[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

2126

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

2126

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

2126

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/lib/CodeGen/MachinePipeliner.cpp

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);
   }
+  --II;
 
   LLVM_DEBUG(dbgs() << "Schedule Found? " << scheduleFound << " (II=" << II
                     << ")\n");
 
   if (scheduleFound) {
     Schedule.finalizeSchedule(this);
     Pass.ORE->emit([&]() {
       return MachineOptimizationRemarkAnalysis(