[PATCH] D90144: [Scheduling] Fall back to the fast cluster algorithm if the DAG is too complex

[Qing Shan Zhang via Phabricator via llvm-commits]

steven.zhang created this revision.
steven.zhang added reviewers: foad, resistor, arsenm, fhahn, evandro, jsji, PowerPC.
Herald added subscribers: ecnelises, mgrang, javed.absar, hiraditya, kristof.beyls, MatzeB.
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steven.zhang requested review of this revision.
Herald added a subscriber: wdng.

We have added a new load/store cluster algorithm in D85517 <https://reviews.llvm.org/D85517>. However, AArch64 see some compiling deg with the new algorithm as the IsReachable() is not cheap if the DAG is complex. O(M+N) See https://bugs.llvm.org/show_bug.cgi?id=47966

So, this patch added a heuristic to switch to old cluster algorithm if the DAG is too complex. For now, I used the heuristic value 5M for NumOfStores * NumOfSUnits. This is a rough threshold as I don't see compiling time impact with it and it is large enough I think. Welcome for more comments.

The case in https://bugs.llvm.org/show_bug.cgi?id=47966 is that, we have ~10000 LdSt and ~15000 SUnits in one region, which blow up the compiling time.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D90144

Files:
  llvm/lib/CodeGen/MachineScheduler.cpp
  llvm/test/CodeGen/AArch64/aarch64-stp-cluster.ll

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