[llvm] [MachineCopyPropagation] Detect and fix suboptimal instruction order to enable optimizations (PR #98087)

[Quentin Colombet via llvm-commits]

https://github.com/qcolombet requested changes to this pull request.

I think this is the kind of optimization that belongs to postRA scheduling.

I feel this is too complicated for MachineCopyPropagation. Or put differently, until now, MCP was not moving things around so I'm not sure this is the right place to do this.

https://github.com/llvm/llvm-project/pull/98087