[llvm] [InstCombine] Fold comparisons of llvm.usub.sat result with its LHS (PR #214108)

[Haram Jeong via llvm-commits]

haramj wrote:

@ParkHanbum @andjo403 @dtcxzyw

Ping — I’ve addressed the previous feedback and left my reasoning regarding the suggested helper refactoring above.

Could you take another look when you have a chance? I’m happy to make further changes if you think the refactoring is still preferable. Thanks!

https://github.com/llvm/llvm-project/pull/214108