[Pipeliner] Fixed optimization remarks and debug dumps Initiation Interval value

[mamai]

Summary

The II value is incremented before exiting the loop, and therefor when used in the optimization remarks and debug dumps it did not reflect the initiation interval actually used in Schedule.

[bcahoon]

Hi Marianne,

Thanks for the patch. Sorry that it took a while to get to this. I just have a couple of questions.

Thanks,
Brendon

llvm/lib/CodeGen/MachinePipeliner.cpp

2125

Does this need to be decremented only if scheduledFound is true?

Another possibility is to use Schedule.getInitiationInterval() instead of II in the subsequent debug and remark messages.

[mamai]

llvm/lib/CodeGen/MachinePipeliner.cpp

2125

In fact, I am not sure what is the point to print the II when the schedule is not found. But, I think it is valid to decrement all the time, since the ++ is done right before exiting the loop, no matter if the schedule is found or not. It will represent the last II that was actually tried.

I thought of using a getInitiationInterval() function, but it doesn't exist. It was more simple to decrement the counter than to create a new getter function.

[bcahoon]

llvm/lib/CodeGen/MachinePipeliner.cpp

2125

You're correct - it is valid to always decrement. I still think it better to add and use a getInitiationInterval() function, and then change the scope of II so that it is limited to the loop. But, it's more important that the correct valid is printed, so either approach is an improvment.

[mamai]

Updated patch with the cleaner approach of creating a getInitiationInterval() function.

[bcahoon]

Thanks for fixing this!

llvm/include/llvm/CodeGen/MachinePipeliner.h

void reset() {
     FirstCycle = 0;
     LastCycle = 0;
     InitiationInterval = 0;
   }
 
   /// Set the initiation interval for this schedule.
   void setInitiationInterval(int ii) { InitiationInterval = ii; }
 
+  /// Return the initiation interval for this schedule.
+  int getInitiationInterval() const { return InitiationInterval; }
+
   /// Return the first cycle in the completed schedule.  This
   /// can be a negative value.
   int getFirstCycle() const { return FirstCycle; }
 
   /// Return the last cycle in the finalized schedule.
   int getFinalCycle() const { return FirstCycle + InitiationInterval - 1; }
 
   /// Return the cycle of the earliest scheduled instruction in the dependence

llvm/lib/CodeGen/MachinePipeliner.cpp

 bool SwingSchedulerDAG::schedulePipeline(SMSchedule &Schedule) {
 
   if (NodeOrder.empty()){
     LLVM_DEBUG(dbgs() << "NodeOrder is empty! abort scheduling\n" );
     return false;
   }
 
   bool scheduleFound = false;
-  unsigned II = 0;
   // Keep increasing II until a valid schedule is found.
-  for (II = MII; II <= MAX_II && !scheduleFound; ++II) {
+  for (unsigned II = MII; II <= MAX_II && !scheduleFound; ++II) {
     Schedule.reset();
     Schedule.setInitiationInterval(II);
     LLVM_DEBUG(dbgs() << "Try to schedule with " << II << "\n");
 
     SetVector<SUnit *>::iterator NI = NodeOrder.begin();
     SetVector<SUnit *>::iterator NE = NodeOrder.end();
     do {
       SUnit *SU = *NI;
do {
           dbgs() << "\tCan't schedule\n";
       });
     } while (++NI != NE && scheduleFound);
 
     // If a schedule is found, check if it is a valid schedule too.
     if (scheduleFound)
       scheduleFound = Schedule.isValidSchedule(this);
   }
 
-  LLVM_DEBUG(dbgs() << "Schedule Found? " << scheduleFound << " (II=" << II
+  LLVM_DEBUG(dbgs() << "Schedule Found? " << scheduleFound
+                    << " (II=" << Schedule.getInitiationInterval()
                     << ")\n");
 
   if (scheduleFound) {
     Schedule.finalizeSchedule(this);
     Pass.ORE->emit([&]() {
       return MachineOptimizationRemarkAnalysis(
                  DEBUG_TYPE, "schedule", Loop.getStartLoc(), Loop.getHeader())
-             << "Schedule found with Initiation Interval: " << ore::NV("II", II)
+             << "Schedule found with Initiation Interval: "
+             << ore::NV("II", Schedule.getInitiationInterval())
              << ", MaxStageCount: "
              << ore::NV("MaxStageCount", Schedule.getMaxStageCount());
     });
   } else
     Schedule.reset();
 
   return scheduleFound && Schedule.getMaxStageCount() > 0;
 }