diff --git a/include/llvm/CodeGen/ScheduleDAG.h b/include/llvm/CodeGen/ScheduleDAG.h
index 9dfb502..125f8ea 100644
--- a/include/llvm/CodeGen/ScheduleDAG.h
+++ b/include/llvm/CodeGen/ScheduleDAG.h
@@ -94,6 +94,7 @@
   struct SUnit {
   private:
     SDNode *Node;                       // Representative node.
+    MachineInstr *Instr;                // Alternatively, a MachineInstr.
   public:
     SUnit *OrigNode;                    // If not this, the node from which
                                         // this node was cloned.
@@ -128,19 +129,53 @@
     const TargetRegisterClass *CopyDstRC; // Is a special copy node if not null.
     const TargetRegisterClass *CopySrcRC;
     
+    /// SUnit - Construct an SUnit for pre-regalloc scheduling to represent
+    /// an SDNode and any nodes flagged to it.
     SUnit(SDNode *node, unsigned nodenum)
-      : Node(node), OrigNode(0), NodeNum(nodenum), NodeQueueId(0), Latency(0),
-        NumPreds(0), NumSuccs(0), NumPredsLeft(0), NumSuccsLeft(0),
+      : Node(node), Instr(0), OrigNode(0), NodeNum(nodenum), NodeQueueId(0),
+        Latency(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0), NumSuccsLeft(0),
+        isTwoAddress(false), isCommutable(false), hasPhysRegDefs(false),
+        isPending(false), isAvailable(false), isScheduled(false),
+        CycleBound(0), Cycle(0), Depth(0), Height(0),
+        CopyDstRC(NULL), CopySrcRC(NULL) {}
+
+    /// SUnit - Construct an SUnit for post-regalloc scheduling to represent
+    /// a MachineInstr.
+    SUnit(MachineInstr *instr, unsigned nodenum)
+      : Node(0), Instr(instr), OrigNode(0), NodeNum(nodenum), NodeQueueId(0),
+        Latency(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0), NumSuccsLeft(0),
         isTwoAddress(false), isCommutable(false), hasPhysRegDefs(false),
         isPending(false), isAvailable(false), isScheduled(false),
         CycleBound(0), Cycle(0), Depth(0), Height(0),
         CopyDstRC(NULL), CopySrcRC(NULL) {}
 
     /// setNode - Assign the representative SDNode for this SUnit.
-    void setNode(SDNode *N) { Node = N; }
+    /// This may be used during pre-regalloc scheduling.
+    void setNode(SDNode *N) {
+      assert(!Instr && "Setting SDNode of SUnit with MachineInstr!");
+      Node = N;
+    }
 
     /// getNode - Return the representative SDNode for this SUnit.
-    SDNode *getNode() const { return Node; }
+    /// This may be used during pre-regalloc scheduling.
+    SDNode *getNode() const {
+      assert(!Instr && "Reading SDNode of SUnit with MachineInstr!");
+      return Node;
+    }
+
+    /// setInstr - Assign the instruction for the SUnit.
+    /// This may be used during post-regalloc scheduling.
+    void setInstr(MachineInstr *MI) {
+      assert(!Node && "Setting MachineInstr of SUnit with SDNode!");
+      Instr = MI;
+    }
+
+    /// getInstr - Return the representative MachineInstr for this SUnit.
+    /// This may be used during post-regalloc scheduling.
+    MachineInstr *getInstr() const {
+      assert(!Node && "Reading MachineInstr of SUnit with SDNode!");
+      return Instr;
+    }
 
     /// addPred - This adds the specified node as a pred of the current node if
     /// not already.  This returns true if this is a new pred.
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGEmit.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGEmit.cpp
index 2c40d97..d60dd49 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGEmit.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGEmit.cpp
@@ -684,6 +684,16 @@
       EmitNoop();
       continue;
     }
+
+    // For post-regalloc scheduling, we already have the instruction;
+    // just append it to the block.
+    if (!DAG) {
+      BB->push_back(SU->getInstr());
+      continue;
+    }
+
+    // For pre-regalloc scheduling, create instructions corresponding to the
+    // SDNode and any flagged SDNodes and append them to the block.
     SmallVector<SDNode *, 4> FlaggedNodes;
     for (SDNode *N = SU->getNode()->getFlaggedNode(); N; N = N->getFlaggedNode())
       FlaggedNodes.push_back(N);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGPrinter.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGPrinter.cpp
index 2774633..8ff50c1 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGPrinter.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGPrinter.cpp
@@ -420,11 +420,24 @@
 
     static void addCustomGraphFeatures(ScheduleDAG *G,
                                        GraphWriter<ScheduleDAG*> &GW) {
+      // Draw a special "GraphRoot" node to indicate the root of the graph.
       GW.emitSimpleNode(0, "plaintext=circle", "GraphRoot");
-      const SDNode *N = G->DAG->getRoot().getNode();
-      if (N && N->getNodeId() != -1)
-        GW.emitEdge(0, -1, &G->SUnits[N->getNodeId()], -1,
-                    "color=blue,style=dashed");
+      if (G->DAG) {
+        // For an SDNode-based ScheduleDAG, point to the root of the ScheduleDAG.
+        const SDNode *N = G->DAG->getRoot().getNode();
+        if (N && N->getNodeId() != -1)
+          GW.emitEdge(0, -1, &G->SUnits[N->getNodeId()], -1,
+                      "color=blue,style=dashed");
+      } else {
+        // For a MachineInstr-based ScheduleDAG, find a root to point to.
+        for (unsigned i = 0, e = G->SUnits.size(); i != e; ++i) {
+          if (G->SUnits[i].Succs.empty()) {
+            GW.emitEdge(0, -1, &G->SUnits[i], -1,
+                        "color=blue,style=dashed");
+            break;
+          }
+        }
+      }
     }
   };
 }