1 //===-- RegisterPressure.cpp - Dynamic Register Pressure ------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the RegisterPressure class which can be used to track
11 // MachineInstr level register pressure.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/CodeGen/RegisterPressure.h"
16 #include "llvm/CodeGen/LiveInterval.h"
17 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
18 #include "llvm/CodeGen/MachineRegisterInfo.h"
19 #include "llvm/CodeGen/RegisterClassInfo.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/raw_ostream.h"
25 /// Increase pressure for each pressure set provided by TargetRegisterInfo.
26 static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
28 unsigned Weight = PSetI.getWeight();
29 for (; PSetI.isValid(); ++PSetI)
30 CurrSetPressure[*PSetI] += Weight;
33 /// Decrease pressure for each pressure set provided by TargetRegisterInfo.
34 static void decreaseSetPressure(std::vector<unsigned> &CurrSetPressure,
36 unsigned Weight = PSetI.getWeight();
37 for (; PSetI.isValid(); ++PSetI) {
38 assert(CurrSetPressure[*PSetI] >= Weight && "register pressure underflow");
39 CurrSetPressure[*PSetI] -= Weight;
44 void llvm::dumpRegSetPressure(ArrayRef<unsigned> SetPressure,
45 const TargetRegisterInfo *TRI) {
47 for (unsigned i = 0, e = SetPressure.size(); i < e; ++i) {
48 if (SetPressure[i] != 0) {
49 dbgs() << TRI->getRegPressureSetName(i) << "=" << SetPressure[i] << '\n';
58 void RegisterPressure::dump(const TargetRegisterInfo *TRI) const {
59 dbgs() << "Max Pressure: ";
60 dumpRegSetPressure(MaxSetPressure, TRI);
61 dbgs() << "Live In: ";
62 for (unsigned i = 0, e = LiveInRegs.size(); i < e; ++i)
63 dbgs() << PrintVRegOrUnit(LiveInRegs[i], TRI) << " ";
65 dbgs() << "Live Out: ";
66 for (unsigned i = 0, e = LiveOutRegs.size(); i < e; ++i)
67 dbgs() << PrintVRegOrUnit(LiveOutRegs[i], TRI) << " ";
72 void RegPressureTracker::dump() const {
73 if (!isTopClosed() || !isBottomClosed()) {
74 dbgs() << "Curr Pressure: ";
75 dumpRegSetPressure(CurrSetPressure, TRI);
80 void PressureDiff::dump(const TargetRegisterInfo &TRI) const {
82 for (const PressureChange &Change : *this) {
83 if (!Change.isValid())
85 dbgs() << sep << TRI.getRegPressureSetName(Change.getPSet())
86 << " " << Change.getUnitInc();
92 /// Increase the current pressure as impacted by these registers and bump
93 /// the high water mark if needed.
94 void RegPressureTracker::increaseRegPressure(ArrayRef<unsigned> RegUnits) {
95 for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) {
96 PSetIterator PSetI = MRI->getPressureSets(RegUnits[i]);
97 unsigned Weight = PSetI.getWeight();
98 for (; PSetI.isValid(); ++PSetI) {
99 CurrSetPressure[*PSetI] += Weight;
100 if (CurrSetPressure[*PSetI] > P.MaxSetPressure[*PSetI]) {
101 P.MaxSetPressure[*PSetI] = CurrSetPressure[*PSetI];
107 /// Simply decrease the current pressure as impacted by these registers.
108 void RegPressureTracker::decreaseRegPressure(ArrayRef<unsigned> RegUnits) {
109 for (unsigned I = 0, E = RegUnits.size(); I != E; ++I)
110 decreaseSetPressure(CurrSetPressure, MRI->getPressureSets(RegUnits[I]));
113 /// Clear the result so it can be used for another round of pressure tracking.
114 void IntervalPressure::reset() {
115 TopIdx = BottomIdx = SlotIndex();
116 MaxSetPressure.clear();
121 /// Clear the result so it can be used for another round of pressure tracking.
122 void RegionPressure::reset() {
123 TopPos = BottomPos = MachineBasicBlock::const_iterator();
124 MaxSetPressure.clear();
129 /// If the current top is not less than or equal to the next index, open it.
130 /// We happen to need the SlotIndex for the next top for pressure update.
131 void IntervalPressure::openTop(SlotIndex NextTop) {
132 if (TopIdx <= NextTop)
134 TopIdx = SlotIndex();
138 /// If the current top is the previous instruction (before receding), open it.
139 void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
140 if (TopPos != PrevTop)
142 TopPos = MachineBasicBlock::const_iterator();
146 /// If the current bottom is not greater than the previous index, open it.
147 void IntervalPressure::openBottom(SlotIndex PrevBottom) {
148 if (BottomIdx > PrevBottom)
150 BottomIdx = SlotIndex();
154 /// If the current bottom is the previous instr (before advancing), open it.
155 void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
156 if (BottomPos != PrevBottom)
158 BottomPos = MachineBasicBlock::const_iterator();
162 void LiveRegSet::init(const MachineRegisterInfo &MRI) {
163 const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
164 unsigned NumRegUnits = TRI.getNumRegs();
165 unsigned NumVirtRegs = MRI.getNumVirtRegs();
166 Regs.setUniverse(NumRegUnits + NumVirtRegs);
167 this->NumRegUnits = NumRegUnits;
170 void LiveRegSet::clear() {
174 const LiveRange *RegPressureTracker::getLiveRange(unsigned Reg) const {
175 if (TargetRegisterInfo::isVirtualRegister(Reg))
176 return &LIS->getInterval(Reg);
177 return LIS->getCachedRegUnit(Reg);
180 void RegPressureTracker::reset() {
184 CurrSetPressure.clear();
185 LiveThruPressure.clear();
186 P.MaxSetPressure.clear();
188 if (RequireIntervals)
189 static_cast<IntervalPressure&>(P).reset();
191 static_cast<RegionPressure&>(P).reset();
197 /// Setup the RegPressureTracker.
199 /// TODO: Add support for pressure without LiveIntervals.
200 void RegPressureTracker::init(const MachineFunction *mf,
201 const RegisterClassInfo *rci,
202 const LiveIntervals *lis,
203 const MachineBasicBlock *mbb,
204 MachineBasicBlock::const_iterator pos,
205 bool ShouldTrackUntiedDefs)
210 TRI = MF->getSubtarget().getRegisterInfo();
212 MRI = &MF->getRegInfo();
214 TrackUntiedDefs = ShouldTrackUntiedDefs;
216 if (RequireIntervals) {
217 assert(lis && "IntervalPressure requires LiveIntervals");
222 CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
224 P.MaxSetPressure = CurrSetPressure;
228 UntiedDefs.setUniverse(MRI->getNumVirtRegs());
231 /// Does this pressure result have a valid top position and live ins.
232 bool RegPressureTracker::isTopClosed() const {
233 if (RequireIntervals)
234 return static_cast<IntervalPressure&>(P).TopIdx.isValid();
235 return (static_cast<RegionPressure&>(P).TopPos ==
236 MachineBasicBlock::const_iterator());
239 /// Does this pressure result have a valid bottom position and live outs.
240 bool RegPressureTracker::isBottomClosed() const {
241 if (RequireIntervals)
242 return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
243 return (static_cast<RegionPressure&>(P).BottomPos ==
244 MachineBasicBlock::const_iterator());
248 SlotIndex RegPressureTracker::getCurrSlot() const {
249 MachineBasicBlock::const_iterator IdxPos = CurrPos;
250 while (IdxPos != MBB->end() && IdxPos->isDebugValue())
252 if (IdxPos == MBB->end())
253 return LIS->getMBBEndIdx(MBB);
254 return LIS->getInstructionIndex(IdxPos).getRegSlot();
257 /// Set the boundary for the top of the region and summarize live ins.
258 void RegPressureTracker::closeTop() {
259 if (RequireIntervals)
260 static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
262 static_cast<RegionPressure&>(P).TopPos = CurrPos;
264 assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
265 P.LiveInRegs.reserve(LiveRegs.size());
266 LiveRegs.appendTo(P.LiveInRegs);
269 /// Set the boundary for the bottom of the region and summarize live outs.
270 void RegPressureTracker::closeBottom() {
271 if (RequireIntervals)
272 static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
274 static_cast<RegionPressure&>(P).BottomPos = CurrPos;
276 assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
277 P.LiveOutRegs.reserve(LiveRegs.size());
278 LiveRegs.appendTo(P.LiveOutRegs);
281 /// Finalize the region boundaries and record live ins and live outs.
282 void RegPressureTracker::closeRegion() {
283 if (!isTopClosed() && !isBottomClosed()) {
284 assert(LiveRegs.size() == 0 && "no region boundary");
287 if (!isBottomClosed())
289 else if (!isTopClosed())
291 // If both top and bottom are closed, do nothing.
294 /// The register tracker is unaware of global liveness so ignores normal
295 /// live-thru ranges. However, two-address or coalesced chains can also lead
296 /// to live ranges with no holes. Count these to inform heuristics that we
297 /// can never drop below this pressure.
298 void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
299 LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
300 assert(isBottomClosed() && "need bottom-up tracking to intialize.");
301 for (unsigned i = 0, e = P.LiveOutRegs.size(); i < e; ++i) {
302 unsigned Reg = P.LiveOutRegs[i];
303 if (TargetRegisterInfo::isVirtualRegister(Reg)
304 && !RPTracker.hasUntiedDef(Reg)) {
305 increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
310 /// \brief Convenient wrapper for checking membership in RegisterOperands.
311 /// (std::count() doesn't have an early exit).
312 static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
313 return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
317 /// Collect this instruction's unique uses and defs into SmallVectors for
318 /// processing defs and uses in order.
320 /// FIXME: always ignore tied opers
321 class RegisterOperands {
322 const TargetRegisterInfo *TRI;
323 const MachineRegisterInfo *MRI;
327 SmallVector<unsigned, 8> Uses;
328 SmallVector<unsigned, 8> Defs;
329 SmallVector<unsigned, 8> DeadDefs;
331 RegisterOperands(const TargetRegisterInfo *tri,
332 const MachineRegisterInfo *mri, bool ID = false):
333 TRI(tri), MRI(mri), IgnoreDead(ID) {}
335 /// Push this operand's register onto the correct vector.
336 void collect(const MachineOperand &MO) {
337 if (!MO.isReg() || !MO.getReg())
340 pushRegUnits(MO.getReg(), Uses);
344 pushRegUnits(MO.getReg(), DeadDefs);
347 pushRegUnits(MO.getReg(), Defs);
352 void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) {
353 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
354 if (containsReg(RegUnits, Reg))
356 RegUnits.push_back(Reg);
358 else if (MRI->isAllocatable(Reg)) {
359 for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) {
360 if (containsReg(RegUnits, *Units))
362 RegUnits.push_back(*Units);
369 /// Collect physical and virtual register operands.
370 static void collectOperands(const MachineInstr *MI,
371 RegisterOperands &RegOpers) {
372 for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
373 RegOpers.collect(*OperI);
375 // Remove redundant physreg dead defs.
376 SmallVectorImpl<unsigned>::iterator I =
377 std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
378 std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
379 RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
382 /// Initialize an array of N PressureDiffs.
383 void PressureDiffs::init(unsigned N) {
386 memset(PDiffArray, 0, N * sizeof(PressureDiff));
391 PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
394 /// Add a change in pressure to the pressure diff of a given instruction.
395 void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
396 const MachineRegisterInfo *MRI) {
397 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
398 int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
399 for (; PSetI.isValid(); ++PSetI) {
400 // Find an existing entry in the pressure diff for this PSet.
401 PressureDiff::iterator I = nonconst_begin(), E = nonconst_end();
402 for (; I != E && I->isValid(); ++I) {
403 if (I->getPSet() >= *PSetI)
406 // If all pressure sets are more constrained, skip the remaining PSets.
409 // Insert this PressureChange.
410 if (!I->isValid() || I->getPSet() != *PSetI) {
411 PressureChange PTmp = PressureChange(*PSetI);
412 for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
415 // Update the units for this pressure set.
416 unsigned NewUnitInc = I->getUnitInc() + Weight;
417 if (NewUnitInc != 0) {
418 I->setUnitInc(NewUnitInc);
421 PressureDiff::iterator J;
422 for (J = std::next(I); J != E && J->isValid(); ++J, ++I)
430 /// Record the pressure difference induced by the given operand list.
431 static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
432 const MachineRegisterInfo *MRI) {
433 assert(!PDiff.begin()->isValid() && "stale PDiff");
435 for (unsigned i = 0, e = RegOpers.Defs.size(); i != e; ++i)
436 PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
438 for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
439 PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
442 /// Force liveness of registers.
443 void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
444 for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
445 if (LiveRegs.insert(Regs[i]))
446 increaseRegPressure(Regs[i]);
450 /// Add Reg to the live in set and increase max pressure.
451 void RegPressureTracker::discoverLiveIn(unsigned Reg) {
452 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
453 if (containsReg(P.LiveInRegs, Reg))
456 // At live in discovery, unconditionally increase the high water mark.
457 P.LiveInRegs.push_back(Reg);
458 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
461 /// Add Reg to the live out set and increase max pressure.
462 void RegPressureTracker::discoverLiveOut(unsigned Reg) {
463 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
464 if (containsReg(P.LiveOutRegs, Reg))
467 // At live out discovery, unconditionally increase the high water mark.
468 P.LiveOutRegs.push_back(Reg);
469 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
472 /// Recede across the previous instruction. If LiveUses is provided, record any
473 /// RegUnits that are made live by the current instruction's uses. This includes
474 /// registers that are both defined and used by the instruction. If a pressure
475 /// difference pointer is provided record the changes is pressure caused by this
476 /// instruction independent of liveness.
477 bool RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
478 PressureDiff *PDiff) {
479 // Check for the top of the analyzable region.
480 if (CurrPos == MBB->begin()) {
484 if (!isBottomClosed())
487 // Open the top of the region using block iterators.
488 if (!RequireIntervals && isTopClosed())
489 static_cast<RegionPressure&>(P).openTop(CurrPos);
491 // Find the previous instruction.
494 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
496 if (CurrPos->isDebugValue()) {
501 if (RequireIntervals)
502 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
504 // Open the top of the region using slot indexes.
505 if (RequireIntervals && isTopClosed())
506 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
508 RegisterOperands RegOpers(TRI, MRI);
509 collectOperands(CurrPos, RegOpers);
512 collectPDiff(*PDiff, RegOpers, MRI);
514 // Boost pressure for all dead defs together.
515 increaseRegPressure(RegOpers.DeadDefs);
516 decreaseRegPressure(RegOpers.DeadDefs);
518 // Kill liveness at live defs.
519 // TODO: consider earlyclobbers?
520 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
521 unsigned Reg = RegOpers.Defs[i];
522 bool DeadDef = false;
523 if (RequireIntervals) {
524 const LiveRange *LR = getLiveRange(Reg);
526 LiveQueryResult LRQ = LR->Query(SlotIdx);
527 DeadDef = LRQ.isDeadDef();
531 // LiveIntervals knows this is a dead even though it's MachineOperand is
532 // not flagged as such. Since this register will not be recorded as
533 // live-out, increase its PDiff value to avoid underflowing pressure.
535 PDiff->addPressureChange(Reg, false, MRI);
537 if (LiveRegs.erase(Reg))
538 decreaseRegPressure(Reg);
540 discoverLiveOut(Reg);
544 // Generate liveness for uses.
545 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
546 unsigned Reg = RegOpers.Uses[i];
547 if (!LiveRegs.contains(Reg)) {
548 // Adjust liveouts if LiveIntervals are available.
549 if (RequireIntervals) {
550 const LiveRange *LR = getLiveRange(Reg);
552 LiveQueryResult LRQ = LR->Query(SlotIdx);
553 if (!LRQ.isKill() && !LRQ.valueDefined())
554 discoverLiveOut(Reg);
557 increaseRegPressure(Reg);
558 LiveRegs.insert(Reg);
559 if (LiveUses && !containsReg(*LiveUses, Reg))
560 LiveUses->push_back(Reg);
563 if (TrackUntiedDefs) {
564 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
565 unsigned Reg = RegOpers.Defs[i];
566 if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
567 UntiedDefs.insert(Reg);
573 /// Advance across the current instruction.
574 bool RegPressureTracker::advance() {
575 assert(!TrackUntiedDefs && "unsupported mode");
577 // Check for the bottom of the analyzable region.
578 if (CurrPos == MBB->end()) {
586 if (RequireIntervals)
587 SlotIdx = getCurrSlot();
589 // Open the bottom of the region using slot indexes.
590 if (isBottomClosed()) {
591 if (RequireIntervals)
592 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
594 static_cast<RegionPressure&>(P).openBottom(CurrPos);
597 RegisterOperands RegOpers(TRI, MRI);
598 collectOperands(CurrPos, RegOpers);
600 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
601 unsigned Reg = RegOpers.Uses[i];
602 // Discover live-ins.
603 bool isLive = LiveRegs.contains(Reg);
606 // Kill liveness at last uses.
607 bool lastUse = false;
608 if (RequireIntervals) {
609 const LiveRange *LR = getLiveRange(Reg);
610 lastUse = LR && LR->Query(SlotIdx).isKill();
613 // Allocatable physregs are always single-use before register rewriting.
614 lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
616 if (lastUse && isLive) {
618 decreaseRegPressure(Reg);
620 else if (!lastUse && !isLive)
621 increaseRegPressure(Reg);
624 // Generate liveness for defs.
625 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
626 unsigned Reg = RegOpers.Defs[i];
627 if (LiveRegs.insert(Reg))
628 increaseRegPressure(Reg);
631 // Boost pressure for all dead defs together.
632 increaseRegPressure(RegOpers.DeadDefs);
633 decreaseRegPressure(RegOpers.DeadDefs);
635 // Find the next instruction.
638 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
642 /// Find the max change in excess pressure across all sets.
643 static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
644 ArrayRef<unsigned> NewPressureVec,
645 RegPressureDelta &Delta,
646 const RegisterClassInfo *RCI,
647 ArrayRef<unsigned> LiveThruPressureVec) {
648 Delta.Excess = PressureChange();
649 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
650 unsigned POld = OldPressureVec[i];
651 unsigned PNew = NewPressureVec[i];
652 int PDiff = (int)PNew - (int)POld;
653 if (!PDiff) // No change in this set in the common case.
655 // Only consider change beyond the limit.
656 unsigned Limit = RCI->getRegPressureSetLimit(i);
657 if (!LiveThruPressureVec.empty())
658 Limit += LiveThruPressureVec[i];
662 PDiff = 0; // Under the limit
664 PDiff = PNew - Limit; // Just exceeded limit.
666 else if (Limit > PNew)
667 PDiff = Limit - POld; // Just obeyed limit.
670 Delta.Excess = PressureChange(i);
671 Delta.Excess.setUnitInc(PDiff);
677 /// Find the max change in max pressure that either surpasses a critical PSet
678 /// limit or exceeds the current MaxPressureLimit.
680 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
681 /// silly. It's done now to demonstrate the concept but will go away with a
682 /// RegPressureTracker API change to work with pressure differences.
683 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
684 ArrayRef<unsigned> NewMaxPressureVec,
685 ArrayRef<PressureChange> CriticalPSets,
686 ArrayRef<unsigned> MaxPressureLimit,
687 RegPressureDelta &Delta) {
688 Delta.CriticalMax = PressureChange();
689 Delta.CurrentMax = PressureChange();
691 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
692 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
693 unsigned POld = OldMaxPressureVec[i];
694 unsigned PNew = NewMaxPressureVec[i];
695 if (PNew == POld) // No change in this set in the common case.
698 if (!Delta.CriticalMax.isValid()) {
699 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
702 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
703 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
705 Delta.CriticalMax = PressureChange(i);
706 Delta.CriticalMax.setUnitInc(PDiff);
710 // Find the first increase above MaxPressureLimit.
711 // (Ignores negative MDiff).
712 if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
713 Delta.CurrentMax = PressureChange(i);
714 Delta.CurrentMax.setUnitInc(PNew - POld);
715 if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
721 /// Record the upward impact of a single instruction on current register
722 /// pressure. Unlike the advance/recede pressure tracking interface, this does
723 /// not discover live in/outs.
725 /// This is intended for speculative queries. It leaves pressure inconsistent
726 /// with the current position, so must be restored by the caller.
727 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
728 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
730 // Account for register pressure similar to RegPressureTracker::recede().
731 RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
732 collectOperands(MI, RegOpers);
734 // Boost max pressure for all dead defs together.
735 // Since CurrSetPressure and MaxSetPressure
736 increaseRegPressure(RegOpers.DeadDefs);
737 decreaseRegPressure(RegOpers.DeadDefs);
739 // Kill liveness at live defs.
740 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
741 unsigned Reg = RegOpers.Defs[i];
742 bool DeadDef = false;
743 if (RequireIntervals) {
744 const LiveRange *LR = getLiveRange(Reg);
746 SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
747 LiveQueryResult LRQ = LR->Query(SlotIdx);
748 DeadDef = LRQ.isDeadDef();
752 if (!containsReg(RegOpers.Uses, Reg))
753 decreaseRegPressure(Reg);
756 // Generate liveness for uses.
757 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
758 unsigned Reg = RegOpers.Uses[i];
759 if (!LiveRegs.contains(Reg))
760 increaseRegPressure(Reg);
764 /// Consider the pressure increase caused by traversing this instruction
765 /// bottom-up. Find the pressure set with the most change beyond its pressure
766 /// limit based on the tracker's current pressure, and return the change in
767 /// number of register units of that pressure set introduced by this
770 /// This assumes that the current LiveOut set is sufficient.
772 /// This is expensive for an on-the-fly query because it calls
773 /// bumpUpwardPressure to recompute the pressure sets based on current
774 /// liveness. This mainly exists to verify correctness, e.g. with
775 /// -verify-misched. getUpwardPressureDelta is the fast version of this query
776 /// that uses the per-SUnit cache of the PressureDiff.
777 void RegPressureTracker::
778 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
779 RegPressureDelta &Delta,
780 ArrayRef<PressureChange> CriticalPSets,
781 ArrayRef<unsigned> MaxPressureLimit) {
782 // Snapshot Pressure.
783 // FIXME: The snapshot heap space should persist. But I'm planning to
784 // summarize the pressure effect so we don't need to snapshot at all.
785 std::vector<unsigned> SavedPressure = CurrSetPressure;
786 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
788 bumpUpwardPressure(MI);
790 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
792 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
793 MaxPressureLimit, Delta);
794 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
795 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
797 // Restore the tracker's state.
798 P.MaxSetPressure.swap(SavedMaxPressure);
799 CurrSetPressure.swap(SavedPressure);
805 // Check if the alternate algorithm yields the same result.
806 RegPressureDelta Delta2;
807 getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
808 if (Delta != Delta2) {
811 dbgs() << "DELTA: " << *MI;
812 if (Delta.Excess.isValid())
813 dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
814 << " " << Delta.Excess.getUnitInc() << "\n";
815 if (Delta.CriticalMax.isValid())
816 dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
817 << " " << Delta.CriticalMax.getUnitInc() << "\n";
818 if (Delta.CurrentMax.isValid())
819 dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
820 << " " << Delta.CurrentMax.getUnitInc() << "\n";
821 if (Delta2.Excess.isValid())
822 dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
823 << " " << Delta2.Excess.getUnitInc() << "\n";
824 if (Delta2.CriticalMax.isValid())
825 dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
826 << " " << Delta2.CriticalMax.getUnitInc() << "\n";
827 if (Delta2.CurrentMax.isValid())
828 dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
829 << " " << Delta2.CurrentMax.getUnitInc() << "\n";
830 llvm_unreachable("RegP Delta Mismatch");
835 /// This is the fast version of querying register pressure that does not
836 /// directly depend on current liveness.
838 /// @param Delta captures information needed for heuristics.
840 /// @param CriticalPSets Are the pressure sets that are known to exceed some
841 /// limit within the region, not necessarily at the current position.
843 /// @param MaxPressureLimit Is the max pressure within the region, not
844 /// necessarily at the current position.
845 void RegPressureTracker::
846 getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
847 RegPressureDelta &Delta,
848 ArrayRef<PressureChange> CriticalPSets,
849 ArrayRef<unsigned> MaxPressureLimit) const {
850 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
851 for (PressureDiff::const_iterator
852 PDiffI = PDiff.begin(), PDiffE = PDiff.end();
853 PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
855 unsigned PSetID = PDiffI->getPSet();
856 unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
857 if (!LiveThruPressure.empty())
858 Limit += LiveThruPressure[PSetID];
860 unsigned POld = CurrSetPressure[PSetID];
861 unsigned MOld = P.MaxSetPressure[PSetID];
862 unsigned MNew = MOld;
863 // Ignore DeadDefs here because they aren't captured by PressureChange.
864 unsigned PNew = POld + PDiffI->getUnitInc();
865 assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld)
866 && "PSet overflow/underflow");
869 // Check if current pressure has exceeded the limit.
870 if (!Delta.Excess.isValid()) {
871 unsigned ExcessInc = 0;
873 ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
874 else if (POld > Limit)
875 ExcessInc = Limit - POld;
877 Delta.Excess = PressureChange(PSetID);
878 Delta.Excess.setUnitInc(ExcessInc);
881 // Check if max pressure has exceeded a critical pressure set max.
884 if (!Delta.CriticalMax.isValid()) {
885 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
888 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
889 int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
890 if (CritInc > 0 && CritInc <= INT16_MAX) {
891 Delta.CriticalMax = PressureChange(PSetID);
892 Delta.CriticalMax.setUnitInc(CritInc);
896 // Check if max pressure has exceeded the current max.
897 if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
898 Delta.CurrentMax = PressureChange(PSetID);
899 Delta.CurrentMax.setUnitInc(MNew - MOld);
904 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
905 static bool findUseBetween(unsigned Reg, SlotIndex PriorUseIdx,
906 SlotIndex NextUseIdx, const MachineRegisterInfo &MRI,
907 const LiveIntervals *LIS) {
908 for (const MachineInstr &MI : MRI.use_nodbg_instructions(Reg)) {
909 SlotIndex InstSlot = LIS->getInstructionIndex(&MI).getRegSlot();
910 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
916 /// Record the downward impact of a single instruction on current register
917 /// pressure. Unlike the advance/recede pressure tracking interface, this does
918 /// not discover live in/outs.
920 /// This is intended for speculative queries. It leaves pressure inconsistent
921 /// with the current position, so must be restored by the caller.
922 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
923 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
925 // Account for register pressure similar to RegPressureTracker::recede().
926 RegisterOperands RegOpers(TRI, MRI);
927 collectOperands(MI, RegOpers);
929 // Kill liveness at last uses. Assume allocatable physregs are single-use
930 // rather than checking LiveIntervals.
932 if (RequireIntervals)
933 SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
935 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
936 unsigned Reg = RegOpers.Uses[i];
937 if (RequireIntervals) {
938 // FIXME: allow the caller to pass in the list of vreg uses that remain
939 // to be bottom-scheduled to avoid searching uses at each query.
940 SlotIndex CurrIdx = getCurrSlot();
941 const LiveRange *LR = getLiveRange(Reg);
943 LiveQueryResult LRQ = LR->Query(SlotIdx);
944 if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, *MRI, LIS))
945 decreaseRegPressure(Reg);
948 else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
949 // Allocatable physregs are always single-use before register rewriting.
950 decreaseRegPressure(Reg);
954 // Generate liveness for defs.
955 increaseRegPressure(RegOpers.Defs);
957 // Boost pressure for all dead defs together.
958 increaseRegPressure(RegOpers.DeadDefs);
959 decreaseRegPressure(RegOpers.DeadDefs);
962 /// Consider the pressure increase caused by traversing this instruction
963 /// top-down. Find the register class with the most change in its pressure limit
964 /// based on the tracker's current pressure, and return the number of excess
965 /// register units of that pressure set introduced by this instruction.
967 /// This assumes that the current LiveIn set is sufficient.
969 /// This is expensive for an on-the-fly query because it calls
970 /// bumpDownwardPressure to recompute the pressure sets based on current
971 /// liveness. We don't yet have a fast version of downward pressure tracking
972 /// analogous to getUpwardPressureDelta.
973 void RegPressureTracker::
974 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
975 ArrayRef<PressureChange> CriticalPSets,
976 ArrayRef<unsigned> MaxPressureLimit) {
977 // Snapshot Pressure.
978 std::vector<unsigned> SavedPressure = CurrSetPressure;
979 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
981 bumpDownwardPressure(MI);
983 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
985 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
986 MaxPressureLimit, Delta);
987 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
988 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
990 // Restore the tracker's state.
991 P.MaxSetPressure.swap(SavedMaxPressure);
992 CurrSetPressure.swap(SavedPressure);
995 /// Get the pressure of each PSet after traversing this instruction bottom-up.
996 void RegPressureTracker::
997 getUpwardPressure(const MachineInstr *MI,
998 std::vector<unsigned> &PressureResult,
999 std::vector<unsigned> &MaxPressureResult) {
1000 // Snapshot pressure.
1001 PressureResult = CurrSetPressure;
1002 MaxPressureResult = P.MaxSetPressure;
1004 bumpUpwardPressure(MI);
1006 // Current pressure becomes the result. Restore current pressure.
1007 P.MaxSetPressure.swap(MaxPressureResult);
1008 CurrSetPressure.swap(PressureResult);
1011 /// Get the pressure of each PSet after traversing this instruction top-down.
1012 void RegPressureTracker::
1013 getDownwardPressure(const MachineInstr *MI,
1014 std::vector<unsigned> &PressureResult,
1015 std::vector<unsigned> &MaxPressureResult) {
1016 // Snapshot pressure.
1017 PressureResult = CurrSetPressure;
1018 MaxPressureResult = P.MaxSetPressure;
1020 bumpDownwardPressure(MI);
1022 // Current pressure becomes the result. Restore current pressure.
1023 P.MaxSetPressure.swap(MaxPressureResult);
1024 CurrSetPressure.swap(PressureResult);