diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index c4addeea25e..d2351a371fb 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -38,8 +38,9 @@ ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
                                      bool IsPostRAFlag,
                                      LiveIntervals *lis)
   : ScheduleDAG(mf), MLI(mli), MDT(mdt), MFI(mf.getFrameInfo()),
-    InstrItins(mf.getTarget().getInstrItineraryData()), IsPostRA(IsPostRAFlag),
-    LIS(lis), UnitLatencies(false), LoopRegs(MLI, MDT), FirstDbgValue(0) {
+    InstrItins(mf.getTarget().getInstrItineraryData()), LIS(lis),
+    IsPostRA(IsPostRAFlag), UnitLatencies(false), LoopRegs(MLI, MDT),
+    FirstDbgValue(0) {
   assert((IsPostRA || LIS) && "PreRA scheduling requires LiveIntervals");
   DbgValues.clear();
   assert(!(IsPostRA && MRI.getNumVirtRegs()) &&
diff --git a/lib/CodeGen/ScheduleDAGInstrs.h b/lib/CodeGen/ScheduleDAGInstrs.h
index 714de4eeff8..27fb11c2fca 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.h
+++ b/lib/CodeGen/ScheduleDAGInstrs.h
@@ -171,16 +171,20 @@ namespace llvm {
     const MachineFrameInfo *MFI;
     const InstrItineraryData *InstrItins;
 
-    /// isPostRA flag indicates vregs cannot be present.
-    bool IsPostRA;
-
     /// Live Intervals provides reaching defs in preRA scheduling.
     LiveIntervals *LIS;
 
-    /// State specific to the current scheduling region.
-    ///
+    /// isPostRA flag indicates vregs cannot be present.
+    bool IsPostRA;
 
-    // The block in which to insert instructions
+    /// UnitLatencies (misnamed) flag avoids computing def-use latencies, using
+    /// the def-side latency only.
+    bool UnitLatencies;
+
+    /// State specific to the current scheduling region.
+    /// ------------------------------------------------
+
+    /// The block in which to insert instructions
     MachineBasicBlock *BB;
 
     /// The beginning of the range to be scheduled.
@@ -196,9 +200,8 @@ namespace llvm {
     /// scheduling region is mapped to an SUnit.
     DenseMap<MachineInstr*, SUnit*> MISUnitMap;
 
-    /// UnitLatencies (misnamed) flag avoids computing def-use latencies, using
-    /// the def-side latency only.
-    bool UnitLatencies;
+    /// State internal to DAG building.
+    /// -------------------------------
 
     /// Defs, Uses - Remember where defs and uses of each register are as we
     /// iterate upward through the instructions. This is allocated here instead
@@ -220,6 +223,8 @@ namespace llvm {
     LoopDependencies LoopRegs;
 
     /// DbgValues - Remember instruction that preceeds DBG_VALUE.
+    /// These are generated by buildSchedGraph but persist so they can be
+    /// referenced when emitting the final schedule.
     typedef std::vector<std::pair<MachineInstr *, MachineInstr *> >
       DbgValueVector;
     DbgValueVector DbgValues;