[llvm] [SelectOpt] Support ADD and SUB with zext operands. (PR #115489)

[David Green via llvm-commits]

davemgreen wrote:

Do you have performance results for this change? I was trying in the past to try and keep it relatively conservative, as based on the predictability of the branch it can make things better or worse. (We found a case when it was worse recently). We have been looking at some other selects that could benefit from the transform, but I had expected they would only be generally profitable once you considered them part of a larger select group.

My understanding was that the Apple cpus did not use this option either. Do you intend to change that?

https://github.com/llvm/llvm-project/pull/115489