[llvm] [InstCombine] Fold `(x < y) ? -1 : zext(x != y)` into `u/scmp(x,y)` (PR #101049)

[Nikita Popov via llvm-commits]

nikic wrote:

> This would close #99746

I don't think this fully addresses that issue, because it doesn't cover the other two classes of ucmp/scmp patterns (nested select and add of ext, https://alive2.llvm.org/ce/z/LV-_iD). As they are somewhat different, it makes sense to handle them separately.

https://github.com/llvm/llvm-project/pull/101049