[llvm] [X86] Fix XOR folding in EmitCmp (PR #210546)

[Alexander Coffin via llvm-commits]

GreenBeard wrote:

> Please reply to this message to confirm that you have read these policies, especially the LLVM AI Tool Use Policy, and that any AI tool usage has been noted in the PR description.

I confirm that I have read through the parts of the contributing guides that seemed relevant. I did not use AI to write any of the code in this PR.

https://github.com/llvm/llvm-project/pull/210546