X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FSelectionDAG%2FScheduleDAGSDNodes.cpp;h=202f7ab4e14f3e72054ab100fb92bc4f4f255c98;hb=4bbf4678e341e9bf899c0faa3e3bcfe134db81eb;hp=b762af5ca9b22da71838656df0f31a06e4cc6b6a;hpb=d1cba8727a1ee713030d9e6bbd72523a9f9e2a60;p=oota-llvm.git

diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index b762af5ca9b..202f7ab4e14 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -419,11 +419,15 @@ void ScheduleDAGSDNodes::AddSchedEdges() {
           ST.adjustSchedDependency(OpSU, SU, const_cast<SDep &>(dep));
         }
 
-        if (!SU->addPred(dep) && !dep.isCtrl() && OpSU->NumRegDefsLeft > 0) {
+        if (!SU->addPred(dep) && !dep.isCtrl() && OpSU->NumRegDefsLeft > 1) {
           // Multiple register uses are combined in the same SUnit. For example,
           // we could have a set of glued nodes with all their defs consumed by
           // another set of glued nodes. Register pressure tracking sees this as
           // a single use, so to keep pressure balanced we reduce the defs.
+          //
+          // We can't tell (without more book-keeping) if this results from
+          // glued nodes or duplicate operands. As long as we don't reduce
+          // NumRegDefsLeft to zero, we handle the common cases well.
           --OpSU->NumRegDefsLeft;
         }
       }