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

[Kan Shengchen via Phabricator via llvm-commits]

skan added a comment.

@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.


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https://reviews.llvm.org/D142834