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

[Jessica Clarke via llvm-commits]

https://github.com/jrtc27 commented:

I don't know m68k well enough to be able to comment on whether this makes sense as a change, so just some drive-by stylistic feedback. If there's really no way to copy a register without clobbering flags though that's quite sad... and I don't think LLVM really wants to have to think about the legality of inserting generic COPY instructions. Does anyone know how GCC avoids this issue?

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