // Handle typeid(T). if (TypeInfoLValue TI = base.dyn_cast()) { llvm::Type *StdTypeInfoPtrTy = CGM.getTypes().ConvertType(base.getTypeInfoType())->getPointerTo(); llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(QualType(TI.getType(), 0)); if (TypeInfo->getType() != StdTypeInfoPtrTy) TypeInfo = llvm::ConstantExpr::getBitCast(TypeInfo, StdTypeInfoPtrTy); return TypeInfo; } // Otherwise, it must be an expression. return Visit(base.get()); } ConstantLValue ConstantLValueEmitter::VisitConstantExpr(const ConstantExpr *E) { if (llvm::Constant *Result = Emitter.tryEmitConstantExpr(E)) return Result; return Visit(E->getSubExpr()); } ConstantLValue ConstantLValueEmitter::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) { return tryEmitGlobalCompoundLiteral(CGM, Emitter.CGF, E); } ConstantLValue ConstantLValueEmitter::VisitStringLiteral(const StringLiteral *E) { return CGM.GetAddrOfConstantStringFromLiteral(E); } ConstantLValue ConstantLValueEmitter::VisitObjCEncodeExpr(const ObjCEncodeExpr *E) { return CGM.GetAddrOfConstantStringFromObjCEncode(E); } static ConstantLValue emitConstantObjCStringLiteral(const StringLiteral *S, QualType T, CodeGenModule &CGM) { auto C = CGM.getObjCRuntime().GenerateConstantString(S); return C.getElementBitCast(CGM.getTypes().ConvertTypeForMem(T)); } ConstantLValue ConstantLValueEmitter::VisitObjCStringLiteral(const ObjCStringLiteral *E) { return emitConstantObjCStringLiteral(E->getString(), E->getType(), CGM); } ConstantLValue ConstantLValueEmitter::VisitObjCBoxedExpr(const ObjCBoxedExpr *E) { assert(E->isExpressibleAsConstantInitializer() && "this boxed expression can't be emitted as a compile-time constant"); auto *SL = cast(E->getSubExpr()->IgnoreParenCasts()); return emitConstantObjCStringLiteral(SL, E->getType(), CGM); } ConstantLValue ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) { return CGM.GetAddrOfConstantStringFromLiteral(E->getFunctionName()); } ConstantLValue ConstantLValueEmitter::VisitAddrLabelExpr(const AddrLabelExpr *E) { assert(Emitter.CGF && "Invalid address of label expression outside function"); llvm::Constant *Ptr = Emitter.CGF->GetAddrOfLabel(E->getLabel()); Ptr = llvm::ConstantExpr::getBitCast(Ptr, CGM.getTypes().ConvertType(E->getType())); return Ptr; } ConstantLValue ConstantLValueEmitter::VisitCallExpr(const CallExpr *E) { unsigned builtin = E->getBuiltinCallee(); if (builtin != Builtin::BI__builtin___CFStringMakeConstantString && builtin != Builtin::BI__builtin___NSStringMakeConstantString) return nullptr; auto literal = cast(E->getArg(0)->IgnoreParenCasts()); if (builtin == Builtin::BI__builtin___NSStringMakeConstantString) { return CGM.getObjCRuntime().GenerateConstantString(literal); } else { // FIXME: need to deal with UCN conversion issues. return CGM.GetAddrOfConstantCFString(literal); } } ConstantLValue ConstantLValueEmitter::VisitBlockExpr(const BlockExpr *E) { StringRef functionName; if (auto CGF = Emitter.CGF) functionName = CGF->CurFn->getName(); else functionName = "global"; return CGM.GetAddrOfGlobalBlock(E, functionName); } ConstantLValue ConstantLValueEmitter::VisitCXXTypeidExpr(const CXXTypeidExpr *E) { QualType T; if (E->isTypeOperand()) T = E->getTypeOperand(CGM.getContext()); else T = E->getExprOperand()->getType(); return CGM.GetAddrOfRTTIDescriptor(T); } ConstantLValue ConstantLValueEmitter::VisitMaterializeTemporaryExpr( const MaterializeTemporaryExpr *E) { assert(E->getStorageDuration() == SD_Static); SmallVector CommaLHSs; SmallVector Adjustments; const Expr *Inner = E->getSubExpr()->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments); return CGM.GetAddrOfGlobalTemporary(E, Inner); } llvm::Constant *ConstantEmitter::tryEmitPrivate(const APValue &Value, QualType DestType) { switch (Value.getKind()) { case APValue::None: case APValue::Indeterminate: // Out-of-lifetime and indeterminate values can be modeled as 'undef'. return llvm::UndefValue::get(CGM.getTypes().ConvertType(DestType)); case APValue::LValue: return ConstantLValueEmitter(*this, Value, DestType).tryEmit(); case APValue::Int: return llvm::ConstantInt::get(CGM.getLLVMContext(), Value.getInt()); case APValue::FixedPoint: return llvm::ConstantInt::get(CGM.getLLVMContext(), Value.getFixedPoint().getValue()); case APValue::ComplexInt: { llvm::Constant *Complex[2]; Complex[0] = llvm::ConstantInt::get(CGM.getLLVMContext(), Value.getComplexIntReal()); Complex[1] = llvm::ConstantInt::get(CGM.getLLVMContext(), 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()); return llvm::ConstantStruct::get(STy, Complex); } case APValue::Float: { const llvm::APFloat &Init = Value.getFloat(); if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf() && !CGM.getContext().getLangOpts().NativeHalfType && CGM.getContext().getTargetInfo().useFP16ConversionIntrinsics()) return llvm::ConstantInt::get(CGM.getLLVMContext(), Init.bitcastToAPInt()); else return llvm::ConstantFP::get(CGM.getLLVMContext(), Init); } case APValue::ComplexFloat: { llvm::Constant *Complex[2]; Complex[0] = llvm::ConstantFP::get(CGM.getLLVMContext(), Value.getComplexFloatReal()); Complex[1] = llvm::ConstantFP::get(CGM.getLLVMContext(), 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()); return llvm::ConstantStruct::get(STy, Complex); } case APValue::Vector: { unsigned NumElts = Value.getVectorLength(); SmallVector Inits(NumElts); for (unsigned I = 0; I != NumElts; ++I) { const APValue &Elt = Value.getVectorElt(I); if (Elt.isInt()) Inits[I] = llvm::ConstantInt::get(CGM.getLLVMContext(), Elt.getInt()); else if (Elt.isFloat()) Inits[I] = llvm::ConstantFP::get(CGM.getLLVMContext(), Elt.getFloat()); else llvm_unreachable("unsupported vector element type"); } return llvm::ConstantVector::get(Inits); } case APValue::AddrLabelDiff: { const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS(); const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS(); llvm::Constant *LHS = tryEmitPrivate(LHSExpr, LHSExpr->getType()); llvm::Constant *RHS = tryEmitPrivate(RHSExpr, RHSExpr->getType()); if (!LHS || !RHS) return nullptr; // Compute difference llvm::Type *ResultType = CGM.getTypes().ConvertType(DestType); LHS = llvm::ConstantExpr::getPtrToInt(LHS, CGM.IntPtrTy); RHS = llvm::ConstantExpr::getPtrToInt(RHS, CGM.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, Value, DestType); case APValue::Array: { const ConstantArrayType *CAT = CGM.getContext().getAsConstantArrayType(DestType); unsigned NumElements = Value.getArraySize(); unsigned NumInitElts = Value.getArrayInitializedElts(); // Emit array filler, if there is one. llvm::Constant *Filler = nullptr; if (Value.hasArrayFiller()) { Filler = tryEmitAbstractForMemory(Value.getArrayFiller(), CAT->getElementType()); if (!Filler) return nullptr; } // Emit initializer elements. SmallVector Elts; if (Filler && Filler->isNullValue()) Elts.reserve(NumInitElts + 1); else Elts.reserve(NumElements); llvm::Type *CommonElementType = nullptr; for (unsigned I = 0; I < NumInitElts; ++I) { llvm::Constant *C = tryEmitPrivateForMemory( Value.getArrayInitializedElt(I), CAT->getElementType()); if (!C) return nullptr; if (I == 0) CommonElementType = C->getType(); else if (C->getType() != CommonElementType) CommonElementType = nullptr; Elts.push_back(C); } // This means that the array type is probably "IncompleteType" or some // type that is not ConstantArray. if (CAT == nullptr && CommonElementType == nullptr && !NumInitElts) { const ArrayType *AT = CGM.getContext().getAsArrayType(DestType); CommonElementType = CGM.getTypes().ConvertType(AT->getElementType()); llvm::ArrayType *AType = llvm::ArrayType::get(CommonElementType, NumElements); return llvm::ConstantAggregateZero::get(AType); } llvm::ArrayType *Desired = cast(CGM.getTypes().ConvertType(DestType)); return EmitArrayConstant(CGM, Desired, CommonElementType, NumElements, Elts, Filler); } case APValue::MemberPointer: return CGM.getCXXABI().EmitMemberPointer(Value, DestType); } llvm_unreachable("Unknown APValue kind"); } llvm::GlobalVariable *CodeGenModule::getAddrOfConstantCompoundLiteralIfEmitted( const CompoundLiteralExpr *E) { return EmittedCompoundLiterals.lookup(E); } void CodeGenModule::setAddrOfConstantCompoundLiteral( const CompoundLiteralExpr *CLE, llvm::GlobalVariable *GV) { bool Ok = EmittedCompoundLiterals.insert(std::make_pair(CLE, GV)).second; (void)Ok; assert(Ok && "CLE has already been emitted!"); } ConstantAddress CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) { assert(E->isFileScope() && "not a file-scope compound literal expr"); return tryEmitGlobalCompoundLiteral(*this, nullptr, 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().EmitMemberFunctionPointer(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 llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, llvm::Type *baseType, const CXXRecordDecl *base); static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, const RecordDecl *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); auto CXXR = dyn_cast(record); // Fill in all the bases. if (CXXR) { for (const auto &I : CXXR->bases()) { 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() || CGM.getContext().getASTRecordLayout(base).getNonVirtualSize() .isZero()) continue; unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); llvm::Type *baseType = structure->getElementType(fieldIndex); elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); } } // Fill in all the fields. for (const auto *Field : record->fields()) { // Fill in non-bitfields. (Bitfields always use a zero pattern, which we // will fill in later.) if (!Field->isBitField() && !Field->isZeroSize(CGM.getContext())) { unsigned fieldIndex = layout.getLLVMFieldNo(Field); elements[fieldIndex] = CGM.EmitNullConstant(Field->getType()); } // For unions, stop after the first named field. if (record->isUnion()) { if (Field->getIdentifier()) break; if (const auto *FieldRD = Field->getType()->getAsRecordDecl()) if (FieldRD->findFirstNamedDataMember()) break; } } // Fill in the virtual bases, if we're working with the complete object. if (CXXR && asCompleteObject) { for (const auto &I : CXXR->vbases()) { 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); // Otherwise, we can just use its null constant. return EmitNullConstant(CGM, base, /*asCompleteObject=*/false); } llvm::Constant *ConstantEmitter::emitNullForMemory(CodeGenModule &CGM, QualType T) { return emitForMemory(CGM, CGM.EmitNullConstant(T), T); } llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { if (T->getAs()) return getNullPointer( cast(getTypes().ConvertTypeForMem(T)), 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 = ConstantEmitter::emitNullForMemory(*this, ElementTy); unsigned NumElements = CAT->getSize().getZExtValue(); SmallVector Array(NumElements, Element); return llvm::ConstantArray::get(ATy, Array); } if (const RecordType *RT = T->getAs()) return ::EmitNullConstant(*this, RT->getDecl(), /*complete object*/ true); assert(T->isMemberDataPointerType() && "Should only see pointers to data members here!"); return getCXXABI().EmitNullMemberPointer(T->castAs()); } llvm::Constant * CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { return ::EmitNullConstant(*this, Record, false); }