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llvm-project/clang/lib/CodeGen/CGExprConstant.cpp

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//===--- 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 "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/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
using namespace clang;
using namespace CodeGen;
//===----------------------------------------------------------------------===//
// ConstStructBuilder
//===----------------------------------------------------------------------===//
namespace {
class ConstExprEmitter;
class ConstStructBuilder {
CodeGenModule &CGM;
ConstantEmitter &Emitter;
bool Packed;
CharUnits NextFieldOffsetInChars;
CharUnits LLVMStructAlignment;
SmallVector<llvm::Constant *, 32> Elements;
public:
static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
ConstExprEmitter *ExprEmitter,
llvm::Constant *Base,
InitListExpr *Updater,
QualType ValTy);
static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
InitListExpr *ILE, QualType StructTy);
static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
const APValue &Value, QualType ValTy);
private:
ConstStructBuilder(ConstantEmitter &emitter)
: CGM(emitter.CGM), Emitter(emitter), Packed(false),
NextFieldOffsetInChars(CharUnits::Zero()),
LLVMStructAlignment(CharUnits::One()) { }
void AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitExpr);
void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst);
void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::ConstantInt *InitExpr);
void AppendPadding(CharUnits PadSize);
void AppendTailPadding(CharUnits RecordSize);
void ConvertStructToPacked();
bool Build(InitListExpr *ILE);
bool Build(ConstExprEmitter *Emitter, llvm::Constant *Base,
InitListExpr *Updater);
bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
const CXXRecordDecl *VTableClass, CharUnits BaseOffset);
llvm::Constant *Finalize(QualType Ty);
CharUnits getAlignment(const llvm::Constant *C) const {
if (Packed) return CharUnits::One();
return CharUnits::fromQuantity(
CGM.getDataLayout().getABITypeAlignment(C->getType()));
}
CharUnits getSizeInChars(const llvm::Constant *C) const {
return CharUnits::fromQuantity(
CGM.getDataLayout().getTypeAllocSize(C->getType()));
}
};
void ConstStructBuilder::
AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitCst) {
const ASTContext &Context = CGM.getContext();
CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset);
AppendBytes(FieldOffsetInChars, InitCst);
}
void ConstStructBuilder::
AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) {
assert(NextFieldOffsetInChars <= FieldOffsetInChars
&& "Field offset mismatch!");
CharUnits FieldAlignment = getAlignment(InitCst);
// Round up the field offset to the alignment of the field type.
CharUnits AlignedNextFieldOffsetInChars =
NextFieldOffsetInChars.alignTo(FieldAlignment);
if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
// We need to append padding.
AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
assert(NextFieldOffsetInChars == FieldOffsetInChars &&
"Did not add enough padding!");
AlignedNextFieldOffsetInChars =
NextFieldOffsetInChars.alignTo(FieldAlignment);
}
if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
assert(!Packed && "Alignment is wrong even with a packed struct!");
// Convert the struct to a packed struct.
ConvertStructToPacked();
// After we pack the struct, we may need to insert padding.
if (NextFieldOffsetInChars < FieldOffsetInChars) {
// We need to append padding.
AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
assert(NextFieldOffsetInChars == FieldOffsetInChars &&
"Did not add enough padding!");
}
AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
}
// Add the field.
Elements.push_back(InitCst);
NextFieldOffsetInChars = AlignedNextFieldOffsetInChars +
getSizeInChars(InitCst);
if (Packed)
assert(LLVMStructAlignment == CharUnits::One() &&
"Packed struct not byte-aligned!");
else
LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
}
void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
uint64_t FieldOffset,
llvm::ConstantInt *CI) {
const ASTContext &Context = CGM.getContext();
const uint64_t CharWidth = Context.getCharWidth();
uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
if (FieldOffset > NextFieldOffsetInBits) {
// We need to add padding.
CharUnits PadSize = Context.toCharUnitsFromBits(
llvm::alignTo(FieldOffset - NextFieldOffsetInBits,
Context.getTargetInfo().getCharAlign()));
AppendPadding(PadSize);
}
uint64_t FieldSize = Field->getBitWidthValue(Context);
llvm::APInt FieldValue = CI->getValue();
// Promote the size of FieldValue if necessary
// FIXME: This should never occur, but currently it can because initializer
// constants are cast to bool, and because clang is not enforcing bitfield
// width limits.
if (FieldSize > FieldValue.getBitWidth())
FieldValue = FieldValue.zext(FieldSize);
// Truncate the size of FieldValue to the bit field size.
if (FieldSize < FieldValue.getBitWidth())
FieldValue = FieldValue.trunc(FieldSize);
NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
if (FieldOffset < NextFieldOffsetInBits) {
// Either part of the field or the entire field can go into the previous
// byte.
assert(!Elements.empty() && "Elements can't be empty!");
unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
bool FitsCompletelyInPreviousByte =
BitsInPreviousByte >= FieldValue.getBitWidth();
llvm::APInt Tmp = FieldValue;
if (!FitsCompletelyInPreviousByte) {
unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
if (CGM.getDataLayout().isBigEndian()) {
Tmp.lshrInPlace(NewFieldWidth);
Tmp = Tmp.trunc(BitsInPreviousByte);
// We want the remaining high bits.
FieldValue = FieldValue.trunc(NewFieldWidth);
} else {
Tmp = Tmp.trunc(BitsInPreviousByte);
// We want the remaining low bits.
FieldValue.lshrInPlace(BitsInPreviousByte);
FieldValue = FieldValue.trunc(NewFieldWidth);
}
}
Tmp = Tmp.zext(CharWidth);
if (CGM.getDataLayout().isBigEndian()) {
if (FitsCompletelyInPreviousByte)
Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
} else {
Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
}
// 'or' in the bits that go into the previous byte.
llvm::Value *LastElt = Elements.back();
if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
Tmp |= Val->getValue();
else {
assert(isa<llvm::UndefValue>(LastElt));
// If there is an undef field that we're adding to, it can either be a
// scalar undef (in which case, we just replace it with our field) or it
// is an array. If it is an array, we have to pull one byte off the
// array so that the other undef bytes stay around.
if (!isa<llvm::IntegerType>(LastElt->getType())) {
// The undef padding will be a multibyte array, create a new smaller
// padding and then an hole for our i8 to get plopped into.
assert(isa<llvm::ArrayType>(LastElt->getType()) &&
"Expected array padding of undefs");
llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
assert(AT->getElementType()->isIntegerTy(CharWidth) &&
AT->getNumElements() != 0 &&
"Expected non-empty array padding of undefs");
// Remove the padding array.
NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements());
Elements.pop_back();
// Add the padding back in two chunks.
AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1));
AppendPadding(CharUnits::One());
assert(isa<llvm::UndefValue>(Elements.back()) &&
Elements.back()->getType()->isIntegerTy(CharWidth) &&
"Padding addition didn't work right");
}
}
Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
if (FitsCompletelyInPreviousByte)
return;
}
while (FieldValue.getBitWidth() > CharWidth) {
llvm::APInt Tmp;
if (CGM.getDataLayout().isBigEndian()) {
// We want the high bits.
Tmp =
FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth);
} else {
// We want the low bits.
Tmp = FieldValue.trunc(CharWidth);
FieldValue.lshrInPlace(CharWidth);
}
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
++NextFieldOffsetInChars;
FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
}
assert(FieldValue.getBitWidth() > 0 &&
"Should have at least one bit left!");
assert(FieldValue.getBitWidth() <= CharWidth &&
"Should not have more than a byte left!");
if (FieldValue.getBitWidth() < CharWidth) {
if (CGM.getDataLayout().isBigEndian()) {
unsigned BitWidth = FieldValue.getBitWidth();
FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
} else
FieldValue = FieldValue.zext(CharWidth);
}
// Append the last element.
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
FieldValue));
++NextFieldOffsetInChars;
}
void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
if (PadSize.isZero())
return;
llvm::Type *Ty = CGM.Int8Ty;
if (PadSize > CharUnits::One())
Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
llvm::Constant *C = llvm::UndefValue::get(Ty);
Elements.push_back(C);
assert(getAlignment(C) == CharUnits::One() &&
"Padding must have 1 byte alignment!");
NextFieldOffsetInChars += getSizeInChars(C);
}
void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) {
assert(NextFieldOffsetInChars <= RecordSize &&
"Size mismatch!");
AppendPadding(RecordSize - NextFieldOffsetInChars);
}
void ConstStructBuilder::ConvertStructToPacked() {
SmallVector<llvm::Constant *, 16> PackedElements;
CharUnits ElementOffsetInChars = CharUnits::Zero();
for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
llvm::Constant *C = Elements[i];
CharUnits ElementAlign = CharUnits::fromQuantity(
CGM.getDataLayout().getABITypeAlignment(C->getType()));
CharUnits AlignedElementOffsetInChars =
ElementOffsetInChars.alignTo(ElementAlign);
if (AlignedElementOffsetInChars > ElementOffsetInChars) {
// We need some padding.
CharUnits NumChars =
AlignedElementOffsetInChars - ElementOffsetInChars;
llvm::Type *Ty = CGM.Int8Ty;
if (NumChars > CharUnits::One())
Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity());
llvm::Constant *Padding = llvm::UndefValue::get(Ty);
PackedElements.push_back(Padding);
ElementOffsetInChars += getSizeInChars(Padding);
}
PackedElements.push_back(C);
ElementOffsetInChars += getSizeInChars(C);
}
assert(ElementOffsetInChars == NextFieldOffsetInChars &&
"Packing the struct changed its size!");
Elements.swap(PackedElements);
LLVMStructAlignment = CharUnits::One();
Packed = true;
}
bool ConstStructBuilder::Build(InitListExpr *ILE) {
RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
unsigned FieldNo = 0;
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 (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() && ILE->getInitializedFieldInUnion() != *Field)
continue;
// Don't emit anonymous bitfields, they just affect layout.
if (Field->isUnnamedBitfield())
continue;
// Get the initializer. A struct can include fields without initializers,
// we just use explicit null values for them.
llvm::Constant *EltInit;
if (ElementNo < ILE->getNumInits())
EltInit = Emitter.tryEmitPrivateForMemory(ILE->getInit(ElementNo++),
Field->getType());
else
EltInit = Emitter.emitNullForMemory(Field->getType());
if (!EltInit)
return false;
if (!Field->isBitField()) {
// Handle non-bitfield members.
AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
} else {
// Otherwise we have a bitfield.
if (auto *CI = dyn_cast<llvm::ConstantInt>(EltInit)) {
AppendBitField(*Field, Layout.getFieldOffset(FieldNo), CI);
} 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 =
CGM.getCXXABI().getVTableAddressPointForConstExpr(
BaseSubobject(CD, Offset), VTableClass);
AppendBytes(Offset, VTableAddressPoint);
}
// 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;
Bases.reserve(CD->getNumBases());
unsigned BaseNo = 0;
for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(),
BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) {
assert(!Base->isVirtual() && "should not have virtual bases here");
const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl();
CharUnits BaseOffset = Layout.getBaseClassOffset(BD);
Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo));
}
std::stable_sort(Bases.begin(), Bases.end());
for (unsigned I = 0, N = Bases.size(); I != N; ++I) {
BaseInfo &Base = Bases[I];
bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl;
Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase,
VTableClass, Offset + Base.Offset);
}
}
unsigned FieldNo = 0;
uint64_t OffsetBits = CGM.getContext().toBits(Offset);
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() && Val.getUnionField() != *Field)
continue;
// Don't emit anonymous bitfields, they just affect layout.
if (Field->isUnnamedBitfield())
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.
AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit);
} else {
// Otherwise we have a bitfield.
AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
cast<llvm::ConstantInt>(EltInit));
}
}
return true;
}
llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) {
RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
CharUnits LayoutSizeInChars = Layout.getSize();
if (NextFieldOffsetInChars > LayoutSizeInChars) {
// If the struct is bigger than the size of the record type,
// we must have a flexible array member at the end.
assert(RD->hasFlexibleArrayMember() &&
"Must have flexible array member if struct is bigger than type!");
// No tail padding is necessary.
} else {
// Append tail padding if necessary.
CharUnits LLVMSizeInChars =
NextFieldOffsetInChars.alignTo(LLVMStructAlignment);
if (LLVMSizeInChars != LayoutSizeInChars)
AppendTailPadding(LayoutSizeInChars);
LLVMSizeInChars = NextFieldOffsetInChars.alignTo(LLVMStructAlignment);
// Check if we need to convert the struct to a packed struct.
if (NextFieldOffsetInChars <= LayoutSizeInChars &&
LLVMSizeInChars > LayoutSizeInChars) {
assert(!Packed && "Size mismatch!");
ConvertStructToPacked();
assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
"Converting to packed did not help!");
}
LLVMSizeInChars = NextFieldOffsetInChars.alignTo(LLVMStructAlignment);
assert(LayoutSizeInChars == LLVMSizeInChars &&
"Tail padding mismatch!");
}
// Pick the type to use. If the type is layout identical to the ConvertType
// type then use it, otherwise use whatever the builder produced for us.
llvm::StructType *STy =
llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(),
Elements, Packed);
llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty);
if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) {
if (ValSTy->isLayoutIdentical(STy))
STy = ValSTy;
}
llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements);
assert(NextFieldOffsetInChars.alignTo(getAlignment(Result)) ==
getSizeInChars(Result) &&
"Size mismatch!");
return Result;
}
llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
ConstExprEmitter *ExprEmitter,
llvm::Constant *Base,
InitListExpr *Updater,
QualType ValTy) {
ConstStructBuilder Builder(Emitter);
if (!Builder.Build(ExprEmitter, Base, Updater))
return nullptr;
return Builder.Finalize(ValTy);
}
llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
InitListExpr *ILE,
QualType ValTy) {
ConstStructBuilder Builder(Emitter);
if (!Builder.Build(ILE))
return nullptr;
return Builder.Finalize(ValTy);
}
llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
const APValue &Val,
QualType ValTy) {
ConstStructBuilder Builder(Emitter);
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);
}
//===----------------------------------------------------------------------===//
// 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.getQuantity());
CGM.setAddrOfConstantCompoundLiteral(E, GV);
return ConstantAddress(GV, Align);
}
static llvm::Constant *
EmitArrayConstant(CodeGenModule &CGM, const ConstantArrayType *DestType,
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())
--NonzeroLength;
}
if (NonzeroLength == 0) {
return llvm::ConstantAggregateZero::get(
CGM.getTypes().ConvertType(QualType(DestType, 0)));
}
// 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
: CGM.getTypes().ConvertType(DestType->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;
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<ConstExprEmitter, llvm::Constant*, QualType> {
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) {
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;
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_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 *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE, QualType T) {
return Visit(DAE->getExpr(), T);
}
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);
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);
}
return EmitArrayConstant(CGM, CAT, 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 *EmitDesignatedInitUpdater(llvm::Constant *Base,
InitListExpr *Updater,
QualType destType) {
if (auto destAT = CGM.getContext().getAsArrayType(destType)) {
llvm::ArrayType *AType = cast<llvm::ArrayType>(ConvertType(destType));
llvm::Type *ElemType = AType->getElementType();
unsigned NumInitElements = Updater->getNumInits();
unsigned NumElements = AType->getNumElements();
std::vector<llvm::Constant *> Elts;
Elts.reserve(NumElements);
QualType destElemType = destAT->getElementType();
if (auto DataArray = dyn_cast<llvm::ConstantDataArray>(Base))
for (unsigned i = 0; i != NumElements; ++i)
Elts.push_back(DataArray->getElementAsConstant(i));
else if (auto Array = dyn_cast<llvm::ConstantArray>(Base))
for (unsigned i = 0; i != NumElements; ++i)
Elts.push_back(Array->getOperand(i));
else
return nullptr; // FIXME: other array types not implemented
llvm::Constant *fillC = nullptr;
if (Expr *filler = Updater->getArrayFiller())
if (!isa<NoInitExpr>(filler))
fillC = Emitter.tryEmitAbstractForMemory(filler, destElemType);
bool RewriteType = (fillC && fillC->getType() != ElemType);
for (unsigned i = 0; i != NumElements; ++i) {
Expr *Init = nullptr;
if (i < NumInitElements)
Init = Updater->getInit(i);
if (!Init && fillC)
Elts[i] = fillC;
else if (!Init || isa<NoInitExpr>(Init))
; // Do nothing.
else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init))
Elts[i] = EmitDesignatedInitUpdater(Elts[i], ChildILE, destElemType);
else
Elts[i] = Emitter.tryEmitPrivateForMemory(Init, destElemType);
if (!Elts[i])
return nullptr;
RewriteType |= (Elts[i]->getType() != ElemType);
}
if (RewriteType) {
std::vector<llvm::Type *> Types;
Types.reserve(NumElements);
for (unsigned i = 0; i != NumElements; ++i)
Types.push_back(Elts[i]->getType());
llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
Types, true);
return llvm::ConstantStruct::get(SType, Elts);
}
return llvm::ConstantArray::get(AType, Elts);
}
if (destType->isRecordType())
return ConstStructBuilder::BuildStruct(Emitter, this, Base, Updater,
destType);
return nullptr;
}
llvm::Constant *VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E,
QualType destType) {
auto C = Visit(E->getBase(), destType);
if (!C) return nullptr;
return EmitDesignatedInitUpdater(C, E->getUpdater(), destType);
}
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 =
CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
// If the class doesn't have a trivial destructor, we can't emit it as a
// constant expr.
if (!RD->hasTrivialDestructor())
return 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.
bool ConstStructBuilder::Build(ConstExprEmitter *ExprEmitter,
llvm::Constant *Base,
InitListExpr *Updater) {
assert(Base && "base expression should not be empty");
QualType ExprType = Updater->getType();
RecordDecl *RD = ExprType->getAs<RecordType>()->getDecl();
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
const llvm::StructLayout *BaseLayout = CGM.getDataLayout().getStructLayout(
cast<llvm::StructType>(Base->getType()));
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()) {
++FieldNo;
if (RD->isUnion() && Updater->getInitializedFieldInUnion() != Field)
continue;
// Skip anonymous bitfields.
if (Field->isUnnamedBitfield())
continue;
llvm::Constant *EltInit = Base->getAggregateElement(ElementNo);
// Bail out if the type of the ConstantStruct does not have the same layout
// as the type of the InitListExpr.
if (CGM.getTypes().ConvertType(Field->getType()) != EltInit->getType() ||
Layout.getFieldOffset(ElementNo) !=
BaseLayout->getElementOffsetInBits(ElementNo))
return false;
// Get the initializer. If we encounter an empty field or a NoInitExpr,
// we use values from the base expression.
Expr *Init = nullptr;
if (ElementNo < Updater->getNumInits())
Init = Updater->getInit(ElementNo);
if (!Init || isa<NoInitExpr>(Init))
; // Do nothing.
else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init))
EltInit = ExprEmitter->EmitDesignatedInitUpdater(EltInit, ChildILE,
Field->getType());
else
EltInit = Emitter.tryEmitPrivateForMemory(Init, Field->getType());
++ElementNo;
if (!EltInit)
return false;
if (!Field->isBitField())
AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit);
else if (llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(EltInit))
AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI);
else
// Initializing a bitfield with a non-trivial constant?
return false;
}
return true;
}
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) {
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<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,
ArrayRef<std::pair<llvm::Constant*,
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.
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<llvm::ConstantAggregate>(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<llvm::ConstantExpr>(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<llvm::ConstantInt>(IndexValues[j]) &&
cast<llvm::ConstantInt>(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<AtomicType>()) {
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<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[] = {
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<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;
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 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,
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<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) {
auto offset = getOffset();
// 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 = offset;
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<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;
}
// Otherwise, it must be an expression.
return Visit(base.get<const Expr*>());
}
ConstantLValue
ConstantLValueEmitter::VisitConstantExpr(const ConstantExpr *E) {
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<StringLiteral>(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<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);
}
}
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::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
return CGM.GetAddrOfUuidDescriptor(E);
}
ConstantLValue
ConstantLValueEmitter::VisitMaterializeTemporaryExpr(
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::Uninitialized:
llvm_unreachable("Constant expressions should be initialized.");
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<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());
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<llvm::Constant*, 16> 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);
}
return EmitArrayConstant(CGM, CAT, 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<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.
continue;
}
const CXXRecordDecl *base =
cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->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()) {
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<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
// Ignore empty bases.
if (base->isEmpty())
continue;
unsigned fieldIndex = layout.getVirtualBaseIndex(base);
// We might have already laid this field out.
if (elements[fieldIndex]) continue;
llvm::Type *baseType = structure->getElementType(fieldIndex);
elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
}
}
// Now go through all other fields and zero them out.
for (unsigned i = 0; i != numElements; ++i) {
if (!elements[i])
elements[i] = llvm::Constant::getNullValue(structure->getElementType(i));
}
return llvm::ConstantStruct::get(structure, elements);
}
/// Emit the null constant for a base subobject.
static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
llvm::Type *baseType,
const CXXRecordDecl *base) {
const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
// Just zero out bases that don't have any pointer to data members.
if (baseLayout.isZeroInitializableAsBase())
return llvm::Constant::getNullValue(baseType);
// 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 =
cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
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);
}
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