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

[Jeffrey Byrnes via llvm-commits]

jrbyrnes 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?

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