[llvm] [InstCombine] Fold afn powi(2.0, x) to ldexp(1.0, x) (PR #202114)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm requested changes to this pull request.

Should just use CreateVectorSplat to handle vector + scalar exp 

https://github.com/llvm/llvm-project/pull/202114