[llvm] [SelectionDAG] Improve ucmp/scmp codegen (PR #190787)

[Takashi Idobe via llvm-commits]

Takashiidobe wrote:

> > Question I have: should I make this change x86 only?
> 
> No

Next question: what are next steps to get this diff to main? I've tested out x86 (zen 4) and aarch64 (with a mac m4) and the x86 shows improvements or is neutral and aarch64 is neutral. I doubt it's practical to benchmark all the backends that are affected by a target independent change. I'll be waiting nonetheless but interested to know for next time so I know what to expect.

https://github.com/llvm/llvm-project/pull/190787