[llvm] [LV] Skip replicating already-scalar casts (PR #195646)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> Is there any particular reason for doing this as new PR instead of updating the existing #140623?

Oh, I didn't mean to step on your toes -- just had some time, so demonstrated the changes we should probably make to #140623.

https://github.com/llvm/llvm-project/pull/195646