sched: Avoid trivially redundant DAG edges. Take the one with higher latency.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158379 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/ScheduleDAG.cpp b/lib/CodeGen/ScheduleDAG.cpp
index 8fd6426..752f8e4 100644
--- a/lib/CodeGen/ScheduleDAG.cpp
+++ b/lib/CodeGen/ScheduleDAG.cpp
@@ -64,10 +64,27 @@
/// specified node.
bool SUnit::addPred(const SDep &D) {
// If this node already has this depenence, don't add a redundant one.
- for (SmallVector<SDep, 4>::const_iterator I = Preds.begin(), E = Preds.end();
- I != E; ++I)
- if (*I == D)
+ for (SmallVector<SDep, 4>::iterator I = Preds.begin(), E = Preds.end();
+ I != E; ++I) {
+ if (I->overlaps(D)) {
+ // Extend the latency if needed. Equivalent to removePred(I) + addPred(D).
+ if (I->getLatency() < D.getLatency()) {
+ SUnit *PredSU = I->getSUnit();
+ // Find the corresponding successor in N.
+ SDep ForwardD = *I;
+ ForwardD.setSUnit(this);
+ for (SmallVector<SDep, 4>::iterator II = PredSU->Succs.begin(),
+ EE = PredSU->Succs.end(); II != EE; ++II) {
+ if (*II == ForwardD) {
+ II->setLatency(D.getLatency());
+ break;
+ }
+ }
+ I->setLatency(D.getLatency());
+ }
return false;
+ }
+ }
// Now add a corresponding succ to N.
SDep P = D;
P.setSUnit(this);