MachineScheduler: Add -misched-print-dags flag

[MatzeB]

Summary

Add a flag to dump the schedule DAG to the debug stream. This will be
used in upcoming commits to test schedule DAG mutations such as macro
fusion.

[MatzeB]

Landed in rL342589

lib/CodeGen/MachineScheduler.cpp

 
 static cl::opt<unsigned> MISchedCutoff("misched-cutoff", cl::Hidden,
   cl::desc("Stop scheduling after N instructions"), cl::init(~0U));
 
 static cl::opt<std::string> SchedOnlyFunc("misched-only-func", cl::Hidden,
   cl::desc("Only schedule this function"));
 static cl::opt<unsigned> SchedOnlyBlock("misched-only-block", cl::Hidden,
                                         cl::desc("Only schedule this MBB#"));
+static cl::opt<bool> PrintDAGs("misched-print-dags", cl::Hidden,
+                              cl::desc("Print schedule DAGs"));
 #else
-static bool ViewMISchedDAGs = false;
+static const bool ViewMISchedDAGs = false;
+static const bool PrintDAGs = false;
 #endif // NDEBUG
 
 /// Avoid quadratic complexity in unusually large basic blocks by limiting the
 /// size of the ready lists.
 static cl::opt<unsigned> ReadyListLimit("misched-limit", cl::Hidden,
   cl::desc("Limit ready list to N instructions"), cl::init(256));
 
 static cl::opt<bool> EnableRegPressure("misched-regpressure", cl::Hidden,
void ScheduleDAGMI::schedule() {
   Topo.InitDAGTopologicalSorting();
 
   postprocessDAG();
 
   SmallVector<SUnit*, 8> TopRoots, BotRoots;
   findRootsAndBiasEdges(TopRoots, BotRoots);
 
   LLVM_DEBUG(dump());
+  if (PrintDAGs) dump();
   if (ViewMISchedDAGs) viewGraph();
 
   // Initialize the strategy before modifying the DAG.
   // This may initialize a DFSResult to be used for queue priority.
   SchedImpl->initialize(this);
 
   // Initialize ready queues now that the DAG and priority data are finalized.
   initQueues(TopRoots, BotRoots);
void ScheduleDAGMILive::schedule() {
   SmallVector<SUnit*, 8> TopRoots, BotRoots;
   findRootsAndBiasEdges(TopRoots, BotRoots);
 
   // Initialize the strategy before modifying the DAG.
   // This may initialize a DFSResult to be used for queue priority.
   SchedImpl->initialize(this);
 
   LLVM_DEBUG(dump());
+  if (PrintDAGs) dump();
   if (ViewMISchedDAGs) viewGraph();
 
   // Initialize ready queues now that the DAG and priority data are finalized.
   initQueues(TopRoots, BotRoots);
 
   bool IsTopNode = false;
   while (true) {
     LLVM_DEBUG(dbgs() << "** ScheduleDAGMILive::schedule picking next node\n");