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

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2007-08-24 10:22:53 +08:00
//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate 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 Aggregate 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"
#include "llvm/Intrinsics.h"
using namespace clang;
using namespace CodeGen;
//===----------------------------------------------------------------------===//
// Aggregate Expression Emitter
//===----------------------------------------------------------------------===//
namespace {
class VISIBILITY_HIDDEN AggExprEmitter : public StmtVisitor<AggExprEmitter> {
CodeGenFunction &CGF;
llvm::IRBuilder &Builder;
llvm::Value *DestPtr;
bool VolatileDest;
public:
AggExprEmitter(CodeGenFunction &cgf, llvm::Value *destPtr, bool volatileDest)
: CGF(cgf), Builder(CGF.Builder),
DestPtr(destPtr), VolatileDest(volatileDest) {
}
//===--------------------------------------------------------------------===//
// Utilities
//===--------------------------------------------------------------------===//
/// EmitAggLoadOfLValue - Given an expression with aggregate type that
/// represents a value lvalue, this method emits the address of the lvalue,
/// then loads the result into DestPtr.
void EmitAggLoadOfLValue(const Expr *E);
void EmitAggregateCopy(llvm::Value *DestPtr, llvm::Value *SrcPtr,
QualType EltTy);
void EmitAggregateClear(llvm::Value *DestPtr, QualType Ty);
void EmitNonConstInit(InitListExpr *E);
//===--------------------------------------------------------------------===//
// Visitor Methods
//===--------------------------------------------------------------------===//
void VisitStmt(Stmt *S) {
CGF.WarnUnsupported(S, "aggregate expression");
}
void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
// l-values.
void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
EmitAggLoadOfLValue(E);
}
// Operators.
// case Expr::UnaryOperatorClass:
// case Expr::CastExprClass:
void VisitImplicitCastExpr(ImplicitCastExpr *E);
void VisitCallExpr(const CallExpr *E);
void VisitStmtExpr(const StmtExpr *E);
void VisitBinaryOperator(const BinaryOperator *BO);
void VisitBinAssign(const BinaryOperator *E);
void VisitOverloadExpr(const OverloadExpr *E);
void VisitBinComma(const BinaryOperator *E);
void VisitConditionalOperator(const ConditionalOperator *CO);
void VisitInitListExpr(InitListExpr *E);
void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
Visit(DAE->getExpr());
}
void EmitInitializationToLValue(Expr *E, LValue Address);
void EmitNullInitializationToLValue(LValue Address, QualType T);
// case Expr::ChooseExprClass:
};
} // end anonymous namespace.
//===----------------------------------------------------------------------===//
// Utilities
//===----------------------------------------------------------------------===//
void AggExprEmitter::EmitAggregateClear(llvm::Value *DestPtr, QualType Ty) {
assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
// Aggregate assignment turns into llvm.memset.
const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
if (DestPtr->getType() != BP)
DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
// Get size and alignment info for this aggregate.
std::pair<uint64_t, unsigned> TypeInfo = CGF.getContext().getTypeInfo(Ty);
// FIXME: Handle variable sized types.
const llvm::Type *IntPtr = llvm::IntegerType::get(CGF.LLVMPointerWidth);
llvm::Value *MemSetOps[4] = {
DestPtr,
llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
// TypeInfo.first describes size in bits.
llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
llvm::ConstantInt::get(llvm::Type::Int32Ty, TypeInfo.second/8)
};
Builder.CreateCall(CGF.CGM.getMemSetFn(), MemSetOps, MemSetOps+4);
}
void AggExprEmitter::EmitAggregateCopy(llvm::Value *DestPtr,
llvm::Value *SrcPtr, QualType Ty) {
assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
// Aggregate assignment turns into llvm.memcpy.
const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
if (DestPtr->getType() != BP)
DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
if (SrcPtr->getType() != BP)
SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
// Get size and alignment info for this aggregate.
std::pair<uint64_t, unsigned> TypeInfo = CGF.getContext().getTypeInfo(Ty);
// FIXME: Handle variable sized types.
const llvm::Type *IntPtr = llvm::IntegerType::get(CGF.LLVMPointerWidth);
llvm::Value *MemCpyOps[4] = {
DestPtr, SrcPtr,
// TypeInfo.first describes size in bits.
llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
llvm::ConstantInt::get(llvm::Type::Int32Ty, TypeInfo.second/8)
};
Builder.CreateCall(CGF.CGM.getMemCpyFn(), MemCpyOps, MemCpyOps+4);
}
/// EmitAggLoadOfLValue - Given an expression with aggregate type that
/// represents a value lvalue, this method emits the address of the lvalue,
/// then loads the result into DestPtr.
void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
LValue LV = CGF.EmitLValue(E);
assert(LV.isSimple() && "Can't have aggregate bitfield, vector, etc");
llvm::Value *SrcPtr = LV.getAddress();
// If the result is ignored, don't copy from the value.
if (DestPtr == 0)
// FIXME: If the source is volatile, we must read from it.
return;
EmitAggregateCopy(DestPtr, SrcPtr, E->getType());
}
//===----------------------------------------------------------------------===//
// Visitor Methods
//===----------------------------------------------------------------------===//
void AggExprEmitter::VisitImplicitCastExpr(ImplicitCastExpr *E)
{
QualType STy = E->getSubExpr()->getType().getCanonicalType();
QualType Ty = E->getType().getCanonicalType();
assert(CGF.getContext().typesAreCompatible(
STy.getUnqualifiedType(), Ty.getUnqualifiedType())
&& "Implicit cast types must be compatible");
Visit(E->getSubExpr());
}
void AggExprEmitter::VisitCallExpr(const CallExpr *E)
{
RValue RV = CGF.EmitCallExpr(E);
assert(RV.isAggregate() && "Return value must be aggregate value!");
// If the result is ignored, don't copy from the value.
if (DestPtr == 0)
// FIXME: If the source is volatile, we must read from it.
return;
EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
}
void AggExprEmitter::VisitOverloadExpr(const OverloadExpr *E)
{
RValue RV = CGF.EmitCallExpr(E->getFn(), E->arg_begin(),
E->getNumArgs(CGF.getContext()));
assert(RV.isAggregate() && "Return value must be aggregate value!");
// If the result is ignored, don't copy from the value.
if (DestPtr == 0)
// FIXME: If the source is volatile, we must read from it.
return;
EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
}
void AggExprEmitter::VisitBinComma(const BinaryOperator *E)
{
CGF.EmitAnyExpr(E->getLHS());
CGF.EmitAggExpr(E->getRHS(), DestPtr, false);
}
void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
CGF.EmitCompoundStmt(*E->getSubStmt(), true, DestPtr, VolatileDest);
}
void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
CGF.WarnUnsupported(E, "aggregate binary expression");
}
void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
// For an assignment to work, the value on the right has
// to be compatible with the value on the left.
assert(CGF.getContext().typesAreCompatible(
E->getLHS()->getType().getUnqualifiedType(),
E->getRHS()->getType().getUnqualifiedType())
&& "Invalid assignment");
LValue LHS = CGF.EmitLValue(E->getLHS());
// Codegen the RHS so that it stores directly into the LHS.
CGF.EmitAggExpr(E->getRHS(), LHS.getAddress(), false /*FIXME: VOLATILE LHS*/);
if (DestPtr == 0)
return;
// If the result of the assignment is used, copy the RHS there also.
EmitAggregateCopy(DestPtr, LHS.getAddress(), E->getType());
}
void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
llvm::BasicBlock *LHSBlock = llvm::BasicBlock::Create("cond.?");
llvm::BasicBlock *RHSBlock = llvm::BasicBlock::Create("cond.:");
llvm::BasicBlock *ContBlock = llvm::BasicBlock::Create("cond.cont");
llvm::Value *Cond = CGF.EvaluateExprAsBool(E->getCond());
Builder.CreateCondBr(Cond, LHSBlock, RHSBlock);
CGF.EmitBlock(LHSBlock);
// Handle the GNU extension for missing LHS.
assert(E->getLHS() && "Must have LHS for aggregate value");
Visit(E->getLHS());
Builder.CreateBr(ContBlock);
LHSBlock = Builder.GetInsertBlock();
CGF.EmitBlock(RHSBlock);
Visit(E->getRHS());
Builder.CreateBr(ContBlock);
RHSBlock = Builder.GetInsertBlock();
CGF.EmitBlock(ContBlock);
}
void AggExprEmitter::EmitNonConstInit(InitListExpr *E) {
const llvm::PointerType *APType =
cast<llvm::PointerType>(DestPtr->getType());
const llvm::Type *DestType = APType->getElementType();
if (const llvm::ArrayType *AType = dyn_cast<llvm::ArrayType>(DestType)) {
unsigned NumInitElements = E->getNumInits();
unsigned i;
for (i = 0; i != NumInitElements; ++i) {
llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
Expr *Init = E->getInit(i);
if (isa<InitListExpr>(Init))
CGF.EmitAggExpr(Init, NextVal, VolatileDest);
else
Builder.CreateStore(CGF.EmitScalarExpr(Init), NextVal);
}
// Emit remaining default initializers
unsigned NumArrayElements = AType->getNumElements();
QualType QType = E->getInit(0)->getType();
const llvm::Type *EType = AType->getElementType();
for (/*Do not initialize i*/; i < NumArrayElements; ++i) {
llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
if (EType->isSingleValueType())
Builder.CreateStore(llvm::Constant::getNullValue(EType), NextVal);
else
EmitAggregateClear(NextVal, QType);
}
} else
assert(false && "Invalid initializer");
}
void AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
// FIXME: Are initializers affected by volatile?
if (E->getType()->isComplexType()) {
CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
} else if (CGF.hasAggregateLLVMType(E->getType())) {
CGF.EmitAnyExpr(E, LV.getAddress(), false);
} else {
CGF.EmitStoreThroughLValue(CGF.EmitAnyExpr(E), LV, E->getType());
}
}
void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
if (!CGF.hasAggregateLLVMType(T)) {
// For non-aggregates, we can store zero
const llvm::Type *T =
cast<llvm::PointerType>(LV.getAddress()->getType())->getElementType();
Builder.CreateStore(llvm::Constant::getNullValue(T), LV.getAddress());
} else {
// Otherwise, just memset the whole thing to zero. This is legal
// because in LLVM, all default initializers are guaranteed to have a
// bit pattern of all zeros.
// There's a potential optimization opportunity in combining
// memsets; that would be easy for arrays, but relatively
// difficult for structures with the current code.
llvm::Value *MemSet = CGF.CGM.getIntrinsic(llvm::Intrinsic::memset_i64);
uint64_t Size = CGF.getContext().getTypeSize(T);
const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
llvm::Value* DestPtr = Builder.CreateBitCast(LV.getAddress(), BP, "tmp");
Builder.CreateCall4(MemSet, DestPtr,
llvm::ConstantInt::get(llvm::Type::Int8Ty, 0),
llvm::ConstantInt::get(llvm::Type::Int64Ty, Size/8),
llvm::ConstantInt::get(llvm::Type::Int32Ty, 0));
}
}
void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
if (E->isConstantExpr(CGF.getContext(), 0)) {
// FIXME: call into const expr emitter so that we can emit
// a memcpy instead of storing the individual members.
// This is purely for perf; both codepaths lead to equivalent
// (although not necessarily identical) code.
// It's worth noting that LLVM keeps on getting smarter, though,
// so it might not be worth bothering.
}
// Handle initialization of an array.
if (E->getType()->isArrayType()) {
const llvm::PointerType *APType =
cast<llvm::PointerType>(DestPtr->getType());
const llvm::ArrayType *AType =
cast<llvm::ArrayType>(APType->getElementType());
uint64_t NumInitElements = E->getNumInits();
if (E->getNumInits() > 0 &&
E->getType().getCanonicalType().getUnqualifiedType() ==
E->getInit(0)->getType().getCanonicalType().getUnqualifiedType()) {
EmitAggLoadOfLValue(E->getInit(0));
return;
}
uint64_t NumArrayElements = AType->getNumElements();
QualType ElementType = E->getType()->getAsArrayType()->getElementType();
for (uint64_t i = 0; i != NumArrayElements; ++i) {
llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
if (i < NumInitElements)
EmitInitializationToLValue(E->getInit(i), LValue::MakeAddr(NextVal));
else
EmitNullInitializationToLValue(LValue::MakeAddr(NextVal),
ElementType);
}
return;
}
assert(E->getType()->isRecordType() && "Only support structs/unions here!");
// Do struct initialization; this code just sets each individual member
// to the approprate value. This makes bitfield support automatic;
// the disadvantage is that the generated code is more difficult for
// the optimizer, especially with bitfields.
unsigned NumInitElements = E->getNumInits();
RecordDecl *SD = E->getType()->getAsRecordType()->getDecl();
unsigned NumMembers = SD->getNumMembers() - SD->hasFlexibleArrayMember();
unsigned CurInitVal = 0;
bool isUnion = E->getType()->isUnionType();
// Here we iterate over the fields; this makes it simpler to both
// default-initialize fields and skip over unnamed fields.
for (unsigned CurFieldNo = 0; CurFieldNo != NumMembers; ++CurFieldNo) {
if (CurInitVal >= NumInitElements) {
// No more initializers; we're done.
break;
}
FieldDecl *CurField = SD->getMember(CurFieldNo);
if (CurField->getIdentifier() == 0) {
// Initializers can't initialize unnamed fields, e.g. "int : 20;"
continue;
}
LValue FieldLoc = CGF.EmitLValueForField(DestPtr, CurField, isUnion);
if (CurInitVal < NumInitElements) {
// Store the initializer into the field
// This will probably have to get a bit smarter when we support
// designators in initializers
EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc);
} else {
// We're out of initalizers; default-initialize to null
EmitNullInitializationToLValue(FieldLoc, CurField->getType());
}
// Unions only initialize one field.
// (things can get weird with designators, but they aren't
// supported yet.)
if (E->getType()->isUnionType())
break;
}
}
//===----------------------------------------------------------------------===//
// Entry Points into this File
//===----------------------------------------------------------------------===//
/// EmitAggExpr - Emit the computation of the specified expression of
/// aggregate type. The result is computed into DestPtr. Note that if
/// DestPtr is null, the value of the aggregate expression is not needed.
void CodeGenFunction::EmitAggExpr(const Expr *E, llvm::Value *DestPtr,
bool VolatileDest) {
assert(E && hasAggregateLLVMType(E->getType()) &&
"Invalid aggregate expression to emit");
AggExprEmitter(*this, DestPtr, VolatileDest).Visit(const_cast<Expr*>(E));
}