[PATCH] D101389: [clang][CodeGen] Fix address space for sret

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

In D101389#2724700 <https://reviews.llvm.org/D101389#2724700>, @yaxunl wrote:

> In D101389#2724636 <https://reviews.llvm.org/D101389#2724636>, @rjmccall wrote:
>
>> I think this is intentional; requiring the indirect-result parameter to be in the alloca address space would prevent direct initialization of non-temporary memory, which is an important optimization in C++.
>
> You mean situations like this? https://godbolt.org/z/KnPs6znK8
>
> Address of a global variable is directly passed as the sret arg to the function returning a struct, instead of creating a temporary struct variable and passing its address as the sret arg?

That's one specific case of copy-elision, but there are others, e.g.: https://godbolt.org/z/boTeMseaM

I suppose you could disable general copy-elision.  But don't you have aggressive optimizations to strength-reduce generic pointer operations?


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