[CodeGen] Return better Changed status from PostRAHazardRecognizer

[piotr]

llvm/lib/CodeGen/PostRAHazardRecognizer.cpp

98

You can check NumNoops here instead?

[myhsu]

llvm/lib/CodeGen/PostRAHazardRecognizer.cpp

89

nit

98

I don't think so, NumNoops is a global variable that accumulates its value through the program's lifetime

[piotr]

llvm/lib/CodeGen/PostRAHazardRecognizer.cpp

98

I don't think so, NumNoops is a global variable that accumulates its value through the program's lifetime

Ah, of course.

[foad]

Fix nit.

[myhsu]

LGTM

llvm/lib/CodeGen/PostRAHazardRecognizer.cpp

bool PostRAHazardRecognizer::runOnMachineFunction(MachineFunction &Fn) {
   std::unique_ptr<ScheduleHazardRecognizer> HazardRec(
       TII->CreateTargetPostRAHazardRecognizer(Fn));
 
   // Return if the target has not implemented a hazard recognizer.
   if (!HazardRec.get())
     return false;
 
   // Loop over all of the basic blocks
+  bool Changed = false;
   for (auto &MBB : Fn) {
     // We do not call HazardRec->reset() here to make sure we are handling noop
     // hazards at the start of basic blocks.
     for (MachineInstr &MI : MBB) {
       // If we need to emit noops prior to this instruction, then do so.
       unsigned NumPreNoops = HazardRec->PreEmitNoops(&MI);
       HazardRec->EmitNoops(NumPreNoops);
       TII->insertNoops(MBB, MachineBasicBlock::iterator(MI), NumPreNoops);
       NumNoops += NumPreNoops;
+      if (NumPreNoops != 0)
+        Changed = true;
 
       HazardRec->EmitInstruction(&MI);
       if (HazardRec->atIssueLimit()) {
         HazardRec->AdvanceCycle();
       }
     }
   }
-  return true;
+  return Changed;
 }