[llvm] [PHIElimination] Verify reappropriated COPY is of similar register class, update livevars. (PR #146337)

[Mikael Holmén via llvm-commits]

mikaelholmen wrote:

Ok, this solves the problems I've seen. Thanks!
Maybe you want someone who reviewed the original change to look at this too, but as far as I'm concerned this looks ok.

https://github.com/llvm/llvm-project/pull/146337