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

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> You can see from this example that when C++ rules force the use of an sret indirect return, a register is consumed:
> https://godbolt.org/z/W3fdn8s5Y

Could you explain more about the example? I didn't find where the register consumed. Don't both `copy_trivial` and `copy_nontrivial` use the same `esp + 4` to pass the pointer of sret?

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