[llvm] [VPlan] Use VPInstruction for uniform binops. (PR #141429)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for the comments. It would probably be good to first focus on https://github.com/llvm/llvm-project/pull/140623 (inlcuded in this PR) which adds IsSingleScalar and uses it for casts only, with the PR here to illustrate how it will look like for binary ops. 

I addressed the comments that are applicable to https://github.com/llvm/llvm-project/pull/140623 directly there

https://github.com/llvm/llvm-project/pull/141429