[CSSPGO] Exclude pseudo probes from slot index

Pseudo probe are currently given a slot index like other regular instructions. This affects register pressure and lifetime weight computation because of enlarged lifetime length with pseudo probe instructions. As a consequence, program could get different code generated w/ and w/o pseudo probes. I'm closing the gap by excluding pseudo probes from stack index and downstream register allocation related passes.

Reviewed By: wmi

Differential Revision: https://reviews.llvm.org/D100334

lib/CodeGen/LexicalScopes.cpp

@@ -75,6 +75,11 @@ void LexicalScopes::extractLexicalScopes(
     const MachineInstr *PrevMI = nullptr;
     const DILocation *PrevDL = nullptr;
     for (const auto &MInsn : MBB) {
+      // Ignore DBG_VALUE and similar instruction that do not contribute to any
+      // instruction in the output.
+      if (MInsn.isMetaInstruction())
+        continue;
+
       // Check if instruction has valid location information.
       const DILocation *MIDL = MInsn.getDebugLoc();
       if (!MIDL) {
@@ -88,11 +93,6 @@ void LexicalScopes::extractLexicalScopes(
         continue;
       }
 
-      // Ignore DBG_VALUE and similar instruction that do not contribute to any
-      // instruction in the output.
-      if (MInsn.isMetaInstruction())
-        continue;
-
       if (RangeBeginMI) {
         // If we have already seen a beginning of an instruction range and
         // current instruction scope does not match scope of first instruction

lib/CodeGen/LiveDebugVariables.cpp

@@ -870,7 +870,7 @@ bool LDVImpl::collectDebugValues(MachineFunction &mf) {
          MBBI != MBBE;) {
       // Use the first debug instruction in the sequence to get a SlotIndex
       // for following consecutive debug instructions.
-      if (!MBBI->isDebugInstr()) {
+      if (!MBBI->isDebugOrPseudoInstr()) {
         ++MBBI;
         continue;
       }
@@ -891,7 +891,7 @@ bool LDVImpl::collectDebugValues(MachineFunction &mf) {
           Changed = true;
         } else
           ++MBBI;
-      } while (MBBI != MBBE && MBBI->isDebugInstr());
+      } while (MBBI != MBBE && MBBI->isDebugOrPseudoInstr());
     }
   }
   return Changed;

lib/CodeGen/LiveIntervals.cpp

@@ -1484,7 +1484,7 @@ private:
 
     MachineBasicBlock::iterator Begin = MBB->begin();
     while (MII != Begin) {
-      if ((--MII)->isDebugInstr())
+      if ((--MII)->isDebugOrPseudoInstr())
         continue;
       SlotIndex Idx = Indexes->getInstructionIndex(*MII);
 
@@ -1579,7 +1579,7 @@ void LiveIntervals::repairOldRegInRange(const MachineBasicBlock::iterator Begin,
   for (MachineBasicBlock::iterator I = End; I != Begin;) {
     --I;
     MachineInstr &MI = *I;
-    if (MI.isDebugInstr())
+    if (MI.isDebugOrPseudoInstr())
       continue;
 
     SlotIndex instrIdx = getInstructionIndex(MI);
@@ -1676,7 +1676,7 @@ LiveIntervals::repairIntervalsInRange(MachineBasicBlock *MBB,
   for (MachineBasicBlock::iterator I = End; I != Begin;) {
     --I;
     MachineInstr &MI = *I;
-    if (MI.isDebugInstr())
+    if (MI.isDebugOrPseudoInstr())
       continue;
     for (MachineInstr::const_mop_iterator MOI = MI.operands_begin(),
                                           MOE = MI.operands_end();

lib/CodeGen/LiveRangeShrink.cpp

@@ -130,7 +130,7 @@ bool LiveRangeShrink::runOnMachineFunction(MachineFunction &MF) {
     for (MachineBasicBlock::iterator Next = MBB.begin(); Next != MBB.end();) {
       MachineInstr &MI = *Next;
       ++Next;
-      if (MI.isPHI() || MI.isDebugInstr())
+      if (MI.isPHI() || MI.isDebugOrPseudoInstr())
         continue;
       if (MI.mayStore())
         SawStore = true;
@@ -219,7 +219,7 @@ bool LiveRangeShrink::runOnMachineFunction(MachineFunction &MF) {
       if (DefMO && Insert && NumEligibleUse > 1 && Barrier <= IOM[Insert]) {
         MachineBasicBlock::iterator I = std::next(Insert->getIterator());
         // Skip all the PHI and debug instructions.
-        while (I != MBB.end() && (I->isPHI() || I->isDebugInstr()))
+        while (I != MBB.end() && (I->isPHI() || I->isDebugOrPseudoInstr()))
           I = std::next(I);
         if (I == MI.getIterator())
           continue;

lib/CodeGen/LiveVariables.cpp

@@ -497,7 +497,7 @@ void LiveVariables::UpdatePhysRegDefs(MachineInstr &MI,
 
 void LiveVariables::runOnInstr(MachineInstr &MI,
                                SmallVectorImpl<unsigned> &Defs) {
-  assert(!MI.isDebugInstr());
+  assert(!MI.isDebugOrPseudoInstr());
   // Process all of the operands of the instruction...
   unsigned NumOperandsToProcess = MI.getNumOperands();
 
@@ -572,7 +572,7 @@ void LiveVariables::runOnBlock(MachineBasicBlock *MBB, const unsigned NumRegs) {
   DistanceMap.clear();
   unsigned Dist = 0;
   for (MachineInstr &MI : *MBB) {
-    if (MI.isDebugInstr())
+    if (MI.isDebugOrPseudoInstr())
       continue;
     DistanceMap.insert(std::make_pair(&MI, Dist++));
 

lib/CodeGen/MachineBasicBlock.cpp

@@ -1515,7 +1515,7 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
   // Try searching forwards from Before, looking for reads or defs.
   const_iterator I(Before);
   for (; I != end() && N > 0; ++I) {
-    if (I->isDebugInstr())
+    if (I->isDebugOrPseudoInstr())
       continue;
 
     --N;
@@ -1553,7 +1553,7 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
     do {
       --I;
 
-      if (I->isDebugInstr())
+      if (I->isDebugOrPseudoInstr())
         continue;
 
       --N;
@@ -1587,7 +1587,7 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
 
   // If all the instructions before this in the block are debug instructions,
   // skip over them.
-  while (I != begin() && std::prev(I)->isDebugInstr())
+  while (I != begin() && std::prev(I)->isDebugOrPseudoInstr())
     --I;
 
   // Did we get to the start of the block?

lib/CodeGen/MachineScheduler.cpp

@@ -297,7 +297,7 @@ priorNonDebug(MachineBasicBlock::const_iterator I,
               MachineBasicBlock::const_iterator Beg) {
   assert(I != Beg && "reached the top of the region, cannot decrement");
   while (--I != Beg) {
-    if (!I->isDebugInstr())
+    if (!I->isDebugOrPseudoInstr())
       break;
   }
   return I;
@@ -317,7 +317,7 @@ static MachineBasicBlock::const_iterator
 nextIfDebug(MachineBasicBlock::const_iterator I,
             MachineBasicBlock::const_iterator End) {
   for(; I != End; ++I) {
-    if (!I->isDebugInstr())
+    if (!I->isDebugOrPseudoInstr())
       break;
   }
   return I;
@@ -508,7 +508,7 @@ getSchedRegions(MachineBasicBlock *MBB,
       MachineInstr &MI = *std::prev(I);
       if (isSchedBoundary(&MI, &*MBB, MF, TII))
         break;
-      if (!MI.isDebugInstr()) {
+      if (!MI.isDebugOrPseudoInstr()) {
         // MBB::size() uses instr_iterator to count. Here we need a bundle to
         // count as a single instruction.
         ++NumRegionInstrs;

lib/CodeGen/MachineSink.cpp

@@ -530,7 +530,7 @@ bool MachineSinking::ProcessBlock(MachineBasicBlock &MBB) {
     if (!ProcessedBegin)
       --I;
 
-    if (MI.isDebugInstr()) {
+    if (MI.isDebugOrPseudoInstr()) {
       if (MI.isDebugValue())
         ProcessDbgInst(MI);
       continue;
@@ -718,7 +718,7 @@ MachineSinking::getBBRegisterPressure(MachineBasicBlock &MBB) {
                                    MIE = MBB.instr_begin();
        MII != MIE; --MII) {
     MachineInstr &MI = *std::prev(MII);
-    if (MI.isDebugValue() || MI.isDebugLabel())
+    if (MI.isDebugValue() || MI.isDebugLabel() || MI.isPseudoProbe())
       continue;
     RegisterOperands RegOpers;
     RegOpers.collect(MI, *TRI, *MRI, false, false);
@@ -1755,7 +1755,7 @@ bool PostRAMachineSinking::tryToSinkCopy(MachineBasicBlock &CurBB,
       continue;
     }
 
-    if (MI->isDebugInstr())
+    if (MI->isDebugOrPseudoInstr())
       continue;
 
     // Do not move any instruction across function call.

lib/CodeGen/RegAllocGreedy.cpp

@@ -1315,7 +1315,8 @@ bool RAGreedy::addThroughConstraints(InterferenceCache::Cursor Intf,
     // Abort if the spill cannot be inserted at the MBB' start
     MachineBasicBlock *MBB = MF->getBlockNumbered(Number);
     if (!MBB->empty() &&
-        SlotIndex::isEarlierInstr(LIS->getInstructionIndex(MBB->instr_front()),
+        SlotIndex::isEarlierInstr(
+            LIS->getInstructionIndex(*MBB->getFirstNonDebugInstr()),
             SA->getFirstSplitPoint(Number)))
       return false;
     // Interference for the live-in value.

lib/CodeGen/RegisterCoalescer.cpp

@@ -2962,7 +2962,7 @@ taintExtent(unsigned ValNo, LaneBitmask TaintedLanes, JoinVals &Other,
 
 bool JoinVals::usesLanes(const MachineInstr &MI, Register Reg, unsigned SubIdx,
                          LaneBitmask Lanes) const {
-  if (MI.isDebugInstr())
+  if (MI.isDebugOrPseudoInstr())
     return false;
   for (const MachineOperand &MO : MI.operands()) {
     if (!MO.isReg() || MO.isDef() || MO.getReg() != Reg)
@@ -3607,7 +3607,7 @@ void RegisterCoalescer::buildVRegToDbgValueMap(MachineFunction &MF)
               return MO.isReg() && MO.getReg().isVirtual();
             }))
           ToInsert.push_back(&MI);
-      } else if (!MI.isDebugInstr()) {
+      } else if (!MI.isDebugOrPseudoInstr()) {
         CurrentSlot = Slots.getInstructionIndex(MI);
         CloseNewDVRange(CurrentSlot);
       }

lib/CodeGen/RegisterPressure.cpp

@@ -764,7 +764,7 @@ void RegPressureTracker::bumpDeadDefs(ArrayRef<RegisterMaskPair> DeadDefs) {
 /// instruction independent of liveness.
 void RegPressureTracker::recede(const RegisterOperands &RegOpers,
                                 SmallVectorImpl<RegisterMaskPair> *LiveUses) {
-  assert(!CurrPos->isDebugInstr());
+  assert(!CurrPos->isDebugOrPseudoInstr());
 
   // Boost pressure for all dead defs together.
   bumpDeadDefs(RegOpers.DeadDefs);
@@ -863,7 +863,7 @@ void RegPressureTracker::recedeSkipDebugValues() {
   CurrPos = prev_nodbg(CurrPos, MBB->begin());
 
   SlotIndex SlotIdx;
-  if (RequireIntervals && !CurrPos->isDebugInstr())
+  if (RequireIntervals && !CurrPos->isDebugOrPseudoInstr())
     SlotIdx = LIS->getInstructionIndex(*CurrPos).getRegSlot();
 
   // Open the top of the region using slot indexes.
@@ -873,9 +873,9 @@ void RegPressureTracker::recedeSkipDebugValues() {
 
 void RegPressureTracker::recede(SmallVectorImpl<RegisterMaskPair> *LiveUses) {
   recedeSkipDebugValues();
-  if (CurrPos->isDebugValue()) {
-    // It's possible to only have debug_value instructions and hit the start of
-    // the block.
+  if (CurrPos->isDebugValue() || CurrPos->isPseudoProbe()) {
+    // It's possible to only have debug_value and pseudo probe instructions and
+    // hit the start of the block.
     assert(CurrPos == MBB->begin());
     return;
   }
@@ -1041,7 +1041,7 @@ static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
 /// This is intended for speculative queries. It leaves pressure inconsistent
 /// with the current position, so must be restored by the caller.
 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
-  assert(!MI->isDebugInstr() && "Expect a nondebug instruction.");
+  assert(!MI->isDebugOrPseudoInstr() && "Expect a nondebug instruction.");
 
   SlotIndex SlotIdx;
   if (RequireIntervals)
@@ -1282,7 +1282,7 @@ LaneBitmask RegPressureTracker::getLiveThroughAt(Register RegUnit,
 /// This is intended for speculative queries. It leaves pressure inconsistent
 /// with the current position, so must be restored by the caller.
 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
-  assert(!MI->isDebugInstr() && "Expect a nondebug instruction.");
+  assert(!MI->isDebugOrPseudoInstr() && "Expect a nondebug instruction.");
 
   SlotIndex SlotIdx;
   if (RequireIntervals)

lib/CodeGen/RegisterScavenging.cpp

@@ -175,7 +175,7 @@ void RegScavenger::forward() {
     I.Restore = nullptr;
   }
 
-  if (MI.isDebugInstr())
+  if (MI.isDebugOrPseudoInstr())
     return;
 
   determineKillsAndDefs();
@@ -298,7 +298,7 @@ Register RegScavenger::findSurvivorReg(MachineBasicBlock::iterator StartMI,
 
   bool inVirtLiveRange = false;
   for (++MI; InstrLimit > 0 && MI != ME; ++MI, --InstrLimit) {
-    if (MI->isDebugInstr()) {
+    if (MI->isDebugOrPseudoInstr()) {
       ++InstrLimit; // Don't count debug instructions
       continue;
     }

lib/CodeGen/ScheduleDAGInstrs.cpp

@@ -514,7 +514,7 @@ void ScheduleDAGInstrs::addVRegDefDeps(SUnit *SU, unsigned OperIdx) {
 /// TODO: Handle ExitSU "uses" properly.
 void ScheduleDAGInstrs::addVRegUseDeps(SUnit *SU, unsigned OperIdx) {
   const MachineInstr *MI = SU->getInstr();
-  assert(!MI->isDebugInstr());
+  assert(!MI->isDebugOrPseudoInstr());
 
   const MachineOperand &MO = MI->getOperand(OperIdx);
   Register Reg = MO.getReg();
@@ -572,7 +572,7 @@ void ScheduleDAGInstrs::initSUnits() {
   SUnits.reserve(NumRegionInstrs);
 
   for (MachineInstr &MI : make_range(RegionBegin, RegionEnd)) {
-    if (MI.isDebugInstr())
+    if (MI.isDebugOrPseudoInstr())
       continue;
 
     SUnit *SU = newSUnit(&MI);
@@ -814,6 +814,9 @@ void ScheduleDAGInstrs::buildSchedGraph(AAResults *AA,
     if (MI.isDebugLabel())
       continue;
 
+    if (MI.isPseudoProbe())
+      continue;
+
     SUnit *SU = MISUnitMap[&MI];
     assert(SU && "No SUnit mapped to this MI");
 
@@ -1117,7 +1120,7 @@ void ScheduleDAGInstrs::fixupKills(MachineBasicBlock &MBB) {
 
   // Examine block from end to start...
   for (MachineInstr &MI : make_range(MBB.rbegin(), MBB.rend())) {
-    if (MI.isDebugInstr())
+    if (MI.isDebugOrPseudoInstr())
       continue;
 
     // Update liveness.  Registers that are defed but not used in this
@@ -1152,7 +1155,7 @@ void ScheduleDAGInstrs::fixupKills(MachineBasicBlock &MBB) {
       while (I->isBundledWithSucc())
         ++I;
       do {
-        if (!I->isDebugInstr())
+        if (!I->isDebugOrPseudoInstr())
           toggleKills(MRI, LiveRegs, *I, true);
         --I;
       } while (I != Bundle);

lib/CodeGen/SlotIndexes.cpp

@@ -83,7 +83,7 @@ bool SlotIndexes::runOnMachineFunction(MachineFunction &fn) {
     SlotIndex blockStartIndex(&indexList.back(), SlotIndex::Slot_Block);
 
     for (MachineInstr &MI : MBB) {
-      if (MI.isDebugInstr())
+      if (MI.isDebugOrPseudoInstr())
         continue;
 
       // Insert a store index for the instr.
@@ -241,7 +241,7 @@ void SlotIndexes::repairIndexesInRange(MachineBasicBlock *MBB,
   for (MachineBasicBlock::iterator I = End; I != Begin;) {
     --I;
     MachineInstr &MI = *I;
-    if (!MI.isDebugInstr() && mi2iMap.find(&MI) == mi2iMap.end())
+    if (!MI.isDebugOrPseudoInstr() && mi2iMap.find(&MI) == mi2iMap.end())
       insertMachineInstrInMaps(MI);
   }
 }

lib/CodeGen/SplitKit.cpp

@@ -819,7 +819,7 @@ void SplitEditor::removeBackCopies(SmallVectorImpl<VNInfo*> &Copies) {
     MachineBasicBlock::iterator MBBI(MI);
     bool AtBegin;
     do AtBegin = MBBI == MBB->begin();
-    while (!AtBegin && (--MBBI)->isDebugInstr());
+    while (!AtBegin && (--MBBI)->isDebugOrPseudoInstr());
 
     LLVM_DEBUG(dbgs() << "Removing " << Def << '\t' << *MI);
     LIS.removeVRegDefAt(*LI, Def);

test/Transforms/SampleProfile/pseudo-probe-slotindex.ll

@@ -0,0 +1,22 @@
+; REQUIRES: x86_64-linux
+; RUN: llc -print-after=slotindexes -stop-after=slotindexes -mtriple=x86_64-- %s -filetype=asm -o %t 2>&1 | FileCheck %s
+
+define void @foo(i32* %p) {
+  store i32 0, i32* %p
+  call void @llvm.pseudoprobe(i64 5116412291814990879, i64 1, i32 0, i64 -1)
+  store i32 0, i32* %p
+  ret void
+}
+
+;; Check the pseudo probe instruction isn't assigned a slot index.
+;CHECK: IR Dump {{.*}}
+;CHECK: # Machine code for function foo{{.*}}
+;CHECK: {{[0-9]+}}B  bb.0 (%ir-block.0)
+;CHECK: {{[0-9]+}}B	 %0:gr64 = COPY killed $rdi
+;CHECK: {{^}}        PSEUDO_PROBE 5116412291814990879
+;CHECK: {{[0-9]+}}B	 MOV32mi
+;CHECK: {{[0-9]+}}B	 RET 0
+
+declare void @llvm.pseudoprobe(i64, i64, i32, i64) #0
+
+attributes #0 = { inaccessiblememonly nounwind willreturn }