[PATCH] D60864: [AMDGPU] Ignore non-SUnits edges

[Piotr Sobczak via Phabricator via llvm-commits]

piotr created this revision.
Herald added subscribers: llvm-commits, javed.absar, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl, arsenm, MatzeB.
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piotr added a reviewer: nhaehnle.

Ignore edges to non-SUnits (e.g. ExitSU) when checking
for low latency instructions.

When calling the function isLowLatencyInstruction(),
an ExitSU could be on the list of successors, not necessarily
a regular SU. In other places in the code there is a check
"Succ->NodeNum >= DAGSize" to prevent further processing of
ExitSU as "Succ->getInstr()" is NULL in such a case.
Also, 8 out of 9 cases of "SUnit *Succ = SuccDep.getSUnit())"
has the guard, so it is clearly an omission here.

Change-Id: Ica86f0327c7b2e6bcb56958e804ea6c71084663b


Repository:
  rL LLVM

https://reviews.llvm.org/D60864

Files:
  lib/Target/AMDGPU/SIMachineScheduler.cpp


Index: lib/Target/AMDGPU/SIMachineScheduler.cpp
===================================================================
--- lib/Target/AMDGPU/SIMachineScheduler.cpp
+++ lib/Target/AMDGPU/SIMachineScheduler.cpp
@@ -1874,6 +1874,8 @@
       bool CopyForLowLat = false;
       for (SDep& SuccDep : SU->Succs) {
         SUnit *Succ = SuccDep.getSUnit();
+        if (SuccDep.isWeak() || Succ->NodeNum >= DAGSize)
+          continue;
         if (SITII->isLowLatencyInstruction(*Succ->getInstr())) {
           CopyForLowLat = true;
         }


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