[llvm] [InstCombine] optimize unnecessary sext instruction with add + cmp (PR #152291)

[Gaurav Dhingra via llvm-commits]

gxyd wrote:

> Please see llvm.org/docs/InstCombineContributorGuide.html. Please add an alive2 proof to the PR description.

Yes, now I've added a link to proof on alive2 platform as well.

https://github.com/llvm/llvm-project/pull/152291