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 {
81 for (const PressureChange &Change : *this) {
82 if (!Change.isValid())
84 dbgs() << " " << TRI.getRegPressureSetName(Change.getPSet())
85 << " " << Change.getUnitInc();
90 /// Increase the current pressure as impacted by these registers and bump
91 /// the high water mark if needed.
92 void RegPressureTracker::increaseRegPressure(ArrayRef<unsigned> RegUnits) {
93 for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) {
94 PSetIterator PSetI = MRI->getPressureSets(RegUnits[i]);
95 unsigned Weight = PSetI.getWeight();
96 for (; PSetI.isValid(); ++PSetI) {
97 CurrSetPressure[*PSetI] += Weight;
98 if (CurrSetPressure[*PSetI] > P.MaxSetPressure[*PSetI]) {
99 P.MaxSetPressure[*PSetI] = CurrSetPressure[*PSetI];
105 /// Simply decrease the current pressure as impacted by these registers.
106 void RegPressureTracker::decreaseRegPressure(ArrayRef<unsigned> RegUnits) {
107 for (unsigned I = 0, E = RegUnits.size(); I != E; ++I)
108 decreaseSetPressure(CurrSetPressure, MRI->getPressureSets(RegUnits[I]));
111 /// Clear the result so it can be used for another round of pressure tracking.
112 void IntervalPressure::reset() {
113 TopIdx = BottomIdx = SlotIndex();
114 MaxSetPressure.clear();
119 /// Clear the result so it can be used for another round of pressure tracking.
120 void RegionPressure::reset() {
121 TopPos = BottomPos = MachineBasicBlock::const_iterator();
122 MaxSetPressure.clear();
127 /// If the current top is not less than or equal to the next index, open it.
128 /// We happen to need the SlotIndex for the next top for pressure update.
129 void IntervalPressure::openTop(SlotIndex NextTop) {
130 if (TopIdx <= NextTop)
132 TopIdx = SlotIndex();
136 /// If the current top is the previous instruction (before receding), open it.
137 void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
138 if (TopPos != PrevTop)
140 TopPos = MachineBasicBlock::const_iterator();
144 /// If the current bottom is not greater than the previous index, open it.
145 void IntervalPressure::openBottom(SlotIndex PrevBottom) {
146 if (BottomIdx > PrevBottom)
148 BottomIdx = SlotIndex();
152 /// If the current bottom is the previous instr (before advancing), open it.
153 void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
154 if (BottomPos != PrevBottom)
156 BottomPos = MachineBasicBlock::const_iterator();
160 const LiveRange *RegPressureTracker::getLiveRange(unsigned Reg) const {
161 if (TargetRegisterInfo::isVirtualRegister(Reg))
162 return &LIS->getInterval(Reg);
163 return LIS->getCachedRegUnit(Reg);
166 void RegPressureTracker::reset() {
170 CurrSetPressure.clear();
171 LiveThruPressure.clear();
172 P.MaxSetPressure.clear();
174 if (RequireIntervals)
175 static_cast<IntervalPressure&>(P).reset();
177 static_cast<RegionPressure&>(P).reset();
179 LiveRegs.PhysRegs.clear();
180 LiveRegs.VirtRegs.clear();
184 /// Setup the RegPressureTracker.
186 /// TODO: Add support for pressure without LiveIntervals.
187 void RegPressureTracker::init(const MachineFunction *mf,
188 const RegisterClassInfo *rci,
189 const LiveIntervals *lis,
190 const MachineBasicBlock *mbb,
191 MachineBasicBlock::const_iterator pos,
192 bool ShouldTrackUntiedDefs)
197 TRI = MF->getSubtarget().getRegisterInfo();
199 MRI = &MF->getRegInfo();
201 TrackUntiedDefs = ShouldTrackUntiedDefs;
203 if (RequireIntervals) {
204 assert(lis && "IntervalPressure requires LiveIntervals");
209 CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
211 P.MaxSetPressure = CurrSetPressure;
213 LiveRegs.PhysRegs.setUniverse(TRI->getNumRegUnits());
214 LiveRegs.VirtRegs.setUniverse(MRI->getNumVirtRegs());
216 UntiedDefs.setUniverse(MRI->getNumVirtRegs());
219 /// Does this pressure result have a valid top position and live ins.
220 bool RegPressureTracker::isTopClosed() const {
221 if (RequireIntervals)
222 return static_cast<IntervalPressure&>(P).TopIdx.isValid();
223 return (static_cast<RegionPressure&>(P).TopPos ==
224 MachineBasicBlock::const_iterator());
227 /// Does this pressure result have a valid bottom position and live outs.
228 bool RegPressureTracker::isBottomClosed() const {
229 if (RequireIntervals)
230 return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
231 return (static_cast<RegionPressure&>(P).BottomPos ==
232 MachineBasicBlock::const_iterator());
236 SlotIndex RegPressureTracker::getCurrSlot() const {
237 MachineBasicBlock::const_iterator IdxPos = CurrPos;
238 while (IdxPos != MBB->end() && IdxPos->isDebugValue())
240 if (IdxPos == MBB->end())
241 return LIS->getMBBEndIdx(MBB);
242 return LIS->getInstructionIndex(IdxPos).getRegSlot();
245 /// Set the boundary for the top of the region and summarize live ins.
246 void RegPressureTracker::closeTop() {
247 if (RequireIntervals)
248 static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
250 static_cast<RegionPressure&>(P).TopPos = CurrPos;
252 assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
253 P.LiveInRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
254 P.LiveInRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
255 P.LiveInRegs.append(LiveRegs.VirtRegs.begin(), LiveRegs.VirtRegs.end());
258 /// Set the boundary for the bottom of the region and summarize live outs.
259 void RegPressureTracker::closeBottom() {
260 if (RequireIntervals)
261 static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
263 static_cast<RegionPressure&>(P).BottomPos = CurrPos;
265 assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
266 P.LiveOutRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
267 P.LiveOutRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
268 P.LiveOutRegs.append(LiveRegs.VirtRegs.begin(), LiveRegs.VirtRegs.end());
271 /// Finalize the region boundaries and record live ins and live outs.
272 void RegPressureTracker::closeRegion() {
273 if (!isTopClosed() && !isBottomClosed()) {
274 assert(LiveRegs.PhysRegs.empty() && LiveRegs.VirtRegs.empty() &&
275 "no region boundary");
278 if (!isBottomClosed())
280 else if (!isTopClosed())
282 // If both top and bottom are closed, do nothing.
285 /// The register tracker is unaware of global liveness so ignores normal
286 /// live-thru ranges. However, two-address or coalesced chains can also lead
287 /// to live ranges with no holes. Count these to inform heuristics that we
288 /// can never drop below this pressure.
289 void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
290 LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
291 assert(isBottomClosed() && "need bottom-up tracking to intialize.");
292 for (unsigned i = 0, e = P.LiveOutRegs.size(); i < e; ++i) {
293 unsigned Reg = P.LiveOutRegs[i];
294 if (TargetRegisterInfo::isVirtualRegister(Reg)
295 && !RPTracker.hasUntiedDef(Reg)) {
296 increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
301 /// \brief Convenient wrapper for checking membership in RegisterOperands.
302 /// (std::count() doesn't have an early exit).
303 static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
304 return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
308 /// Collect this instruction's unique uses and defs into SmallVectors for
309 /// processing defs and uses in order.
311 /// FIXME: always ignore tied opers
312 class RegisterOperands {
313 const TargetRegisterInfo *TRI;
314 const MachineRegisterInfo *MRI;
318 SmallVector<unsigned, 8> Uses;
319 SmallVector<unsigned, 8> Defs;
320 SmallVector<unsigned, 8> DeadDefs;
322 RegisterOperands(const TargetRegisterInfo *tri,
323 const MachineRegisterInfo *mri, bool ID = false):
324 TRI(tri), MRI(mri), IgnoreDead(ID) {}
326 /// Push this operand's register onto the correct vector.
327 void collect(const MachineOperand &MO) {
328 if (!MO.isReg() || !MO.getReg())
331 pushRegUnits(MO.getReg(), Uses);
335 pushRegUnits(MO.getReg(), DeadDefs);
338 pushRegUnits(MO.getReg(), Defs);
343 void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) {
344 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
345 if (containsReg(RegUnits, Reg))
347 RegUnits.push_back(Reg);
349 else if (MRI->isAllocatable(Reg)) {
350 for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) {
351 if (containsReg(RegUnits, *Units))
353 RegUnits.push_back(*Units);
360 /// Collect physical and virtual register operands.
361 static void collectOperands(const MachineInstr *MI,
362 RegisterOperands &RegOpers) {
363 for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
364 RegOpers.collect(*OperI);
366 // Remove redundant physreg dead defs.
367 SmallVectorImpl<unsigned>::iterator I =
368 std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
369 std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
370 RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
373 /// Initialize an array of N PressureDiffs.
374 void PressureDiffs::init(unsigned N) {
377 memset(PDiffArray, 0, N * sizeof(PressureDiff));
382 PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
385 /// Add a change in pressure to the pressure diff of a given instruction.
386 void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
387 const MachineRegisterInfo *MRI) {
388 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
389 int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
390 for (; PSetI.isValid(); ++PSetI) {
391 // Find an existing entry in the pressure diff for this PSet.
392 PressureDiff::iterator I = nonconst_begin(), E = nonconst_end();
393 for (; I != E && I->isValid(); ++I) {
394 if (I->getPSet() >= *PSetI)
397 // If all pressure sets are more constrained, skip the remaining PSets.
400 // Insert this PressureChange.
401 if (!I->isValid() || I->getPSet() != *PSetI) {
402 PressureChange PTmp = PressureChange(*PSetI);
403 for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
406 // Update the units for this pressure set.
407 unsigned NewUnitInc = I->getUnitInc() + Weight;
408 if (NewUnitInc != 0) {
409 I->setUnitInc(NewUnitInc);
412 PressureDiff::iterator J;
413 for (J = std::next(I); J != E && J->isValid(); ++J, ++I)
421 /// Record the pressure difference induced by the given operand list.
422 static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
423 const MachineRegisterInfo *MRI) {
424 assert(!PDiff.begin()->isValid() && "stale PDiff");
426 for (unsigned i = 0, e = RegOpers.Defs.size(); i != e; ++i)
427 PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
429 for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
430 PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
433 /// Force liveness of registers.
434 void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
435 for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
436 if (LiveRegs.insert(Regs[i]))
437 increaseRegPressure(Regs[i]);
441 /// Add Reg to the live in set and increase max pressure.
442 void RegPressureTracker::discoverLiveIn(unsigned Reg) {
443 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
444 if (containsReg(P.LiveInRegs, Reg))
447 // At live in discovery, unconditionally increase the high water mark.
448 P.LiveInRegs.push_back(Reg);
449 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
452 /// Add Reg to the live out set and increase max pressure.
453 void RegPressureTracker::discoverLiveOut(unsigned Reg) {
454 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
455 if (containsReg(P.LiveOutRegs, Reg))
458 // At live out discovery, unconditionally increase the high water mark.
459 P.LiveOutRegs.push_back(Reg);
460 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
463 /// Recede across the previous instruction. If LiveUses is provided, record any
464 /// RegUnits that are made live by the current instruction's uses. This includes
465 /// registers that are both defined and used by the instruction. If a pressure
466 /// difference pointer is provided record the changes is pressure caused by this
467 /// instruction independent of liveness.
468 bool RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
469 PressureDiff *PDiff) {
470 // Check for the top of the analyzable region.
471 if (CurrPos == MBB->begin()) {
475 if (!isBottomClosed())
478 // Open the top of the region using block iterators.
479 if (!RequireIntervals && isTopClosed())
480 static_cast<RegionPressure&>(P).openTop(CurrPos);
482 // Find the previous instruction.
485 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
487 if (CurrPos->isDebugValue()) {
492 if (RequireIntervals)
493 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
495 // Open the top of the region using slot indexes.
496 if (RequireIntervals && isTopClosed())
497 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
499 RegisterOperands RegOpers(TRI, MRI);
500 collectOperands(CurrPos, RegOpers);
503 collectPDiff(*PDiff, RegOpers, MRI);
505 // Boost pressure for all dead defs together.
506 increaseRegPressure(RegOpers.DeadDefs);
507 decreaseRegPressure(RegOpers.DeadDefs);
509 // Kill liveness at live defs.
510 // TODO: consider earlyclobbers?
511 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
512 unsigned Reg = RegOpers.Defs[i];
513 bool DeadDef = false;
514 if (RequireIntervals) {
515 const LiveRange *LR = getLiveRange(Reg);
517 LiveQueryResult LRQ = LR->Query(SlotIdx);
518 DeadDef = LRQ.isDeadDef();
522 // LiveIntervals knows this is a dead even though it's MachineOperand is
523 // not flagged as such. Since this register will not be recorded as
524 // live-out, increase its PDiff value to avoid underflowing pressure.
526 PDiff->addPressureChange(Reg, false, MRI);
528 if (LiveRegs.erase(Reg))
529 decreaseRegPressure(Reg);
531 discoverLiveOut(Reg);
535 // Generate liveness for uses.
536 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
537 unsigned Reg = RegOpers.Uses[i];
538 if (!LiveRegs.contains(Reg)) {
539 // Adjust liveouts if LiveIntervals are available.
540 if (RequireIntervals) {
541 const LiveRange *LR = getLiveRange(Reg);
543 LiveQueryResult LRQ = LR->Query(SlotIdx);
544 if (!LRQ.isKill() && !LRQ.valueDefined())
545 discoverLiveOut(Reg);
548 increaseRegPressure(Reg);
549 LiveRegs.insert(Reg);
550 if (LiveUses && !containsReg(*LiveUses, Reg))
551 LiveUses->push_back(Reg);
554 if (TrackUntiedDefs) {
555 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
556 unsigned Reg = RegOpers.Defs[i];
557 if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
558 UntiedDefs.insert(Reg);
564 bool RegPressureTracker::isLastUse(unsigned VRegOrUnit, SlotIndex Pos) const {
565 // Allocatable physregs are always single-use before register rewriting.
566 if (!TargetRegisterInfo::isVirtualRegister(VRegOrUnit))
568 // Without liveness information we conservatively assume "no last use".
569 if (!RequireIntervals)
571 const LiveRange *LR = getLiveRange(VRegOrUnit);
572 return LR && LR->Query(Pos).isKill();
575 /// Advance across the current instruction.
576 bool RegPressureTracker::advance() {
577 assert(!TrackUntiedDefs && "unsupported mode");
579 // Check for the bottom of the analyzable region.
580 if (CurrPos == MBB->end()) {
588 if (RequireIntervals)
589 SlotIdx = getCurrSlot();
591 // Open the bottom of the region using slot indexes.
592 if (isBottomClosed()) {
593 if (RequireIntervals)
594 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
596 static_cast<RegionPressure&>(P).openBottom(CurrPos);
599 RegisterOperands RegOpers(TRI, MRI);
600 collectOperands(CurrPos, RegOpers);
602 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
603 unsigned Reg = RegOpers.Uses[i];
604 // Discover live-ins.
605 bool isLive = LiveRegs.contains(Reg);
608 // Kill liveness at last uses.
609 if (isLastUse(Reg, SlotIdx)) {
612 decreaseRegPressure(Reg);
615 // We discovered a live which was not last used here, adjust pressure.
616 increaseRegPressure(Reg);
620 // Generate liveness for defs.
621 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
622 unsigned Reg = RegOpers.Defs[i];
623 if (LiveRegs.insert(Reg))
624 increaseRegPressure(Reg);
627 // Boost pressure for all dead defs together.
628 increaseRegPressure(RegOpers.DeadDefs);
629 decreaseRegPressure(RegOpers.DeadDefs);
631 // Find the next instruction.
634 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.
662 else if (Limit > PNew)
663 PDiff = Limit - POld; // Just obeyed limit.
666 Delta.Excess = PressureChange(i);
667 Delta.Excess.setUnitInc(PDiff);
673 /// Find the max change in max pressure that either surpasses a critical PSet
674 /// limit or exceeds the current MaxPressureLimit.
676 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
677 /// silly. It's done now to demonstrate the concept but will go away with a
678 /// RegPressureTracker API change to work with pressure differences.
679 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
680 ArrayRef<unsigned> NewMaxPressureVec,
681 ArrayRef<PressureChange> CriticalPSets,
682 ArrayRef<unsigned> MaxPressureLimit,
683 RegPressureDelta &Delta) {
684 Delta.CriticalMax = PressureChange();
685 Delta.CurrentMax = PressureChange();
687 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
688 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
689 unsigned POld = OldMaxPressureVec[i];
690 unsigned PNew = NewMaxPressureVec[i];
691 if (PNew == POld) // No change in this set in the common case.
694 if (!Delta.CriticalMax.isValid()) {
695 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
698 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
699 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
701 Delta.CriticalMax = PressureChange(i);
702 Delta.CriticalMax.setUnitInc(PDiff);
706 // Find the first increase above MaxPressureLimit.
707 // (Ignores negative MDiff).
708 if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
709 Delta.CurrentMax = PressureChange(i);
710 Delta.CurrentMax.setUnitInc(PNew - POld);
711 if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
717 /// Record the upward impact of a single instruction on current register
718 /// pressure. Unlike the advance/recede pressure tracking interface, this does
719 /// not discover live in/outs.
721 /// This is intended for speculative queries. It leaves pressure inconsistent
722 /// with the current position, so must be restored by the caller.
723 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
724 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
726 // Account for register pressure similar to RegPressureTracker::recede().
727 RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
728 collectOperands(MI, RegOpers);
730 // Boost max pressure for all dead defs together.
731 // Since CurrSetPressure and MaxSetPressure
732 increaseRegPressure(RegOpers.DeadDefs);
733 decreaseRegPressure(RegOpers.DeadDefs);
735 // Kill liveness at live defs.
736 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
737 unsigned Reg = RegOpers.Defs[i];
738 bool DeadDef = false;
739 if (RequireIntervals) {
740 const LiveRange *LR = getLiveRange(Reg);
742 SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
743 LiveQueryResult LRQ = LR->Query(SlotIdx);
744 DeadDef = LRQ.isDeadDef();
748 if (!containsReg(RegOpers.Uses, Reg))
749 decreaseRegPressure(Reg);
752 // Generate liveness for uses.
753 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
754 unsigned Reg = RegOpers.Uses[i];
755 if (!LiveRegs.contains(Reg))
756 increaseRegPressure(Reg);
760 /// Consider the pressure increase caused by traversing this instruction
761 /// bottom-up. Find the pressure set with the most change beyond its pressure
762 /// limit based on the tracker's current pressure, and return the change in
763 /// number of register units of that pressure set introduced by this
766 /// This assumes that the current LiveOut set is sufficient.
768 /// This is expensive for an on-the-fly query because it calls
769 /// bumpUpwardPressure to recompute the pressure sets based on current
770 /// liveness. This mainly exists to verify correctness, e.g. with
771 /// -verify-misched. getUpwardPressureDelta is the fast version of this query
772 /// that uses the per-SUnit cache of the PressureDiff.
773 void RegPressureTracker::
774 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
775 RegPressureDelta &Delta,
776 ArrayRef<PressureChange> CriticalPSets,
777 ArrayRef<unsigned> MaxPressureLimit) {
778 // Snapshot Pressure.
779 // FIXME: The snapshot heap space should persist. But I'm planning to
780 // summarize the pressure effect so we don't need to snapshot at all.
781 std::vector<unsigned> SavedPressure = CurrSetPressure;
782 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
784 bumpUpwardPressure(MI);
786 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
788 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
789 MaxPressureLimit, Delta);
790 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
791 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
793 // Restore the tracker's state.
794 P.MaxSetPressure.swap(SavedMaxPressure);
795 CurrSetPressure.swap(SavedPressure);
801 // Check if the alternate algorithm yields the same result.
802 RegPressureDelta Delta2;
803 getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
804 if (Delta != Delta2) {
807 dbgs() << "DELTA: " << *MI;
808 if (Delta.Excess.isValid())
809 dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
810 << " " << Delta.Excess.getUnitInc() << "\n";
811 if (Delta.CriticalMax.isValid())
812 dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
813 << " " << Delta.CriticalMax.getUnitInc() << "\n";
814 if (Delta.CurrentMax.isValid())
815 dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
816 << " " << Delta.CurrentMax.getUnitInc() << "\n";
817 if (Delta2.Excess.isValid())
818 dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
819 << " " << Delta2.Excess.getUnitInc() << "\n";
820 if (Delta2.CriticalMax.isValid())
821 dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
822 << " " << Delta2.CriticalMax.getUnitInc() << "\n";
823 if (Delta2.CurrentMax.isValid())
824 dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
825 << " " << Delta2.CurrentMax.getUnitInc() << "\n";
826 llvm_unreachable("RegP Delta Mismatch");
831 /// This is the fast version of querying register pressure that does not
832 /// directly depend on current liveness.
834 /// @param Delta captures information needed for heuristics.
836 /// @param CriticalPSets Are the pressure sets that are known to exceed some
837 /// limit within the region, not necessarily at the current position.
839 /// @param MaxPressureLimit Is the max pressure within the region, not
840 /// necessarily at the current position.
841 void RegPressureTracker::
842 getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
843 RegPressureDelta &Delta,
844 ArrayRef<PressureChange> CriticalPSets,
845 ArrayRef<unsigned> MaxPressureLimit) const {
846 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
847 for (PressureDiff::const_iterator
848 PDiffI = PDiff.begin(), PDiffE = PDiff.end();
849 PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
851 unsigned PSetID = PDiffI->getPSet();
852 unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
853 if (!LiveThruPressure.empty())
854 Limit += LiveThruPressure[PSetID];
856 unsigned POld = CurrSetPressure[PSetID];
857 unsigned MOld = P.MaxSetPressure[PSetID];
858 unsigned MNew = MOld;
859 // Ignore DeadDefs here because they aren't captured by PressureChange.
860 unsigned PNew = POld + PDiffI->getUnitInc();
861 assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
864 // Check if current pressure has exceeded the limit.
865 if (!Delta.Excess.isValid()) {
866 unsigned ExcessInc = 0;
868 ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
869 else if (POld > Limit)
870 ExcessInc = Limit - POld;
872 Delta.Excess = PressureChange(PSetID);
873 Delta.Excess.setUnitInc(ExcessInc);
876 // Check if max pressure has exceeded a critical pressure set max.
879 if (!Delta.CriticalMax.isValid()) {
880 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
883 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
884 int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
885 if (CritInc > 0 && CritInc <= INT16_MAX) {
886 Delta.CriticalMax = PressureChange(PSetID);
887 Delta.CriticalMax.setUnitInc(CritInc);
891 // Check if max pressure has exceeded the current max.
892 if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
893 Delta.CurrentMax = PressureChange(PSetID);
894 Delta.CurrentMax.setUnitInc(MNew - MOld);
899 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
900 static bool findUseBetween(unsigned Reg, SlotIndex PriorUseIdx,
901 SlotIndex NextUseIdx, const MachineRegisterInfo &MRI,
902 const LiveIntervals *LIS) {
903 for (const MachineInstr &MI : MRI.use_nodbg_instructions(Reg)) {
904 SlotIndex InstSlot = LIS->getInstructionIndex(&MI).getRegSlot();
905 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
911 /// Record the downward impact of a single instruction on current register
912 /// pressure. Unlike the advance/recede pressure tracking interface, this does
913 /// not discover live in/outs.
915 /// This is intended for speculative queries. It leaves pressure inconsistent
916 /// with the current position, so must be restored by the caller.
917 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
918 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
920 // Account for register pressure similar to RegPressureTracker::recede().
921 RegisterOperands RegOpers(TRI, MRI);
922 collectOperands(MI, RegOpers);
924 // Kill liveness at last uses. Assume allocatable physregs are single-use
925 // rather than checking LiveIntervals.
927 if (RequireIntervals)
928 SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
930 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
931 unsigned Reg = RegOpers.Uses[i];
932 bool IsLastUse = isLastUse(Reg, SlotIdx);
933 // We had a last use at MIs position. To know the situation for the current
934 // position we have to check if there exist other uses in between.
935 if (IsLastUse && TargetRegisterInfo::isVirtualRegister(Reg)) {
936 SlotIndex CurrIdx = getCurrSlot();
937 // FIXME: allow the caller to pass in the list of vreg uses that remain
938 // to be bottom-scheduled to avoid searching uses at each query.
939 if (findUseBetween(Reg, CurrIdx, SlotIdx, *MRI, LIS))
943 decreaseRegPressure(Reg);
946 // Generate liveness for defs.
947 increaseRegPressure(RegOpers.Defs);
949 // Boost pressure for all dead defs together.
950 increaseRegPressure(RegOpers.DeadDefs);
951 decreaseRegPressure(RegOpers.DeadDefs);
954 /// Consider the pressure increase caused by traversing this instruction
955 /// top-down. Find the register class with the most change in its pressure limit
956 /// based on the tracker's current pressure, and return the number of excess
957 /// register units of that pressure set introduced by this instruction.
959 /// This assumes that the current LiveIn set is sufficient.
961 /// This is expensive for an on-the-fly query because it calls
962 /// bumpDownwardPressure to recompute the pressure sets based on current
963 /// liveness. We don't yet have a fast version of downward pressure tracking
964 /// analogous to getUpwardPressureDelta.
965 void RegPressureTracker::
966 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
967 ArrayRef<PressureChange> CriticalPSets,
968 ArrayRef<unsigned> MaxPressureLimit) {
969 // Snapshot Pressure.
970 std::vector<unsigned> SavedPressure = CurrSetPressure;
971 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
973 bumpDownwardPressure(MI);
975 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
977 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
978 MaxPressureLimit, Delta);
979 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
980 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
982 // Restore the tracker's state.
983 P.MaxSetPressure.swap(SavedMaxPressure);
984 CurrSetPressure.swap(SavedPressure);
987 /// Get the pressure of each PSet after traversing this instruction bottom-up.
988 void RegPressureTracker::
989 getUpwardPressure(const MachineInstr *MI,
990 std::vector<unsigned> &PressureResult,
991 std::vector<unsigned> &MaxPressureResult) {
992 // Snapshot pressure.
993 PressureResult = CurrSetPressure;
994 MaxPressureResult = P.MaxSetPressure;
996 bumpUpwardPressure(MI);
998 // Current pressure becomes the result. Restore current pressure.
999 P.MaxSetPressure.swap(MaxPressureResult);
1000 CurrSetPressure.swap(PressureResult);
1003 /// Get the pressure of each PSet after traversing this instruction top-down.
1004 void RegPressureTracker::
1005 getDownwardPressure(const MachineInstr *MI,
1006 std::vector<unsigned> &PressureResult,
1007 std::vector<unsigned> &MaxPressureResult) {
1008 // Snapshot pressure.
1009 PressureResult = CurrSetPressure;
1010 MaxPressureResult = P.MaxSetPressure;
1012 bumpDownwardPressure(MI);
1014 // Current pressure becomes the result. Restore current pressure.
1015 P.MaxSetPressure.swap(MaxPressureResult);
1016 CurrSetPressure.swap(PressureResult);