[llvm] [LV] Remove common extends and selects in CSE (PR #147731)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Does VPlan-based CSE cover most of the cases here? https://github.com/llvm/llvm-project/pull/151872

If so, I'd prefer to not extend the logic in the legacy pass, but rather work towards removing it. VPlan-based CSE also has the advantage to impact cost estimates

https://github.com/llvm/llvm-project/pull/147731