[llvm] [InstCombine] Infer exact for lshr by cttz (PR #136696)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw commented:

Please add some tests to demonstrate the change. See also https://llvm.org/docs/InstCombineContributorGuide.html#tests

https://github.com/llvm/llvm-project/pull/136696