[llvm] [CodeGen] check artificial subregister before propagate copy (PR #185751)

[Brox Chen via llvm-commits]

broxigarchen wrote:

> machine copy propagation pass

created an issue here https://github.com/llvm/llvm-project/issues/186140. Please free feel to add more details

https://github.com/llvm/llvm-project/pull/185751