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//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate Expressions --------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This contains code to emit Aggregate Expr nodes as LLVM code.
#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "CodeGenModule.h"
#include "ConstantEmitter.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicInst.h"
using namespace clang;
using namespace CodeGen;
// Aggregate Expression Emitter
namespace {
class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
CodeGenFunction &CGF;
CGBuilderTy &Builder;
AggValueSlot Dest;
bool IsResultUnused;
AggValueSlot EnsureSlot(QualType T) {
if (!Dest.isIgnored()) return Dest;
return CGF.CreateAggTemp(T, "agg.tmp.ensured");
void EnsureDest(QualType T) {
if (!Dest.isIgnored()) return;
Dest = CGF.CreateAggTemp(T, "agg.tmp.ensured");
// Calls `Fn` with a valid return value slot, potentially creating a temporary
// to do so. If a temporary is created, an appropriate copy into `Dest` will
// be emitted, as will lifetime markers.
// The given function should take a ReturnValueSlot, and return an RValue that
// points to said slot.
void withReturnValueSlot(const Expr *E,
llvm::function_ref<RValue(ReturnValueSlot)> Fn);
AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest, bool IsResultUnused)
: CGF(cgf), Builder(CGF.Builder), Dest(Dest),
IsResultUnused(IsResultUnused) { }
// 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);
enum ExprValueKind {
/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
/// SrcIsRValue is true if source comes from an RValue.
void EmitFinalDestCopy(QualType type, const LValue &src,
ExprValueKind SrcValueKind = EVK_NonRValue);
void EmitFinalDestCopy(QualType type, RValue src);
void EmitCopy(QualType type, const AggValueSlot &dest,
const AggValueSlot &src);
void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
void EmitArrayInit(Address DestPtr, llvm::ArrayType *AType,
QualType ArrayQTy, 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 Visit(Expr *E) {
ApplyDebugLocation DL(CGF, E);
void VisitStmt(Stmt *S) {
CGF.ErrorUnsupported(S, "aggregate expression");
void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
void VisitCoawaitExpr(CoawaitExpr *E) {
CGF.EmitCoawaitExpr(*E, Dest, IsResultUnused);
void VisitCoyieldExpr(CoyieldExpr *E) {
CGF.EmitCoyieldExpr(*E, Dest, IsResultUnused);
void VisitUnaryCoawait(UnaryOperator *E) { Visit(E->getSubExpr()); }
void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
return Visit(E->getReplacement());
void VisitConstantExpr(ConstantExpr *E) {
return Visit(E->getSubExpr());
// l-values.
void VisitDeclRefExpr(DeclRefExpr *E) { EmitAggLoadOfLValue(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 VisitBinCmp(const BinaryOperator *E);
void VisitCXXRewrittenBinaryOperator(CXXRewrittenBinaryOperator *E) {
void VisitObjCMessageExpr(ObjCMessageExpr *E);
void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
void VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E);
void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
void VisitChooseExpr(const ChooseExpr *CE);
void VisitInitListExpr(InitListExpr *E);
void VisitArrayInitLoopExpr(const ArrayInitLoopExpr *E,
llvm::Value *outerBegin = nullptr);
void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
void VisitNoInitExpr(NoInitExpr *E) { } // Do nothing.
void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
CodeGenFunction::CXXDefaultArgExprScope Scope(CGF, DAE);
void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
CodeGenFunction::CXXDefaultInitExprScope Scope(CGF, DIE);
void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
void VisitCXXConstructExpr(const CXXConstructExpr *E);
void VisitCXXInheritedCtorInitExpr(const CXXInheritedCtorInitExpr *E);
void VisitLambdaExpr(LambdaExpr *E);
void VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *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->getType(), 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) {
RValue Res = CGF.EmitAtomicExpr(E);
EmitFinalDestCopy(E->getType(), Res);
} // 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);
// If the type of the l-value is atomic, then do an atomic load.
if (LV.getType()->isAtomicType() || CGF.LValueIsSuitableForInlineAtomic(LV)) {
CGF.EmitAtomicLoad(LV, E->getExprLoc(), Dest);
EmitFinalDestCopy(E->getType(), LV);
/// 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)->hasNonTrivialCopyConstructor() ||
return false;
// Check whether the type has an object member.
return Record->hasObjectMember();
void AggExprEmitter::withReturnValueSlot(
const Expr *E, llvm::function_ref<RValue(ReturnValueSlot)> EmitCall) {
QualType RetTy = E->getType();
bool RequiresDestruction =
Dest.isIgnored() &&
RetTy.isDestructedType() == QualType::DK_nontrivial_c_struct;
// If it makes no observable difference, save a memcpy + temporary.
// We need to always provide our own temporary if destruction is required.
// Otherwise, EmitCall will emit its own, notice that it's "unused", and end
// its lifetime before we have the chance to emit a proper destructor call.
bool UseTemp = Dest.isPotentiallyAliased() || Dest.requiresGCollection() ||
(RequiresDestruction && !Dest.getAddress().isValid());
Address RetAddr = Address::invalid();
Address RetAllocaAddr = Address::invalid();
EHScopeStack::stable_iterator LifetimeEndBlock;
llvm::Value *LifetimeSizePtr = nullptr;
llvm::IntrinsicInst *LifetimeStartInst = nullptr;
if (!UseTemp) {
RetAddr = Dest.getAddress();
} else {
RetAddr = CGF.CreateMemTemp(RetTy, "tmp", &RetAllocaAddr);
uint64_t Size =
LifetimeSizePtr = CGF.EmitLifetimeStart(Size, RetAllocaAddr.getPointer());
if (LifetimeSizePtr) {
LifetimeStartInst =
assert(LifetimeStartInst->getIntrinsicID() ==
llvm::Intrinsic::lifetime_start &&
"Last insertion wasn't a lifetime.start?");
NormalEHLifetimeMarker, RetAllocaAddr, LifetimeSizePtr);
LifetimeEndBlock = CGF.EHStack.stable_begin();
RValue Src =
EmitCall(ReturnValueSlot(RetAddr, Dest.isVolatile(), IsResultUnused));
if (RequiresDestruction)
CGF.pushDestroy(RetTy.isDestructedType(), Src.getAggregateAddress(), RetTy);
if (!UseTemp)
assert(Dest.getPointer() != Src.getAggregatePointer());
EmitFinalDestCopy(E->getType(), Src);
if (!RequiresDestruction && LifetimeStartInst) {
// If there's no dtor to run, the copy was the last use of our temporary.
// Since we're not guaranteed to be in an ExprWithCleanups, clean up
// eagerly.
CGF.DeactivateCleanupBlock(LifetimeEndBlock, LifetimeStartInst);
CGF.EmitLifetimeEnd(LifetimeSizePtr, RetAllocaAddr.getPointer());
/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
void AggExprEmitter::EmitFinalDestCopy(QualType type, RValue src) {
assert(src.isAggregate() && "value must be aggregate value!");
LValue srcLV = CGF.MakeAddrLValue(src.getAggregateAddress(), type);
EmitFinalDestCopy(type, srcLV, EVK_RValue);
/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
void AggExprEmitter::EmitFinalDestCopy(QualType type, const LValue &src,
ExprValueKind SrcValueKind) {
// If Dest is ignored, then we're evaluating an aggregate expression
// in a context that doesn't care about the result. Note that loads
// from volatile l-values force the existence of a non-ignored
// destination.
if (Dest.isIgnored())
// Copy non-trivial C structs here.
LValue DstLV = CGF.MakeAddrLValue(
Dest.getAddress(), Dest.isVolatile() ? type.withVolatile() : type);
if (SrcValueKind == EVK_RValue) {
if (type.isNonTrivialToPrimitiveDestructiveMove() == QualType::PCK_Struct) {
if (Dest.isPotentiallyAliased())
CGF.callCStructMoveAssignmentOperator(DstLV, src);
CGF.callCStructMoveConstructor(DstLV, src);
} else {
if (type.isNonTrivialToPrimitiveCopy() == QualType::PCK_Struct) {
if (Dest.isPotentiallyAliased())
CGF.callCStructCopyAssignmentOperator(DstLV, src);
CGF.callCStructCopyConstructor(DstLV, src);
AggValueSlot srcAgg =
AggValueSlot::forLValue(src, AggValueSlot::IsDestructed,
needsGC(type), AggValueSlot::IsAliased,
EmitCopy(type, Dest, srcAgg);
/// Perform a copy from the source into the destination.
/// \param type - the type of the aggregate being copied; qualifiers are
/// ignored
void AggExprEmitter::EmitCopy(QualType type, const AggValueSlot &dest,
const AggValueSlot &src) {
if (dest.requiresGCollection()) {
CharUnits sz = dest.getPreferredSize(CGF.getContext(), type);
llvm::Value *size = llvm::ConstantInt::get(CGF.SizeTy, sz.getQuantity());
// If the result of the assignment is used, copy the LHS there also.
// It's volatile if either side is. Use the minimum alignment of
// the two sides.
LValue DestLV = CGF.MakeAddrLValue(dest.getAddress(), type);
LValue SrcLV = CGF.MakeAddrLValue(src.getAddress(), type);
CGF.EmitAggregateCopy(DestLV, SrcLV, type, dest.mayOverlap(),
dest.isVolatile() || src.isVolatile());
/// Emit the initializer for a std::initializer_list initialized with a
/// real initializer list.
AggExprEmitter::VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E) {
// Emit an array containing the elements. The array is externally destructed
// if the std::initializer_list object is.
ASTContext &Ctx = CGF.getContext();
LValue Array = CGF.EmitLValue(E->getSubExpr());
assert(Array.isSimple() && "initializer_list array not a simple lvalue");
Address ArrayPtr = Array.getAddress();
const ConstantArrayType *ArrayType =
assert(ArrayType && "std::initializer_list constructed from non-array");
// FIXME: Perform the checks on the field types in SemaInit.
RecordDecl *Record = E->getType()->castAs<RecordType>()->getDecl();
RecordDecl::field_iterator Field = Record->field_begin();
if (Field == Record->field_end()) {
CGF.ErrorUnsupported(E, "weird std::initializer_list");
// Start pointer.
if (!Field->getType()->isPointerType() ||
ArrayType->getElementType())) {
CGF.ErrorUnsupported(E, "weird std::initializer_list");
AggValueSlot Dest = EnsureSlot(E->getType());
LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
LValue Start = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
llvm::Value *Zero = llvm::ConstantInt::get(CGF.PtrDiffTy, 0);
llvm::Value *IdxStart[] = { Zero, Zero };
llvm::Value *ArrayStart =
Builder.CreateInBoundsGEP(ArrayPtr.getPointer(), IdxStart, "arraystart");
CGF.EmitStoreThroughLValue(RValue::get(ArrayStart), Start);
if (Field == Record->field_end()) {
CGF.ErrorUnsupported(E, "weird std::initializer_list");
llvm::Value *Size = Builder.getInt(ArrayType->getSize());
LValue EndOrLength = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
if (Field->getType()->isPointerType() &&
ArrayType->getElementType())) {
// End pointer.
llvm::Value *IdxEnd[] = { Zero, Size };
llvm::Value *ArrayEnd =
Builder.CreateInBoundsGEP(ArrayPtr.getPointer(), IdxEnd, "arrayend");
CGF.EmitStoreThroughLValue(RValue::get(ArrayEnd), EndOrLength);
} else if (Ctx.hasSameType(Field->getType(), Ctx.getSizeType())) {
// Length.
CGF.EmitStoreThroughLValue(RValue::get(Size), EndOrLength);
} else {
CGF.ErrorUnsupported(E, "weird std::initializer_list");
/// Determine if E is a trivial array filler, that is, one that is
/// equivalent to zero-initialization.
static bool isTrivialFiller(Expr *E) {
if (!E)
return true;
if (isa<ImplicitValueInitExpr>(E))
return true;
if (auto *ILE = dyn_cast<InitListExpr>(E)) {
if (ILE->getNumInits())
return false;
return isTrivialFiller(ILE->getArrayFiller());
if (auto *Cons = dyn_cast_or_null<CXXConstructExpr>(E))
return Cons->getConstructor()->isDefaultConstructor() &&
// FIXME: Are there other cases where we can avoid emitting an initializer?
return false;
/// Emit initialization of an array from an initializer list.
void AggExprEmitter::EmitArrayInit(Address DestPtr, llvm::ArrayType *AType,
QualType ArrayQTy, InitListExpr *E) {
uint64_t NumInitElements = E->getNumInits();
uint64_t NumArrayElements = AType->getNumElements();
assert(NumInitElements <= NumArrayElements);
QualType elementType =
// 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.getPointer(), indices, "arrayinit.begin");
CharUnits elementSize = CGF.getContext().getTypeSizeInChars(elementType);
CharUnits elementAlign =
// Consider initializing the array by copying from a global. For this to be
// more efficient than per-element initialization, the size of the elements
// with explicit initializers should be large enough.
if (NumInitElements * elementSize.getQuantity() > 16 &&
elementType.isTriviallyCopyableType(CGF.getContext())) {
CodeGen::CodeGenModule &CGM = CGF.CGM;
ConstantEmitter Emitter(CGM);
LangAS AS = ArrayQTy.getAddressSpace();
if (llvm::Constant *C = Emitter.tryEmitForInitializer(E, AS, ArrayQTy)) {
auto GV = new llvm::GlobalVariable(
CGM.getModule(), C->getType(),
CGM.isTypeConstant(ArrayQTy, /* ExcludeCtorDtor= */ true),
llvm::GlobalValue::PrivateLinkage, C, "constinit",
/* InsertBefore= */ nullptr, llvm::GlobalVariable::NotThreadLocal,
CharUnits Align = CGM.getContext().getTypeAlignInChars(ArrayQTy);
EmitFinalDestCopy(ArrayQTy, CGF.MakeAddrLValue(GV, ArrayQTy, Align));
// 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();
Address endOfInit = Address::invalid();
EHScopeStack::stable_iterator cleanup;
llvm::Instruction *cleanupDominator = nullptr;
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(), CGF.getPointerAlign(),
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.isValid()) Builder.CreateStore(element, endOfInit);
LValue elementLV =
CGF.MakeAddrLValue(Address(element, elementAlign), elementType);
EmitInitializationToLValue(E->getInit(i), elementLV);
// Check whether there's a non-trivial array-fill expression.
Expr *filler = E->getArrayFiller();
bool hasTrivialFiller = isTrivialFiller(filler);
// 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.isValid()) 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.
// C++1z [class.temporary]p5:
// when a default constructor is called to initialize an element of
// an array with no corresponding initializer [...] the destruction of
// every temporary created in a default argument is sequenced before
// the construction of the next array element, if any
CodeGenFunction::RunCleanupsScope CleanupsScope(CGF);
LValue elementLV =
CGF.MakeAddrLValue(Address(currentElement, elementAlign), 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.isValid()) 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) {
// If this is a unique OVE, just visit its source expression.
if (e->isUnique())
EmitFinalDestCopy(e->getType(), CGF.getOrCreateOpaqueLValueMapping(e));
AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
if (Dest.isPotentiallyAliased() &&
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.
AggValueSlot Slot = EnsureSlot(E->getType());
CGF.EmitAggExpr(E->getInitializer(), Slot);
/// Attempt to look through various unimportant expressions to find a
/// cast of the given kind.
static Expr *findPeephole(Expr *op, CastKind kind) {
while (true) {
op = op->IgnoreParens();
if (CastExpr *castE = dyn_cast<CastExpr>(op)) {
if (castE->getCastKind() == kind)
return castE->getSubExpr();
if (castE->getCastKind() == CK_NoOp)
return nullptr;
void AggExprEmitter::VisitCastExpr(CastExpr *E) {
if (const auto *ECE = dyn_cast<ExplicitCastExpr>(E))
CGF.CGM.EmitExplicitCastExprType(ECE, &CGF);
switch (E->getCastKind()) {
case CK_Dynamic: {
// FIXME: Can this actually happen? We have no test coverage for it.
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: {
// Evaluate even if the destination is ignored.
if (Dest.isIgnored()) {
CGF.EmitAnyExpr(E->getSubExpr(), AggValueSlot::ignored(),
// GCC union extension
QualType Ty = E->getSubExpr()->getType();
Address CastPtr =
Builder.CreateElementBitCast(Dest.getAddress(), CGF.ConvertType(Ty));
CGF.MakeAddrLValue(CastPtr, Ty));
case CK_LValueToRValueBitCast: {
if (Dest.isIgnored()) {
CGF.EmitAnyExpr(E->getSubExpr(), AggValueSlot::ignored(),
LValue SourceLV = CGF.EmitLValue(E->getSubExpr());
Address SourceAddress =
Builder.CreateElementBitCast(SourceLV.getAddress(), CGF.Int8Ty);
Address DestAddress =
Builder.CreateElementBitCast(Dest.getAddress(), CGF.Int8Ty);
llvm::Value *SizeVal = llvm::ConstantInt::get(
Builder.CreateMemCpy(DestAddress, SourceAddress, SizeVal);
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_NonAtomicToAtomic:
case CK_AtomicToNonAtomic: {
bool isToAtomic = (E->getCastKind() == CK_NonAtomicToAtomic);
// Determine the atomic and value types.
QualType atomicType = E->getSubExpr()->getType();
QualType valueType = E->getType();
if (isToAtomic) std::swap(atomicType, valueType);
// Just recurse normally if we're ignoring the result or the
// atomic type doesn't change representation.
if (Dest.isIgnored() || !CGF.CGM.isPaddedAtomicType(atomicType)) {
return Visit(E->getSubExpr());
CastKind peepholeTarget =
(isToAtomic ? CK_AtomicToNonAtomic : CK_NonAtomicToAtomic);
// These two cases are reverses of each other; try to peephole them.
if (Expr *op = findPeephole(E->getSubExpr(), peepholeTarget)) {
E->getType()) &&
"peephole significantly changed types?");
return Visit(op);
// If we're converting an r-value of non-atomic type to an r-value
// of atomic type, just emit directly into the relevant sub-object.
if (isToAtomic) {
AggValueSlot valueDest = Dest;
if (!valueDest.isIgnored() && CGF.CGM.isPaddedAtomicType(atomicType)) {
// Zero-initialize. (Strictly speaking, we only need to initialize
// the padding at the end, but this is simpler.)
if (!Dest.isZeroed())
CGF.EmitNullInitialization(Dest.getAddress(), atomicType);
// Build a GEP to refer to the subobject.
Address valueAddr =
CGF.Builder.CreateStructGEP(valueDest.getAddress(), 0);
valueDest = AggValueSlot::forAddr(valueAddr,
CGF.EmitAggExpr(E->getSubExpr(), valueDest);
// Otherwise, we're converting an atomic type to a non-atomic type.
// Make an atomic temporary, emit into that, and then copy the value out.
AggValueSlot atomicSlot =
CGF.CreateAggTemp(atomicType, "atomic-to-nonatomic.temp");
CGF.EmitAggExpr(E->getSubExpr(), atomicSlot);
Address valueAddr = Builder.CreateStructGEP(atomicSlot.getAddress(), 0);
RValue rvalue = RValue::getAggregate(valueAddr, atomicSlot.isVolatile());
return EmitFinalDestCopy(valueType, rvalue);
case CK_AddressSpaceConversion:
return Visit(E->getSubExpr());
case CK_LValueToRValue:
// If we're loading from a volatile type, force the destination
// into existence.
if (E->getSubExpr()->getType().isVolatileQualified()) {
return Visit(E->getSubExpr());
case CK_NoOp:
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_BooleanToSignedIntegral:
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:
case CK_BuiltinFnToFnPtr:
case CK_ZeroToOCLOpaqueType:
case CK_IntToOCLSampler:
case CK_FixedPointCast:
case CK_FixedPointToBoolean:
case CK_FixedPointToIntegral:
case CK_IntegralToFixedPoint:
llvm_unreachable("cast kind invalid for aggregate types");
void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
if (E->getCallReturnType(CGF.getContext())->isReferenceType()) {
withReturnValueSlot(E, [&](ReturnValueSlot Slot) {
return CGF.EmitCallExpr(E, Slot);
void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
withReturnValueSlot(E, [&](ReturnValueSlot Slot) {
return CGF.EmitObjCMessageExpr(E, Slot);
void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
CodeGenFunction::StmtExprEvaluation eval(CGF);
CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
enum CompareKind {
static llvm::Value *EmitCompare(CGBuilderTy &Builder, CodeGenFunction &CGF,
const BinaryOperator *E, llvm::Value *LHS,
llvm::Value *RHS, CompareKind Kind,
const char *NameSuffix = "") {
QualType ArgTy = E->getLHS()->getType();
if (const ComplexType *CT = ArgTy->getAs<ComplexType>())
ArgTy = CT->getElementType();
if (const auto *MPT = ArgTy->getAs<MemberPointerType>()) {
assert(Kind == CK_Equal &&
"member pointers may only be compared for equality");
return CGF.CGM.getCXXABI().EmitMemberPointerComparison(
CGF, LHS, RHS, MPT, /*IsInequality*/ false);
// Compute the comparison instructions for the specified comparison kind.
struct CmpInstInfo {
const char *Name;
llvm::CmpInst::Predicate FCmp;
llvm::CmpInst::Predicate SCmp;
llvm::CmpInst::Predicate UCmp;
CmpInstInfo InstInfo = [&]() -> CmpInstInfo {
using FI = llvm::FCmpInst;
using II = llvm::ICmpInst;
switch (Kind) {
case CK_Less:
return {"", FI::FCMP_OLT, II::ICMP_SLT, II::ICMP_ULT};
case CK_Greater:
return {"", FI::FCMP_OGT, II::ICMP_SGT, II::ICMP_UGT};
case CK_Equal:
return {"cmp.eq", FI::FCMP_OEQ, II::ICMP_EQ, II::ICMP_EQ};
llvm_unreachable("Unrecognised CompareKind enum");
if (ArgTy->hasFloatingRepresentation())
return Builder.CreateFCmp(InstInfo.FCmp, LHS, RHS,
llvm::Twine(InstInfo.Name) + NameSuffix);
if (ArgTy->isIntegralOrEnumerationType() || ArgTy->isPointerType()) {
auto Inst =
ArgTy->hasSignedIntegerRepresentation() ? InstInfo.SCmp : InstInfo.UCmp;
return Builder.CreateICmp(Inst, LHS, RHS,
llvm::Twine(InstInfo.Name) + NameSuffix);
llvm_unreachable("unsupported aggregate binary expression should have "
"already been handled");
void AggExprEmitter::VisitBinCmp(const BinaryOperator *E) {
using llvm::BasicBlock;
using llvm::PHINode;
using llvm::Value;
const ComparisonCategoryInfo &CmpInfo =
assert(CmpInfo.Record->isTriviallyCopyable() &&
"cannot copy non-trivially copyable aggregate");
QualType ArgTy = E->getLHS()->getType();
// TODO: Handle comparing these types.
if (ArgTy->isVectorType())
return CGF.ErrorUnsupported(
E, "aggregate three-way comparison with vector arguments");
if (!ArgTy->isIntegralOrEnumerationType() && !ArgTy->isRealFloatingType() &&
!ArgTy->isNullPtrType() && !ArgTy->isPointerType() &&
!ArgTy->isMemberPointerType() && !ArgTy->isAnyComplexType()) {
return CGF.ErrorUnsupported(E, "aggregate three-way comparison");
bool IsComplex = ArgTy->isAnyComplexType();
// Evaluate the operands to the expression and extract their values.
auto EmitOperand = [&](Expr *E) -> std::pair<Value *, Value *> {
RValue RV = CGF.EmitAnyExpr(E);
if (RV.isScalar())
return {RV.getScalarVal(), nullptr};
if (RV.isAggregate())
return {RV.getAggregatePointer(), nullptr};
return RV.getComplexVal();
auto LHSValues = EmitOperand(E->getLHS()),
RHSValues = EmitOperand(E->getRHS());
auto EmitCmp = [&](CompareKind K) {
Value *Cmp = EmitCompare(Builder, CGF, E, LHSValues.first, RHSValues.first,
K, IsComplex ? ".r" : "");
if (!IsComplex)
return Cmp;
assert(K == CompareKind::CK_Equal);
Value *CmpImag = EmitCompare(Builder, CGF, E, LHSValues.second,
RHSValues.second, K, ".i");
return Builder.CreateAnd(Cmp, CmpImag, "and.eq");
auto EmitCmpRes = [&](const ComparisonCategoryInfo::ValueInfo *VInfo) {
return Builder.getInt(VInfo->getIntValue());
Value *Select;
if (ArgTy->isNullPtrType()) {
Select = EmitCmpRes(CmpInfo.getEqualOrEquiv());
} else if (CmpInfo.isEquality()) {
Select = Builder.CreateSelect(
EmitCmp(CK_Equal), EmitCmpRes(CmpInfo.getEqualOrEquiv()),
EmitCmpRes(CmpInfo.getNonequalOrNonequiv()), "sel.eq");
} else if (!CmpInfo.isPartial()) {
Value *SelectOne =
Builder.CreateSelect(EmitCmp(CK_Less), EmitCmpRes(CmpInfo.getLess()),
EmitCmpRes(CmpInfo.getGreater()), "");
Select = Builder.CreateSelect(EmitCmp(CK_Equal),
SelectOne, "sel.eq");
} else {
Value *SelectEq = Builder.CreateSelect(
EmitCmp(CK_Equal), EmitCmpRes(CmpInfo.getEqualOrEquiv()),
EmitCmpRes(CmpInfo.getUnordered()), "sel.eq");
Value *SelectGT = Builder.CreateSelect(EmitCmp(CK_Greater),
SelectEq, "");
Select = Builder.CreateSelect(
EmitCmp(CK_Less), EmitCmpRes(CmpInfo.getLess()), SelectGT, "");
// Create the return value in the destination slot.
LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
// Emit the address of the first (and only) field in the comparison category
// type, and initialize it from the constant integer value selected above.
LValue FieldLV = CGF.EmitLValueForFieldInitialization(
DestLV, *CmpInfo.Record->field_begin());
CGF.EmitStoreThroughLValue(RValue::get(Select), FieldLV, /*IsInit*/ true);
// All done! The result is in the Dest slot.
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->getType(), LV);
/// Is the value of the given expression possibly a reference to or
/// into a __block variable?
static bool isBlockVarRef(const Expr *E) {
// Make sure we look through parens.
E = E->IgnoreParens();
// Check for a direct reference to a __block variable.
if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
const VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
return (var && var->hasAttr<BlocksAttr>());
// More complicated stuff.
// Binary operators.
if (const BinaryOperator *op = dyn_cast<BinaryOperator>(E)) {
// For an assignment or pointer-to-member operation, just care
// about the LHS.
if (op->isAssignmentOp() || op->isPtrMemOp())
return isBlockVarRef(op->getLHS());
// For a comma, just care about the RHS.
if (op->getOpcode() == BO_Comma)
return isBlockVarRef(op->getRHS());
// FIXME: pointer arithmetic?
return false;
// Check both sides of a conditional operator.
} else if (const AbstractConditionalOperator *op
= dyn_cast<AbstractConditionalOperator>(E)) {
return isBlockVarRef(op->getTrueExpr())
|| isBlockVarRef(op->getFalseExpr());
// OVEs are required to support BinaryConditionalOperators.
} else if (const OpaqueValueExpr *op
= dyn_cast<OpaqueValueExpr>(E)) {
if (const Expr *src = op->getSourceExpr())
return isBlockVarRef(src);
// Casts are necessary to get things like (*(int*)&var) = foo().
// We don't really care about the kind of cast here, except
// we don't want to look through l2r casts, because it's okay
// to get the *value* in a __block variable.
} else if (const CastExpr *cast = dyn_cast<CastExpr>(E)) {
if (cast->getCastKind() == CK_LValueToRValue)
return false;
return isBlockVarRef(cast->getSubExpr());
// Handle unary operators. Again, just aggressively look through
// it, ignoring the operation.
} else if (const UnaryOperator *uop = dyn_cast<UnaryOperator>(E)) {
return isBlockVarRef(uop->getSubExpr());
// Look into the base of a field access.
} else if (const MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
return isBlockVarRef(mem->getBase());
// Look into the base of a subscript.
} else if (const ArraySubscriptExpr *sub = dyn_cast<ArraySubscriptExpr>(E)) {
return isBlockVarRef(sub->getBase());
return false;
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 the LHS might be a __block variable, and the RHS can
// potentially cause a block copy, we need to evaluate the RHS first
// so that the assignment goes the right place.
// This is pretty semantically fragile.
if (isBlockVarRef(E->getLHS()) &&
E->getRHS()->HasSideEffects(CGF.getContext())) {
// Ensure that we have a destination, and evaluate the RHS into that.
// Now emit the LHS and copy into it.
LValue LHS = CGF.EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
// That copy is an atomic copy if the LHS is atomic.
if (LHS.getType()->isAtomicType() ||
CGF.LValueIsSuitableForInlineAtomic(LHS)) {
CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
LValue LHS = CGF.EmitLValue(E->getLHS());
// If we have an atomic type, evaluate into the destination and then
// do an atomic copy.
if (LHS.getType()->isAtomicType() ||
CGF.LValueIsSuitableForInlineAtomic(LHS)) {
CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
// Codegen the RHS so that it stores directly into the LHS.
AggValueSlot LHSSlot =
AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
// A non-volatile aggregate destination might have volatile member.
if (!LHSSlot.isVolatile() &&
CGF.EmitAggExpr(E->getRHS(), LHSSlot);
// Copy into the destination if the assignment isn't ignored.
EmitFinalDestCopy(E->getType(), LHS);
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) {
Address ArgValue = Address::invalid();
Address ArgPtr = CGF.EmitVAArg(VE, ArgValue);
// If EmitVAArg fails, emit an error.
if (!ArgPtr.isValid()) {
CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
EmitFinalDestCopy(VE->getType(), 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();
// 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.getAddress());
AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
AggValueSlot Slot = EnsureSlot(E->getType());
CGF.EmitCXXConstructExpr(E, Slot);
void AggExprEmitter::VisitCXXInheritedCtorInitExpr(
const CXXInheritedCtorInitExpr *E) {
AggValueSlot Slot = EnsureSlot(E->getType());
E->getConstructor(), E->constructsVBase(), Slot.getAddress(),
E->inheritedFromVBase(), E);
AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
AggValueSlot Slot = EnsureSlot(E->getType());
LValue SlotLV = CGF.MakeAddrLValue(Slot.getAddress(), E->getType());
// We'll need to enter cleanup scopes in case any of the element
// initializers throws an exception.
SmallVector<EHScopeStack::stable_iterator, 16> Cleanups;
llvm::Instruction *CleanupDominator = nullptr;
CXXRecordDecl::field_iterator CurField = E->getLambdaClass()->field_begin();
for (LambdaExpr::const_capture_init_iterator i = E->capture_init_begin(),
e = E->capture_init_end();
i != e; ++i, ++CurField) {
// Emit initialization
LValue LV = CGF.EmitLValueForFieldInitialization(SlotLV, *CurField);
if (CurField->hasCapturedVLAType()) {
CGF.EmitLambdaVLACapture(CurField->getCapturedVLAType(), LV);
EmitInitializationToLValue(*i, LV);
// Push a destructor if necessary.
if (QualType::DestructionKind DtorKind =
CurField->getType().isDestructedType()) {
if (CGF.needsEHCleanup(DtorKind)) {
if (!CleanupDominator)
CleanupDominator = CGF.Builder.CreateAlignedLoad(
CharUnits::One()); // placeholder
CGF.pushDestroy(EHCleanup, LV.getAddress(), CurField->getType(),
CGF.getDestroyer(DtorKind), false);
// 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)
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.getAddress(), T));
void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
QualType T = E->getType();
AggValueSlot Slot = EnsureSlot(T);
EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddress(), 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 &&
CGF.getTypes().isPointerZeroInitializable(E->getType()) &&
// '\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) || isa<CXXScalarValueInitExpr>(E)) {
return EmitNullInitializationToLValue(LV);
} else if (isa<NoInitExpr>(E)) {
// Do nothing.
} else if (type->isReferenceType()) {
RValue RV = CGF.EmitReferenceBindingToExpr(E);
return CGF.EmitStoreThroughLValue(RV, LV);
switch (CGF.getEvaluationKind(type)) {
case TEK_Complex:
CGF.EmitComplexExprIntoLValue(E, LV, /*isInit*/ true);
case TEK_Aggregate:
CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
case TEK_Scalar:
if (LV.isSimple()) {
CGF.EmitScalarInit(E, /*D=*/nullptr, LV, /*Captured=*/false);
} else {
CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
llvm_unreachable("bad evaluation kind");
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.hasScalarEvaluationKind(type)) {
// For non-aggregates, we can store the appropriate null constant.
llvm::Value *null = CGF.CGM.EmitNullConstant(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->getType(), CGF.MakeAddrLValue(GV, E->getType()));
if (E->hadArrayRangeDesignator())
CGF.ErrorUnsupported(E, "GNU array range designator extension");
if (E->isTransparent())
return Visit(E->getInit(0));
AggValueSlot Dest = EnsureSlot(E->getType());
LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
// Handle initialization of an array.
if (E->getType()->isArrayType()) {
auto AType = cast<llvm::ArrayType>(Dest.getAddress().getElementType());
EmitArrayInit(Dest.getAddress(), AType, E->getType(), 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();
// We'll need to enter cleanup scopes in case any of the element
// initializers throws an exception.
SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
llvm::Instruction *cleanupDominator = nullptr;
auto addCleanup = [&](const EHScopeStack::stable_iterator &cleanup) {
if (!cleanupDominator) // create placeholder once needed
cleanupDominator = CGF.Builder.CreateAlignedLoad(
CGF.Int8Ty, llvm::Constant::getNullValue(CGF.Int8PtrTy),
unsigned curInitIndex = 0;
// Emit initialization of base classes.
if (auto *CXXRD = dyn_cast<CXXRecordDecl>(record)) {
assert(E->getNumInits() >= CXXRD->getNumBases() &&
"missing initializer for base class");
for (auto &Base : CXXRD->bases()) {
assert(!Base.isVirtual() && "should not see vbases here");
auto *BaseRD = Base.getType()->getAsCXXRecordDecl();
Address V = CGF.GetAddressOfDirectBaseInCompleteClass(
Dest.getAddress(), CXXRD, BaseRD,
/*isBaseVirtual*/ false);
AggValueSlot AggSlot = AggValueSlot::forAddr(
V, Qualifiers(),
CGF.getOverlapForBaseInit(CXXRD, BaseRD, Base.isVirtual()));
CGF.EmitAggExpr(E->getInit(curInitIndex++), AggSlot);
if (QualType::DestructionKind dtorKind =
Base.getType().isDestructedType()) {
CGF.pushDestroy(dtorKind, V, Base.getType());
// Prepare a 'this' for CXXDefaultInitExprs.
CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddress());
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 (const auto *Field : record->fields())
assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
// FIXME: volatility
FieldDecl *Field = E->getInitializedFieldInUnion();
LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestLV, Field);
if (NumInitElements) {
// Store the initializer into the field
EmitInitializationToLValue(E->getInit(0), FieldLoc);
} else {
// Default-initialize to null.
// Here we iterate over the fields; this makes it simpler to both
// default-initialize fields and skip over unnamed fields.
for (const auto *field : record->fields()) {
// 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() &&
LValue LV = CGF.EmitLValueForFieldInitialization(DestLV, field);
// 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 initializers; 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)) {
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.
assert((cleanupDominator || cleanups.empty()) &&
"Missing cleanupDominator before deactivating cleanup blocks");
for (unsigned i = cleanups.size(); i != 0; --i)
CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
// Destroy the placeholder if we made one.
if (cleanupDominator)
void AggExprEmitter::VisitArrayInitLoopExpr(const ArrayInitLoopExpr *E,
llvm::Value *outerBegin) {
// Emit the common subexpression.
CodeGenFunction::OpaqueValueMapping binding(CGF, E->getCommonExpr());
Address destPtr = EnsureSlot(E->getType()).getAddress();
uint64_t numElements = E->getArraySize().getZExtValue();
if (!numElements)
// 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.getPointer(), indices,
// Prepare to special-case multidimensional array initialization: we avoid
// emitting multiple destructor loops in that case.
if (!outerBegin)
outerBegin = begin;
ArrayInitLoopExpr *InnerLoop = dyn_cast<ArrayInitLoopExpr>(E->getSubExpr());
QualType elementType =
CharUnits elementSize = CGF.getContext().getTypeSizeInChars(elementType);
CharUnits elementAlign =
llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
// Jump into the body.
llvm::PHINode *index =
Builder.CreatePHI(zero->getType(), 2, "arrayinit.index");
index->addIncoming(zero, entryBB);
llvm::Value *element = Builder.CreateInBoundsGEP(begin, index);
// Prepare for a cleanup.
QualType::DestructionKind dtorKind = elementType.isDestructedType();
EHScopeStack::stable_iterator cleanup;
if (CGF.needsEHCleanup(dtorKind) && !InnerLoop) {
if (outerBegin->getType() != element->getType())
outerBegin = Builder.CreateBitCast(outerBegin, element->getType());
CGF.pushRegularPartialArrayCleanup(outerBegin, element, elementType,
cleanup = CGF.EHStack.stable_begin();
} else {
dtorKind = QualType::DK_none;
// Emit the actual filler expression.
// Temporaries created in an array initialization loop are destroyed
// at the end of each iteration.
CodeGenFunction::RunCleanupsScope CleanupsScope(CGF);
CodeGenFunction::ArrayInitLoopExprScope Scope(CGF, index);
LValue elementLV =
CGF.MakeAddrLValue(Address(element, elementAlign), elementType);
if (InnerLoop) {
// If the subexpression is an ArrayInitLoopExpr, share its cleanup.
auto elementSlot = AggValueSlot::forLValue(
elementLV, AggValueSlot::IsDestructed,
AggExprEmitter(CGF, elementSlot, false)
.VisitArrayInitLoopExpr(InnerLoop, outerBegin);
} else
EmitInitializationToLValue(E->getSubExpr(), elementLV);
// Move on to the next element.
llvm::Value *nextIndex = Builder.CreateNUWAdd(
index, llvm::ConstantInt::get(CGF.SizeTy, 1), "");
index->addIncoming(nextIndex, Builder.GetInsertBlock());
// Leave the loop if we're done.
llvm::Value *done = Builder.CreateICmpEQ(
nextIndex, llvm::ConstantInt::get(CGF.SizeTy, numElements),
llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
Builder.CreateCondBr(done, endBB, bodyBB);
// Leave the partial-array cleanup if we entered one.
if (dtorKind)
CGF.DeactivateCleanupBlock(cleanup, index);
void AggExprEmitter::VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E) {
AggValueSlot Dest = EnsureSlot(E->getType());
LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
EmitInitializationToLValue(E->getBase(), DestLV);
// 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);
while (ILE && ILE->isTransparent())
ILE = dyn_cast<InitListExpr>(ILE->getInit(0));
if (!ILE || !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 = RT->getDecl();
CharUnits NumNonZeroBytes = CharUnits::Zero();
unsigned ILEElement = 0;
if (auto *CXXRD = dyn_cast<CXXRecordDecl>(SD))
while (ILEElement != CXXRD->getNumBases())
NumNonZeroBytes +=
GetNumNonZeroBytesInInit(ILE->getInit(ILEElement++), CGF);
for (const auto *Field : SD->fields()) {
// 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.getAddress().isValid())
// C++ objects with a user-declared constructor don't need zero'ing.
if (CGF.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.
CharUnits Size = Slot.getPreferredSize(CGF.getContext(), E->getType());
if (Size <= 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 > Size)
// Okay, it seems like a good idea to use an initial memset, emit the call.
llvm::Constant *SizeVal = CGF.Builder.getInt64(Size.getQuantity());
Address Loc = Slot.getAddress();
Loc = CGF.Builder.CreateElementBitCast(Loc, CGF.Int8Ty);
CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, 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.
void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot) {
assert(E && hasAggregateEvaluationKind(E->getType()) &&
"Invalid aggregate expression to emit");
assert((Slot.getAddress().isValid() || Slot.isIgnored()) &&
"slot has bits but no address");
// Optimize the slot if possible.
CheckAggExprForMemSetUse(Slot, E, *this);
AggExprEmitter(*this, Slot, Slot.isIgnored()).Visit(const_cast<Expr*>(E));
LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
assert(hasAggregateEvaluationKind(E->getType()) && "Invalid argument!");
Address Temp = CreateMemTemp(E->getType());
LValue LV = MakeAddrLValue(Temp, E->getType());
EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
return LV;
CodeGenFunction::getOverlapForFieldInit(const FieldDecl *FD) {
if (!FD->hasAttr<NoUniqueAddressAttr>() || !FD->getType()->isRecordType())
return AggValueSlot::DoesNotOverlap;
// If the field lies entirely within the enclosing class's nvsize, its tail
// padding cannot overlap any already-initialized object. (The only subobjects
// with greater addresses that might already be initialized are vbases.)
const RecordDecl *ClassRD = FD->getParent();
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(ClassRD);
if (Layout.getFieldOffset(FD->getFieldIndex()) +
getContext().getTypeSize(FD->getType()) <=
return AggValueSlot::DoesNotOverlap;
// The tail padding may contain values we need to preserve.
return AggValueSlot::MayOverlap;
AggValueSlot::Overlap_t CodeGenFunction::getOverlapForBaseInit(
const CXXRecordDecl *RD, const CXXRecordDecl *BaseRD, bool IsVirtual) {
// If the most-derived object is a field declared with [[no_unique_address]],
// the tail padding of any virtual base could be reused for other subobjects
// of that field's class.
if (IsVirtual)
return AggValueSlot::MayOverlap;
// If the base class is laid out entirely within the nvsize of the derived
// class, its tail padding cannot yet be initialized, so we can issue
// stores at the full width of the base class.
const ASTRecordLayout &Layout = getContext().getASTRecordLayout(RD);
if (Layout.getBaseClassOffset(BaseRD) +
getContext().getASTRecordLayout(BaseRD).getSize() <=
return AggValueSlot::DoesNotOverlap;
// The tail padding may contain values we need to preserve.
return AggValueSlot::MayOverlap;
void CodeGenFunction::EmitAggregateCopy(LValue Dest, LValue Src, QualType Ty,
AggValueSlot::Overlap_t MayOverlap,
bool isVolatile) {
assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
Address DestPtr = Dest.getAddress();
Address SrcPtr = Src.getAddress();
if (getLangOpts().CPlusPlus) {
if (const RecordType *RT = Ty->getAs<RecordType>()) {
CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
assert((Record->hasTrivialCopyConstructor() ||
Record->hasTrivialCopyAssignment() ||
Record->hasTrivialMoveConstructor() ||
Record->hasTrivialMoveAssignment() ||
Record->isUnion()) &&
"Trying to aggregate-copy a type without a trivial copy/move "
"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 data size info for this aggregate. Don't copy the tail padding if this
// might be a potentially-overlapping subobject, since the tail padding might
// be occupied by a different object. Otherwise, copying it is fine.
std::pair<CharUnits, CharUnits> TypeInfo;
if (MayOverlap)
TypeInfo = getContext().getTypeInfoDataSizeInChars(Ty);
TypeInfo = getContext().getTypeInfoInChars(Ty);
llvm::Value *SizeVal = nullptr;
if (TypeInfo.first.isZero()) {
// But note that getTypeInfo returns 0 for a VLA.
if (auto *VAT = dyn_cast_or_null<VariableArrayType>(
getContext().getAsArrayType(Ty))) {
QualType BaseEltTy;
SizeVal = emitArrayLength(VAT, BaseEltTy, DestPtr);
TypeInfo = getContext().getTypeInfoInChars(BaseEltTy);
SizeVal = Builder.CreateNUWMul(
llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity()));
if (!SizeVal) {
SizeVal = llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity());
// 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.
DestPtr = Builder.CreateElementBitCast(DestPtr, Int8Ty);
SrcPtr = Builder.CreateElementBitCast(SrcPtr, Int8Ty);
// 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()) {
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()) {
CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
auto Inst = Builder.CreateMemCpy(DestPtr, SrcPtr, SizeVal, isVolatile);
// Determine the metadata to describe the position of any padding in this
// memcpy, as well as the TBAA tags for the members of the struct, in case
// the optimizer wishes to expand it in to scalar memory operations.
if (llvm::MDNode *TBAAStructTag = CGM.getTBAAStructInfo(Ty))
Inst->setMetadata(llvm::LLVMContext::MD_tbaa_struct, TBAAStructTag);
if (CGM.getCodeGenOpts().NewStructPathTBAA) {
TBAAAccessInfo TBAAInfo = CGM.mergeTBAAInfoForMemoryTransfer(
Dest.getTBAAInfo(), Src.getTBAAInfo());
CGM.DecorateInstructionWithTBAA(Inst, TBAAInfo);