[Hexagon] HVX .new store uses different resources

When checking resources in the post RA scheduler, see if a .new
vector store should be used instead of a regular vector store.

It may not be possible to schedule a regular vector store, but
it may be possible to schedule a .new version. If the correct one
isn't used, then the post RA scheduler may not generate the best
schedule.

Author: SANTANU DAS

llvm/lib/Target/Hexagon/HexagonHazardRecognizer.cpp

@@ -44,12 +44,7 @@ HexagonHazardRecognizer::getHazardType(SUnit *SU, int stalls) {
   if (!Resources->canReserveResources(*MI)) {
     LLVM_DEBUG(dbgs() << "*** Hazard in cycle " << PacketNum << ", " << *MI);
     HazardType RetVal = Hazard;
-    if (TII->mayBeNewStore(*MI)) {
-      // Make sure the register to be stored is defined by an instruction in the
-      // packet.
-      MachineOperand &MO = MI->getOperand(MI->getNumOperands() - 1);
-      if (!MO.isReg() || RegDefs.count(MO.getReg()) == 0)
-        return Hazard;
+    if (isNewStore(*MI)) {
       // The .new store version uses different resources so check if it
       // causes a hazard.
       MachineFunction *MF = MI->getParent()->getParent();
@@ -105,6 +100,15 @@ bool HexagonHazardRecognizer::ShouldPreferAnother(SUnit *SU) {
   return UsesDotCur && ((SU == UsesDotCur) ^ (DotCurPNum == (int)PacketNum));
 }
 
+/// Return true if the instruction would be converted to a new value store when
+/// packetized.
+bool HexagonHazardRecognizer::isNewStore(MachineInstr &MI) {
+  if (!TII->mayBeNewStore(MI))
+    return false;
+  MachineOperand &MO = MI.getOperand(MI.getNumOperands() - 1);
+  return (MO.isReg() && RegDefs.count(MO.getReg()) != 0);
+}
+
 void HexagonHazardRecognizer::EmitInstruction(SUnit *SU) {
   MachineInstr *MI = SU->getInstr();
   if (!MI)
@@ -119,19 +123,20 @@ void HexagonHazardRecognizer::EmitInstruction(SUnit *SU) {
   if (TII->isZeroCost(MI->getOpcode()))
     return;
 
-  if (!Resources->canReserveResources(*MI)) {
+  if (!Resources->canReserveResources(*MI) || isNewStore(*MI)) {
     // It must be a .new store since other instructions must be able to be
     // reserved at this point.
     assert(TII->mayBeNewStore(*MI) && "Expecting .new store");
     MachineFunction *MF = MI->getParent()->getParent();
     MachineInstr *NewMI =
         MF->CreateMachineInstr(TII->get(TII->getDotNewOp(*MI)),
                                MI->getDebugLoc());
-    assert(Resources->canReserveResources(*NewMI));
-    Resources->reserveResources(*NewMI);
+    if (Resources->canReserveResources(*NewMI))
+      Resources->reserveResources(*NewMI);
+    else
+      Resources->reserveResources(*MI);
     MF->deleteMachineInstr(NewMI);
-  }
-  else
+  } else
     Resources->reserveResources(*MI);
   LLVM_DEBUG(dbgs() << " Add instruction " << *MI);
 

llvm/lib/Target/Hexagon/HexagonHazardRecognizer.h

@@ -40,6 +40,10 @@ class HexagonHazardRecognizer : public ScheduleHazardRecognizer {
   // The set of registers defined by instructions in the current packet.
   SmallSet<unsigned, 8> RegDefs;
 
+  // Return true if the instruction is a store that is converted to a new value
+  // store because its value is defined in the same packet.
+  bool isNewStore(MachineInstr &MI);
+
 public:
   HexagonHazardRecognizer(const InstrItineraryData *II,
                           const HexagonInstrInfo *HII,