blob: 03ef4ab18422e09c8b88106e333cc25c0fe7affc [file] [log] [blame]
//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This contains code to emit Constant Expr nodes as LLVM code.
#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "CGRecordLayout.h"
#include "CodeGenModule.h"
#include "ConstantEmitter.h"
#include "TargetInfo.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/ADT/Sequence.h"
#include "llvm/ADT/STLExtras.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(
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<llvm::Constant*, 32> Elems;
llvm::SmallVector<CharUnits, 32> 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<size_t> splitAt(CharUnits Pos);
static llvm::Constant *buildFrom(CodeGenModule &CGM,
ArrayRef<llvm::Constant *> Elems,
ArrayRef<CharUnits> Offsets,
CharUnits StartOffset, CharUnits Size,
bool NaturalLayout, llvm::Type *DesiredTy,
bool AllowOversized);
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<typename Container, typename Range = std::initializer_list<
typename Container::value_type>>
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));
Size = Offset + getSize(C);
return true;
// Uncommon case: constant overlaps what we've already created.
llvm::Optional<size_t> FirstElemToReplace = splitAt(Offset);
if (!FirstElemToReplace)
return false;
CharUnits CSize = getSize(C);
llvm::Optional<size_t> 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)
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<size_t> FirstElemToUpdate = splitAt(OffsetInChars);
if (!FirstElemToUpdate)
return false;
llvm::Optional<size_t> 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);
UpdateMask.setBits(OffsetWithinChar, OffsetWithinChar + WantedBits);
BitsThisChar &= UpdateMask;
if (*FirstElemToUpdate == *LastElemToUpdate ||
Elems[*FirstElemToUpdate]->isNullValue() ||
isa<llvm::UndefValue>(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<llvm::ConstantInt>(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())
// Remove the consumed bits from Bits.
if (!CGM.getDataLayout().isBigEndian())
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<size_t> 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<llvm::ConstantAggregate>(C)) {
replace(Elems, Index, Index + 1,
llvm::map_range(llvm::seq(0u, CA->getNumOperands()),
[&](unsigned Op) { return CA->getOperand(Op); }));
if (auto *Seq = dyn_cast<llvm::SequentialType>(CA->getType())) {
// Array or vector.
CharUnits ElemSize = getSize(Seq->getElementType());
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<llvm::StructType>(CA->getType());
const llvm::StructLayout *Layout =
replace(Offsets, Index, Index + 1,
llvm::seq(0u, CA->getNumOperands()), [&](unsigned Op) {
return Offset + CharUnits::fromQuantity(
return true;
if (auto *CDS = dyn_cast<llvm::ConstantDataSequential>(C)) {
// 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::seq(0u, CDS->getNumElements()),
[&](unsigned Elem) { return Offset + Elem * ElemSize; }));
return true;
if (isa<llvm::ConstantAggregateZero>(C)) {
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<llvm::UndefValue>(C)) {
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<llvm::Constant *> &Elements,
llvm::Constant *Filler);
llvm::Constant *ConstantAggregateBuilder::buildFrom(
CodeGenModule &CGM, ArrayRef<llvm::Constant *> Elems,
ArrayRef<CharUnits> 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<llvm::ArrayType>(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<llvm::Constant*, 32> 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())
// All remaining elements must be the same type.
if (Elems[I]->getType() != CommonType ||
Offset(I) % ElemSize != 0) {
CanEmitArray = false;
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<llvm::Constant*> UnpackedElems = Elems;
llvm::SmallVector<llvm::Constant*, 32> 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<llvm::Constant*, 32> 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));
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<llvm::StructType>(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<size_t> FirstElemToReplace = splitAt(Offset);
if (!FirstElemToReplace)
size_t First = *FirstElemToReplace;
llvm::Optional<size_t> LastElemToReplace = splitAt(Offset + Size);
if (!LastElemToReplace)
size_t Last = *LastElemToReplace;
size_t Length = Last - First;
if (Length == 0)
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<llvm::StructType>(DesiredTy);
if (STy && STy->getNumElements() == 1 &&
STy->getElementType(0) == Elems[First]->getType())
Elems[First] = llvm::ConstantStruct::get(STy, Elems[First]);
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;
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);
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) {
uint64_t FieldSize = Field->getBitWidthValue(CGM.getContext());
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);
return Builder.addBits(FieldValue,
CGM.getContext().toBits(StartOffset) + FieldOffset,
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<NoInitExpr>(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<NoInitExpr>(Init)) {
} else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init)) {
if (!EmitDesignatedInitUpdater(Emitter, Const, Offset, ElemType,
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<RecordType>()->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<CXXRecordDecl>(RD))
if (CXXRD->getNumBases())
return false;
for (FieldDecl *Field : RD->fields()) {
// If this is a union, skip all the fields that aren't being initialized.
if (RD->isUnion() &&
!declaresSameEntity(ILE->getInitializedFieldInUnion(), Field))
// Don't emit anonymous bitfields or zero-sized fields.
if (Field->isUnnamedBitfield() || Field->isZeroSize(CGM.getContext()))
// 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<NoInitExpr>(Init))
// 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<InitListExpr>(Init)) {
CharUnits Offset = CGM.getContext().toCharUnitsFromBits(
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,
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,
return false;
// After emitting a non-empty field with [[no_unique_address]], we may
// need to overwrite its tail padding.
if (Field->hasAttr<NoUniqueAddressAttr>())
AllowOverwrite = true;
} else {
// Otherwise we have a bitfield.
if (auto *CI = dyn_cast<llvm::ConstantInt>(EltInit)) {
if (!AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI,
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<CXXRecordDecl>(RD)) {
// Add a vtable pointer, if we need one and it hasn't already been added.
if (CD->isDynamicClass() && !IsPrimaryBase) {
llvm::Constant *VTableAddressPoint =
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<BaseInfo, 8> Bases;
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));
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))
// Don't emit anonymous bitfields or zero-sized fields.
if (Field->isUnnamedBitfield() || Field->isZeroSize(CGM.getContext()))
// 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<NoUniqueAddressAttr>())
AllowOverwrite = true;
} else {
// Otherwise we have a bitfield.
if (!AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
cast<llvm::ConstantInt>(EltInit), AllowOverwrite))
return false;
return true;
llvm::Constant *ConstStructBuilder::Finalize(QualType Type) {
RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
llvm::Type *ValTy = CGM.getTypes().ConvertType(Type);
return, 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<RecordType>()->getDecl();
const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(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 =
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),
C, ".compoundliteral", nullptr,
CGM.setAddrOfConstantCompoundLiteral(E, GV);
return ConstantAddress(GV, Align);
static llvm::Constant *
EmitArrayConstant(CodeGenModule &CGM, llvm::ArrayType *DesiredType,
llvm::Type *CommonElementType, unsigned ArrayBound,
SmallVectorImpl<llvm::Constant *> &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())
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),
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<llvm::Type *, 16> Types;
for (llvm::Constant *Elt : Elements)
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<ConstExprEmitter, llvm::Constant*, QualType> {
CodeGenModule &CGM;
ConstantEmitter &Emitter;
llvm::LLVMContext &VMContext;
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) {
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<ExplicitCastExpr>(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<llvm::Constant*, 2> Elts;
SmallVector<llvm::Type*, 2> Types;
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);
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) {
if (!E->cleanupsHaveSideEffects())
return Visit(E->getSubExpr(), T);
return nullptr;
llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E,
QualType T) {
return Visit(E->GetTemporaryExpr(), 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<llvm::Constant*, 16> Elts;
if (fillC && fillC->isNullValue())
Elts.reserve(NumInitableElts + 1);
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;
llvm::ArrayType *Desired =
return EmitArrayConstant(CGM, Desired, CommonElementType, NumElements, Elts,
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,
return nullptr;
llvm::Type *ValTy = CGM.getTypes().ConvertType(destType);
bool HasFlexibleArray = false;
if (auto *RT = destType->getAs<RecordType>())
HasFlexibleArray = RT->getDecl()->hasFlexibleArrayMember();
return, HasFlexibleArray);
llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E, QualType Ty) {
if (!E->getConstructor()->isTrivial())
return nullptr;
// FIXME: We should not have to call getBaseElementType here.
const RecordType *RT =
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 nullptr;
// 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, 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::emitAbstract(const Expr *E, QualType destType) {
auto state = pushAbstract();
auto C = tryEmitPrivate(E, destType);
C = validateAndPopAbstract(C, state);
if (!C) {
"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) {
"internal error: could not emit constant value \"abstractly\"");
C = CGM.EmitNullConstant(destType);
return C;
llvm::Constant *ConstantEmitter::tryEmitForInitializer(const VarDecl &D) {
return markIfFailed(tryEmitPrivateForVarInit(D));
llvm::Constant *ConstantEmitter::tryEmitForInitializer(const Expr *E,
LangAS destAddrSpace,
QualType destType) {
return markIfFailed(tryEmitPrivateForMemory(E, destType));
llvm::Constant *ConstantEmitter::emitForInitializer(const APValue &value,
LangAS destAddrSpace,
QualType destType) {
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,
/*init*/ nullptr,
/*name*/ "",
/*before*/ nullptr,
PlaceholderAddresses.push_back(std::make_pair(nullptr, global));
return global;
void ConstantEmitter::registerCurrentAddrPrivate(llvm::Constant *signal,
llvm::GlobalValue *placeholder) {
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<llvm::Constant*, llvm::GlobalVariable*> PlaceholderAddresses;
/// The locations of the placeholder signals.
llvm::DenseMap<llvm::GlobalVariable*, llvm::Constant*> 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<unsigned, 8> Indices;
llvm::SmallVector<llvm::Constant*, 8> IndexValues;
ReplacePlaceholders(CodeGenModule &CGM, llvm::Constant *base,
llvm::GlobalVariable*>> 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.
// Recurse into the initializer.
// 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!");
void findLocations(llvm::Constant *init) {
// Recurse into aggregates.
if (auto agg = dyn_cast<llvm::ConstantAggregate>(init)) {
for (unsigned i = 0, e = agg->getNumOperands(); i != e; ++i) {
// Otherwise, check for registered constants.
while (true) {
auto it = PlaceholderAddresses.find(init);
if (it != PlaceholderAddresses.end()) {
// Look through bitcasts or other expressions.
if (auto expr = dyn_cast<llvm::ConstantExpr>(init)) {
init = expr->getOperand(0);
} else {
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<llvm::ConstantInt>(IndexValues[j]) &&
== Indices[j]);
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 =
Base, IndexValues);
location = llvm::ConstantExpr::getBitCast(location,
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");
// Note that we might also be Failed.
Finalized = true;
if (!PlaceholderAddresses.empty()) {
ReplacePlaceholders(CGM, global, PlaceholderAddresses)
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<AtomicType>()) {
return CGM.getContext().getQualifiedType(AT->getValueType(),
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<CXXConstructExpr>(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<Expr*>(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<AtomicType>()) {
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[] = {
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());
Success = E->EvaluateAsRValue(Result, CGM.getContext(), InConstantContext);
llvm::Constant *C;
if (Success && !Result.HasSideEffects)
C = tryEmitPrivate(Result.Val, destType);
C = ConstExprEmitter(*this).Visit(const_cast<Expr*>(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(false) {}
/*implicit*/ ConstantLValue(ConstantAddress address)
: ConstantLValue(address.getPointer()) {}
/// A helper class for emitting constant l-values.
class ConstantLValueEmitter : public ConstStmtVisitor<ConstantLValueEmitter,
ConstantLValue> {
CodeGenModule &CGM;
ConstantEmitter &Emitter;
const APValue &Value;
QualType DestType;
// Befriend StmtVisitorBase so that we don't have to expose Visit*.
friend StmtVisitorBase;
ConstantLValueEmitter(ConstantEmitter &emitter, const APValue &value,
QualType destType)
: CGM(emitter.CGM), Emitter(emitter), Value(value), DestType(destType) {}
llvm::Constant *tryEmit();
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 VisitCXXUuidofExpr(const CXXUuidofExpr *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,
/// 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<llvm::IntegerType>(destTy) || isa<llvm::PointerType>(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<llvm::PointerType>(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<llvm::PointerType>(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;
ConstantLValueEmitter::tryEmitBase(const APValue::LValueBase &base) {
// Handle values.
if (const ValueDecl *D = base.dyn_cast<const ValueDecl*>()) {
if (D->hasAttr<WeakRefAttr>())
return CGM.GetWeakRefReference(D).getPointer();
if (auto FD = dyn_cast<FunctionDecl>(D))
return CGM.GetAddrOfFunction(FD);
if (auto VD = dyn_cast<VarDecl>(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));
return nullptr;
// Handle typeid(T).
if (TypeInfoLValue TI = base.dyn_cast<TypeInfoLValue>()) {
llvm::Type *StdTypeInfoPtrTy =
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<const Expr*>());
ConstantLValueEmitter::VisitConstantExpr(const ConstantExpr *E) {
return Visit(E->getSubExpr());
ConstantLValueEmitter::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
return tryEmitGlobalCompoundLiteral(CGM, Emitter.CGF, E);
ConstantLValueEmitter::VisitStringLiteral(const StringLiteral *E) {
return CGM.GetAddrOfConstantStringFromLiteral(E);
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));
ConstantLValueEmitter::VisitObjCStringLiteral(const ObjCStringLiteral *E) {
return emitConstantObjCStringLiteral(E->getString(), E->getType(), CGM);
ConstantLValueEmitter::VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
assert(E->isExpressibleAsConstantInitializer() &&
"this boxed expression can't be emitted as a compile-time constant");
auto *SL = cast<StringLiteral>(E->getSubExpr()->IgnoreParenCasts());
return emitConstantObjCStringLiteral(SL, E->getType(), CGM);
ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) {
return CGM.GetAddrOfConstantStringFromLiteral(E->getFunctionName());
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,
return Ptr;
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<StringLiteral>(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);
ConstantLValueEmitter::VisitBlockExpr(const BlockExpr *E) {
StringRef functionName;
if (auto CGF = Emitter.CGF)
functionName = CGF->CurFn->getName();
functionName = "global";
return CGM.GetAddrOfGlobalBlock(E, functionName);
ConstantLValueEmitter::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
QualType T;
if (E->isTypeOperand())
T = E->getTypeOperand(CGM.getContext());
T = E->getExprOperand()->getType();
return CGM.GetAddrOfRTTIDescriptor(T);
ConstantLValueEmitter::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
return CGM.GetAddrOfUuidDescriptor(E);
const MaterializeTemporaryExpr *E) {
assert(E->getStorageDuration() == SD_Static);
SmallVector<const Expr *, 2> CommaLHSs;
SmallVector<SubobjectAdjustment, 2> Adjustments;
const Expr *Inner = E->GetTemporaryExpr()
->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(),
case APValue::ComplexInt: {
llvm::Constant *Complex[2];
Complex[0] = llvm::ConstantInt::get(CGM.getLLVMContext(),
Complex[1] = llvm::ConstantInt::get(CGM.getLLVMContext(),
// 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 &&
return llvm::ConstantInt::get(CGM.getLLVMContext(),
return llvm::ConstantFP::get(CGM.getLLVMContext(), Init);
case APValue::ComplexFloat: {
llvm::Constant *Complex[2];
Complex[0] = llvm::ConstantFP::get(CGM.getLLVMContext(),
Complex[1] = llvm::ConstantFP::get(CGM.getLLVMContext(),
// 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<llvm::Constant *, 4> 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());
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 =
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(),
if (!Filler)
return nullptr;
// Emit initializer elements.
SmallVector<llvm::Constant*, 16> Elts;
if (Filler && Filler->isNullValue())
Elts.reserve(NumInitElts + 1);
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;
// 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,
return llvm::ConstantAggregateZero::get(AType);
llvm::ArrayType *Desired =
return EmitArrayConstant(CGM, Desired, CommonElementType, NumElements, Elts,
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;
assert(Ok && "CLE has already been emitted!");
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<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().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<llvm::Constant *> elements(numElements);
auto CXXR = dyn_cast<CXXRecordDecl>(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.
const CXXRecordDecl *base =
// Ignore empty bases.
if (base->isEmpty() ||
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())
if (const auto *FieldRD = Field->getType()->getAsRecordDecl())
if (FieldRD->findFirstNamedDataMember())
// 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 =
// Ignore empty bases.
if (base->isEmpty())
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<PointerType>())
return getNullPointer(
cast<llvm::PointerType>(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 =
QualType ElementTy = CAT->getElementType();
llvm::Constant *Element =
ConstantEmitter::emitNullForMemory(*this, ElementTy);
unsigned NumElements = CAT->getSize().getZExtValue();
SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
return llvm::ConstantArray::get(ATy, Array);
if (const RecordType *RT = T->getAs<RecordType>())
return ::EmitNullConstant(*this, RT->getDecl(), /*complete object*/ true);
assert(T->isMemberDataPointerType() &&
"Should only see pointers to data members here!");
return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
llvm::Constant *
CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
return ::EmitNullConstant(*this, Record, false);