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

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//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code to emit Constant Expr nodes as LLVM code.
//
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "CGRecordLayout.h"
#include "CodeGenModule.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/Builtins.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
using namespace clang;
using namespace CodeGen;
//===----------------------------------------------------------------------===//
// ConstStructBuilder
//===----------------------------------------------------------------------===//
namespace {
class ConstStructBuilder {
CodeGenModule &CGM;
CodeGenFunction *CGF;
bool Packed;
CharUnits NextFieldOffsetInChars;
CharUnits LLVMStructAlignment;
SmallVector<llvm::Constant *, 32> Elements;
public:
static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
InitListExpr *ILE);
static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
const APValue &Value, QualType ValTy);
private:
ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
: CGM(CGM), CGF(CGF), Packed(false),
NextFieldOffsetInChars(CharUnits::Zero()),
LLVMStructAlignment(CharUnits::One()) { }
void AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitExpr);
void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst);
void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::ConstantInt *InitExpr);
void AppendPadding(CharUnits PadSize);
void AppendTailPadding(CharUnits RecordSize);
void ConvertStructToPacked();
bool Build(InitListExpr *ILE);
void Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
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.RoundUpToAlignment(FieldAlignment);
if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
// We need to append padding.
AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
assert(NextFieldOffsetInChars == FieldOffsetInChars &&
"Did not add enough padding!");
AlignedNextFieldOffsetInChars =
NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment);
}
if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
assert(!Packed && "Alignment is wrong even with a packed struct!");
// Convert the struct to a packed struct.
ConvertStructToPacked();
// 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::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits,
Context.getTargetInfo().getCharAlign()));
AppendPadding(PadSize);
}
uint64_t FieldSize = Field->getBitWidthValue(Context);
llvm::APInt FieldValue = CI->getValue();
// Promote the size of FieldValue if necessary
// FIXME: This should never occur, but currently it can because initializer
// constants are cast to bool, and because clang is not enforcing bitfield
// width limits.
if (FieldSize > FieldValue.getBitWidth())
FieldValue = FieldValue.zext(FieldSize);
// Truncate the size of FieldValue to the bit field size.
if (FieldSize < FieldValue.getBitWidth())
FieldValue = FieldValue.trunc(FieldSize);
NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
if (FieldOffset < NextFieldOffsetInBits) {
// Either part of the field or the entire field can go into the previous
// byte.
assert(!Elements.empty() && "Elements can't be empty!");
unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
bool FitsCompletelyInPreviousByte =
BitsInPreviousByte >= FieldValue.getBitWidth();
llvm::APInt Tmp = FieldValue;
if (!FitsCompletelyInPreviousByte) {
unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
if (CGM.getDataLayout().isBigEndian()) {
Tmp = Tmp.lshr(NewFieldWidth);
Tmp = Tmp.trunc(BitsInPreviousByte);
// We want the remaining high bits.
FieldValue = FieldValue.trunc(NewFieldWidth);
} else {
Tmp = Tmp.trunc(BitsInPreviousByte);
// We want the remaining low bits.
FieldValue = FieldValue.lshr(BitsInPreviousByte);
FieldValue = FieldValue.trunc(NewFieldWidth);
}
}
Tmp = Tmp.zext(CharWidth);
if (CGM.getDataLayout().isBigEndian()) {
if (FitsCompletelyInPreviousByte)
Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
} else {
Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
}
// 'or' in the bits that go into the previous byte.
llvm::Value *LastElt = Elements.back();
if (llvm::ConstantInt *Val = dyn_cast<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 = FieldValue.lshr(CharWidth);
}
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
++NextFieldOffsetInChars;
FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
}
assert(FieldValue.getBitWidth() > 0 &&
"Should have at least one bit left!");
assert(FieldValue.getBitWidth() <= CharWidth &&
"Should not have more than a byte left!");
if (FieldValue.getBitWidth() < CharWidth) {
if (CGM.getDataLayout().isBigEndian()) {
unsigned BitWidth = FieldValue.getBitWidth();
FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
} else
FieldValue = FieldValue.zext(CharWidth);
}
// Append the last element.
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
FieldValue));
++NextFieldOffsetInChars;
}
void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
if (PadSize.isZero())
return;
llvm::Type *Ty = CGM.Int8Ty;
if (PadSize > CharUnits::One())
Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
llvm::Constant *C = llvm::UndefValue::get(Ty);
Elements.push_back(C);
assert(getAlignment(C) == CharUnits::One() &&
"Padding must have 1 byte alignment!");
NextFieldOffsetInChars += getSizeInChars(C);
}
void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) {
assert(NextFieldOffsetInChars <= RecordSize &&
"Size mismatch!");
AppendPadding(RecordSize - NextFieldOffsetInChars);
}
void ConstStructBuilder::ConvertStructToPacked() {
SmallVector<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.RoundUpToAlignment(ElementAlign);
if (AlignedElementOffsetInChars > ElementOffsetInChars) {
// We need some padding.
CharUnits NumChars =
AlignedElementOffsetInChars - ElementOffsetInChars;
llvm::Type *Ty = CGM.Int8Ty;
if (NumChars > CharUnits::One())
Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity());
llvm::Constant *Padding = llvm::UndefValue::get(Ty);
PackedElements.push_back(Padding);
ElementOffsetInChars += getSizeInChars(Padding);
}
PackedElements.push_back(C);
ElementOffsetInChars += getSizeInChars(C);
}
assert(ElementOffsetInChars == NextFieldOffsetInChars &&
"Packing the struct changed its size!");
Elements.swap(PackedElements);
LLVMStructAlignment = CharUnits::One();
Packed = true;
}
bool ConstStructBuilder::Build(InitListExpr *ILE) {
RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
unsigned FieldNo = 0;
unsigned ElementNo = 0;
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 = CGM.EmitConstantExpr(ILE->getInit(ElementNo++),
Field->getType(), CGF);
else
EltInit = CGM.EmitNullConstant(Field->getType());
if (!EltInit)
return false;
if (!Field->isBitField()) {
// Handle non-bitfield members.
AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
} else {
// Otherwise we have a bitfield.
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; }
};
}
void 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 =
CGM.EmitConstantValueForMemory(FieldValue, Field->getType(), CGF);
assert(EltInit && "EmitConstantValue can't fail");
if (!Field->isBitField()) {
// Handle non-bitfield members.
AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit);
} else {
// Otherwise we have a bitfield.
AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
cast<llvm::ConstantInt>(EltInit));
}
}
}
llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) {
RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
CharUnits LayoutSizeInChars = Layout.getSize();
if (NextFieldOffsetInChars > LayoutSizeInChars) {
// If the struct is bigger than the size of the record type,
// we must have a flexible array member at the end.
assert(RD->hasFlexibleArrayMember() &&
"Must have flexible array member if struct is bigger than type!");
// No tail padding is necessary.
} else {
// Append tail padding if necessary.
CharUnits LLVMSizeInChars =
NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
if (LLVMSizeInChars != LayoutSizeInChars)
AppendTailPadding(LayoutSizeInChars);
LLVMSizeInChars =
NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
// Check if we need to convert the struct to a packed struct.
if (NextFieldOffsetInChars <= LayoutSizeInChars &&
LLVMSizeInChars > LayoutSizeInChars) {
assert(!Packed && "Size mismatch!");
ConvertStructToPacked();
assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
"Converting to packed did not help!");
}
LLVMSizeInChars =
NextFieldOffsetInChars.RoundUpToAlignment(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.RoundUpToAlignment(getAlignment(Result)) ==
getSizeInChars(Result) && "Size mismatch!");
return Result;
}
llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
CodeGenFunction *CGF,
InitListExpr *ILE) {
ConstStructBuilder Builder(CGM, CGF);
if (!Builder.Build(ILE))
return nullptr;
return Builder.Finalize(ILE->getType());
}
llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
CodeGenFunction *CGF,
const APValue &Val,
QualType ValTy) {
ConstStructBuilder Builder(CGM, CGF);
const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl();
const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD);
Builder.Build(Val, RD, false, CD, CharUnits::Zero());
return Builder.Finalize(ValTy);
}
//===----------------------------------------------------------------------===//
// ConstExprEmitter
//===----------------------------------------------------------------------===//
/// This class only needs to handle two cases:
/// 1) Literals (this is used by APValue emission to emit literals).
/// 2) Arrays, structs and unions (outside C++11 mode, we don't currently
/// constant fold these types).
class ConstExprEmitter :
public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
CodeGenModule &CGM;
CodeGenFunction *CGF;
llvm::LLVMContext &VMContext;
public:
ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
: CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
}
//===--------------------------------------------------------------------===//
// Visitor Methods
//===--------------------------------------------------------------------===//
llvm::Constant *VisitStmt(Stmt *S) {
return nullptr;
}
llvm::Constant *VisitParenExpr(ParenExpr *PE) {
return Visit(PE->getSubExpr());
}
llvm::Constant *
VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) {
return Visit(PE->getReplacement());
}
llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
return Visit(GE->getResultExpr());
}
llvm::Constant *VisitChooseExpr(ChooseExpr *CE) {
return Visit(CE->getChosenSubExpr());
}
llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
return Visit(E->getInitializer());
}
llvm::Constant *VisitCastExpr(CastExpr* E) {
Expr *subExpr = E->getSubExpr();
llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF);
if (!C) return nullptr;
llvm::Type *destType = ConvertType(E->getType());
switch (E->getCastKind()) {
case CK_ToUnion: {
// GCC cast to union extension
assert(E->getType()->isUnionType() &&
"Destination type is not union type!");
// Build a struct with the union sub-element as the first member,
// and padded to the appropriate size
SmallVector<llvm::Constant*, 2> Elts;
SmallVector<llvm::Type*, 2> Types;
Elts.push_back(C);
Types.push_back(C->getType());
unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType());
unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destType);
assert(CurSize <= TotalSize && "Union size mismatch!");
if (unsigned NumPadBytes = TotalSize - CurSize) {
llvm::Type *Ty = CGM.Int8Ty;
if (NumPadBytes > 1)
Ty = llvm::ArrayType::get(Ty, NumPadBytes);
Elts.push_back(llvm::UndefValue::get(Ty));
Types.push_back(Ty);
}
llvm::StructType* STy =
llvm::StructType::get(C->getType()->getContext(), Types, false);
return llvm::ConstantStruct::get(STy, Elts);
}
case CK_AddressSpaceConversion:
return llvm::ConstantExpr::getAddrSpaceCast(C, destType);
case CK_LValueToRValue:
case CK_AtomicToNonAtomic:
case CK_NonAtomicToAtomic:
case CK_NoOp:
case CK_ConstructorConversion:
return C;
case CK_Dependent: llvm_unreachable("saw dependent cast!");
case CK_BuiltinFnToFnPtr:
llvm_unreachable("builtin functions are handled elsewhere");
case CK_ReinterpretMemberPointer:
case CK_DerivedToBaseMemberPointer:
case CK_BaseToDerivedMemberPointer:
return CGM.getCXXABI().EmitMemberPointerConversion(E, C);
// These will never be supported.
case CK_ObjCObjectLValueCast:
case CK_ARCProduceObject:
case CK_ARCConsumeObject:
case CK_ARCReclaimReturnedObject:
case CK_ARCExtendBlockObject:
case CK_CopyAndAutoreleaseBlockObject:
return 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_IntegralToPointer:
case CK_IntegralToBoolean:
case CK_IntegralToFloating:
case CK_FloatingToIntegral:
case CK_FloatingToBoolean:
case CK_FloatingCast:
case CK_ZeroToOCLEvent:
return nullptr;
}
llvm_unreachable("Invalid CastKind");
}
llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
return Visit(DAE->getExpr());
}
llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
// No need for a DefaultInitExprScope: we don't handle 'this' in a
// constant expression.
return Visit(DIE->getExpr());
}
llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
return Visit(E->GetTemporaryExpr());
}
llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
if (ILE->isStringLiteralInit())
return Visit(ILE->getInit(0));
llvm::ArrayType *AType =
cast<llvm::ArrayType>(ConvertType(ILE->getType()));
llvm::Type *ElemTy = AType->getElementType();
unsigned NumInitElements = ILE->getNumInits();
unsigned NumElements = AType->getNumElements();
// Initialising an array requires us to automatically
// initialise any elements that have not been initialised explicitly
unsigned NumInitableElts = std::min(NumInitElements, NumElements);
// Initialize remaining array elements.
// FIXME: This doesn't handle member pointers correctly!
llvm::Constant *fillC;
if (Expr *filler = ILE->getArrayFiller())
fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF);
else
fillC = llvm::Constant::getNullValue(ElemTy);
if (!fillC)
return nullptr;
// Try to use a ConstantAggregateZero if we can.
if (fillC->isNullValue() && !NumInitableElts)
return llvm::ConstantAggregateZero::get(AType);
// Copy initializer elements.
std::vector<llvm::Constant*> Elts;
Elts.reserve(NumInitableElts + NumElements);
bool RewriteType = false;
for (unsigned i = 0; i < NumInitableElts; ++i) {
Expr *Init = ILE->getInit(i);
llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
if (!C)
return nullptr;
RewriteType |= (C->getType() != ElemTy);
Elts.push_back(C);
}
RewriteType |= (fillC->getType() != ElemTy);
Elts.resize(NumElements, fillC);
if (RewriteType) {
// FIXME: Try to avoid packing the array
std::vector<llvm::Type*> Types;
Types.reserve(NumInitableElts + NumElements);
for (unsigned i = 0, e = Elts.size(); i < e; ++i)
Types.push_back(Elts[i]->getType());
llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
Types, true);
return llvm::ConstantStruct::get(SType, Elts);
}
return llvm::ConstantArray::get(AType, Elts);
}
llvm::Constant *EmitRecordInitialization(InitListExpr *ILE) {
return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
}
llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
return CGM.EmitNullConstant(E->getType());
}
llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
if (ILE->getType()->isArrayType())
return EmitArrayInitialization(ILE);
if (ILE->getType()->isRecordType())
return EmitRecordInitialization(ILE);
return nullptr;
}
llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
if (!E->getConstructor()->isTrivial())
return nullptr;
QualType Ty = E->getType();
// FIXME: We should not have to call getBaseElementType here.
const RecordType *RT =
CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
// If the class doesn't have a trivial destructor, we can't emit it as a
// constant expr.
if (!RD->hasTrivialDestructor())
return 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);
}
return CGM.EmitNullConstant(Ty);
}
llvm::Constant *VisitStringLiteral(StringLiteral *E) {
return CGM.GetConstantArrayFromStringLiteral(E);
}
llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
// This must be an @encode initializing an array in a static initializer.
// Don't emit it as the address of the string, emit the string data itself
// as an inline array.
std::string Str;
CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
QualType T = E->getType();
if (T->getTypeClass() == Type::TypeOfExpr)
T = cast<TypeOfExprType>(T)->getUnderlyingExpr()->getType();
const ConstantArrayType *CAT = cast<ConstantArrayType>(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) {
return Visit(E->getSubExpr());
}
// Utility methods
llvm::Type *ConvertType(QualType T) {
return CGM.getTypes().ConvertType(T);
}
public:
llvm::Constant *EmitLValue(APValue::LValueBase LVBase) {
if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) {
if (Decl->hasAttr<WeakRefAttr>())
return CGM.GetWeakRefReference(Decl);
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
return CGM.GetAddrOfFunction(FD);
if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
// We can never refer to a variable with local storage.
if (!VD->hasLocalStorage()) {
if (VD->isFileVarDecl() || VD->hasExternalStorage())
return CGM.GetAddrOfGlobalVar(VD);
else if (VD->isLocalVarDecl())
return CGM.getOrCreateStaticVarDecl(
*VD, CGM.getLLVMLinkageVarDefinition(VD, /*isConstant=*/false));
}
}
return nullptr;
}
Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>());
switch (E->getStmtClass()) {
default: break;
case Expr::CompoundLiteralExprClass: {
// Note that due to the nature of compound literals, this is guaranteed
// to be the only use of the variable, so we just generate it here.
CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(),
CLE->getType(), CGF);
// FIXME: "Leaked" on failure.
if (C)
C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
E->getType().isConstant(CGM.getContext()),
llvm::GlobalValue::InternalLinkage,
C, ".compoundliteral", nullptr,
llvm::GlobalVariable::NotThreadLocal,
CGM.getContext().getTargetAddressSpace(E->getType()));
return C;
}
case Expr::StringLiteralClass:
return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
case Expr::ObjCEncodeExprClass:
return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
case Expr::ObjCStringLiteralClass: {
ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
llvm::Constant *C =
CGM.getObjCRuntime().GenerateConstantString(SL->getString());
return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
}
case Expr::PredefinedExprClass: {
unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
if (CGF) {
LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
return cast<llvm::Constant>(Res.getAddress());
} else if (Type == PredefinedExpr::PrettyFunction) {
return CGM.GetAddrOfConstantCString("top level", ".tmp");
}
return CGM.GetAddrOfConstantCString("", ".tmp");
}
case Expr::AddrLabelExprClass: {
assert(CGF && "Invalid address of label expression outside function.");
llvm::Constant *Ptr =
CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
}
case Expr::CallExprClass: {
CallExpr* CE = cast<CallExpr>(E);
unsigned builtin = CE->getBuiltinCallee();
if (builtin !=
Builtin::BI__builtin___CFStringMakeConstantString &&
builtin !=
Builtin::BI__builtin___NSStringMakeConstantString)
break;
const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
const StringLiteral *Literal = cast<StringLiteral>(Arg);
if (builtin ==
Builtin::BI__builtin___NSStringMakeConstantString) {
return CGM.getObjCRuntime().GenerateConstantString(Literal);
}
// FIXME: need to deal with UCN conversion issues.
return CGM.GetAddrOfConstantCFString(Literal);
}
case Expr::BlockExprClass: {
std::string FunctionName;
if (CGF)
FunctionName = CGF->CurFn->getName();
else
FunctionName = "global";
return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
}
case Expr::CXXTypeidExprClass: {
CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E);
QualType T;
if (Typeid->isTypeOperand())
T = Typeid->getTypeOperand(CGM.getContext());
else
T = Typeid->getExprOperand()->getType();
return CGM.GetAddrOfRTTIDescriptor(T);
}
case Expr::CXXUuidofExprClass: {
return CGM.GetAddrOfUuidDescriptor(cast<CXXUuidofExpr>(E));
}
case Expr::MaterializeTemporaryExprClass: {
MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(E);
assert(MTE->getStorageDuration() == SD_Static);
SmallVector<const Expr *, 2> CommaLHSs;
SmallVector<SubobjectAdjustment, 2> Adjustments;
const Expr *Inner = MTE->GetTemporaryExpr()
->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
return CGM.GetAddrOfGlobalTemporary(MTE, Inner);
}
}
return nullptr;
}
};
} // end anonymous namespace.
llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D,
CodeGenFunction *CGF) {
// Make a quick check if variable can be default NULL initialized
// and avoid going through rest of code which may do, for c++11,
// initialization of memory to all NULLs.
if (!D.hasLocalStorage()) {
QualType Ty = D.getType();
if (Ty->isArrayType())
Ty = Context.getBaseElementType(Ty);
if (Ty->isRecordType())
if (const CXXConstructExpr *E =
dyn_cast_or_null<CXXConstructExpr>(D.getInit())) {
const CXXConstructorDecl *CD = E->getConstructor();
if (CD->isTrivial() && CD->isDefaultConstructor())
return EmitNullConstant(D.getType());
}
}
if (const APValue *Value = D.evaluateValue())
return EmitConstantValueForMemory(*Value, D.getType(), CGF);
// FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a
// reference is a constant expression, and the reference binds to a temporary,
// then constant initialization is performed. ConstExprEmitter will
// incorrectly emit a prvalue constant in this case, and the calling code
// interprets that as the (pointer) value of the reference, rather than the
// desired value of the referee.
if (D.getType()->isReferenceType())
return nullptr;
const Expr *E = D.getInit();
assert(E && "No initializer to emit");
llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
if (C && C->getType()->isIntegerTy(1)) {
llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
C = llvm::ConstantExpr::getZExt(C, BoolTy);
}
return C;
}
llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
QualType DestType,
CodeGenFunction *CGF) {
Expr::EvalResult Result;
bool Success = false;
if (DestType->isReferenceType())
Success = E->EvaluateAsLValue(Result, Context);
else
Success = E->EvaluateAsRValue(Result, Context);
llvm::Constant *C = nullptr;
if (Success && !Result.HasSideEffects)
C = EmitConstantValue(Result.Val, DestType, CGF);
else
C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
if (C && C->getType()->isIntegerTy(1)) {
llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
C = llvm::ConstantExpr::getZExt(C, BoolTy);
}
return C;
}
llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
QualType DestType,
CodeGenFunction *CGF) {
// For an _Atomic-qualified constant, we may need to add tail padding.
if (auto *AT = DestType->getAs<AtomicType>()) {
QualType InnerType = AT->getValueType();
auto *Inner = EmitConstantValue(Value, InnerType, CGF);
uint64_t InnerSize = Context.getTypeSize(InnerType);
uint64_t OuterSize = Context.getTypeSize(DestType);
if (InnerSize == OuterSize)
return Inner;
assert(InnerSize < OuterSize && "emitted over-large constant for atomic");
llvm::Constant *Elts[] = {
Inner,
llvm::ConstantAggregateZero::get(
llvm::ArrayType::get(Int8Ty, (OuterSize - InnerSize) / 8))
};
return llvm::ConstantStruct::getAnon(Elts);
}
switch (Value.getKind()) {
case APValue::Uninitialized:
llvm_unreachable("Constant expressions should be initialized.");
case APValue::LValue: {
llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
llvm::Constant *Offset =
llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity());
llvm::Constant *C;
if (APValue::LValueBase LVBase = Value.getLValueBase()) {
// An array can be represented as an lvalue referring to the base.
if (isa<llvm::ArrayType>(DestTy)) {
assert(Offset->isNullValue() && "offset on array initializer");
return ConstExprEmitter(*this, CGF).Visit(
const_cast<Expr*>(LVBase.get<const Expr*>()));
}
C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase);
// Apply offset if necessary.
if (!Offset->isNullValue()) {
unsigned AS = C->getType()->getPointerAddressSpace();
llvm::Type *CharPtrTy = Int8Ty->getPointerTo(AS);
llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, CharPtrTy);
Casted = llvm::ConstantExpr::getGetElementPtr(Int8Ty, Casted, Offset);
C = llvm::ConstantExpr::getPointerCast(Casted, C->getType());
}
// Convert to the appropriate type; this could be an lvalue for
// an integer.
if (isa<llvm::PointerType>(DestTy))
return llvm::ConstantExpr::getPointerCast(C, DestTy);
return llvm::ConstantExpr::getPtrToInt(C, DestTy);
} else {
C = Offset;
// Convert to the appropriate type; this could be an lvalue for
// an integer.
if (isa<llvm::PointerType>(DestTy))
return llvm::ConstantExpr::getIntToPtr(C, DestTy);
// If the types don't match this should only be a truncate.
if (C->getType() != DestTy)
return llvm::ConstantExpr::getTrunc(C, DestTy);
return C;
}
}
case APValue::Int:
return llvm::ConstantInt::get(VMContext, Value.getInt());
case APValue::ComplexInt: {
llvm::Constant *Complex[2];
Complex[0] = llvm::ConstantInt::get(VMContext,
Value.getComplexIntReal());
Complex[1] = llvm::ConstantInt::get(VMContext,
Value.getComplexIntImag());
// FIXME: the target may want to specify that this is packed.
llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
Complex[1]->getType(),
nullptr);
return llvm::ConstantStruct::get(STy, Complex);
}
case APValue::Float: {
const llvm::APFloat &Init = Value.getFloat();
if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf &&
!Context.getLangOpts().NativeHalfType &&
!Context.getLangOpts().HalfArgsAndReturns)
return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt());
else
return llvm::ConstantFP::get(VMContext, Init);
}
case APValue::ComplexFloat: {
llvm::Constant *Complex[2];
Complex[0] = llvm::ConstantFP::get(VMContext,
Value.getComplexFloatReal());
Complex[1] = llvm::ConstantFP::get(VMContext,
Value.getComplexFloatImag());
// FIXME: the target may want to specify that this is packed.
llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
Complex[1]->getType(),
nullptr);
return llvm::ConstantStruct::get(STy, Complex);
}
case APValue::Vector: {
SmallVector<llvm::Constant *, 4> Inits;
unsigned NumElts = Value.getVectorLength();
for (unsigned i = 0; i != NumElts; ++i) {
const APValue &Elt = Value.getVectorElt(i);
if (Elt.isInt())
Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
else
Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
}
return llvm::ConstantVector::get(Inits);
}
case APValue::AddrLabelDiff: {
const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS();
const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS();
llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF);
llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF);
// Compute difference
llvm::Type *ResultType = getTypes().ConvertType(DestType);
LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy);
RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy);
llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS);
// LLVM is a bit sensitive about the exact format of the
// address-of-label difference; make sure to truncate after
// the subtraction.
return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType);
}
case APValue::Struct:
case APValue::Union:
return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType);
case APValue::Array: {
const ArrayType *CAT = Context.getAsArrayType(DestType);
unsigned NumElements = Value.getArraySize();
unsigned NumInitElts = Value.getArrayInitializedElts();
// Emit array filler, if there is one.
llvm::Constant *Filler = nullptr;
if (Value.hasArrayFiller())
Filler = EmitConstantValueForMemory(Value.getArrayFiller(),
CAT->getElementType(), CGF);
// Emit initializer elements.
llvm::Type *CommonElementType =
getTypes().ConvertType(CAT->getElementType());
// Try to use a ConstantAggregateZero if we can.
if (Filler && Filler->isNullValue() && !NumInitElts) {
llvm::ArrayType *AType =
llvm::ArrayType::get(CommonElementType, NumElements);
return llvm::ConstantAggregateZero::get(AType);
}
std::vector<llvm::Constant*> Elts;
Elts.reserve(NumElements);
for (unsigned I = 0; I < NumElements; ++I) {
llvm::Constant *C = Filler;
if (I < NumInitElts)
C = EmitConstantValueForMemory(Value.getArrayInitializedElt(I),
CAT->getElementType(), CGF);
else
assert(Filler && "Missing filler for implicit elements of initializer");
if (I == 0)
CommonElementType = C->getType();
else if (C->getType() != CommonElementType)
CommonElementType = nullptr;
Elts.push_back(C);
}
if (!CommonElementType) {
// FIXME: Try to avoid packing the array
std::vector<llvm::Type*> Types;
Types.reserve(NumElements);
for (unsigned i = 0, e = Elts.size(); i < e; ++i)
Types.push_back(Elts[i]->getType());
llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true);
return llvm::ConstantStruct::get(SType, Elts);
}
llvm::ArrayType *AType =
llvm::ArrayType::get(CommonElementType, NumElements);
return llvm::ConstantArray::get(AType, Elts);
}
case APValue::MemberPointer:
return getCXXABI().EmitMemberPointer(Value, DestType);
}
llvm_unreachable("Unknown APValue kind");
}
llvm::Constant *
CodeGenModule::EmitConstantValueForMemory(const APValue &Value,
QualType DestType,
CodeGenFunction *CGF) {
llvm::Constant *C = EmitConstantValue(Value, DestType, CGF);
if (C->getType()->isIntegerTy(1)) {
llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType);
C = llvm::ConstantExpr::getZExt(C, BoolTy);
}
return C;
}
llvm::Constant *
CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) {
assert(E->isFileScope() && "not a file-scope compound literal expr");
return ConstExprEmitter(*this, nullptr).EmitLValue(E);
}
llvm::Constant *
CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
// Member pointer constants always have a very particular form.
const MemberPointerType *type = cast<MemberPointerType>(uo->getType());
const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl();
// A member function pointer.
if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl))
return getCXXABI().EmitMemberPointer(method);
// Otherwise, a member data pointer.
uint64_t fieldOffset = getContext().getFieldOffset(decl);
CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset);
return getCXXABI().EmitMemberDataPointer(type, chars);
}
static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
llvm::Type *baseType,
const CXXRecordDecl *base);
static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
const CXXRecordDecl *record,
bool asCompleteObject) {
const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
llvm::StructType *structure =
(asCompleteObject ? layout.getLLVMType()
: layout.getBaseSubobjectLLVMType());
unsigned numElements = structure->getNumElements();
std::vector<llvm::Constant *> elements(numElements);
// Fill in all the bases.
for (const auto &I : record->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())
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() && Field->getDeclName())
break;
}
// Fill in the virtual bases, if we're working with the complete object.
if (asCompleteObject) {
for (const auto &I : record->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 *CodeGenModule::EmitNullConstant(QualType T) {
if (getTypes().isZeroInitializable(T))
return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
llvm::ArrayType *ATy =
cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
QualType ElementTy = CAT->getElementType();
llvm::Constant *Element = EmitNullConstant(ElementTy);
unsigned NumElements = CAT->getSize().getZExtValue();
if (Element->isNullValue())
return llvm::ConstantAggregateZero::get(ATy);
SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
return llvm::ConstantArray::get(ATy, Array);
}
if (const RecordType *RT = T->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
return ::EmitNullConstant(*this, RD, /*complete object*/ true);
}
assert(T->isMemberPointerType() && "Should only see member pointers here!");
assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
"Should only see pointers to data members here!");
return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
}
llvm::Constant *
CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
return ::EmitNullConstant(*this, Record, false);
}
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