[llvm] [InstCombine] Do not perform binop-of-shuffle when mask is poison (PR #82185)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

@goldsteinn, don't have a strong opinion, but considering this looks quite of a corner case and it is fuzzer-generated, I'd rather favour readability / not make the code uglier, and rather being more conservative (the input space looks already quite small anyways).

https://github.com/llvm/llvm-project/pull/82185