[llvm] [PHIElimination] Reuse existing COPY in predecessor basic block (PR #131837)

[Guy David via llvm-commits]

guy-david wrote:

Now I feel bad 😆 Can you verify whether [c4c9e0eef98d9c480fcdb2604735ca855c94364d](https://github.com/llvm/llvm-project/commit/c4c9e0eef98d9c480fcdb2604735ca855c94364d) solves your issue?

https://github.com/llvm/llvm-project/pull/131837