[llvm] [InstCombine] Implement vp.reverse elimination through binop/unop (PR #143963)

[Philip Reames via llvm-commits]

preames wrote:

See also https://github.com/llvm/llvm-project/pull/144112.  Waiting on discussion in https://github.com/llvm/llvm-project/pull/143967 to converge, but I'm guessing that I'm going to end of reworking the approach on this patch, so review attention is probably better focused on the instsimplify patch for the moment.  

https://github.com/llvm/llvm-project/pull/143963