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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 "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;
unsigned NextFieldOffsetInBytes;
unsigned 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), NextFieldOffsetInBytes(0),
LLVMStructAlignment(1) { }
bool AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitExpr);
void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::ConstantInt *InitExpr);
void AppendPadding(uint64_t NumBytes);
void AppendTailPadding(uint64_t RecordSize);
void ConvertStructToPacked();
bool Build(InitListExpr *ILE);
unsigned getAlignment(const llvm::Constant *C) const {
if (Packed) return 1;
return CGM.getTargetData().getABITypeAlignment(C->getType());
}
uint64_t getSizeInBytes(const llvm::Constant *C) const {
return CGM.getTargetData().getTypeAllocSize(C->getType());
}
};
bool ConstStructBuilder::
AppendField(const FieldDecl *Field, uint64_t FieldOffset,
llvm::Constant *InitCst) {
uint64_t FieldOffsetInBytes = FieldOffset / 8;
assert(NextFieldOffsetInBytes <= FieldOffsetInBytes
&& "Field offset mismatch!");
unsigned FieldAlignment = getAlignment(InitCst);
// Round up the field offset to the alignment of the field type.
uint64_t AlignedNextFieldOffsetInBytes =
llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment);
if (AlignedNextFieldOffsetInBytes > FieldOffsetInBytes) {
assert(!Packed && "Alignment is wrong even with a packed struct!");
// Convert the struct to a packed struct.
ConvertStructToPacked();
AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
}
if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) {
// We need to append padding.
AppendPadding(FieldOffsetInBytes - NextFieldOffsetInBytes);
assert(NextFieldOffsetInBytes == FieldOffsetInBytes &&
"Did not add enough padding!");
AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
}
// Add the field.
Elements.push_back(InitCst);
NextFieldOffsetInBytes = AlignedNextFieldOffsetInBytes +
getSizeInBytes(InitCst);
if (Packed)
assert(LLVMStructAlignment == 1 && "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) {
if (FieldOffset > NextFieldOffsetInBytes * 8) {
// We need to add padding.
uint64_t NumBytes =
llvm::RoundUpToAlignment(FieldOffset -
NextFieldOffsetInBytes * 8, 8) / 8;
AppendPadding(NumBytes);
}
uint64_t FieldSize =
Field->getBitWidth()->EvaluateAsInt(CGM.getContext()).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);
if (FieldOffset < NextFieldOffsetInBytes * 8) {
// 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 =
NextFieldOffsetInBytes * 8 - 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(8);
if (CGM.getTargetData().isBigEndian()) {
if (FitsCompletelyInPreviousByte)
Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
} else {
Tmp = Tmp.shl(8 - 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");
const llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
assert(AT->getElementType()->isIntegerTy(8) &&
AT->getNumElements() != 0 &&
"Expected non-empty array padding of undefs");
// Remove the padding array.
NextFieldOffsetInBytes -= AT->getNumElements();
Elements.pop_back();
// Add the padding back in two chunks.
AppendPadding(AT->getNumElements()-1);
AppendPadding(1);
assert(isa<llvm::UndefValue>(Elements.back()) &&
Elements.back()->getType()->isIntegerTy(8) &&
"Padding addition didn't work right");
}
}
Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
if (FitsCompletelyInPreviousByte)
return;
}
while (FieldValue.getBitWidth() > 8) {
llvm::APInt Tmp;
if (CGM.getTargetData().isBigEndian()) {
// We want the high bits.
Tmp = FieldValue.lshr(Tmp.getBitWidth() - 8).trunc(8);
} else {
// We want the low bits.
Tmp = FieldValue.trunc(8);
FieldValue = FieldValue.lshr(8);
}
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
NextFieldOffsetInBytes++;
FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - 8);
}
assert(FieldValue.getBitWidth() > 0 &&
"Should have at least one bit left!");
assert(FieldValue.getBitWidth() <= 8 &&
"Should not have more than a byte left!");
if (FieldValue.getBitWidth() < 8) {
if (CGM.getTargetData().isBigEndian()) {
unsigned BitWidth = FieldValue.getBitWidth();
FieldValue = FieldValue.zext(8) << (8 - BitWidth);
} else
FieldValue = FieldValue.zext(8);
}
// Append the last element.
Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
FieldValue));
NextFieldOffsetInBytes++;
}
void ConstStructBuilder::AppendPadding(uint64_t NumBytes) {
if (!NumBytes)
return;
const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
if (NumBytes > 1)
Ty = llvm::ArrayType::get(Ty, NumBytes);
llvm::Constant *C = llvm::UndefValue::get(Ty);
Elements.push_back(C);
assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
NextFieldOffsetInBytes += getSizeInBytes(C);
}
void ConstStructBuilder::AppendTailPadding(uint64_t RecordSize) {
assert(RecordSize % 8 == 0 && "Invalid record size!");
uint64_t RecordSizeInBytes = RecordSize / 8;
assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!");
unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes;
AppendPadding(NumPadBytes);
}
void ConstStructBuilder::ConvertStructToPacked() {
std::vector<llvm::Constant *> PackedElements;
uint64_t ElementOffsetInBytes = 0;
for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
llvm::Constant *C = Elements[i];
unsigned ElementAlign =
CGM.getTargetData().getABITypeAlignment(C->getType());
uint64_t AlignedElementOffsetInBytes =
llvm::RoundUpToAlignment(ElementOffsetInBytes, ElementAlign);
if (AlignedElementOffsetInBytes > ElementOffsetInBytes) {
// We need some padding.
uint64_t NumBytes =
AlignedElementOffsetInBytes - ElementOffsetInBytes;
const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
if (NumBytes > 1)
Ty = llvm::ArrayType::get(Ty, NumBytes);
llvm::Constant *Padding = llvm::UndefValue::get(Ty);
PackedElements.push_back(Padding);
ElementOffsetInBytes += getSizeInBytes(Padding);
}
PackedElements.push_back(C);
ElementOffsetInBytes += getSizeInBytes(C);
}
assert(ElementOffsetInBytes == NextFieldOffsetInBytes &&
"Packing the struct changed its size!");
Elements = PackedElements;
LLVMStructAlignment = 1;
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->isBitField() && !Field->getIdentifier())
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));
}
}
uint64_t LayoutSizeInBytes = Layout.getSize() / 8;
if (NextFieldOffsetInBytes > LayoutSizeInBytes) {
// 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;
}
uint64_t LLVMSizeInBytes = llvm::RoundUpToAlignment(NextFieldOffsetInBytes,
LLVMStructAlignment);
// Check if we need to convert the struct to a packed struct.
if (NextFieldOffsetInBytes <= LayoutSizeInBytes &&
LLVMSizeInBytes > LayoutSizeInBytes) {
assert(!Packed && "Size mismatch!");
ConvertStructToPacked();
assert(NextFieldOffsetInBytes <= LayoutSizeInBytes &&
"Converting to packed did not help!");
}
// Append tail padding if necessary.
AppendTailPadding(Layout.getSize());
assert(Layout.getSize() / 8 == NextFieldOffsetInBytes &&
"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;
llvm::Constant *Result =
llvm::ConstantStruct::get(CGM.getLLVMContext(),
Builder.Elements, Builder.Packed);
assert(llvm::RoundUpToAlignment(Builder.NextFieldOffsetInBytes,
Builder.getAlignment(Result)) ==
Builder.getSizeInBytes(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 *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
return Visit(E->getInitializer());
}
llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) {
if (const MemberPointerType *MPT =
E->getType()->getAs<MemberPointerType>()) {
DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
NamedDecl *ND = DRE->getDecl();
if (MPT->isMemberFunctionPointer())
return CGM.getCXXABI().EmitMemberPointer(cast<CXXMethodDecl>(ND));
else
return CGM.getCXXABI().EmitMemberPointer(cast<FieldDecl>(ND));
}
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);
const 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) {
switch (E->getCastKind()) {
case CK_ToUnion: {
// GCC cast to union extension
assert(E->getType()->isUnionType() &&
"Destination type is not union type!");
const llvm::Type *Ty = ConvertType(E->getType());
Expr *SubExpr = E->getSubExpr();
llvm::Constant *C =
CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
if (!C)
return 0;
// 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<const llvm::Type*> Types;
Elts.push_back(C);
Types.push_back(C->getType());
unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty);
assert(CurSize <= TotalSize && "Union size mismatch!");
if (unsigned NumPadBytes = TotalSize - CurSize) {
const 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_BaseToDerivedMemberPointer: {
Expr *SubExpr = E->getSubExpr();
llvm::Constant *C =
CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
if (!C) return 0;
return CGM.getCXXABI().EmitMemberPointerConversion(C, E);
}
case CK_BitCast:
// This must be a member function pointer cast.
return Visit(E->getSubExpr());
default: {
// FIXME: This should be handled by the CK_NoOp cast kind.
// Explicit and implicit no-op casts
QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType();
if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy))
return Visit(E->getSubExpr());
// Handle integer->integer casts for address-of-label differences.
if (Ty->isIntegerType() && SubTy->isIntegerType() &&
CGF) {
llvm::Value *Src = Visit(E->getSubExpr());
if (Src == 0) return 0;
// Use EmitScalarConversion to perform the conversion.
return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty));
}
return 0;
}
}
}
llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
return Visit(DAE->getExpr());
}
llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
unsigned NumInitElements = ILE->getNumInits();
if (NumInitElements == 1 &&
(isa<StringLiteral>(ILE->getInit(0)) ||
isa<ObjCEncodeExpr>(ILE->getInit(0))))
return Visit(ILE->getInit(0));
std::vector<llvm::Constant*> Elts;
const llvm::ArrayType *AType =
cast<llvm::ArrayType>(ConvertType(ILE->getType()));
const 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!
for (; i < NumElements; ++i)
Elts.push_back(llvm::Constant::getNullValue(ElemTy));
if (RewriteType) {
// FIXME: Try to avoid packing the array
std::vector<const llvm::Type*> Types;
for (unsigned i = 0; i < Elts.size(); ++i)
Types.push_back(Elts[i]->getType());
const 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()->isCopyConstructor() &&
"trivial ctor has argument but isn't a copy 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
const 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,
E->getType().getAddressSpace());
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: {
const 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()) {
const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext);
llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1);
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)) {
const 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.
return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
}
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.
return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
}
case APValue::Vector: {
llvm::SmallVector<llvm::Constant *, 4> Inits;
unsigned NumElts = Result.Val.getVectorLength();
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[0], Inits.size());
}
}
}
llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
if (C && C->getType()->isIntegerTy(1)) {
const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
C = llvm::ConstantExpr::getZExt(C, BoolTy);
}
return C;
}
static void
FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
std::vector<llvm::Constant *> &Elements,
uint64_t StartOffset) {
assert(StartOffset % 8 == 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!");
uint64_t StartIndex = StartOffset / 8;
uint64_t EndIndex = StartIndex + CGM.getContext().getTypeSize(T) / 8;
llvm::Constant *NegativeOne =
llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()),
-1ULL, /*isSigned=*/true);
// Fill in the null data member pointer.
for (uint64_t I = StartIndex; I != EndIndex; ++I)
Elements[I] = NegativeOne;
}
}
static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
const CXXRecordDecl *RD) {
QualType T = CGM.getContext().getTagDeclType(RD);
const llvm::StructType *STy =
cast<llvm::StructType>(CGM.getTypes().ConvertTypeForMem(T));
unsigned NumElements = STy->getNumElements();
std::vector<llvm::Constant *> Elements(NumElements);
const CGRecordLayout &Layout = CGM.getTypes().getCGRecordLayout(RD);
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;
unsigned BaseFieldNo = Layout.getNonVirtualBaseLLVMFieldNo(BaseDecl);
const llvm::Type *BaseTy = STy->getElementType(BaseFieldNo);
if (isa<llvm::StructType>(BaseTy)) {
// We can just emit the base as a null constant.
Elements[BaseFieldNo] = EmitNullConstant(CGM, BaseDecl);
continue;
}
// 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.
const llvm::ArrayType *BaseArrayTy = cast<llvm::ArrayType>(BaseTy);
unsigned NumBaseElements = BaseArrayTy->getNumElements();
// Fill in null data member pointers.
std::vector<llvm::Constant *> BaseElements(NumBaseElements);
FillInNullDataMemberPointers(CGM, I->getType(), BaseElements, 0);
// Now go through all other elements and zero them out.
if (NumBaseElements) {
const llvm::Type* Int8Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
llvm::Constant *Zero = llvm::Constant::getNullValue(Int8Ty);
for (unsigned I = 0; I != NumBaseElements; ++I) {
if (!BaseElements[I])
BaseElements[I] = Zero;
}
}
Elements[BaseFieldNo] = llvm::ConstantArray::get(BaseArrayTy, BaseElements);
}
// Visit all fields.
for (RecordDecl::field_iterator I = RD->field_begin(), E = RD->field_end();
I != E; ++I) {
const FieldDecl *FD = *I;
// Ignore bit fields.
if (FD->isBitField())
continue;
unsigned FieldNo = Layout.getLLVMFieldNo(FD);
Elements[FieldNo] = CGM.EmitNullConstant(FD->getType());
}
// 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(STy->getElementType(i));
}
return llvm::ConstantStruct::get(STy, Elements);
}
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;
const 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);
}
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 llvm::ConstantInt::get(getTypes().ConvertTypeForMem(T), -1ULL,
/*isSigned=*/true);
}
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