[llvm] [InstCombine] Fold reconstruction across select (PR #145102)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

@nikic 
Do you have a better idea to generalize this pattern? Always folding `%zext_low` into the select addresses the issue: https://godbolt.org/z/xoKex34TE But we cannot do that as `select i8` is more canonical than `select i40`.


https://github.com/llvm/llvm-project/pull/145102