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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 "clang/AST/AST.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Support/Compiler.h"
using namespace clang;
using namespace CodeGen;
namespace {
class VISIBILITY_HIDDEN ConstExprEmitter :
public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
CodeGenModule &CGM;
public:
ConstExprEmitter(CodeGenModule &cgm)
: CGM(cgm) {
}
//===--------------------------------------------------------------------===//
// Visitor Methods
//===--------------------------------------------------------------------===//
llvm::Constant *VisitStmt(Stmt *S) {
CGM.WarnUnsupported(S, "constant expression");
return llvm::UndefValue::get(CGM.getTypes().ConvertType(cast<Expr>(S)->getType()));
}
llvm::Constant *VisitParenExpr(ParenExpr *PE) {
return Visit(PE->getSubExpr());
}
// Leaves
llvm::Constant *VisitIntegerLiteral(const IntegerLiteral *E) {
return llvm::ConstantInt::get(E->getValue());
}
llvm::Constant *VisitFloatingLiteral(const FloatingLiteral *E) {
return llvm::ConstantFP::get(ConvertType(E->getType()), E->getValue());
}
llvm::Constant *VisitCharacterLiteral(const CharacterLiteral *E) {
return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
}
llvm::Constant *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
}
llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
return Visit(E->getInitializer());
}
llvm::Constant *VisitCastExpr(const CastExpr* E) {
llvm::Constant *C = Visit(E->getSubExpr());
return EmitConversion(C, E->getSubExpr()->getType(), E->getType());
}
llvm::Constant *EmitArrayInitialization(InitListExpr *ILE,
const llvm::ArrayType *AType) {
std::vector<llvm::Constant*> Elts;
unsigned NumInitElements = ILE->getNumInits();
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;
for (; i < NumInitableElts; ++i) {
llvm::Constant *C = Visit(ILE->getInit(i));
// FIXME: Remove this when sema of initializers is finished (and the code
// above).
if (C == 0 && ILE->getInit(i)->getType()->isVoidType()) {
if (ILE->getType()->isVoidType()) return 0;
return llvm::UndefValue::get(AType);
}
assert (C && "Failed to create initializer expression");
Elts.push_back(C);
}
// Initialize remaining array elements.
for (; i < NumElements; ++i)
Elts.push_back(llvm::Constant::getNullValue(ElemTy));
return llvm::ConstantArray::get(AType, Elts);
}
llvm::Constant *EmitStructInitialization(InitListExpr *ILE,
const llvm::StructType *SType) {
TagDecl *TD = ILE->getType()->getAsRecordType()->getDecl();
std::vector<llvm::Constant*> Elts;
const CGRecordLayout *CGR = CGM.getTypes().getCGRecordLayout(TD);
unsigned NumInitElements = ILE->getNumInits();
unsigned NumElements = SType->getNumElements();
// Initialising an structure requires us to automatically
// initialise any elements that have not been initialised explicitly
unsigned NumInitableElts = std::min(NumInitElements, NumElements);
// Copy initializer elements. Skip padding fields.
unsigned EltNo = 0; // Element no in ILE
unsigned FieldNo = 0; // Field no in SType
while (EltNo < NumInitableElts) {
// Zero initialize padding field.
if (CGR->isPaddingField(FieldNo)) {
const llvm::Type *FieldTy = SType->getElementType(FieldNo);
Elts.push_back(llvm::Constant::getNullValue(FieldTy));
FieldNo++;
continue;
}
llvm::Constant *C = Visit(ILE->getInit(EltNo));
// FIXME: Remove this when sema of initializers is finished (and the code
// above).
if (C == 0 && ILE->getInit(EltNo)->getType()->isVoidType()) {
if (ILE->getType()->isVoidType()) return 0;
return llvm::UndefValue::get(SType);
}
assert (C && "Failed to create initializer expression");
Elts.push_back(C);
EltNo++;
FieldNo++;
}
// Initialize remaining structure elements.
for (unsigned i = Elts.size(); i < NumElements; ++i) {
const llvm::Type *FieldTy = SType->getElementType(i);
Elts.push_back(llvm::Constant::getNullValue(FieldTy));
}
return llvm::ConstantStruct::get(SType, Elts);
}
llvm::Constant *EmitVectorInitialization(InitListExpr *ILE,
const llvm::VectorType *VType) {
std::vector<llvm::Constant*> Elts;
unsigned NumInitElements = ILE->getNumInits();
unsigned NumElements = VType->getNumElements();
assert (NumInitElements == NumElements
&& "Unsufficient vector init elelments");
// Copy initializer elements.
unsigned i = 0;
for (; i < NumElements; ++i) {
llvm::Constant *C = Visit(ILE->getInit(i));
// FIXME: Remove this when sema of initializers is finished (and the code
// above).
if (C == 0 && ILE->getInit(i)->getType()->isVoidType()) {
if (ILE->getType()->isVoidType()) return 0;
return llvm::UndefValue::get(VType);
}
assert (C && "Failed to create initializer expression");
Elts.push_back(C);
}
return llvm::ConstantVector::get(VType, Elts);
}
llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
const llvm::CompositeType *CType =
dyn_cast<llvm::CompositeType>(ConvertType(ILE->getType()));
if (!CType) {
// We have a scalar in braces. Just use the first element.
return Visit(ILE->getInit(0));
}
if (const llvm::ArrayType *AType = dyn_cast<llvm::ArrayType>(CType))
return EmitArrayInitialization(ILE, AType);
if (const llvm::StructType *SType = dyn_cast<llvm::StructType>(CType))
return EmitStructInitialization(ILE, SType);
if (const llvm::VectorType *VType = dyn_cast<llvm::VectorType>(CType))
return EmitVectorInitialization(ILE, VType);
// Make sure we have an array at this point
assert(0 && "Unable to handle InitListExpr");
}
llvm::Constant *VisitImplicitCastExpr(ImplicitCastExpr *ICExpr) {
// If this is due to array->pointer conversion, emit the array expression as
// an l-value.
if (ICExpr->getSubExpr()->getType()->isArrayType()) {
// Note that VLAs can't exist for global variables.
llvm::Constant *C = EmitLValue(ICExpr->getSubExpr());
assert(isa<llvm::PointerType>(C->getType()) &&
isa<llvm::ArrayType>(cast<llvm::PointerType>(C->getType())
->getElementType()));
llvm::Constant *Idx0 = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
llvm::Constant *Ops[] = {Idx0, Idx0};
C = llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
// The resultant pointer type can be implicitly cast to other pointer
// types as well, for example void*.
const llvm::Type *DestPTy = ConvertType(ICExpr->getType());
assert(isa<llvm::PointerType>(DestPTy) &&
"Only expect implicit cast to pointer");
return llvm::ConstantExpr::getBitCast(C, DestPTy);
}
llvm::Constant *C = Visit(ICExpr->getSubExpr());
return EmitConversion(C, ICExpr->getSubExpr()->getType(),ICExpr->getType());
}
llvm::Constant *VisitStringLiteral(StringLiteral *E) {
const char *StrData = E->getStrData();
unsigned Len = E->getByteLength();
assert(!E->getType()->isPointerType() && "Strings are always arrays");
// Otherwise 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.
const ConstantArrayType *CAT = E->getType()->getAsConstantArrayType();
assert(CAT && "String isn't pointer or array!");
std::string Str(StrData, StrData + Len);
// Null terminate the string before potentially truncating it.
// FIXME: What about wchar_t strings?
Str.push_back(0);
uint64_t RealLen = CAT->getSize().getZExtValue();
// String or grow the initializer to the required size.
if (RealLen != Str.size())
Str.resize(RealLen);
return llvm::ConstantArray::get(Str, false);
}
llvm::Constant *VisitDeclRefExpr(DeclRefExpr *E) {
const ValueDecl *Decl = E->getDecl();
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
return CGM.GetAddrOfFunctionDecl(FD, false);
if (const EnumConstantDecl *EC = dyn_cast<EnumConstantDecl>(Decl))
return llvm::ConstantInt::get(EC->getInitVal());
assert(0 && "Unsupported decl ref type!");
return 0;
}
llvm::Constant *VisitSizeOfAlignOfTypeExpr(const SizeOfAlignOfTypeExpr *E) {
return EmitSizeAlignOf(E->getArgumentType(), E->getType(), E->isSizeOf());
}
// Unary operators
llvm::Constant *VisitUnaryPlus(const UnaryOperator *E) {
return Visit(E->getSubExpr());
}
llvm::Constant *VisitUnaryMinus(const UnaryOperator *E) {
return llvm::ConstantExpr::getNeg(Visit(E->getSubExpr()));
}
llvm::Constant *VisitUnaryNot(const UnaryOperator *E) {
return llvm::ConstantExpr::getNot(Visit(E->getSubExpr()));
}
llvm::Constant *VisitUnaryLNot(const UnaryOperator *E) {
llvm::Constant *SubExpr = Visit(E->getSubExpr());
if (E->getSubExpr()->getType()->isRealFloatingType()) {
// Compare against 0.0 for fp scalars.
llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
SubExpr = llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UEQ, SubExpr,
Zero);
} else {
assert((E->getSubExpr()->getType()->isIntegerType() ||
E->getSubExpr()->getType()->isPointerType()) &&
"Unknown scalar type to convert");
// Compare against an integer or pointer null.
llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
SubExpr = llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, SubExpr,
Zero);
}
return llvm::ConstantExpr::getZExt(SubExpr, ConvertType(E->getType()));
}
llvm::Constant *VisitUnarySizeOf(const UnaryOperator *E) {
return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), true);
}
llvm::Constant *VisitUnaryAlignOf(const UnaryOperator *E) {
return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), false);
}
llvm::Constant *VisitUnaryAddrOf(const UnaryOperator *E) {
return EmitLValue(E->getSubExpr());
}
llvm::Constant *VisitUnaryOffsetOf(const UnaryOperator *E) {
int64_t Val = E->evaluateOffsetOf(CGM.getContext());
assert(E->getType()->isIntegerType() && "Result type must be an integer!");
uint32_t ResultWidth = static_cast<uint32_t>(
CGM.getContext().getTypeSize(E->getType(), SourceLocation()));
return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
}
// Binary operators
llvm::Constant *VisitBinOr(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
return llvm::ConstantExpr::getOr(LHS, RHS);
}
llvm::Constant *VisitBinSub(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
if (!isa<llvm::PointerType>(RHS->getType())) {
// pointer - int
if (isa<llvm::PointerType>(LHS->getType())) {
llvm::Constant *Idx = llvm::ConstantExpr::getNeg(RHS);
return llvm::ConstantExpr::getGetElementPtr(LHS, &Idx, 1);
}
// int - int
return llvm::ConstantExpr::getSub(LHS, RHS);
}
assert(0 && "Unhandled bin sub case!");
return 0;
}
llvm::Constant *VisitBinShl(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
// LLVM requires the LHS and RHS to be the same type: promote or truncate the
// RHS to the same size as the LHS.
if (LHS->getType() != RHS->getType())
RHS = llvm::ConstantExpr::getIntegerCast(RHS, LHS->getType(), false);
return llvm::ConstantExpr::getShl(LHS, RHS);
}
llvm::Constant *VisitBinMul(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
return llvm::ConstantExpr::getMul(LHS, RHS);
}
llvm::Constant *VisitBinDiv(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
if (LHS->getType()->isFPOrFPVector())
return llvm::ConstantExpr::getFDiv(LHS, RHS);
else if (E->getType()->isUnsignedIntegerType())
return llvm::ConstantExpr::getUDiv(LHS, RHS);
else
return llvm::ConstantExpr::getSDiv(LHS, RHS);
}
llvm::Constant *VisitBinAdd(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
if (!E->getType()->isPointerType())
return llvm::ConstantExpr::getAdd(LHS, RHS);
llvm::Constant *Ptr, *Idx;
if (isa<llvm::PointerType>(LHS->getType())) { // pointer + int
Ptr = LHS;
Idx = RHS;
} else { // int + pointer
Ptr = RHS;
Idx = LHS;
}
return llvm::ConstantExpr::getGetElementPtr(Ptr, &Idx, 1);
}
llvm::Constant *VisitBinAnd(const BinaryOperator *E) {
llvm::Constant *LHS = Visit(E->getLHS());
llvm::Constant *RHS = Visit(E->getRHS());
return llvm::ConstantExpr::getAnd(LHS, RHS);
}
// Utility methods
const llvm::Type *ConvertType(QualType T) {
return CGM.getTypes().ConvertType(T);
}
llvm::Constant *EmitConversionToBool(llvm::Constant *Src, QualType SrcType) {
assert(SrcType->isCanonical() && "EmitConversion strips typedefs");
if (SrcType->isRealFloatingType()) {
// Compare against 0.0 for fp scalars.
llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
return llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UNE, Src, Zero);
}
assert((SrcType->isIntegerType() || SrcType->isPointerType()) &&
"Unknown scalar type to convert");
// Compare against an integer or pointer null.
llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
return llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_NE, Src, Zero);
}
llvm::Constant *EmitConversion(llvm::Constant *Src, QualType SrcType,
QualType DstType) {
SrcType = SrcType.getCanonicalType();
DstType = DstType.getCanonicalType();
if (SrcType == DstType) return Src;
// Handle conversions to bool first, they are special: comparisons against 0.
if (DstType->isBooleanType())
return EmitConversionToBool(Src, SrcType);
const llvm::Type *DstTy = ConvertType(DstType);
// Ignore conversions like int -> uint.
if (Src->getType() == DstTy)
return Src;
// Handle pointer conversions next: pointers can only be converted to/from
// other pointers and integers.
if (isa<PointerType>(DstType)) {
// The source value may be an integer, or a pointer.
if (isa<llvm::PointerType>(Src->getType()))
return llvm::ConstantExpr::getBitCast(Src, DstTy);
assert(SrcType->isIntegerType() &&"Not ptr->ptr or int->ptr conversion?");
return llvm::ConstantExpr::getIntToPtr(Src, DstTy);
}
if (isa<PointerType>(SrcType)) {
// Must be an ptr to int cast.
assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
return llvm::ConstantExpr::getPtrToInt(Src, DstTy);
}
// A scalar source can be splatted to a vector of the same element type
if (isa<llvm::VectorType>(DstTy) && !isa<VectorType>(SrcType)) {
const llvm::VectorType *VT = cast<llvm::VectorType>(DstTy);
assert((VT->getElementType() == Src->getType()) &&
"Vector element type must match scalar type to splat.");
unsigned NumElements = DstType->getAsVectorType()->getNumElements();
llvm::SmallVector<llvm::Constant*, 16> Elements;
for (unsigned i = 0; i < NumElements; i++)
Elements.push_back(Src);
return llvm::ConstantVector::get(&Elements[0], NumElements);
}
if (isa<llvm::VectorType>(Src->getType()) ||
isa<llvm::VectorType>(DstTy)) {
return llvm::ConstantExpr::getBitCast(Src, DstTy);
}
// Finally, we have the arithmetic types: real int/float.
if (isa<llvm::IntegerType>(Src->getType())) {
bool InputSigned = SrcType->isSignedIntegerType();
if (isa<llvm::IntegerType>(DstTy))
return llvm::ConstantExpr::getIntegerCast(Src, DstTy, InputSigned);
else if (InputSigned)
return llvm::ConstantExpr::getSIToFP(Src, DstTy);
else
return llvm::ConstantExpr::getUIToFP(Src, DstTy);
}
assert(Src->getType()->isFloatingPoint() && "Unknown real conversion");
if (isa<llvm::IntegerType>(DstTy)) {
if (DstType->isSignedIntegerType())
return llvm::ConstantExpr::getFPToSI(Src, DstTy);
else
return llvm::ConstantExpr::getFPToUI(Src, DstTy);
}
assert(DstTy->isFloatingPoint() && "Unknown real conversion");
if (DstTy->getTypeID() < Src->getType()->getTypeID())
return llvm::ConstantExpr::getFPTrunc(Src, DstTy);
else
return llvm::ConstantExpr::getFPExtend(Src, DstTy);
}
llvm::Constant *EmitSizeAlignOf(QualType TypeToSize,
QualType RetType, bool isSizeOf) {
std::pair<uint64_t, unsigned> Info =
CGM.getContext().getTypeInfo(TypeToSize, SourceLocation());
uint64_t Val = isSizeOf ? Info.first : Info.second;
Val /= 8; // Return size in bytes, not bits.
assert(RetType->isIntegerType() && "Result type must be an integer!");
uint32_t ResultWidth = static_cast<uint32_t>(
CGM.getContext().getTypeSize(RetType, SourceLocation()));
return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
}
llvm::Constant *EmitLValue(Expr *E) {
switch (E->getStmtClass()) {
default: break;
case Expr::ParenExprClass:
// Elide parenthesis
return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
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());
C = new llvm::GlobalVariable(C->getType(),E->getType().isConstQualified(),
llvm::GlobalValue::InternalLinkage,
C, ".compoundliteral", &CGM.getModule());
return C;
}
case Expr::DeclRefExprClass: {
ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
return CGM.GetAddrOfFunctionDecl(FD, false);
if (const FileVarDecl* VD = dyn_cast<FileVarDecl>(Decl))
return CGM.GetAddrOfGlobalVar(VD, false);
// We can end up here with static block-scope variables (and others?)
// FIXME: How do we implement block-scope variables?!
break;
}
case Expr::MemberExprClass: {
MemberExpr* ME = cast<MemberExpr>(E);
llvm::Constant *Base;
if (ME->isArrow())
Base = Visit(ME->getBase());
else
Base = EmitLValue(ME->getBase());
unsigned FieldNumber = CGM.getTypes().getLLVMFieldNo(ME->getMemberDecl());
llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
FieldNumber);
llvm::Value *Ops[] = {Zero, Idx};
return llvm::ConstantExpr::getGetElementPtr(Base, Ops, 2);
}
case Expr::ArraySubscriptExprClass: {
ArraySubscriptExpr* ASExpr = cast<ArraySubscriptExpr>(E);
llvm::Constant *Base = Visit(ASExpr->getBase());
llvm::Constant *Index = Visit(ASExpr->getIdx());
assert(!ASExpr->getBase()->getType()->isVectorType() &&
"Taking the address of a vector component is illegal!");
return llvm::ConstantExpr::getGetElementPtr(Base, &Index, 1);
}
case Expr::StringLiteralClass: {
StringLiteral *String = cast<StringLiteral>(E);
assert(!String->isWide() && "Cannot codegen wide strings yet");
const char *StrData = String->getStrData();
unsigned Len = String->getByteLength();
return CGM.GetAddrOfConstantString(std::string(StrData, StrData + Len));
}
case Expr::UnaryOperatorClass: {
UnaryOperator *Exp = cast<UnaryOperator>(E);
switch (Exp->getOpcode()) {
default: break;
case UnaryOperator::Extension:
// Extension is just a wrapper for expressions
return EmitLValue(Exp->getSubExpr());
case UnaryOperator::Real:
case UnaryOperator::Imag: {
// The address of __real or __imag is just a GEP off the address
// of the internal expression
llvm::Constant* C = EmitLValue(Exp->getSubExpr());
llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
Exp->getOpcode() == UnaryOperator::Imag);
llvm::Value *Ops[] = {Zero, Idx};
return llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
}
case UnaryOperator::Deref:
// The address of a deref is just the value of the expression
return Visit(Exp->getSubExpr());
}
break;
}
}
CGM.WarnUnsupported(E, "constant l-value expression");
llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
return llvm::UndefValue::get(Ty);
}
};
} // end anonymous namespace.
llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E)
{
QualType type = E->getType().getCanonicalType();
if (type->isIntegerType()) {
llvm::APSInt
Value(static_cast<uint32_t>(Context.getTypeSize(type, SourceLocation())));
if (E->isIntegerConstantExpr(Value, Context)) {
return llvm::ConstantInt::get(Value);
}
}
return ConstExprEmitter(*this).Visit(const_cast<Expr*>(E));
}