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//===--- 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 "CGObjCRuntime.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Intrinsics.h"
using namespace clang;
using namespace CodeGen;
// Aggregate Expression Emitter
namespace {
class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
CodeGenFunction &CGF;
CGBuilderTy &Builder;
AggValueSlot Dest;
bool IgnoreResult;
/// We want to use 'dest' as the return slot except under two
/// conditions:
/// - The destination slot requires garbage collection, so we
/// need to use the GC API.
/// - The destination slot is potentially aliased.
bool shouldUseDestForReturnSlot() const {
return !(Dest.requiresGCollection() || Dest.isPotentiallyAliased());
ReturnValueSlot getReturnValueSlot() const {
if (!shouldUseDestForReturnSlot())
return ReturnValueSlot();
return ReturnValueSlot(Dest.getAddr(), Dest.isVolatile());
AggValueSlot EnsureSlot(QualType T) {
if (!Dest.isIgnored()) return Dest;
return CGF.CreateAggTemp(T, "agg.tmp.ensured");
AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest,
bool ignore)
: CGF(cgf), Builder(CGF.Builder), Dest(Dest),
IgnoreResult(ignore) {
// 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);
/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false,
unsigned Alignment = 0);
void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
void EmitStdInitializerList(llvm::Value *DestPtr, InitListExpr *InitList);
void EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
QualType elementType, InitListExpr *E);
AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
if (CGF.getLangOpts().getGC() && TypeRequiresGCollection(T))
return AggValueSlot::NeedsGCBarriers;
return AggValueSlot::DoesNotNeedGCBarriers;
bool TypeRequiresGCollection(QualType T);
// Visitor Methods
void VisitStmt(Stmt *S) {
CGF.ErrorUnsupported(S, "aggregate expression");
void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
return Visit(E->getReplacement());
// l-values.
void VisitDeclRefExpr(DeclRefExpr *E) {
// For aggregates, we should always be able to emit the variable
// as an l-value unless it's a reference. This is due to the fact
// that we can't actually ever see a normal l2r conversion on an
// aggregate in C++, and in C there's no language standard
// actively preventing us from listing variables in the captures
// list of a block.
if (E->getDecl()->getType()->isReferenceType()) {
if (CodeGenFunction::ConstantEmission result
= CGF.tryEmitAsConstant(E)) {
EmitFinalDestCopy(E, result.getReferenceLValue(CGF, E));
void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
void VisitPredefinedExpr(const PredefinedExpr *E) {
// Operators.
void VisitCastExpr(CastExpr *E);
void VisitCallExpr(const CallExpr *E);
void VisitStmtExpr(const StmtExpr *E);
void VisitBinaryOperator(const BinaryOperator *BO);
void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
void VisitBinAssign(const BinaryOperator *E);
void VisitBinComma(const BinaryOperator *E);
void VisitObjCMessageExpr(ObjCMessageExpr *E);
void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
void VisitChooseExpr(const ChooseExpr *CE);
void VisitInitListExpr(InitListExpr *E);
void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
void VisitCXXConstructExpr(const CXXConstructExpr *E);
void VisitLambdaExpr(LambdaExpr *E);
void VisitExprWithCleanups(ExprWithCleanups *E);
void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
void VisitOpaqueValueExpr(OpaqueValueExpr *E);
void VisitPseudoObjectExpr(PseudoObjectExpr *E) {
if (E->isGLValue()) {
LValue LV = CGF.EmitPseudoObjectLValue(E);
return EmitFinalDestCopy(E, LV);
CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
void VisitVAArgExpr(VAArgExpr *E);
void EmitInitializationToLValue(Expr *E, LValue Address);
void EmitNullInitializationToLValue(LValue Address);
// case Expr::ChooseExprClass:
void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
void VisitAtomicExpr(AtomicExpr *E) {
CGF.EmitAtomicExpr(E, EnsureSlot(E->getType()).getAddr());
} // end anonymous namespace.
// 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 AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
LValue LV = CGF.EmitLValue(E);
EmitFinalDestCopy(E, LV);
/// \brief True if the given aggregate type requires special GC API calls.
bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
// Only record types have members that might require garbage collection.
const RecordType *RecordTy = T->getAs<RecordType>();
if (!RecordTy) return false;
// Don't mess with non-trivial C++ types.
RecordDecl *Record = RecordTy->getDecl();
if (isa<CXXRecordDecl>(Record) &&
(!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
return false;
// Check whether the type has an object member.
return Record->hasObjectMember();
/// \brief Perform the final move to DestPtr if for some reason
/// getReturnValueSlot() didn't use it directly.
/// The idea is that you do something like this:
/// RValue Result = EmitSomething(..., getReturnValueSlot());
/// EmitMoveFromReturnSlot(E, Result);
/// If nothing interferes, this will cause the result to be emitted
/// directly into the return value slot. Otherwise, a final move
/// will be performed.
void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue Src) {
if (shouldUseDestForReturnSlot()) {
// Logically, Dest.getAddr() should equal Src.getAggregateAddr().
// The possibility of undef rvalues complicates that a lot,
// though, so we can't really assert.
// Otherwise, do a final copy,
assert(Dest.getAddr() != Src.getAggregateAddr());
EmitFinalDestCopy(E, Src, /*Ignore*/ true);
/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore,
unsigned Alignment) {
assert(Src.isAggregate() && "value must be aggregate value!");
// If Dest is ignored, then we're evaluating an aggregate expression
// in a context (like an expression statement) that doesn't care
// about the result. C says that an lvalue-to-rvalue conversion is
// performed in these cases; C++ says that it is not. In either
// case, we don't actually need to do anything unless the value is
// volatile.
if (Dest.isIgnored()) {
if (!Src.isVolatileQualified() ||
CGF.CGM.getLangOpts().CPlusPlus ||
(IgnoreResult && Ignore))
// If the source is volatile, we must read from it; to do that, we need
// some place to put it.
Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
if (Dest.requiresGCollection()) {
CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
// If the result of the assignment is used, copy the LHS there also.
// FIXME: Pass VolatileDest as well. I think we also need to merge volatile
// from the source as well, as we can't eliminate it if either operand
// is volatile, unless copy has volatile for both source and destination..
CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
CharUnits Alignment = std::min(Src.getAlignment(), Dest.getAlignment());
EmitFinalDestCopy(E, Src.asAggregateRValue(), Ignore, Alignment.getQuantity());
static QualType GetStdInitializerListElementType(QualType T) {
// Just assume that this is really std::initializer_list.
ClassTemplateSpecializationDecl *specialization =
return specialization->getTemplateArgs()[0].getAsType();
/// \brief Prepare cleanup for the temporary array.
static void EmitStdInitializerListCleanup(CodeGenFunction &CGF,
QualType arrayType,
llvm::Value *addr,
const InitListExpr *initList) {
QualType::DestructionKind dtorKind = arrayType.isDestructedType();
if (!dtorKind)
return; // Type doesn't need destroying.
if (dtorKind != QualType::DK_cxx_destructor) {
CGF.ErrorUnsupported(initList, "ObjC ARC type in initializer_list");
CodeGenFunction::Destroyer *destroyer = CGF.getDestroyer(dtorKind);
CGF.pushDestroy(NormalAndEHCleanup, addr, arrayType, destroyer,
/// \brief Emit the initializer for a std::initializer_list initialized with a
/// real initializer list.
void AggExprEmitter::EmitStdInitializerList(llvm::Value *destPtr,
InitListExpr *initList) {
// We emit an array containing the elements, then have the init list point
// at the array.
ASTContext &ctx = CGF.getContext();
unsigned numInits = initList->getNumInits();
QualType element = GetStdInitializerListElementType(initList->getType());
llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
QualType array = ctx.getConstantArrayType(element, size, ArrayType::Normal,0);
llvm::Type *LTy = CGF.ConvertTypeForMem(array);
llvm::AllocaInst *alloc = CGF.CreateTempAlloca(LTy);
EmitArrayInit(alloc, cast<llvm::ArrayType>(LTy), element, initList);
// FIXME: The diagnostics are somewhat out of place here.
RecordDecl *record = initList->getType()->castAs<RecordType>()->getDecl();
RecordDecl::field_iterator field = record->field_begin();
if (field == record->field_end()) {
CGF.ErrorUnsupported(initList, "weird std::initializer_list");
QualType elementPtr = ctx.getPointerType(element.withConst());
// Start pointer.
if (!ctx.hasSameType(field->getType(), elementPtr)) {
CGF.ErrorUnsupported(initList, "weird std::initializer_list");
LValue start = CGF.EmitLValueForFieldInitialization(destPtr, *field, 0);
llvm::Value *arrayStart = Builder.CreateStructGEP(alloc, 0, "arraystart");
CGF.EmitStoreThroughLValue(RValue::get(arrayStart), start);
if (field == record->field_end()) {
CGF.ErrorUnsupported(initList, "weird std::initializer_list");
LValue endOrLength = CGF.EmitLValueForFieldInitialization(destPtr, *field, 0);
if (ctx.hasSameType(field->getType(), elementPtr)) {
// End pointer.
llvm::Value *arrayEnd = Builder.CreateStructGEP(alloc,numInits, "arrayend");
CGF.EmitStoreThroughLValue(RValue::get(arrayEnd), endOrLength);
} else if(ctx.hasSameType(field->getType(), ctx.getSizeType())) {
// Length.
CGF.EmitStoreThroughLValue(RValue::get(Builder.getInt(size)), endOrLength);
} else {
CGF.ErrorUnsupported(initList, "weird std::initializer_list");
if (!Dest.isExternallyDestructed())
EmitStdInitializerListCleanup(CGF, array, alloc, initList);
/// \brief Emit initialization of an array from an initializer list.
void AggExprEmitter::EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
QualType elementType, InitListExpr *E) {
uint64_t NumInitElements = E->getNumInits();
uint64_t NumArrayElements = AType->getNumElements();
assert(NumInitElements <= NumArrayElements);
// DestPtr is an array*. Construct an elementType* by drilling
// down a level.
llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
llvm::Value *indices[] = { zero, zero };
llvm::Value *begin =
Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
// Exception safety requires us to destroy all the
// already-constructed members if an initializer throws.
// For that, we'll need an EH cleanup.
QualType::DestructionKind dtorKind = elementType.isDestructedType();
llvm::AllocaInst *endOfInit = 0;
EHScopeStack::stable_iterator cleanup;
llvm::Instruction *cleanupDominator = 0;
if (CGF.needsEHCleanup(dtorKind)) {
// In principle we could tell the cleanup where we are more
// directly, but the control flow can get so varied here that it
// would actually be quite complex. Therefore we go through an
// alloca.
endOfInit = CGF.CreateTempAlloca(begin->getType(),
cleanupDominator = Builder.CreateStore(begin, endOfInit);
CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
cleanup = CGF.EHStack.stable_begin();
// Otherwise, remember that we didn't need a cleanup.
} else {
dtorKind = QualType::DK_none;
llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
// The 'current element to initialize'. The invariants on this
// variable are complicated. Essentially, after each iteration of
// the loop, it points to the last initialized element, except
// that it points to the beginning of the array before any
// elements have been initialized.
llvm::Value *element = begin;
// Emit the explicit initializers.
for (uint64_t i = 0; i != NumInitElements; ++i) {
// Advance to the next element.
if (i > 0) {
element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
// Tell the cleanup that it needs to destroy up to this
// element. TODO: some of these stores can be trivially
// observed to be unnecessary.
if (endOfInit) Builder.CreateStore(element, endOfInit);
// If these are nested std::initializer_list inits, do them directly,
// because they are conceptually the same "location".
InitListExpr *initList = dyn_cast<InitListExpr>(E->getInit(i));
if (initList && initList->initializesStdInitializerList()) {
EmitStdInitializerList(element, initList);
} else {
LValue elementLV = CGF.MakeAddrLValue(element, elementType);
EmitInitializationToLValue(E->getInit(i), elementLV);
// Check whether there's a non-trivial array-fill expression.
// Note that this will be a CXXConstructExpr even if the element
// type is an array (or array of array, etc.) of class type.
Expr *filler = E->getArrayFiller();
bool hasTrivialFiller = true;
if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
hasTrivialFiller = cons->getConstructor()->isTrivial();
// Any remaining elements need to be zero-initialized, possibly
// using the filler expression. We can skip this if the we're
// emitting to zeroed memory.
if (NumInitElements != NumArrayElements &&
!(Dest.isZeroed() && hasTrivialFiller &&
CGF.getTypes().isZeroInitializable(elementType))) {
// Use an actual loop. This is basically
// do { *array++ = filler; } while (array != end);
// Advance to the start of the rest of the array.
if (NumInitElements) {
element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
if (endOfInit) Builder.CreateStore(element, endOfInit);
// Compute the end of the array.
llvm::Value *end = Builder.CreateInBoundsGEP(begin,
llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
// Jump into the body.
llvm::PHINode *currentElement =
Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
currentElement->addIncoming(element, entryBB);
// Emit the actual filler expression.
LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
if (filler)
EmitInitializationToLValue(filler, elementLV);
// Move on to the next element.
llvm::Value *nextElement =
Builder.CreateInBoundsGEP(currentElement, one, "");
// Tell the EH cleanup that we finished with the last element.
if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
// Leave the loop if we're done.
llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
Builder.CreateCondBr(done, endBB, bodyBB);
currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
// Leave the partial-array cleanup if we entered one.
if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
// Visitor Methods
void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
if (E->getType().isPODType(CGF.getContext())) {
// For a POD type, just emit a load of the lvalue + a copy, because our
// compound literal might alias the destination.
// FIXME: This is a band-aid; the real problem appears to be in our handling
// of assignments, where we store directly into the LHS without checking
// whether anything in the RHS aliases.
AggValueSlot Slot = EnsureSlot(E->getType());
CGF.EmitAggExpr(E->getInitializer(), Slot);
void AggExprEmitter::VisitCastExpr(CastExpr *E) {
switch (E->getCastKind()) {
case CK_Dynamic: {
assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
// FIXME: Do we also need to handle property references here?
if (LV.isSimple())
CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
if (!Dest.isIgnored())
CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
case CK_ToUnion: {
if (Dest.isIgnored()) break;
// GCC union extension
QualType Ty = E->getSubExpr()->getType();
QualType PtrTy = CGF.getContext().getPointerType(Ty);
llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
CGF.MakeAddrLValue(CastPtr, Ty));
case CK_DerivedToBase:
case CK_BaseToDerived:
case CK_UncheckedDerivedToBase: {
llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
"should have been unpacked before we got here");
case CK_LValueToRValue: // hope for downstream optimization
case CK_NoOp:
case CK_AtomicToNonAtomic:
case CK_NonAtomicToAtomic:
case CK_UserDefinedConversion:
case CK_ConstructorConversion:
E->getType()) &&
"Implicit cast types must be compatible");
case CK_LValueBitCast:
llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
case CK_Dependent:
case CK_BitCast:
case CK_ArrayToPointerDecay:
case CK_FunctionToPointerDecay:
case CK_NullToPointer:
case CK_NullToMemberPointer:
case CK_BaseToDerivedMemberPointer:
case CK_DerivedToBaseMemberPointer:
case CK_MemberPointerToBoolean:
case CK_ReinterpretMemberPointer:
case CK_IntegralToPointer:
case CK_PointerToIntegral:
case CK_PointerToBoolean:
case CK_ToVoid:
case CK_VectorSplat:
case CK_IntegralCast:
case CK_IntegralToBoolean:
case CK_IntegralToFloating:
case CK_FloatingToIntegral:
case CK_FloatingToBoolean:
case CK_FloatingCast:
case CK_CPointerToObjCPointerCast:
case CK_BlockPointerToObjCPointerCast:
case CK_AnyPointerToBlockPointerCast:
case CK_ObjCObjectLValueCast:
case CK_FloatingRealToComplex:
case CK_FloatingComplexToReal:
case CK_FloatingComplexToBoolean:
case CK_FloatingComplexCast:
case CK_FloatingComplexToIntegralComplex:
case CK_IntegralRealToComplex:
case CK_IntegralComplexToReal:
case CK_IntegralComplexToBoolean:
case CK_IntegralComplexCast:
case CK_IntegralComplexToFloatingComplex:
case CK_ARCProduceObject:
case CK_ARCConsumeObject:
case CK_ARCReclaimReturnedObject:
case CK_ARCExtendBlockObject:
case CK_CopyAndAutoreleaseBlockObject:
llvm_unreachable("cast kind invalid for aggregate types");
void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
if (E->getCallReturnType()->isReferenceType()) {
RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
EmitMoveFromReturnSlot(E, RV);
void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
EmitMoveFromReturnSlot(E, RV);
void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
CodeGenFunction::StmtExprEvaluation eval(CGF);
CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
CGF.ErrorUnsupported(E, "aggregate binary expression");
void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
const BinaryOperator *E) {
LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
EmitFinalDestCopy(E, LV);
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.
&& "Invalid assignment");
if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
if (VD->hasAttr<BlocksAttr>() &&
E->getRHS()->HasSideEffects(CGF.getContext())) {
// When __block variable on LHS, the RHS must be evaluated first
// as it may change the 'forwarding' field via call to Block_copy.
LValue RHS = CGF.EmitLValue(E->getRHS());
LValue LHS = CGF.EmitLValue(E->getLHS());
Dest = AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
EmitFinalDestCopy(E, RHS, true);
LValue LHS = CGF.EmitLValue(E->getLHS());
// Codegen the RHS so that it stores directly into the LHS.
AggValueSlot LHSSlot =
AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
EmitFinalDestCopy(E, LHS, true);
void AggExprEmitter::
VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
// Bind the common expression if necessary.
CodeGenFunction::OpaqueValueMapping binding(CGF, E);
CodeGenFunction::ConditionalEvaluation eval(CGF);
CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
// Save whether the destination's lifetime is externally managed.
bool isExternallyDestructed = Dest.isExternallyDestructed();
assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
// If the result of an agg expression is unused, then the emission
// of the LHS might need to create a destination slot. That's fine
// with us, and we can safely emit the RHS into the same slot, but
// we shouldn't claim that it's already being destructed.
void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
if (!ArgPtr) {
CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
// Ensure that we have a slot, but if we already do, remember
// whether it was externally destructed.
bool wasExternallyDestructed = Dest.isExternallyDestructed();
Dest = EnsureSlot(E->getType());
// We're going to push a destructor if there isn't already one.
// Push that destructor we promised.
if (!wasExternallyDestructed)
CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
AggValueSlot Slot = EnsureSlot(E->getType());
CGF.EmitCXXConstructExpr(E, Slot);
AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
AggValueSlot Slot = EnsureSlot(E->getType());
CGF.EmitLambdaExpr(E, Slot);
void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
CodeGenFunction::RunCleanupsScope cleanups(CGF);
void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
QualType T = E->getType();
AggValueSlot Slot = EnsureSlot(T);
EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
QualType T = E->getType();
AggValueSlot Slot = EnsureSlot(T);
EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
/// isSimpleZero - If emitting this value will obviously just cause a store of
/// zero to memory, return true. This can return false if uncertain, so it just
/// handles simple cases.
static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
E = E->IgnoreParens();
// 0
if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
return IL->getValue() == 0;
// +0.0
if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
return FL->getValue().isPosZero();
// int()
if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
return true;
// (int*)0 - Null pointer expressions.
if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
return ICE->getCastKind() == CK_NullToPointer;
// '\0'
if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
return CL->getValue() == 0;
// Otherwise, hard case: conservatively return false.
return false;
AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
QualType type = LV.getType();
// FIXME: Ignore result?
// FIXME: Are initializers affected by volatile?
if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
// Storing "i32 0" to a zero'd memory location is a noop.
} else if (isa<ImplicitValueInitExpr>(E)) {
} else if (type->isReferenceType()) {
RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
CGF.EmitStoreThroughLValue(RV, LV);
} else if (type->isAnyComplexType()) {
CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
} else if (CGF.hasAggregateLLVMType(type)) {
CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
} else if (LV.isSimple()) {
CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
} else {
CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
QualType type = lv.getType();
// If the destination slot is already zeroed out before the aggregate is
// copied into it, we don't have to emit any zeros here.
if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
if (!CGF.hasAggregateLLVMType(type)) {
// For non-aggregates, we can store zero.
llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
// Note that the following is not equivalent to
// EmitStoreThroughBitfieldLValue for ARC types.
if (lv.isBitField()) {
CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
} else {
CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
} else {
// There's a potential optimization opportunity in combining
// memsets; that would be easy for arrays, but relatively
// difficult for structures with the current code.
CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
#if 0
// FIXME: Assess perf here? Figure out what cases are worth optimizing here
// (Length of globals? Chunks of zeroed-out space?).
// If we can, prefer a copy from a global; this is a lot less code for long
// globals, and it's easier for the current optimizers to analyze.
if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
llvm::GlobalVariable* GV =
new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
llvm::GlobalValue::InternalLinkage, C, "");
EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
if (E->hadArrayRangeDesignator())
CGF.ErrorUnsupported(E, "GNU array range designator extension");
if (E->initializesStdInitializerList()) {
EmitStdInitializerList(Dest.getAddr(), E);
llvm::Value *DestPtr = EnsureSlot(E->getType()).getAddr();
// Handle initialization of an array.
if (E->getType()->isArrayType()) {
if (E->isStringLiteralInit())
return Visit(E->getInit(0));
QualType elementType =
llvm::PointerType *APType =
llvm::ArrayType *AType =
EmitArrayInit(DestPtr, AType, elementType, E);
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 *record = E->getType()->castAs<RecordType>()->getDecl();
if (record->isUnion()) {
// Only initialize one field of a union. The field itself is
// specified by the initializer list.
if (!E->getInitializedFieldInUnion()) {
// Empty union; we have nothing to do.
#ifndef NDEBUG
// Make sure that it's really an empty and not a failure of
// semantic analysis.
for (RecordDecl::field_iterator Field = record->field_begin(),
FieldEnd = record->field_end();
Field != FieldEnd; ++Field)
assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
// FIXME: volatility
FieldDecl *Field = E->getInitializedFieldInUnion();
LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
if (NumInitElements) {
// Store the initializer into the field
EmitInitializationToLValue(E->getInit(0), FieldLoc);
} else {
// Default-initialize to null.
// We'll need to enter cleanup scopes in case any of the member
// initializers throw an exception.
SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
llvm::Instruction *cleanupDominator = 0;
// Here we iterate over the fields; this makes it simpler to both
// default-initialize fields and skip over unnamed fields.
unsigned curInitIndex = 0;
for (RecordDecl::field_iterator field = record->field_begin(),
fieldEnd = record->field_end();
field != fieldEnd; ++field) {
// We're done once we hit the flexible array member.
if (field->getType()->isIncompleteArrayType())
// Always skip anonymous bitfields.
if (field->isUnnamedBitfield())
// We're done if we reach the end of the explicit initializers, we
// have a zeroed object, and the rest of the fields are
// zero-initializable.
if (curInitIndex == NumInitElements && Dest.isZeroed() &&
// FIXME: volatility
LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
// We never generate write-barries for initialized fields.
if (curInitIndex < NumInitElements) {
// Store the initializer into the field.
EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
} else {
// We're out of initalizers; default-initialize to null
// Push a destructor if necessary.
// FIXME: if we have an array of structures, all explicitly
// initialized, we can end up pushing a linear number of cleanups.
bool pushedCleanup = false;
if (QualType::DestructionKind dtorKind
= field->getType().isDestructedType()) {
if (CGF.needsEHCleanup(dtorKind)) {
if (!cleanupDominator)
cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
CGF.getDestroyer(dtorKind), false);
pushedCleanup = true;
// If the GEP didn't get used because of a dead zero init or something
// else, clean it up for -O0 builds and general tidiness.
if (!pushedCleanup && LV.isSimple())
if (llvm::GetElementPtrInst *GEP =
if (GEP->use_empty())
// Deactivate all the partial cleanups in reverse order, which
// generally means popping them.
for (unsigned i = cleanups.size(); i != 0; --i)
CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
// Destroy the placeholder if we made one.
if (cleanupDominator)
// Entry Points into this File
/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
/// non-zero bytes that will be stored when outputting the initializer for the
/// specified initializer expression.
static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
E = E->IgnoreParens();
// 0 and 0.0 won't require any non-zero stores!
if (isSimpleZero(E, CGF)) return CharUnits::Zero();
// If this is an initlist expr, sum up the size of sizes of the (present)
// elements. If this is something weird, assume the whole thing is non-zero.
const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
return CGF.getContext().getTypeSizeInChars(E->getType());
// InitListExprs for structs have to be handled carefully. If there are
// reference members, we need to consider the size of the reference, not the
// referencee. InitListExprs for unions and arrays can't have references.
if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
if (!RT->isUnionType()) {
RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
CharUnits NumNonZeroBytes = CharUnits::Zero();
unsigned ILEElement = 0;
for (RecordDecl::field_iterator Field = SD->field_begin(),
FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
// We're done once we hit the flexible array member or run out of
// InitListExpr elements.
if (Field->getType()->isIncompleteArrayType() ||
ILEElement == ILE->getNumInits())
if (Field->isUnnamedBitfield())
const Expr *E = ILE->getInit(ILEElement++);
// Reference values are always non-null and have the width of a pointer.
if (Field->getType()->isReferenceType())
NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
return NumNonZeroBytes;
CharUnits NumNonZeroBytes = CharUnits::Zero();
for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
return NumNonZeroBytes;
/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
/// zeros in it, emit a memset and avoid storing the individual zeros.
static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
CodeGenFunction &CGF) {
// If the slot is already known to be zeroed, nothing to do. Don't mess with
// volatile stores.
if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
// C++ objects with a user-declared constructor don't need zero'ing.
if (CGF.getContext().getLangOpts().CPlusPlus)
if (const RecordType *RT = CGF.getContext()
.getBaseElementType(E->getType())->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
if (RD->hasUserDeclaredConstructor())
// If the type is 16-bytes or smaller, prefer individual stores over memset.
std::pair<CharUnits, CharUnits> TypeInfo =
if (TypeInfo.first <= CharUnits::fromQuantity(16))
// Check to see if over 3/4 of the initializer are known to be zero. If so,
// we prefer to emit memset + individual stores for the rest.
CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
if (NumNonZeroBytes*4 > TypeInfo.first)
// Okay, it seems like a good idea to use an initial memset, emit the call.
llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
CharUnits Align = TypeInfo.second;
llvm::Value *Loc = Slot.getAddr();
Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
Align.getQuantity(), false);
// Tell the AggExprEmitter that the slot is known zero.
/// 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. If VolatileDest is
/// true, DestPtr cannot be 0.
/// \param IsInitializer - true if this evaluation is initializing an
/// object whose lifetime is already being managed.
void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
bool IgnoreResult) {
assert(E && hasAggregateLLVMType(E->getType()) &&
"Invalid aggregate expression to emit");
assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
"slot has bits but no address");
// Optimize the slot if possible.
CheckAggExprForMemSetUse(Slot, E, *this);
AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
llvm::Value *Temp = CreateMemTemp(E->getType());
LValue LV = MakeAddrLValue(Temp, E->getType());
EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
return LV;
void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
llvm::Value *SrcPtr, QualType Ty,
bool isVolatile, unsigned Alignment) {
assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
if (getContext().getLangOpts().CPlusPlus) {
if (const RecordType *RT = Ty->getAs<RecordType>()) {
CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
assert((Record->hasTrivialCopyConstructor() ||
Record->hasTrivialCopyAssignment() ||
Record->hasTrivialMoveConstructor() ||
Record->hasTrivialMoveAssignment()) &&
"Trying to aggregate-copy a type without a trivial copy "
"constructor or assignment operator");
// Ignore empty classes in C++.
if (Record->isEmpty())
// Aggregate assignment turns into llvm.memcpy. This is almost valid per
// C99, which states "If the value being stored in an object is
// read from another object that overlaps in anyway the storage of the first
// object, then the overlap shall be exact and the two objects shall have
// qualified or unqualified versions of a compatible type."
// memcpy is not defined if the source and destination pointers are exactly
// equal, but other compilers do this optimization, and almost every memcpy
// implementation handles this case safely. If there is a libc that does not
// safely handle this, we can add a target hook.
// Get size and alignment info for this aggregate.
std::pair<CharUnits, CharUnits> TypeInfo =
if (!Alignment)
Alignment = TypeInfo.second.getQuantity();
// FIXME: Handle variable sized types.
// FIXME: If we have a volatile struct, the optimizer can remove what might
// appear to be `extra' memory ops:
// volatile struct { int i; } a, b;
// int main() {
// a = b;
// a = b;
// }
// we need to use a different call here. We use isVolatile to indicate when
// either the source or the destination is volatile.
llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
llvm::Type *DBP =
llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
DestPtr = Builder.CreateBitCast(DestPtr, DBP);
llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
llvm::Type *SBP =
llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
// Don't do any of the memmove_collectable tests if GC isn't set.
if (CGM.getLangOpts().getGC() == LangOptions::NonGC) {
// fall through
} else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
RecordDecl *Record = RecordTy->getDecl();
if (Record->hasObjectMember()) {
CharUnits size = TypeInfo.first;
llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
} else if (Ty->isArrayType()) {
QualType BaseType = getContext().getBaseElementType(Ty);
if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
if (RecordTy->getDecl()->hasObjectMember()) {
CharUnits size = TypeInfo.first;
llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
llvm::Value *SizeVal =
llvm::ConstantInt::get(SizeTy, size.getQuantity());
CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
Builder.CreateMemCpy(DestPtr, SrcPtr,
Alignment, isVolatile);
void CodeGenFunction::MaybeEmitStdInitializerListCleanup(llvm::Value *loc,
const Expr *init) {
const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
if (cleanups)
init = cleanups->getSubExpr();
if (isa<InitListExpr>(init) &&
cast<InitListExpr>(init)->initializesStdInitializerList()) {
// We initialized this std::initializer_list with an initializer list.
// A backing array was created. Push a cleanup for it.
EmitStdInitializerListCleanup(loc, cast<InitListExpr>(init));
static void EmitRecursiveStdInitializerListCleanup(CodeGenFunction &CGF,
llvm::Value *arrayStart,
const InitListExpr *init) {
// Check if there are any recursive cleanups to do, i.e. if we have
// std::initializer_list<std::initializer_list<obj>> list = {{obj()}};
// then we need to destroy the inner array as well.
for (unsigned i = 0, e = init->getNumInits(); i != e; ++i) {
const InitListExpr *subInit = dyn_cast<InitListExpr>(init->getInit(i));
if (!subInit || !subInit->initializesStdInitializerList())
// This one needs to be destroyed. Get the address of the std::init_list.
llvm::Value *offset = llvm::ConstantInt::get(CGF.SizeTy, i);
llvm::Value *loc = CGF.Builder.CreateInBoundsGEP(arrayStart, offset,
CGF.EmitStdInitializerListCleanup(loc, subInit);
void CodeGenFunction::EmitStdInitializerListCleanup(llvm::Value *loc,
const InitListExpr *init) {
ASTContext &ctx = getContext();
QualType element = GetStdInitializerListElementType(init->getType());
unsigned numInits = init->getNumInits();
llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
QualType arrayPtr = ctx.getPointerType(array);
llvm::Type *arrayPtrType = ConvertType(arrayPtr);
// lvalue is the location of a std::initializer_list, which as its first
// element has a pointer to the array we want to destroy.
llvm::Value *startPointer = Builder.CreateStructGEP(loc, 0, "startPointer");
llvm::Value *startAddress = Builder.CreateLoad(startPointer, "startAddress");
::EmitRecursiveStdInitializerListCleanup(*this, startAddress, init);
llvm::Value *arrayAddress =
Builder.CreateBitCast(startAddress, arrayPtrType, "arrayAddress");
::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);