[llvm] [AMDGPU] Add target hook to isGlobalMemoryObject (PR #112781)

[Austin Kerbow via llvm-commits]

kerbowa wrote:

> The changes to IGLP / GCNSched look fine.
> 
> FWIW, I'm okay with the approach (though I think Matt has an outstanding concern).
> 
> I guess another alternative is to manually add the true edges between the preds and succs of the iglpInst during resetEdges. Perhaps this could be optimized a bit, but it seems needlessly expensive. However, maybe this could suffice until we have a better way to express the side effects these should and shouldn't have?

I don't know how we would manually add the correct edges in `resetEdges` without just redoing a bunch of the login in the DAG builder? So I'm not sure that would work.

https://github.com/llvm/llvm-project/pull/112781