[llvm] [SelectOpt] Add handling for Select-like operations. (PR #77284)

[Sotiris Apostolakis via llvm-commits]

https://github.com/sapostolakis commented:

Thanks. This sounds like a good idea.
Left some comments. 
Main issue is that I would like to have a flag that could disable, if needed, the select-like (but not proper select) part. The rest of the comments are nits.

https://github.com/llvm/llvm-project/pull/77284