[clang] [X86][vectorcall] Do not consume register for indirect return value (PR #97939)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> I lost the `__fastcall` or `__vectorcall` during editing, here's a fixed link: https://godbolt.org/z/46j33z8bc
> 
> You can see the load from [edx] and store to [ecx]:
> 
> ```
> NonTrivial copy_nontrivial(NonTrivial *) PROC   ; copy_nontrivial, COMDAT
>         mov     eax, DWORD PTR [edx]
>         mov     DWORD PTR [ecx], eax
> ...
> ```

Got it, thanks for the information!

https://github.com/llvm/llvm-project/pull/97939