[llvm] [SelectOpt] Support ADD and SUB with zext operands. (PR #115489)

[David Green via llvm-commits]

davemgreen wrote:

As an example of something that I thought of with adds, a i128 addition using i64 values has a zext and add that we would usually hope to transform into an adc. https://godbolt.org/z/nY1xfzE5M. That will not transform due to the cost model, and would need more going on to transform, but would be the kind of thing we might need to worry about.

https://github.com/llvm/llvm-project/pull/115489