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llvm-project/clang/lib/CodeGen/CGExprConstant.cpp
Douglas Gregor e8bbc12152 Extend the ASTContext constructor to delay the initialization of 
builtin types (When requested). This is another step toward making
ASTUnit build the ASTContext as needed when loading an AST file,
rather than doing so after the fact. No actual functionality change (yet).

llvm-svn: 138985
2011-09-02 00:18:52 +00:00

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47 KiB
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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 "CodeGenModule.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "CGRecordLayout.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/Builtins.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Target/TargetData.h"
using namespace clang;
using namespace CodeGen;
//===----------------------------------------------------------------------===//
// ConstStructBuilder
//===----------------------------------------------------------------------===//
namespace {
class ConstStructBuilder {
CodeGenModule &CGM;
CodeGenFunction *CGF;
bool Packed;
CharUnits NextFieldOffsetInChars;
CharUnits LLVMStructAlignment;
std::vector<llvm::Constant *> Elements;
public:
static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
InitListExpr *ILE);
private:
ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
: CGM(CGM), CGF(CGF), Packed(false),
NextFieldOffsetInChars(CharUnits::Zero()),
LLVMStructAlignment(CharUnits::One()) { }
bool AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitExpr);
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);
CharUnits getAlignment(const llvm::Constant *C) const {
if (Packed) return CharUnits::One();
return CharUnits::fromQuantity(
CGM.getTargetData().getABITypeAlignment(C->getType()));
}
CharUnits getSizeInChars(const llvm::Constant *C) const {
return CharUnits::fromQuantity(
CGM.getTargetData().getTypeAllocSize(C->getType()));
}
};
bool ConstStructBuilder::
AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitCst) {
const ASTContext &Context = CGM.getContext();
CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset);
assert(NextFieldOffsetInChars <= FieldOffsetInChars
&& "Field offset mismatch!");
CharUnits FieldAlignment = getAlignment(InitCst);
// Round up the field offset to the alignment of the field type.
CharUnits AlignedNextFieldOffsetInChars =
NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment);
if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
assert(!Packed && "Alignment is wrong even with a packed struct!");
// Convert the struct to a packed struct.
ConvertStructToPacked();
AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
}
if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
// We need to append padding.
AppendPadding(
FieldOffsetInChars - NextFieldOffsetInChars);
assert(NextFieldOffsetInChars == FieldOffsetInChars &&
"Did not add enough padding!");
AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
}
// Add the field.
Elements.push_back(InitCst);
NextFieldOffsetInChars = AlignedNextFieldOffsetInChars +
getSizeInChars(InitCst);
if (Packed)
assert(LLVMStructAlignment == CharUnits::One() &&
"Packed struct not byte-aligned!");
else
LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
return true;
}
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->getBitWidth()->EvaluateAsInt(Context).getZExtValue();
llvm::APInt FieldValue = CI->getValue();
// Promote the size of FieldValue if necessary
// FIXME: This should never occur, but currently it can because initializer
// constants are cast to bool, and because clang is not enforcing bitfield
// width limits.
if (FieldSize > FieldValue.getBitWidth())
FieldValue = FieldValue.zext(FieldSize);
// Truncate the size of FieldValue to the bit field size.
if (FieldSize < FieldValue.getBitWidth())
FieldValue = FieldValue.trunc(FieldSize);
NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
if (FieldOffset < NextFieldOffsetInBits) {
// Either part of the field or the entire field can go into the previous
// byte.
assert(!Elements.empty() && "Elements can't be empty!");
unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
bool FitsCompletelyInPreviousByte =
BitsInPreviousByte >= FieldValue.getBitWidth();
llvm::APInt Tmp = FieldValue;
if (!FitsCompletelyInPreviousByte) {
unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
if (CGM.getTargetData().isBigEndian()) {
Tmp = Tmp.lshr(NewFieldWidth);
Tmp = Tmp.trunc(BitsInPreviousByte);
// We want the remaining high bits.
FieldValue = FieldValue.trunc(NewFieldWidth);
} else {
Tmp = Tmp.trunc(BitsInPreviousByte);
// We want the remaining low bits.
FieldValue = FieldValue.lshr(BitsInPreviousByte);
FieldValue = FieldValue.trunc(NewFieldWidth);
}
}
Tmp = Tmp.zext(CharWidth);
if (CGM.getTargetData().isBigEndian()) {
if (FitsCompletelyInPreviousByte)
Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
} else {
Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
}
// 'or' in the bits that go into the previous byte.
llvm::Value *LastElt = Elements.back();
if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
Tmp |= Val->getValue();
else {
assert(isa<llvm::UndefValue>(LastElt));
// If there is an undef field that we're adding to, it can either be a
// scalar undef (in which case, we just replace it with our field) or it
// is an array. If it is an array, we have to pull one byte off the
// array so that the other undef bytes stay around.
if (!isa<llvm::IntegerType>(LastElt->getType())) {
// The undef padding will be a multibyte array, create a new smaller
// padding and then an hole for our i8 to get plopped into.
assert(isa<llvm::ArrayType>(LastElt->getType()) &&
"Expected array padding of undefs");
llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
assert(AT->getElementType()->isIntegerTy(CharWidth) &&
AT->getNumElements() != 0 &&
"Expected non-empty array padding of undefs");
// Remove the padding array.
NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements());
Elements.pop_back();
// Add the padding back in two chunks.
AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1));
AppendPadding(CharUnits::One());
assert(isa<llvm::UndefValue>(Elements.back()) &&
Elements.back()->getType()->isIntegerTy(CharWidth) &&
"Padding addition didn't work right");
}
}
Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
if (FitsCompletelyInPreviousByte)
return;
}
while (FieldValue.getBitWidth() > CharWidth) {
llvm::APInt Tmp;
if (CGM.getTargetData().isBigEndian()) {
// We want the high bits.
Tmp =
FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth);
} else {
// We want the low bits.
Tmp = FieldValue.trunc(CharWidth);
FieldValue = FieldValue.lshr(CharWidth);
}
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
++NextFieldOffsetInChars;
FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
}
assert(FieldValue.getBitWidth() > 0 &&
"Should have at least one bit left!");
assert(FieldValue.getBitWidth() <= CharWidth &&
"Should not have more than a byte left!");
if (FieldValue.getBitWidth() < CharWidth) {
if (CGM.getTargetData().isBigEndian()) {
unsigned BitWidth = FieldValue.getBitWidth();
FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
} else
FieldValue = FieldValue.zext(CharWidth);
}
// Append the last element.
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
FieldValue));
++NextFieldOffsetInChars;
}
void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
if (PadSize.isZero())
return;
llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
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() {
std::vector<llvm::Constant *> PackedElements;
CharUnits ElementOffsetInChars = CharUnits::Zero();
for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
llvm::Constant *C = Elements[i];
CharUnits ElementAlign = CharUnits::fromQuantity(
CGM.getTargetData().getABITypeAlignment(C->getType()));
CharUnits AlignedElementOffsetInChars =
ElementOffsetInChars.RoundUpToAlignment(ElementAlign);
if (AlignedElementOffsetInChars > ElementOffsetInChars) {
// We need some padding.
CharUnits NumChars =
AlignedElementOffsetInChars - ElementOffsetInChars;
llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
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 = 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;
const FieldDecl *LastFD = 0;
bool IsMsStruct = RD->hasAttr<MsStructAttr>();
for (RecordDecl::field_iterator Field = RD->field_begin(),
FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
if (IsMsStruct) {
// Zero-length bitfields following non-bitfield members are
// ignored:
if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) {
--FieldNo;
continue;
}
LastFD = (*Field);
}
// If this is a union, skip all the fields that aren't being initialized.
if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
continue;
// Don't emit anonymous bitfields, they just affect layout.
if (Field->isUnnamedBitfield()) {
LastFD = (*Field);
continue;
}
// Get the initializer. A struct can include fields without initializers,
// we just use explicit null values for them.
llvm::Constant *EltInit;
if (ElementNo < ILE->getNumInits())
EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++),
Field->getType(), CGF);
else
EltInit = CGM.EmitNullConstant(Field->getType());
if (!EltInit)
return false;
if (!Field->isBitField()) {
// Handle non-bitfield members.
if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit))
return false;
} else {
// Otherwise we have a bitfield.
AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
cast<llvm::ConstantInt>(EltInit));
}
}
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.
return true;
}
CharUnits LLVMSizeInChars =
NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
// Check if we need to convert the struct to a packed struct.
if (NextFieldOffsetInChars <= LayoutSizeInChars &&
LLVMSizeInChars > LayoutSizeInChars) {
assert(!Packed && "Size mismatch!");
ConvertStructToPacked();
assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
"Converting to packed did not help!");
}
// Append tail padding if necessary.
AppendTailPadding(LayoutSizeInChars);
assert(LayoutSizeInChars == NextFieldOffsetInChars &&
"Tail padding mismatch!");
return true;
}
llvm::Constant *ConstStructBuilder::
BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) {
ConstStructBuilder Builder(CGM, CGF);
if (!Builder.Build(ILE))
return 0;
// 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(),
Builder.Elements,Builder.Packed);
llvm::Type *ILETy = CGM.getTypes().ConvertType(ILE->getType());
if (llvm::StructType *ILESTy = dyn_cast<llvm::StructType>(ILETy)) {
if (ILESTy->isLayoutIdentical(STy))
STy = ILESTy;
}
llvm::Constant *Result =
llvm::ConstantStruct::get(STy, Builder.Elements);
assert(Builder.NextFieldOffsetInChars.RoundUpToAlignment(
Builder.getAlignment(Result)) ==
Builder.getSizeInChars(Result) && "Size mismatch!");
return Result;
}
//===----------------------------------------------------------------------===//
// ConstExprEmitter
//===----------------------------------------------------------------------===//
class ConstExprEmitter :
public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
CodeGenModule &CGM;
CodeGenFunction *CGF;
llvm::LLVMContext &VMContext;
public:
ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
: CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
}
//===--------------------------------------------------------------------===//
// Visitor Methods
//===--------------------------------------------------------------------===//
llvm::Constant *VisitStmt(Stmt *S) {
return 0;
}
llvm::Constant *VisitParenExpr(ParenExpr *PE) {
return Visit(PE->getSubExpr());
}
llvm::Constant *
VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) {
return Visit(PE->getReplacement());
}
llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
return Visit(GE->getResultExpr());
}
llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
return Visit(E->getInitializer());
}
llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) {
if (E->getType()->isMemberPointerType())
return CGM.getMemberPointerConstant(E);
return 0;
}
llvm::Constant *VisitBinSub(BinaryOperator *E) {
// This must be a pointer/pointer subtraction. This only happens for
// address of label.
if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) ||
!isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext())))
return 0;
llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(),
E->getLHS()->getType(), CGF);
llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(),
E->getRHS()->getType(), CGF);
llvm::Type *ResultType = ConvertType(E->getType());
LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
// No need to divide by element size, since addr of label is always void*,
// which has size 1 in GNUish.
return llvm::ConstantExpr::getSub(LHS, RHS);
}
llvm::Constant *VisitCastExpr(CastExpr* E) {
Expr *subExpr = E->getSubExpr();
llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF);
if (!C) return 0;
llvm::Type *destType = ConvertType(E->getType());
switch (E->getCastKind()) {
case CK_ToUnion: {
// GCC cast to union extension
assert(E->getType()->isUnionType() &&
"Destination type is not union type!");
// Build a struct with the union sub-element as the first member,
// and padded to the appropriate size
std::vector<llvm::Constant*> Elts;
std::vector<llvm::Type*> Types;
Elts.push_back(C);
Types.push_back(C->getType());
unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType);
assert(CurSize <= TotalSize && "Union size mismatch!");
if (unsigned NumPadBytes = TotalSize - CurSize) {
llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
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_NullToMemberPointer: {
const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>();
return CGM.getCXXABI().EmitNullMemberPointer(MPT);
}
case CK_DerivedToBaseMemberPointer:
case CK_BaseToDerivedMemberPointer:
return CGM.getCXXABI().EmitMemberPointerConversion(C, E);
case CK_LValueToRValue:
case CK_NoOp:
return C;
case CK_AnyPointerToObjCPointerCast:
case CK_AnyPointerToBlockPointerCast:
case CK_LValueBitCast:
case CK_BitCast:
if (C->getType() == destType) return C;
return llvm::ConstantExpr::getBitCast(C, destType);
case CK_Dependent: llvm_unreachable("saw dependent cast!");
// These will never be supported.
case CK_ObjCObjectLValueCast:
case CK_GetObjCProperty:
case CK_ToVoid:
case CK_Dynamic:
case CK_ObjCProduceObject:
case CK_ObjCConsumeObject:
case CK_ObjCReclaimReturnedObject:
return 0;
// These might need to be supported for constexpr.
case CK_UserDefinedConversion:
case CK_ConstructorConversion:
return 0;
// These should eventually be supported.
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:
return 0;
case CK_PointerToIntegral:
if (!E->getType()->isBooleanType())
return llvm::ConstantExpr::getPtrToInt(C, destType);
// fallthrough
case CK_PointerToBoolean:
return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C,
llvm::ConstantPointerNull::get(cast<llvm::PointerType>(C->getType())));
case CK_NullToPointer:
return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(destType));
case CK_IntegralCast: {
bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType();
return llvm::ConstantExpr::getIntegerCast(C, destType, isSigned);
}
case CK_IntegralToPointer: {
bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType();
C = llvm::ConstantExpr::getIntegerCast(C, CGM.IntPtrTy, isSigned);
return llvm::ConstantExpr::getIntToPtr(C, destType);
}
case CK_IntegralToBoolean:
return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C,
llvm::Constant::getNullValue(C->getType()));
case CK_IntegralToFloating:
if (subExpr->getType()->isSignedIntegerOrEnumerationType())
return llvm::ConstantExpr::getSIToFP(C, destType);
else
return llvm::ConstantExpr::getUIToFP(C, destType);
case CK_FloatingToIntegral:
if (E->getType()->isSignedIntegerOrEnumerationType())
return llvm::ConstantExpr::getFPToSI(C, destType);
else
return llvm::ConstantExpr::getFPToUI(C, destType);
case CK_FloatingToBoolean:
return llvm::ConstantExpr::getFCmp(llvm::CmpInst::FCMP_UNE, C,
llvm::Constant::getNullValue(C->getType()));
case CK_FloatingCast:
return llvm::ConstantExpr::getFPCast(C, destType);
}
llvm_unreachable("Invalid CastKind");
}
llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
return Visit(DAE->getExpr());
}
llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
return Visit(E->GetTemporaryExpr());
}
llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
unsigned NumInitElements = ILE->getNumInits();
if (NumInitElements == 1 && ILE->getType() == ILE->getInit(0)->getType() &&
(isa<StringLiteral>(ILE->getInit(0)) ||
isa<ObjCEncodeExpr>(ILE->getInit(0))))
return Visit(ILE->getInit(0));
std::vector<llvm::Constant*> Elts;
llvm::ArrayType *AType =
cast<llvm::ArrayType>(ConvertType(ILE->getType()));
llvm::Type *ElemTy = AType->getElementType();
unsigned NumElements = AType->getNumElements();
// Initialising an array requires us to automatically
// initialise any elements that have not been initialised explicitly
unsigned NumInitableElts = std::min(NumInitElements, NumElements);
// Copy initializer elements.
unsigned i = 0;
bool RewriteType = false;
for (; i < NumInitableElts; ++i) {
Expr *Init = ILE->getInit(i);
llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
if (!C)
return 0;
RewriteType |= (C->getType() != ElemTy);
Elts.push_back(C);
}
// Initialize remaining array elements.
// FIXME: This doesn't handle member pointers correctly!
llvm::Constant *fillC;
if (Expr *filler = ILE->getArrayFiller())
fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF);
else
fillC = llvm::Constant::getNullValue(ElemTy);
if (!fillC)
return 0;
RewriteType |= (fillC->getType() != ElemTy);
for (; i < NumElements; ++i)
Elts.push_back(fillC);
if (RewriteType) {
// FIXME: Try to avoid packing the array
std::vector<llvm::Type*> Types;
for (unsigned i = 0; i < Elts.size(); ++i)
Types.push_back(Elts[i]->getType());
llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
Types, true);
return llvm::ConstantStruct::get(SType, Elts);
}
return llvm::ConstantArray::get(AType, Elts);
}
llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
}
llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
}
llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
return CGM.EmitNullConstant(E->getType());
}
llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
if (ILE->getType()->isScalarType()) {
// We have a scalar in braces. Just use the first element.
if (ILE->getNumInits() > 0) {
Expr *Init = ILE->getInit(0);
return CGM.EmitConstantExpr(Init, Init->getType(), CGF);
}
return CGM.EmitNullConstant(ILE->getType());
}
if (ILE->getType()->isArrayType())
return EmitArrayInitialization(ILE);
if (ILE->getType()->isRecordType())
return EmitStructInitialization(ILE);
if (ILE->getType()->isUnionType())
return EmitUnionInitialization(ILE);
// If ILE was a constant vector, we would have handled it already.
if (ILE->getType()->isVectorType())
return 0;
assert(0 && "Unable to handle InitListExpr");
// Get rid of control reaches end of void function warning.
// Not reached.
return 0;
}
llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
if (!E->getConstructor()->isTrivial())
return 0;
QualType Ty = E->getType();
// FIXME: We should not have to call getBaseElementType here.
const RecordType *RT =
CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
// If the class doesn't have a trivial destructor, we can't emit it as a
// constant expr.
if (!RD->hasTrivialDestructor())
return 0;
// Only copy and default constructors can be trivial.
if (E->getNumArgs()) {
assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
assert(E->getConstructor()->isCopyOrMoveConstructor() &&
"trivial ctor has argument but isn't a copy/move ctor");
Expr *Arg = E->getArg(0);
assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
"argument to copy ctor is of wrong type");
return Visit(Arg);
}
return CGM.EmitNullConstant(Ty);
}
llvm::Constant *VisitStringLiteral(StringLiteral *E) {
assert(!E->getType()->isPointerType() && "Strings are always arrays");
// This must be a string 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.
return llvm::ConstantArray::get(VMContext,
CGM.GetStringForStringLiteral(E), false);
}
llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
// This must be an @encode initializing an array in a static initializer.
// Don't emit it as the address of the string, emit the string data itself
// as an inline array.
std::string Str;
CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
// Resize the string to the right size, adding zeros at the end, or
// truncating as needed.
Str.resize(CAT->getSize().getZExtValue(), '\0');
return llvm::ConstantArray::get(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(Expr *E) {
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 = Visit(CLE->getInitializer());
// FIXME: "Leaked" on failure.
if (C)
C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
E->getType().isConstant(CGM.getContext()),
llvm::GlobalValue::InternalLinkage,
C, ".compoundliteral", 0, false,
CGM.getContext().getTargetAddressSpace(E->getType()));
return C;
}
case Expr::DeclRefExprClass: {
ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
if (Decl->hasAttr<WeakRefAttr>())
return CGM.GetWeakRefReference(Decl);
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
return CGM.GetAddrOfFunction(FD);
if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
// We can never refer to a variable with local storage.
if (!VD->hasLocalStorage()) {
if (VD->isFileVarDecl() || VD->hasExternalStorage())
return CGM.GetAddrOfGlobalVar(VD);
else if (VD->isLocalVarDecl()) {
assert(CGF && "Can't access static local vars without CGF");
return CGF->GetAddrOfStaticLocalVar(VD);
}
}
}
break;
}
case Expr::StringLiteralClass:
return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
case Expr::ObjCEncodeExprClass:
return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
case Expr::ObjCStringLiteralClass: {
ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
llvm::Constant *C =
CGM.getObjCRuntime().GenerateConstantString(SL->getString());
return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
}
case Expr::PredefinedExprClass: {
unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
if (CGF) {
LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
return cast<llvm::Constant>(Res.getAddress());
} else if (Type == PredefinedExpr::PrettyFunction) {
return CGM.GetAddrOfConstantCString("top level", ".tmp");
}
return CGM.GetAddrOfConstantCString("", ".tmp");
}
case Expr::AddrLabelExprClass: {
assert(CGF && "Invalid address of label expression outside function.");
llvm::Constant *Ptr =
CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
}
case Expr::CallExprClass: {
CallExpr* CE = cast<CallExpr>(E);
unsigned builtin = CE->isBuiltinCall(CGM.getContext());
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());
}
}
return 0;
}
};
} // end anonymous namespace.
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->Evaluate(Result, Context);
if (Success && !Result.HasSideEffects) {
switch (Result.Val.getKind()) {
case APValue::Uninitialized:
assert(0 && "Constant expressions should be initialized.");
return 0;
case APValue::LValue: {
llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
llvm::Constant *Offset =
llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
Result.Val.getLValueOffset().getQuantity());
llvm::Constant *C;
if (const Expr *LVBase = Result.Val.getLValueBase()) {
C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
// Apply offset if necessary.
if (!Offset->isNullValue()) {
llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext);
llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset);
C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
}
// Convert to the appropriate type; this could be an lvalue for
// an integer.
if (isa<llvm::PointerType>(DestTy))
return llvm::ConstantExpr::getBitCast(C, DestTy);
return llvm::ConstantExpr::getPtrToInt(C, DestTy);
} else {
C = Offset;
// Convert to the appropriate type; this could be an lvalue for
// an integer.
if (isa<llvm::PointerType>(DestTy))
return llvm::ConstantExpr::getIntToPtr(C, DestTy);
// If the types don't match this should only be a truncate.
if (C->getType() != DestTy)
return llvm::ConstantExpr::getTrunc(C, DestTy);
return C;
}
}
case APValue::Int: {
llvm::Constant *C = llvm::ConstantInt::get(VMContext,
Result.Val.getInt());
if (C->getType()->isIntegerTy(1)) {
llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
C = llvm::ConstantExpr::getZExt(C, BoolTy);
}
return C;
}
case APValue::ComplexInt: {
llvm::Constant *Complex[2];
Complex[0] = llvm::ConstantInt::get(VMContext,
Result.Val.getComplexIntReal());
Complex[1] = llvm::ConstantInt::get(VMContext,
Result.Val.getComplexIntImag());
// FIXME: the target may want to specify that this is packed.
llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
Complex[1]->getType(),
NULL);
return llvm::ConstantStruct::get(STy, Complex);
}
case APValue::Float:
return llvm::ConstantFP::get(VMContext, Result.Val.getFloat());
case APValue::ComplexFloat: {
llvm::Constant *Complex[2];
Complex[0] = llvm::ConstantFP::get(VMContext,
Result.Val.getComplexFloatReal());
Complex[1] = llvm::ConstantFP::get(VMContext,
Result.Val.getComplexFloatImag());
// FIXME: the target may want to specify that this is packed.
llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
Complex[1]->getType(),
NULL);
return llvm::ConstantStruct::get(STy, Complex);
}
case APValue::Vector: {
SmallVector<llvm::Constant *, 4> Inits;
unsigned NumElts = Result.Val.getVectorLength();
if (Context.getLangOptions().AltiVec &&
isa<CastExpr>(E) &&
cast<CastExpr>(E)->getCastKind() == CK_VectorSplat) {
// AltiVec vector initialization with a single literal
APValue &Elt = Result.Val.getVectorElt(0);
llvm::Constant* InitValue = Elt.isInt()
? cast<llvm::Constant>
(llvm::ConstantInt::get(VMContext, Elt.getInt()))
: cast<llvm::Constant>
(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
for (unsigned i = 0; i != NumElts; ++i)
Inits.push_back(InitValue);
} else {
for (unsigned i = 0; i != NumElts; ++i) {
APValue &Elt = Result.Val.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);
}
}
}
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;
}
static uint64_t getFieldOffset(ASTContext &C, const FieldDecl *field) {
const ASTRecordLayout &layout = C.getASTRecordLayout(field->getParent());
return layout.getFieldOffset(field->getFieldIndex());
}
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;
if (const FieldDecl *field = dyn_cast<FieldDecl>(decl))
fieldOffset = getFieldOffset(getContext(), field);
else {
const IndirectFieldDecl *ifield = cast<IndirectFieldDecl>(decl);
fieldOffset = 0;
for (IndirectFieldDecl::chain_iterator ci = ifield->chain_begin(),
ce = ifield->chain_end(); ci != ce; ++ci)
fieldOffset += getFieldOffset(getContext(), cast<FieldDecl>(*ci));
}
CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset);
return getCXXABI().EmitMemberDataPointer(type, chars);
}
static void
FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
std::vector<llvm::Constant *> &Elements,
uint64_t StartOffset) {
assert(StartOffset % CGM.getContext().getCharWidth() == 0 &&
"StartOffset not byte aligned!");
if (CGM.getTypes().isZeroInitializable(T))
return;
if (const ConstantArrayType *CAT =
CGM.getContext().getAsConstantArrayType(T)) {
QualType ElementTy = CAT->getElementType();
uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy);
for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) {
FillInNullDataMemberPointers(CGM, ElementTy, Elements,
StartOffset + I * ElementSize);
}
} else if (const RecordType *RT = T->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
// Go through all bases and fill in any null pointer to data members.
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
if (I->isVirtual()) {
// Ignore virtual bases.
continue;
}
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
// Ignore empty bases.
if (BaseDecl->isEmpty())
continue;
// Ignore bases that don't have any pointer to data members.
if (CGM.getTypes().isZeroInitializable(BaseDecl))
continue;
uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl);
FillInNullDataMemberPointers(CGM, I->getType(),
Elements, StartOffset + BaseOffset);
}
// Visit all fields.
unsigned FieldNo = 0;
for (RecordDecl::field_iterator I = RD->field_begin(),
E = RD->field_end(); I != E; ++I, ++FieldNo) {
QualType FieldType = I->getType();
if (CGM.getTypes().isZeroInitializable(FieldType))
continue;
uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo);
FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset);
}
} else {
assert(T->isMemberPointerType() && "Should only see member pointers here!");
assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
"Should only see pointers to data members here!");
CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset);
CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T);
// FIXME: hardcodes Itanium member pointer representation!
llvm::Constant *NegativeOne =
llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()),
-1ULL, /*isSigned*/true);
// Fill in the null data member pointer.
for (CharUnits I = StartIndex; I != EndIndex; ++I)
Elements[I.getQuantity()] = NegativeOne;
}
}
static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
llvm::Type *baseType,
const CXXRecordDecl *base);
static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
const CXXRecordDecl *record,
bool asCompleteObject) {
const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
llvm::StructType *structure =
(asCompleteObject ? layout.getLLVMType()
: layout.getBaseSubobjectLLVMType());
unsigned numElements = structure->getNumElements();
std::vector<llvm::Constant *> elements(numElements);
// Fill in all the bases.
for (CXXRecordDecl::base_class_const_iterator
I = record->bases_begin(), E = record->bases_end(); I != E; ++I) {
if (I->isVirtual()) {
// Ignore virtual bases; if we're laying out for a complete
// object, we'll lay these out later.
continue;
}
const CXXRecordDecl *base =
cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
// Ignore empty bases.
if (base->isEmpty())
continue;
unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
llvm::Type *baseType = structure->getElementType(fieldIndex);
elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
}
// Fill in all the fields.
for (RecordDecl::field_iterator I = record->field_begin(),
E = record->field_end(); I != E; ++I) {
const FieldDecl *field = *I;
// Ignore bit fields.
if (field->isBitField())
continue;
unsigned fieldIndex = layout.getLLVMFieldNo(field);
elements[fieldIndex] = CGM.EmitNullConstant(field->getType());
}
// Fill in the virtual bases, if we're working with the complete object.
if (asCompleteObject) {
for (CXXRecordDecl::base_class_const_iterator
I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) {
const CXXRecordDecl *base =
cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
// Ignore empty bases.
if (base->isEmpty())
continue;
unsigned fieldIndex = layout.getVirtualBaseIndex(base);
// We might have already laid this field out.
if (elements[fieldIndex]) continue;
llvm::Type *baseType = structure->getElementType(fieldIndex);
elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
}
}
// Now go through all other fields and zero them out.
for (unsigned i = 0; i != numElements; ++i) {
if (!elements[i])
elements[i] = llvm::Constant::getNullValue(structure->getElementType(i));
}
return llvm::ConstantStruct::get(structure, elements);
}
/// Emit the null constant for a base subobject.
static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
llvm::Type *baseType,
const CXXRecordDecl *base) {
const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
// Just zero out bases that don't have any pointer to data members.
if (baseLayout.isZeroInitializableAsBase())
return llvm::Constant::getNullValue(baseType);
// If the base type is a struct, we can just use its null constant.
if (isa<llvm::StructType>(baseType)) {
return EmitNullConstant(CGM, base, /*complete*/ false);
}
// Otherwise, some bases are represented as arrays of i8 if the size
// of the base is smaller than its corresponding LLVM type. Figure
// out how many elements this base array has.
llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType);
unsigned numBaseElements = baseArrayType->getNumElements();
// Fill in null data member pointers.
std::vector<llvm::Constant *> baseElements(numBaseElements);
FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base),
baseElements, 0);
// Now go through all other elements and zero them out.
if (numBaseElements) {
llvm::Type *i8 = llvm::Type::getInt8Ty(CGM.getLLVMContext());
llvm::Constant *i8_zero = llvm::Constant::getNullValue(i8);
for (unsigned i = 0; i != numBaseElements; ++i) {
if (!baseElements[i])
baseElements[i] = i8_zero;
}
}
return llvm::ConstantArray::get(baseArrayType, baseElements);
}
llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
if (getTypes().isZeroInitializable(T))
return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
QualType ElementTy = CAT->getElementType();
llvm::Constant *Element = EmitNullConstant(ElementTy);
unsigned NumElements = CAT->getSize().getZExtValue();
std::vector<llvm::Constant *> Array(NumElements);
for (unsigned i = 0; i != NumElements; ++i)
Array[i] = Element;
llvm::ArrayType *ATy =
cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
return llvm::ConstantArray::get(ATy, Array);
}
if (const RecordType *RT = T->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
return ::EmitNullConstant(*this, RD, /*complete object*/ true);
}
assert(T->isMemberPointerType() && "Should only see member pointers here!");
assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
"Should only see pointers to data members here!");
// Itanium C++ ABI 2.3:
// A NULL pointer is represented as -1.
return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
}
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