misched comments

llvm-svn: 152173

llvm/include/llvm/CodeGen/ScheduleDAG.h

@@ -8,7 +8,8 @@
 //===----------------------------------------------------------------------===//
 //
 // This file implements the ScheduleDAG class, which is used as the common
-// base class for instruction schedulers.
+// base class for instruction schedulers. This encapsulates the scheduling DAG,
+// which is shared between SelectionDAG and MachineInstr scheduling.
 //
 //===----------------------------------------------------------------------===//
 

llvm/lib/CodeGen/ScheduleDAGInstrs.h

@@ -112,6 +112,8 @@ namespace llvm {
     /// Live Intervals provides reaching defs in preRA scheduling.
     LiveIntervals *LIS;
 
+    /// After calling BuildSchedGraph, each machine instruction in the current
+    /// scheduling region is mapped to an SUnit.
     DenseMap<MachineInstr*, SUnit*> MISUnitMap;
 
     /// UnitLatencies (misnamed) flag avoids computing def-use latencies, using