[llvm] [InstCombine] Canonicalize `switch(X^C)` expressions to `switch(X)` (PR #143677)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

@nikic Think we should proceed with this canonicalization? If so, should try `xor X, INT_MIN -> sub X, INT_MIN` first?

https://github.com/llvm/llvm-project/pull/143677