[PATCH] D142834: [RFC][X86][MC] Update and clarify the behavior of functions getX86SubSuperRegister*

Sun Jan 29 05:16:10 PST 2023

skan added a comment.

In D142834#4088767 <https://reviews.llvm.org/D142834#4088767>, @skan wrote:

> @pengfei I noticed and mentioned this commit in the summary. I think the special purpose is only for AH, DH, CH and DH b/c they are the only 8-bit high registers that are not artifical. For others, X86 backend does not have subregister liveness tracking enabled, so either `16` or `64` can work.
> There is no reason to make a difference for SI, DI, BP and SP.

I checked that there is no LIT test fail no matter we use `getX86SubSuperRegisterOrZero(Reg, 16)` or `getX86SubSuperRegisterOrZero(Reg, 64)` here.

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  https://reviews.llvm.org/D142834/new/

https://reviews.llvm.org/D142834