[llvm] [AMDGPU] Machine-CP is deleting incorrect copy instr. (PR #114773)

[Jay Foad via llvm-commits]

jayfoad wrote:

MachineCopyPropagation is not doing anything wrong; the implicit-def is wrong. So this issue needs a proper test case that starts before the implicit-def is added, so we can see why it was added and what we can do instead.

https://github.com/llvm/llvm-project/pull/114773