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();
318 /// List of register defined and used by a machine instruction.
319 class RegisterOperands {
321 SmallVector<unsigned, 8> Uses;
322 SmallVector<unsigned, 8> Defs;
323 SmallVector<unsigned, 8> DeadDefs;
325 void collect(const MachineInstr &MI, const TargetRegisterInfo &TRI,
326 const MachineRegisterInfo &MRI, bool IgnoreDead = false);
329 /// Collect this instruction's unique uses and defs into SmallVectors for
330 /// processing defs and uses in order.
332 /// FIXME: always ignore tied opers
333 class RegisterOperandsCollector {
334 RegisterOperands &RegOpers;
335 const TargetRegisterInfo &TRI;
336 const MachineRegisterInfo &MRI;
339 RegisterOperandsCollector(RegisterOperands &RegOpers,
340 const TargetRegisterInfo &TRI,
341 const MachineRegisterInfo &MRI,
343 : RegOpers(RegOpers), TRI(TRI), MRI(MRI), IgnoreDead(IgnoreDead) {}
345 void collectInstr(const MachineInstr &MI) const {
346 for (ConstMIBundleOperands OperI(&MI); OperI.isValid(); ++OperI)
347 collectOperand(*OperI);
349 // Remove redundant physreg dead defs.
350 SmallVectorImpl<unsigned>::iterator I =
351 std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
352 std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
353 RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
356 /// Push this operand's register onto the correct vectors.
357 void collectOperand(const MachineOperand &MO) const {
358 if (!MO.isReg() || !MO.getReg())
360 unsigned Reg = MO.getReg();
362 pushRegUnits(Reg, RegOpers.Uses);
366 pushRegUnits(Reg, RegOpers.DeadDefs);
368 pushRegUnits(Reg, RegOpers.Defs);
372 void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) const {
373 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
374 if (containsReg(RegUnits, Reg))
376 RegUnits.push_back(Reg);
377 } else if (MRI.isAllocatable(Reg)) {
378 for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units) {
379 if (containsReg(RegUnits, *Units))
381 RegUnits.push_back(*Units);
386 friend class RegisterOperands;
389 void RegisterOperands::collect(const MachineInstr &MI,
390 const TargetRegisterInfo &TRI,
391 const MachineRegisterInfo &MRI,
393 RegisterOperandsCollector Collector(*this, TRI, MRI, IgnoreDead);
394 Collector.collectInstr(MI);
399 /// Initialize an array of N PressureDiffs.
400 void PressureDiffs::init(unsigned N) {
403 memset(PDiffArray, 0, N * sizeof(PressureDiff));
408 PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
411 /// Add a change in pressure to the pressure diff of a given instruction.
412 void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
413 const MachineRegisterInfo *MRI) {
414 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
415 int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
416 for (; PSetI.isValid(); ++PSetI) {
417 // Find an existing entry in the pressure diff for this PSet.
418 PressureDiff::iterator I = nonconst_begin(), E = nonconst_end();
419 for (; I != E && I->isValid(); ++I) {
420 if (I->getPSet() >= *PSetI)
423 // If all pressure sets are more constrained, skip the remaining PSets.
426 // Insert this PressureChange.
427 if (!I->isValid() || I->getPSet() != *PSetI) {
428 PressureChange PTmp = PressureChange(*PSetI);
429 for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
432 // Update the units for this pressure set.
433 unsigned NewUnitInc = I->getUnitInc() + Weight;
434 if (NewUnitInc != 0) {
435 I->setUnitInc(NewUnitInc);
438 PressureDiff::iterator J;
439 for (J = std::next(I); J != E && J->isValid(); ++J, ++I)
447 /// Record the pressure difference induced by the given operand list.
448 static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
449 const MachineRegisterInfo *MRI) {
450 assert(!PDiff.begin()->isValid() && "stale PDiff");
452 for (unsigned i = 0, e = RegOpers.Defs.size(); i != e; ++i)
453 PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
455 for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
456 PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
459 /// Force liveness of registers.
460 void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
461 for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
462 if (LiveRegs.insert(Regs[i]))
463 increaseRegPressure(Regs[i]);
467 /// Add Reg to the live in set and increase max pressure.
468 void RegPressureTracker::discoverLiveIn(unsigned Reg) {
469 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
470 if (containsReg(P.LiveInRegs, Reg))
473 // At live in discovery, unconditionally increase the high water mark.
474 P.LiveInRegs.push_back(Reg);
475 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
478 /// Add Reg to the live out set and increase max pressure.
479 void RegPressureTracker::discoverLiveOut(unsigned Reg) {
480 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
481 if (containsReg(P.LiveOutRegs, Reg))
484 // At live out discovery, unconditionally increase the high water mark.
485 P.LiveOutRegs.push_back(Reg);
486 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
489 /// Recede across the previous instruction. If LiveUses is provided, record any
490 /// RegUnits that are made live by the current instruction's uses. This includes
491 /// registers that are both defined and used by the instruction. If a pressure
492 /// difference pointer is provided record the changes is pressure caused by this
493 /// instruction independent of liveness.
494 void RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
495 PressureDiff *PDiff) {
496 assert(CurrPos != MBB->begin());
497 if (!isBottomClosed())
500 // Open the top of the region using block iterators.
501 if (!RequireIntervals && isTopClosed())
502 static_cast<RegionPressure&>(P).openTop(CurrPos);
504 // Find the previous instruction.
507 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
508 assert(!CurrPos->isDebugValue());
511 if (RequireIntervals)
512 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
514 // Open the top of the region using slot indexes.
515 if (RequireIntervals && isTopClosed())
516 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
518 RegisterOperands RegOpers;
519 RegOpers.collect(*CurrPos, *TRI, *MRI);
522 collectPDiff(*PDiff, RegOpers, MRI);
524 // Boost pressure for all dead defs together.
525 increaseRegPressure(RegOpers.DeadDefs);
526 decreaseRegPressure(RegOpers.DeadDefs);
528 // Kill liveness at live defs.
529 // TODO: consider earlyclobbers?
530 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
531 unsigned Reg = RegOpers.Defs[i];
532 bool DeadDef = false;
533 if (RequireIntervals) {
534 const LiveRange *LR = getLiveRange(Reg);
536 LiveQueryResult LRQ = LR->Query(SlotIdx);
537 DeadDef = LRQ.isDeadDef();
541 // LiveIntervals knows this is a dead even though it's MachineOperand is
542 // not flagged as such. Since this register will not be recorded as
543 // live-out, increase its PDiff value to avoid underflowing pressure.
545 PDiff->addPressureChange(Reg, false, MRI);
547 if (LiveRegs.erase(Reg))
548 decreaseRegPressure(Reg);
550 discoverLiveOut(Reg);
554 // Generate liveness for uses.
555 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
556 unsigned Reg = RegOpers.Uses[i];
557 if (!LiveRegs.contains(Reg)) {
558 // Adjust liveouts if LiveIntervals are available.
559 if (RequireIntervals) {
560 const LiveRange *LR = getLiveRange(Reg);
562 LiveQueryResult LRQ = LR->Query(SlotIdx);
563 if (!LRQ.isKill() && !LRQ.valueDefined())
564 discoverLiveOut(Reg);
567 increaseRegPressure(Reg);
568 LiveRegs.insert(Reg);
569 if (LiveUses && !containsReg(*LiveUses, Reg))
570 LiveUses->push_back(Reg);
573 if (TrackUntiedDefs) {
574 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
575 unsigned Reg = RegOpers.Defs[i];
576 if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
577 UntiedDefs.insert(Reg);
582 /// Advance across the current instruction.
583 void RegPressureTracker::advance() {
584 assert(!TrackUntiedDefs && "unsupported mode");
586 assert(CurrPos != MBB->end());
591 if (RequireIntervals)
592 SlotIdx = getCurrSlot();
594 // Open the bottom of the region using slot indexes.
595 if (isBottomClosed()) {
596 if (RequireIntervals)
597 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
599 static_cast<RegionPressure&>(P).openBottom(CurrPos);
602 RegisterOperands RegOpers;
603 RegOpers.collect(*CurrPos, *TRI, *MRI);
605 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
606 unsigned Reg = RegOpers.Uses[i];
607 // Discover live-ins.
608 bool isLive = LiveRegs.contains(Reg);
611 // Kill liveness at last uses.
612 bool lastUse = false;
613 if (RequireIntervals) {
614 const LiveRange *LR = getLiveRange(Reg);
615 lastUse = LR && LR->Query(SlotIdx).isKill();
618 // Allocatable physregs are always single-use before register rewriting.
619 lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
621 if (lastUse && isLive) {
623 decreaseRegPressure(Reg);
625 else if (!lastUse && !isLive)
626 increaseRegPressure(Reg);
629 // Generate liveness for defs.
630 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
631 unsigned Reg = RegOpers.Defs[i];
632 if (LiveRegs.insert(Reg))
633 increaseRegPressure(Reg);
636 // Boost pressure for all dead defs together.
637 increaseRegPressure(RegOpers.DeadDefs);
638 decreaseRegPressure(RegOpers.DeadDefs);
640 // Find the next instruction.
643 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
646 /// Find the max change in excess pressure across all sets.
647 static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
648 ArrayRef<unsigned> NewPressureVec,
649 RegPressureDelta &Delta,
650 const RegisterClassInfo *RCI,
651 ArrayRef<unsigned> LiveThruPressureVec) {
652 Delta.Excess = PressureChange();
653 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
654 unsigned POld = OldPressureVec[i];
655 unsigned PNew = NewPressureVec[i];
656 int PDiff = (int)PNew - (int)POld;
657 if (!PDiff) // No change in this set in the common case.
659 // Only consider change beyond the limit.
660 unsigned Limit = RCI->getRegPressureSetLimit(i);
661 if (!LiveThruPressureVec.empty())
662 Limit += LiveThruPressureVec[i];
666 PDiff = 0; // Under the limit
668 PDiff = PNew - Limit; // Just exceeded limit.
670 else if (Limit > PNew)
671 PDiff = Limit - POld; // Just obeyed limit.
674 Delta.Excess = PressureChange(i);
675 Delta.Excess.setUnitInc(PDiff);
681 /// Find the max change in max pressure that either surpasses a critical PSet
682 /// limit or exceeds the current MaxPressureLimit.
684 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
685 /// silly. It's done now to demonstrate the concept but will go away with a
686 /// RegPressureTracker API change to work with pressure differences.
687 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
688 ArrayRef<unsigned> NewMaxPressureVec,
689 ArrayRef<PressureChange> CriticalPSets,
690 ArrayRef<unsigned> MaxPressureLimit,
691 RegPressureDelta &Delta) {
692 Delta.CriticalMax = PressureChange();
693 Delta.CurrentMax = PressureChange();
695 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
696 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
697 unsigned POld = OldMaxPressureVec[i];
698 unsigned PNew = NewMaxPressureVec[i];
699 if (PNew == POld) // No change in this set in the common case.
702 if (!Delta.CriticalMax.isValid()) {
703 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
706 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
707 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
709 Delta.CriticalMax = PressureChange(i);
710 Delta.CriticalMax.setUnitInc(PDiff);
714 // Find the first increase above MaxPressureLimit.
715 // (Ignores negative MDiff).
716 if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
717 Delta.CurrentMax = PressureChange(i);
718 Delta.CurrentMax.setUnitInc(PNew - POld);
719 if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
725 /// Record the upward impact of a single instruction on current register
726 /// pressure. Unlike the advance/recede pressure tracking interface, this does
727 /// not discover live in/outs.
729 /// This is intended for speculative queries. It leaves pressure inconsistent
730 /// with the current position, so must be restored by the caller.
731 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
732 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
734 // Account for register pressure similar to RegPressureTracker::recede().
735 RegisterOperands RegOpers;
736 RegOpers.collect(*MI, *TRI, *MRI, /*IgnoreDead=*/true);
738 // Boost max pressure for all dead defs together.
739 // Since CurrSetPressure and MaxSetPressure
740 increaseRegPressure(RegOpers.DeadDefs);
741 decreaseRegPressure(RegOpers.DeadDefs);
743 // Kill liveness at live defs.
744 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
745 unsigned Reg = RegOpers.Defs[i];
746 bool DeadDef = false;
747 if (RequireIntervals) {
748 const LiveRange *LR = getLiveRange(Reg);
750 SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
751 LiveQueryResult LRQ = LR->Query(SlotIdx);
752 DeadDef = LRQ.isDeadDef();
756 if (!containsReg(RegOpers.Uses, Reg))
757 decreaseRegPressure(Reg);
760 // Generate liveness for uses.
761 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
762 unsigned Reg = RegOpers.Uses[i];
763 if (!LiveRegs.contains(Reg))
764 increaseRegPressure(Reg);
768 /// Consider the pressure increase caused by traversing this instruction
769 /// bottom-up. Find the pressure set with the most change beyond its pressure
770 /// limit based on the tracker's current pressure, and return the change in
771 /// number of register units of that pressure set introduced by this
774 /// This assumes that the current LiveOut set is sufficient.
776 /// This is expensive for an on-the-fly query because it calls
777 /// bumpUpwardPressure to recompute the pressure sets based on current
778 /// liveness. This mainly exists to verify correctness, e.g. with
779 /// -verify-misched. getUpwardPressureDelta is the fast version of this query
780 /// that uses the per-SUnit cache of the PressureDiff.
781 void RegPressureTracker::
782 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
783 RegPressureDelta &Delta,
784 ArrayRef<PressureChange> CriticalPSets,
785 ArrayRef<unsigned> MaxPressureLimit) {
786 // Snapshot Pressure.
787 // FIXME: The snapshot heap space should persist. But I'm planning to
788 // summarize the pressure effect so we don't need to snapshot at all.
789 std::vector<unsigned> SavedPressure = CurrSetPressure;
790 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
792 bumpUpwardPressure(MI);
794 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
796 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
797 MaxPressureLimit, Delta);
798 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
799 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
801 // Restore the tracker's state.
802 P.MaxSetPressure.swap(SavedMaxPressure);
803 CurrSetPressure.swap(SavedPressure);
809 // Check if the alternate algorithm yields the same result.
810 RegPressureDelta Delta2;
811 getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
812 if (Delta != Delta2) {
815 dbgs() << "DELTA: " << *MI;
816 if (Delta.Excess.isValid())
817 dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
818 << " " << Delta.Excess.getUnitInc() << "\n";
819 if (Delta.CriticalMax.isValid())
820 dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
821 << " " << Delta.CriticalMax.getUnitInc() << "\n";
822 if (Delta.CurrentMax.isValid())
823 dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
824 << " " << Delta.CurrentMax.getUnitInc() << "\n";
825 if (Delta2.Excess.isValid())
826 dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
827 << " " << Delta2.Excess.getUnitInc() << "\n";
828 if (Delta2.CriticalMax.isValid())
829 dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
830 << " " << Delta2.CriticalMax.getUnitInc() << "\n";
831 if (Delta2.CurrentMax.isValid())
832 dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
833 << " " << Delta2.CurrentMax.getUnitInc() << "\n";
834 llvm_unreachable("RegP Delta Mismatch");
839 /// This is the fast version of querying register pressure that does not
840 /// directly depend on current liveness.
842 /// @param Delta captures information needed for heuristics.
844 /// @param CriticalPSets Are the pressure sets that are known to exceed some
845 /// limit within the region, not necessarily at the current position.
847 /// @param MaxPressureLimit Is the max pressure within the region, not
848 /// necessarily at the current position.
849 void RegPressureTracker::
850 getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
851 RegPressureDelta &Delta,
852 ArrayRef<PressureChange> CriticalPSets,
853 ArrayRef<unsigned> MaxPressureLimit) const {
854 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
855 for (PressureDiff::const_iterator
856 PDiffI = PDiff.begin(), PDiffE = PDiff.end();
857 PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
859 unsigned PSetID = PDiffI->getPSet();
860 unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
861 if (!LiveThruPressure.empty())
862 Limit += LiveThruPressure[PSetID];
864 unsigned POld = CurrSetPressure[PSetID];
865 unsigned MOld = P.MaxSetPressure[PSetID];
866 unsigned MNew = MOld;
867 // Ignore DeadDefs here because they aren't captured by PressureChange.
868 unsigned PNew = POld + PDiffI->getUnitInc();
869 assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld)
870 && "PSet overflow/underflow");
873 // Check if current pressure has exceeded the limit.
874 if (!Delta.Excess.isValid()) {
875 unsigned ExcessInc = 0;
877 ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
878 else if (POld > Limit)
879 ExcessInc = Limit - POld;
881 Delta.Excess = PressureChange(PSetID);
882 Delta.Excess.setUnitInc(ExcessInc);
885 // Check if max pressure has exceeded a critical pressure set max.
888 if (!Delta.CriticalMax.isValid()) {
889 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
892 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
893 int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
894 if (CritInc > 0 && CritInc <= INT16_MAX) {
895 Delta.CriticalMax = PressureChange(PSetID);
896 Delta.CriticalMax.setUnitInc(CritInc);
900 // Check if max pressure has exceeded the current max.
901 if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
902 Delta.CurrentMax = PressureChange(PSetID);
903 Delta.CurrentMax.setUnitInc(MNew - MOld);
908 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
909 static bool findUseBetween(unsigned Reg, SlotIndex PriorUseIdx,
910 SlotIndex NextUseIdx, const MachineRegisterInfo &MRI,
911 const LiveIntervals *LIS) {
912 for (const MachineInstr &MI : MRI.use_nodbg_instructions(Reg)) {
913 SlotIndex InstSlot = LIS->getInstructionIndex(&MI).getRegSlot();
914 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
920 /// Record the downward impact of a single instruction on current register
921 /// pressure. Unlike the advance/recede pressure tracking interface, this does
922 /// not discover live in/outs.
924 /// This is intended for speculative queries. It leaves pressure inconsistent
925 /// with the current position, so must be restored by the caller.
926 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
927 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
929 // Account for register pressure similar to RegPressureTracker::recede().
930 RegisterOperands RegOpers;
931 RegOpers.collect(*MI, *TRI, *MRI);
933 // Kill liveness at last uses. Assume allocatable physregs are single-use
934 // rather than checking LiveIntervals.
936 if (RequireIntervals)
937 SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
939 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
940 unsigned Reg = RegOpers.Uses[i];
941 if (RequireIntervals) {
942 // FIXME: allow the caller to pass in the list of vreg uses that remain
943 // to be bottom-scheduled to avoid searching uses at each query.
944 SlotIndex CurrIdx = getCurrSlot();
945 const LiveRange *LR = getLiveRange(Reg);
947 LiveQueryResult LRQ = LR->Query(SlotIdx);
948 if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, *MRI, LIS))
949 decreaseRegPressure(Reg);
952 else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
953 // Allocatable physregs are always single-use before register rewriting.
954 decreaseRegPressure(Reg);
958 // Generate liveness for defs.
959 increaseRegPressure(RegOpers.Defs);
961 // Boost pressure for all dead defs together.
962 increaseRegPressure(RegOpers.DeadDefs);
963 decreaseRegPressure(RegOpers.DeadDefs);
966 /// Consider the pressure increase caused by traversing this instruction
967 /// top-down. Find the register class with the most change in its pressure limit
968 /// based on the tracker's current pressure, and return the number of excess
969 /// register units of that pressure set introduced by this instruction.
971 /// This assumes that the current LiveIn set is sufficient.
973 /// This is expensive for an on-the-fly query because it calls
974 /// bumpDownwardPressure to recompute the pressure sets based on current
975 /// liveness. We don't yet have a fast version of downward pressure tracking
976 /// analogous to getUpwardPressureDelta.
977 void RegPressureTracker::
978 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
979 ArrayRef<PressureChange> CriticalPSets,
980 ArrayRef<unsigned> MaxPressureLimit) {
981 // Snapshot Pressure.
982 std::vector<unsigned> SavedPressure = CurrSetPressure;
983 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
985 bumpDownwardPressure(MI);
987 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
989 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
990 MaxPressureLimit, Delta);
991 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
992 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
994 // Restore the tracker's state.
995 P.MaxSetPressure.swap(SavedMaxPressure);
996 CurrSetPressure.swap(SavedPressure);
999 /// Get the pressure of each PSet after traversing this instruction bottom-up.
1000 void RegPressureTracker::
1001 getUpwardPressure(const MachineInstr *MI,
1002 std::vector<unsigned> &PressureResult,
1003 std::vector<unsigned> &MaxPressureResult) {
1004 // Snapshot pressure.
1005 PressureResult = CurrSetPressure;
1006 MaxPressureResult = P.MaxSetPressure;
1008 bumpUpwardPressure(MI);
1010 // Current pressure becomes the result. Restore current pressure.
1011 P.MaxSetPressure.swap(MaxPressureResult);
1012 CurrSetPressure.swap(PressureResult);
1015 /// Get the pressure of each PSet after traversing this instruction top-down.
1016 void RegPressureTracker::
1017 getDownwardPressure(const MachineInstr *MI,
1018 std::vector<unsigned> &PressureResult,
1019 std::vector<unsigned> &MaxPressureResult) {
1020 // Snapshot pressure.
1021 PressureResult = CurrSetPressure;
1022 MaxPressureResult = P.MaxSetPressure;
1024 bumpDownwardPressure(MI);
1026 // Current pressure becomes the result. Restore current pressure.
1027 P.MaxSetPressure.swap(MaxPressureResult);
1028 CurrSetPressure.swap(PressureResult);