================
@@ -1328,15 +1328,15 @@ void AggExprEmitter::VisitChooseExpr(const ChooseExpr
*CE) {
void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
Address ArgValue = Address::invalid();
- Address ArgPtr = CGF.EmitVAArg(VE, ArgValue);
+ RValue ArgPtr = CGF.EmitVAArg(VE, ArgValue);
// If EmitVAArg fails, emit an error.
- if (!ArgPtr.isValid()) {
+ if (!ArgValue.isValid()) {
CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
return;
}
- EmitFinalDestCopy(VE->getType(), CGF.MakeAddrLValue(ArgPtr, VE->getType()));
+ EmitFinalDestCopy(VE->getType(), ArgPtr);
----------------
rjmccall wrote:
CodeGen handles aggregates by keeping them in memory. Everything to do with
aggregate expression emission generally works by passing around a destination
address that the value should be placed in — you evaluate the expression into
that address, then just put that address into the `RValue` you return. If you
don't pass an address down, generally operations have to evaluate into a
temporary, which can create redundant `memcpy`s.
In `AggExprEmitter`, the destination address is the `Dest` member. We may just
be doing an assignment into `Dest` and not an initialization, though, which has
important semantic differences in some cases and is (confusingly, sorry)
tracked with `.isPotentiallyAliased()`. The easiest way to handle that is to
make sure the final copy is done with `EmitFinalDestCopy`. You'll need to add
a method like this to `CodeGenFunction`:
```c++
void EmitAggFinalDestCopy(QualType type, AggValueSlot dest, const LValue &src,
ExprValueKind srcKind);
```
which makes an `AggExprEmitter` and calls `EmitFinalDestCopy` on it.
https://github.com/llvm/llvm-project/pull/94635
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