Index: include/llvm/CodeGen/ScheduleDAG.h
===================================================================
--- include/llvm/CodeGen/ScheduleDAG.h
+++ include/llvm/CodeGen/ScheduleDAG.h
@@ -738,6 +738,11 @@
     /// current node \p M.
     void RemovePred(SUnit *M, SUnit *N);
 
+    /// Maps SUnits to indexes of a topological ordering.
+    /// The index is between 0 and SUnits.count()-1.
+    /// Boundary SUnits are not mapped.
+    int getSUTopoIndex(SUnit &SU);
+
     typedef std::vector<int>::iterator iterator;
     typedef std::vector<int>::const_iterator const_iterator;
     iterator begin() { return Index2Node.begin(); }
Index: lib/CodeGen/ScheduleDAG.cpp
===================================================================
--- lib/CodeGen/ScheduleDAG.cpp
+++ lib/CodeGen/ScheduleDAG.cpp
@@ -682,6 +682,12 @@
   return HasLoop;
 }
 
+int ScheduleDAGTopologicalSort::getNodeTopoIndex(SUnit &SU)
+{
+  assert(!SU.isBoundaryNode());
+  return Node2Index[SU.NodeNum];
+}
+
 void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
   Node2Index[n] = index;
   Index2Node[index] = n;