[llvm] [InstCombine] Reducing rust i128::midpoint instructions (PR #99614)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

I am not sure whether it is appropriate to do this transform in InstCombine. It would be better to do this in SDAG.
cc @RKSimon @topperc 



https://github.com/llvm/llvm-project/pull/99614