[llvm-commits] [llvm] r67554 - /llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp

[Dan Gohman]

Author: djg
Date: Mon Mar 23 15:20:43 2009
New Revision: 67554

URL: http://llvm.org/viewvc/llvm-project?rev=67554&view=rev
Log:
When unfolding a load during scheduling, the new operator node has
a data dependency on the load node, so it really needs a
data-dependence edge to the load node, even if the load previously
existed.

And add a few comments.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp?rev=67554&r1=67553&r2=67554&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp Mon Mar 23 15:20:43 2009
@@ -410,6 +410,7 @@
       NewSU->isCommutable = true;
     ComputeLatency(NewSU);
 
+    // Record all the edges to and from the old SU, by category.
     SmallVector<SDep, 4> ChainPreds;
     SmallVector<SDep, 4> ChainSuccs;
     SmallVector<SDep, 4> LoadPreds;
@@ -433,6 +434,7 @@
         NodeSuccs.push_back(*I);
     }
 
+    // Now assign edges to the newly-created nodes.
     for (unsigned i = 0, e = ChainPreds.size(); i != e; ++i) {
       const SDep &Pred = ChainPreds[i];
       RemovePred(SU, Pred);
@@ -468,9 +470,10 @@
         AddPred(SuccDep, D);
       }
     } 
-    if (isNewLoad) {
-      AddPred(NewSU, SDep(LoadSU, SDep::Order, LoadSU->Latency));
-    }
+
+    // Add a data dependency to reflect that NewSU reads the value defined
+    // by LoadSU.
+    AddPred(NewSU, SDep(LoadSU, SDep::Data, LoadSU->Latency));
 
     if (isNewLoad)
       AvailableQueue->addNode(LoadSU);