[llvm] [InstCombine] Fold `(X & Mask) == 0 ? TC : FC -> TC binop (X & Mask)` (PR #100437)

[via llvm-commits]

goldsteinn wrote:

> > It would be better to only keep the add variant. `imm sub/shl/lshr/ashr X` cannot be encoded in one instruction (e.g., RISC-V/ARM).
> 
> Sounds like a good starting point. I assume add was the motivating case anyway?

Yeah if `add` is the motivating case think its fine to only handle that, although think we can fit the `or` and `xor` case into the new loop.

https://github.com/llvm/llvm-project/pull/100437