[llvm] [InstCombine] Remove `sub nuw C_Mask, X` -> `xor X, C_Mask` canoncalization (PR #122607)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

TODO List:
+ [ ] Address codegen regressions in the backend: https://godbolt.org/z/bbrGjq7ev. We cannot emit single instruction for `sub Mask, X` on Arm-v8 and RISC-V.
+ [ ] Fix opt regressions. I believe most of them can be addressed with `m_XorLike` matchers.
+ [ ] Canonicalize `xor X, C_Mask` into `sub nuw C_Mask, X` if possible. It will expose more CSE opportunities.


https://github.com/llvm/llvm-project/pull/122607