[llvm] [MacroFusion] Early return when insts already clustered (PR #191710)

[Tomer Shafir via llvm-commits]

tomershafir wrote:

I guess my answer would have a similar theme - should probably work on machine scheduler, and no AArch64-specific violation I'm aware of. Have you observed cases where it went wrong?

I think this is only relevant to ld/st clustering (and other if exist, none for AArch64 AFAIK) as macro fusion creates a new cluster for fused pairs. Also ld/st clustering uses a union-find data structure, so the node which create the clusters can change over time, if that matters.

https://github.com/llvm/llvm-project/pull/191710