================
@@ -283,30 +283,47 @@ void AggExprEmitter::withReturnValueSlot(
// If it makes no observable difference, save a memcpy + temporary.
//
- // We need to always provide our own temporary if destruction is required.
+ // We need to always provide an address 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.
- //
- // We also need a temporary if the destination is in a different address
space
- // from the sret AS. Use the target hook to get the actual sret AS for this
- // return type.
const CXXRecordDecl *RD = RetTy->getAsCXXRecordDecl();
- LangAS SRetLangAS = CGF.CGM.getTargetCodeGenInfo().getSRetAddrSpace(RD);
- unsigned SRetAS = CGF.getContext().getTargetAddressSpace(SRetLangAS);
- bool CanAggregateCopy =
- RD ? (RD->hasTrivialCopyConstructor() ||
- RD->hasTrivialMoveConstructor() || RD->hasTrivialCopyAssignment()
||
- RD->hasTrivialMoveAssignment() || RD->hasAttr<TrivialABIAttr>() ||
- RD->isUnion())
- : RetTy.isTriviallyCopyableType(CGF.getContext());
- bool DestASMismatch = !Dest.isIgnored() && CanAggregateCopy &&
- Dest.getAddress()
- .getBasePointer()
- ->stripPointerCasts()
- ->getType()
- ->getPointerAddressSpace() != SRetAS;
- bool UseTemp = Dest.isPotentiallyAliased() || Dest.requiresGCollection() ||
- (RequiresDestruction && Dest.isIgnored()) || DestASMismatch;
+ // Initially assume we will need to pass through the destination memory.
+ unsigned SRetAS =
+ CGF.getContext().getTargetAddressSpace(RetTy.getAddressSpace());
+ bool DestASMismatch = false;
+ // However, ABIInfo might be permitted to make this return indirect. If it
+ // does, and RetTy doesn't specify an address space, it is also permitted
(but
+ // not required) to change the ABI addrspace to alloca. We don't yet know
what
+ // it will decide, so make a copy here for the optimizer to remove if it can
+ // prove it unnecessary later.
+ if (!RD || RD->canPassInRegisters()) {
+ if (!RetTy.hasAddressSpace()) {
+ SRetAS = CGF.CGM.getDataLayout().getAllocaAddrSpace();
+ // This will now require a copy unless we can find an underlying object
+ // with the correct addrspace to use for dest.
+ if (!Dest.isIgnored()) {
+ llvm::Value *DestV = Dest.getAddress().getBasePointer();
+ if (DestV->getType()->getPointerAddressSpace() != SRetAS) {
+ DestV = DestV->stripPointerCasts();
+ if (DestV->getType()->getPointerAddressSpace() != SRetAS)
+ DestASMismatch = true;
+ }
+ }
+ }
+ }
----------------
arsenm wrote:
Would be nicer to write this as a helper function / initialize DestASMismatch
to an expression
https://github.com/llvm/llvm-project/pull/181256
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