[llvm] [M68k] Prevent COPY instruction from killing live condition flags (PR #168485)

[Dan Salvato via llvm-commits]

dansalvato wrote:

> @dansalvato Does this change also address the clobbering of the CCR register of MOVE instructions?
> 
> We recently discovered that CCR clobbering problem when working on a Rust compiler for the m68k target.

If your issue is that a `MOVE` instruction is clobbering the CCR just before it's used, e.g. `CMP` -> `MOVE` -> `Bcc`, then yes, that's the exact scenario that this patch addresses. But if you mean something else, feel free to share some example ASM of the issue you ran into, and I can let you know whether it's relevant to this.

https://github.com/llvm/llvm-project/pull/168485