[llvm] [RISCV] Move VMV0 elimination past machine SSA opts (PR #126850)

[Luke Lau via llvm-commits]

lukel97 wrote:

@newgre Thanks for the minimal reproducer, I think I'll be able to commit a fix for this soon. The issue is to do with dead COPYs being left around. I would have thought that they would have been mopped up by another pass but it looks like when we've moved it this close to regalloc we have to do it ourselves.

https://github.com/llvm/llvm-project/pull/126850