[PATCH] D124678: [AMDGPU] Allow for MFMA Inst Clustering

[Austin Kerbow via Phabricator via llvm-commits]

kerbowa added a comment.

In D124678#3483673 <https://reviews.llvm.org/D124678#3483673>, @rampitec wrote:

> In D124678#3483663 <https://reviews.llvm.org/D124678#3483663>, @jrbyrnes wrote:
>
>> Regarding your note -- yes this is something I spent some time thinking about – Sdep::Cluster doesn’t gaurantee a single cluster. In fact, I believe there is a hardware dependency between MFMA’s, so the scheduler will try to fill this gap with an independent instruction.
>
> This is conflicting thing, we need to make sure it does not succeed to fill the gap. Probably it needs some tweaking in FillMFMAShadowMutation and GCNHazardRecognizer::ShouldPreferAnother if this option is set. In any way you need some more tests with different clustering/non-clustering scenarios and check the final code, do we get resulting clusters? Especially given that post-RA scheduler will try to torn them.

It may be that we want the cluster edges to be a suggestion rather than a hard limit, the cluster edges already work this way but the priority for them is low so it usually doesn't matter.

I believe GCNHazardRecognizer::ShouldPreferAnother will not be used now that we use post-RA machine scheduler.


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https://reviews.llvm.org/D124678