[PATCH] D56291: ScheduleDAG: Don't break the dependence in clustering neighboring loads.

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added inline comments.


================
Comment at: lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp:258
+    // We continue to search for other candidates.
+    if (Load->isOperandOf(BaseLoad))
+      continue;
----------------
I see two flaws in this logic:

1. A load can depend on any previous load, not just base.
2. A dependency can be indirect, not necessarily as a direct operand.

The problem is if you use a loop over the whole chain and also use isPredecessorOf instead of isOperandOf that will make this loop extremely expensive. It needs to be somehow simplified. Maybe do such check only if getIROrder() of successor is less or equal getIROrder() of a predecessor in the assumption if it was located higher in the IR and given all of that happens in the same basic block, there can be no dependency?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56291/new/

https://reviews.llvm.org/D56291