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 Reg : LiveInRegs)
63 dbgs() << PrintVRegOrUnit(Reg, TRI) << " ";
65 dbgs() << "Live Out: ";
66 for (unsigned Reg : LiveOutRegs)
67 dbgs() << PrintVRegOrUnit(Reg, 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 RegUnit : RegUnits) {
96 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
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 RegUnit : RegUnits)
110 decreaseSetPressure(CurrSetPressure, MRI->getPressureSets(RegUnit));
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 Reg : P.LiveOutRegs) {
302 if (TargetRegisterInfo::isVirtualRegister(Reg)
303 && !RPTracker.hasUntiedDef(Reg)) {
304 increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
309 /// \brief Convenient wrapper for checking membership in RegisterOperands.
310 /// (std::count() doesn't have an early exit).
311 static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
312 return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
317 /// List of register defined and used by a machine instruction.
318 class RegisterOperands {
320 SmallVector<unsigned, 8> Uses;
321 SmallVector<unsigned, 8> Defs;
322 SmallVector<unsigned, 8> DeadDefs;
324 void collect(const MachineInstr &MI, const TargetRegisterInfo &TRI,
325 const MachineRegisterInfo &MRI, bool IgnoreDead = false);
328 /// Collect this instruction's unique uses and defs into SmallVectors for
329 /// processing defs and uses in order.
331 /// FIXME: always ignore tied opers
332 class RegisterOperandsCollector {
333 RegisterOperands &RegOpers;
334 const TargetRegisterInfo &TRI;
335 const MachineRegisterInfo &MRI;
338 RegisterOperandsCollector(RegisterOperands &RegOpers,
339 const TargetRegisterInfo &TRI,
340 const MachineRegisterInfo &MRI,
342 : RegOpers(RegOpers), TRI(TRI), MRI(MRI), IgnoreDead(IgnoreDead) {}
344 void collectInstr(const MachineInstr &MI) const {
345 for (ConstMIBundleOperands OperI(&MI); OperI.isValid(); ++OperI)
346 collectOperand(*OperI);
348 // Remove redundant physreg dead defs.
349 SmallVectorImpl<unsigned>::iterator I =
350 std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
351 std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
352 RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
355 /// Push this operand's register onto the correct vectors.
356 void collectOperand(const MachineOperand &MO) const {
357 if (!MO.isReg() || !MO.getReg())
359 unsigned Reg = MO.getReg();
361 pushRegUnits(Reg, RegOpers.Uses);
365 pushRegUnits(Reg, RegOpers.DeadDefs);
367 pushRegUnits(Reg, RegOpers.Defs);
371 void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) const {
372 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
373 if (containsReg(RegUnits, Reg))
375 RegUnits.push_back(Reg);
376 } else if (MRI.isAllocatable(Reg)) {
377 for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units) {
378 if (containsReg(RegUnits, *Units))
380 RegUnits.push_back(*Units);
385 friend class RegisterOperands;
388 void RegisterOperands::collect(const MachineInstr &MI,
389 const TargetRegisterInfo &TRI,
390 const MachineRegisterInfo &MRI,
392 RegisterOperandsCollector Collector(*this, TRI, MRI, IgnoreDead);
393 Collector.collectInstr(MI);
398 /// Initialize an array of N PressureDiffs.
399 void PressureDiffs::init(unsigned N) {
402 memset(PDiffArray, 0, N * sizeof(PressureDiff));
407 PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
410 /// Add a change in pressure to the pressure diff of a given instruction.
411 void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
412 const MachineRegisterInfo *MRI) {
413 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
414 int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
415 for (; PSetI.isValid(); ++PSetI) {
416 // Find an existing entry in the pressure diff for this PSet.
417 PressureDiff::iterator I = nonconst_begin(), E = nonconst_end();
418 for (; I != E && I->isValid(); ++I) {
419 if (I->getPSet() >= *PSetI)
422 // If all pressure sets are more constrained, skip the remaining PSets.
425 // Insert this PressureChange.
426 if (!I->isValid() || I->getPSet() != *PSetI) {
427 PressureChange PTmp = PressureChange(*PSetI);
428 for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
431 // Update the units for this pressure set.
432 unsigned NewUnitInc = I->getUnitInc() + Weight;
433 if (NewUnitInc != 0) {
434 I->setUnitInc(NewUnitInc);
437 PressureDiff::iterator J;
438 for (J = std::next(I); J != E && J->isValid(); ++J, ++I)
446 /// Record the pressure difference induced by the given operand list.
447 static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
448 const MachineRegisterInfo *MRI) {
449 assert(!PDiff.begin()->isValid() && "stale PDiff");
451 for (unsigned Reg : RegOpers.Defs)
452 PDiff.addPressureChange(Reg, true, MRI);
454 for (unsigned Reg : RegOpers.Uses)
455 PDiff.addPressureChange(Reg, false, MRI);
458 /// Force liveness of registers.
459 void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
460 for (unsigned Reg : Regs) {
461 if (LiveRegs.insert(Reg))
462 increaseRegPressure(Reg);
466 /// Add Reg to the live in set and increase max pressure.
467 void RegPressureTracker::discoverLiveIn(unsigned Reg) {
468 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
469 if (containsReg(P.LiveInRegs, Reg))
472 // At live in discovery, unconditionally increase the high water mark.
473 P.LiveInRegs.push_back(Reg);
474 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
477 /// Add Reg to the live out set and increase max pressure.
478 void RegPressureTracker::discoverLiveOut(unsigned Reg) {
479 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
480 if (containsReg(P.LiveOutRegs, Reg))
483 // At live out discovery, unconditionally increase the high water mark.
484 P.LiveOutRegs.push_back(Reg);
485 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
488 /// Recede across the previous instruction. If LiveUses is provided, record any
489 /// RegUnits that are made live by the current instruction's uses. This includes
490 /// registers that are both defined and used by the instruction. If a pressure
491 /// difference pointer is provided record the changes is pressure caused by this
492 /// instruction independent of liveness.
493 void RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
494 PressureDiff *PDiff) {
495 assert(CurrPos != MBB->begin());
496 if (!isBottomClosed())
499 // Open the top of the region using block iterators.
500 if (!RequireIntervals && isTopClosed())
501 static_cast<RegionPressure&>(P).openTop(CurrPos);
503 // Find the previous instruction.
506 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
507 assert(!CurrPos->isDebugValue());
510 if (RequireIntervals)
511 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
513 // Open the top of the region using slot indexes.
514 if (RequireIntervals && isTopClosed())
515 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
517 RegisterOperands RegOpers;
518 RegOpers.collect(*CurrPos, *TRI, *MRI);
521 collectPDiff(*PDiff, RegOpers, MRI);
523 // Boost pressure for all dead defs together.
524 increaseRegPressure(RegOpers.DeadDefs);
525 decreaseRegPressure(RegOpers.DeadDefs);
527 // Kill liveness at live defs.
528 // TODO: consider earlyclobbers?
529 for (unsigned Reg : RegOpers.Defs) {
530 bool DeadDef = false;
531 if (RequireIntervals) {
532 const LiveRange *LR = getLiveRange(Reg);
534 LiveQueryResult LRQ = LR->Query(SlotIdx);
535 DeadDef = LRQ.isDeadDef();
539 // LiveIntervals knows this is a dead even though it's MachineOperand is
540 // not flagged as such. Since this register will not be recorded as
541 // live-out, increase its PDiff value to avoid underflowing pressure.
543 PDiff->addPressureChange(Reg, false, MRI);
545 if (LiveRegs.erase(Reg))
546 decreaseRegPressure(Reg);
548 discoverLiveOut(Reg);
552 // Generate liveness for uses.
553 for (unsigned Reg : RegOpers.Uses) {
554 if (!LiveRegs.contains(Reg)) {
555 // Adjust liveouts if LiveIntervals are available.
556 if (RequireIntervals) {
557 const LiveRange *LR = getLiveRange(Reg);
559 LiveQueryResult LRQ = LR->Query(SlotIdx);
560 if (!LRQ.isKill() && !LRQ.valueDefined())
561 discoverLiveOut(Reg);
564 increaseRegPressure(Reg);
565 LiveRegs.insert(Reg);
566 if (LiveUses && !containsReg(*LiveUses, Reg))
567 LiveUses->push_back(Reg);
570 if (TrackUntiedDefs) {
571 for (unsigned Reg : RegOpers.Defs) {
572 if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
573 UntiedDefs.insert(Reg);
578 /// Advance across the current instruction.
579 void RegPressureTracker::advance() {
580 assert(!TrackUntiedDefs && "unsupported mode");
582 assert(CurrPos != MBB->end());
587 if (RequireIntervals)
588 SlotIdx = getCurrSlot();
590 // Open the bottom of the region using slot indexes.
591 if (isBottomClosed()) {
592 if (RequireIntervals)
593 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
595 static_cast<RegionPressure&>(P).openBottom(CurrPos);
598 RegisterOperands RegOpers;
599 RegOpers.collect(*CurrPos, *TRI, *MRI);
601 for (unsigned Reg : RegOpers.Uses) {
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();
612 // Allocatable physregs are always single-use before register rewriting.
613 lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
615 if (lastUse && isLive) {
617 decreaseRegPressure(Reg);
618 } else if (!lastUse && !isLive)
619 increaseRegPressure(Reg);
622 // Generate liveness for defs.
623 for (unsigned Reg : RegOpers.Defs) {
624 if (LiveRegs.insert(Reg))
625 increaseRegPressure(Reg);
628 // Boost pressure for all dead defs together.
629 increaseRegPressure(RegOpers.DeadDefs);
630 decreaseRegPressure(RegOpers.DeadDefs);
632 // Find the next instruction.
635 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
638 /// Find the max change in excess pressure across all sets.
639 static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
640 ArrayRef<unsigned> NewPressureVec,
641 RegPressureDelta &Delta,
642 const RegisterClassInfo *RCI,
643 ArrayRef<unsigned> LiveThruPressureVec) {
644 Delta.Excess = PressureChange();
645 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
646 unsigned POld = OldPressureVec[i];
647 unsigned PNew = NewPressureVec[i];
648 int PDiff = (int)PNew - (int)POld;
649 if (!PDiff) // No change in this set in the common case.
651 // Only consider change beyond the limit.
652 unsigned Limit = RCI->getRegPressureSetLimit(i);
653 if (!LiveThruPressureVec.empty())
654 Limit += LiveThruPressureVec[i];
658 PDiff = 0; // Under the limit
660 PDiff = PNew - Limit; // Just exceeded limit.
661 } else if (Limit > PNew)
662 PDiff = Limit - POld; // Just obeyed limit.
665 Delta.Excess = PressureChange(i);
666 Delta.Excess.setUnitInc(PDiff);
672 /// Find the max change in max pressure that either surpasses a critical PSet
673 /// limit or exceeds the current MaxPressureLimit.
675 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
676 /// silly. It's done now to demonstrate the concept but will go away with a
677 /// RegPressureTracker API change to work with pressure differences.
678 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
679 ArrayRef<unsigned> NewMaxPressureVec,
680 ArrayRef<PressureChange> CriticalPSets,
681 ArrayRef<unsigned> MaxPressureLimit,
682 RegPressureDelta &Delta) {
683 Delta.CriticalMax = PressureChange();
684 Delta.CurrentMax = PressureChange();
686 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
687 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
688 unsigned POld = OldMaxPressureVec[i];
689 unsigned PNew = NewMaxPressureVec[i];
690 if (PNew == POld) // No change in this set in the common case.
693 if (!Delta.CriticalMax.isValid()) {
694 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
697 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
698 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
700 Delta.CriticalMax = PressureChange(i);
701 Delta.CriticalMax.setUnitInc(PDiff);
705 // Find the first increase above MaxPressureLimit.
706 // (Ignores negative MDiff).
707 if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
708 Delta.CurrentMax = PressureChange(i);
709 Delta.CurrentMax.setUnitInc(PNew - POld);
710 if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
716 /// Record the upward impact of a single instruction on current register
717 /// pressure. Unlike the advance/recede pressure tracking interface, this does
718 /// not discover live in/outs.
720 /// This is intended for speculative queries. It leaves pressure inconsistent
721 /// with the current position, so must be restored by the caller.
722 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
723 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
725 // Account for register pressure similar to RegPressureTracker::recede().
726 RegisterOperands RegOpers;
727 RegOpers.collect(*MI, *TRI, *MRI, /*IgnoreDead=*/true);
728 assert(RegOpers.DeadDefs.size() == 0);
730 // Kill liveness at live defs.
731 for (unsigned Reg : RegOpers.Defs) {
732 bool DeadDef = false;
733 if (RequireIntervals) {
734 const LiveRange *LR = getLiveRange(Reg);
736 SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
737 LiveQueryResult LRQ = LR->Query(SlotIdx);
738 DeadDef = LRQ.isDeadDef();
742 if (!containsReg(RegOpers.Uses, Reg))
743 decreaseRegPressure(Reg);
746 // Generate liveness for uses.
747 for (unsigned Reg : RegOpers.Uses) {
748 if (!LiveRegs.contains(Reg))
749 increaseRegPressure(Reg);
753 /// Consider the pressure increase caused by traversing this instruction
754 /// bottom-up. Find the pressure set with the most change beyond its pressure
755 /// limit based on the tracker's current pressure, and return the change in
756 /// number of register units of that pressure set introduced by this
759 /// This assumes that the current LiveOut set is sufficient.
761 /// This is expensive for an on-the-fly query because it calls
762 /// bumpUpwardPressure to recompute the pressure sets based on current
763 /// liveness. This mainly exists to verify correctness, e.g. with
764 /// -verify-misched. getUpwardPressureDelta is the fast version of this query
765 /// that uses the per-SUnit cache of the PressureDiff.
766 void RegPressureTracker::
767 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
768 RegPressureDelta &Delta,
769 ArrayRef<PressureChange> CriticalPSets,
770 ArrayRef<unsigned> MaxPressureLimit) {
771 // Snapshot Pressure.
772 // FIXME: The snapshot heap space should persist. But I'm planning to
773 // summarize the pressure effect so we don't need to snapshot at all.
774 std::vector<unsigned> SavedPressure = CurrSetPressure;
775 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
777 bumpUpwardPressure(MI);
779 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
781 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
782 MaxPressureLimit, Delta);
783 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
784 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
786 // Restore the tracker's state.
787 P.MaxSetPressure.swap(SavedMaxPressure);
788 CurrSetPressure.swap(SavedPressure);
794 // Check if the alternate algorithm yields the same result.
795 RegPressureDelta Delta2;
796 getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
797 if (Delta != Delta2) {
800 dbgs() << "DELTA: " << *MI;
801 if (Delta.Excess.isValid())
802 dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
803 << " " << Delta.Excess.getUnitInc() << "\n";
804 if (Delta.CriticalMax.isValid())
805 dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
806 << " " << Delta.CriticalMax.getUnitInc() << "\n";
807 if (Delta.CurrentMax.isValid())
808 dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
809 << " " << Delta.CurrentMax.getUnitInc() << "\n";
810 if (Delta2.Excess.isValid())
811 dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
812 << " " << Delta2.Excess.getUnitInc() << "\n";
813 if (Delta2.CriticalMax.isValid())
814 dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
815 << " " << Delta2.CriticalMax.getUnitInc() << "\n";
816 if (Delta2.CurrentMax.isValid())
817 dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
818 << " " << Delta2.CurrentMax.getUnitInc() << "\n";
819 llvm_unreachable("RegP Delta Mismatch");
824 /// This is the fast version of querying register pressure that does not
825 /// directly depend on current liveness.
827 /// @param Delta captures information needed for heuristics.
829 /// @param CriticalPSets Are the pressure sets that are known to exceed some
830 /// limit within the region, not necessarily at the current position.
832 /// @param MaxPressureLimit Is the max pressure within the region, not
833 /// necessarily at the current position.
834 void RegPressureTracker::
835 getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
836 RegPressureDelta &Delta,
837 ArrayRef<PressureChange> CriticalPSets,
838 ArrayRef<unsigned> MaxPressureLimit) const {
839 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
840 for (PressureDiff::const_iterator
841 PDiffI = PDiff.begin(), PDiffE = PDiff.end();
842 PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
844 unsigned PSetID = PDiffI->getPSet();
845 unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
846 if (!LiveThruPressure.empty())
847 Limit += LiveThruPressure[PSetID];
849 unsigned POld = CurrSetPressure[PSetID];
850 unsigned MOld = P.MaxSetPressure[PSetID];
851 unsigned MNew = MOld;
852 // Ignore DeadDefs here because they aren't captured by PressureChange.
853 unsigned PNew = POld + PDiffI->getUnitInc();
854 assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld)
855 && "PSet overflow/underflow");
858 // Check if current pressure has exceeded the limit.
859 if (!Delta.Excess.isValid()) {
860 unsigned ExcessInc = 0;
862 ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
863 else if (POld > Limit)
864 ExcessInc = Limit - POld;
866 Delta.Excess = PressureChange(PSetID);
867 Delta.Excess.setUnitInc(ExcessInc);
870 // Check if max pressure has exceeded a critical pressure set max.
873 if (!Delta.CriticalMax.isValid()) {
874 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
877 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
878 int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
879 if (CritInc > 0 && CritInc <= INT16_MAX) {
880 Delta.CriticalMax = PressureChange(PSetID);
881 Delta.CriticalMax.setUnitInc(CritInc);
885 // Check if max pressure has exceeded the current max.
886 if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
887 Delta.CurrentMax = PressureChange(PSetID);
888 Delta.CurrentMax.setUnitInc(MNew - MOld);
893 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
894 static bool findUseBetween(unsigned Reg, SlotIndex PriorUseIdx,
895 SlotIndex NextUseIdx, const MachineRegisterInfo &MRI,
896 const LiveIntervals *LIS) {
897 for (const MachineInstr &MI : MRI.use_nodbg_instructions(Reg)) {
898 SlotIndex InstSlot = LIS->getInstructionIndex(&MI).getRegSlot();
899 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
905 /// Record the downward impact of a single instruction on current register
906 /// pressure. Unlike the advance/recede pressure tracking interface, this does
907 /// not discover live in/outs.
909 /// This is intended for speculative queries. It leaves pressure inconsistent
910 /// with the current position, so must be restored by the caller.
911 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
912 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
914 // Account for register pressure similar to RegPressureTracker::recede().
915 RegisterOperands RegOpers;
916 RegOpers.collect(*MI, *TRI, *MRI);
918 // Kill liveness at last uses. Assume allocatable physregs are single-use
919 // rather than checking LiveIntervals.
921 if (RequireIntervals)
922 SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
924 for (unsigned Reg : RegOpers.Uses) {
925 if (RequireIntervals) {
926 // FIXME: allow the caller to pass in the list of vreg uses that remain
927 // to be bottom-scheduled to avoid searching uses at each query.
928 SlotIndex CurrIdx = getCurrSlot();
929 const LiveRange *LR = getLiveRange(Reg);
931 LiveQueryResult LRQ = LR->Query(SlotIdx);
932 if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, *MRI, LIS))
933 decreaseRegPressure(Reg);
935 } else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
936 // Allocatable physregs are always single-use before register rewriting.
937 decreaseRegPressure(Reg);
941 // Generate liveness for defs.
942 increaseRegPressure(RegOpers.Defs);
944 // Boost pressure for all dead defs together.
945 increaseRegPressure(RegOpers.DeadDefs);
946 decreaseRegPressure(RegOpers.DeadDefs);
949 /// Consider the pressure increase caused by traversing this instruction
950 /// top-down. Find the register class with the most change in its pressure limit
951 /// based on the tracker's current pressure, and return the number of excess
952 /// register units of that pressure set introduced by this instruction.
954 /// This assumes that the current LiveIn set is sufficient.
956 /// This is expensive for an on-the-fly query because it calls
957 /// bumpDownwardPressure to recompute the pressure sets based on current
958 /// liveness. We don't yet have a fast version of downward pressure tracking
959 /// analogous to getUpwardPressureDelta.
960 void RegPressureTracker::
961 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
962 ArrayRef<PressureChange> CriticalPSets,
963 ArrayRef<unsigned> MaxPressureLimit) {
964 // Snapshot Pressure.
965 std::vector<unsigned> SavedPressure = CurrSetPressure;
966 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
968 bumpDownwardPressure(MI);
970 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
972 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
973 MaxPressureLimit, Delta);
974 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
975 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
977 // Restore the tracker's state.
978 P.MaxSetPressure.swap(SavedMaxPressure);
979 CurrSetPressure.swap(SavedPressure);
982 /// Get the pressure of each PSet after traversing this instruction bottom-up.
983 void RegPressureTracker::
984 getUpwardPressure(const MachineInstr *MI,
985 std::vector<unsigned> &PressureResult,
986 std::vector<unsigned> &MaxPressureResult) {
987 // Snapshot pressure.
988 PressureResult = CurrSetPressure;
989 MaxPressureResult = P.MaxSetPressure;
991 bumpUpwardPressure(MI);
993 // Current pressure becomes the result. Restore current pressure.
994 P.MaxSetPressure.swap(MaxPressureResult);
995 CurrSetPressure.swap(PressureResult);
998 /// Get the pressure of each PSet after traversing this instruction top-down.
999 void RegPressureTracker::
1000 getDownwardPressure(const MachineInstr *MI,
1001 std::vector<unsigned> &PressureResult,
1002 std::vector<unsigned> &MaxPressureResult) {
1003 // Snapshot pressure.
1004 PressureResult = CurrSetPressure;
1005 MaxPressureResult = P.MaxSetPressure;
1007 bumpDownwardPressure(MI);
1009 // Current pressure becomes the result. Restore current pressure.
1010 P.MaxSetPressure.swap(MaxPressureResult);
1011 CurrSetPressure.swap(PressureResult);