[llvm] [InstCombine] Decompose constant xor operand if possible (PR #147599)

[Sumanth Gundapaneni via llvm-commits]

sgundapa wrote:

Thanks for reviewing @nikic. Due to the addressing mode concern, I gave this another try here https://github.com/llvm/llvm-project/pull/150438 

https://github.com/llvm/llvm-project/pull/147599