[llvm] MachineScheduler: Improve instruction clustering (PR #137784)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > Even after this patch, we still add weak "cluster" edges to the DAG. Is that still necessary?
> > Oh I see you mentioned that already. The DAG edges are only needed for some sort of check in MacroFusion, right? I don't really understand that part.
> 
> For the edge in `clusterNeighboringMemOps`, Removing it just causes more test changes. That's one of the reasons why I leave it there. I slightly prefer we remove it but no clear idea yet. I think it needs some more investigation, and it would be better done separately.

OK, but please do follow up on this. It would be great if we can remove the cluster edges from the DAG.

https://github.com/llvm/llvm-project/pull/137784