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() || Change.getUnitInc() == 0)
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->getNumRegs());
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 for (SparseSet<unsigned>::const_iterator I =
256 LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
257 P.LiveInRegs.push_back(*I);
258 std::sort(P.LiveInRegs.begin(), P.LiveInRegs.end());
259 P.LiveInRegs.erase(std::unique(P.LiveInRegs.begin(), P.LiveInRegs.end()),
263 /// Set the boundary for the bottom of the region and summarize live outs.
264 void RegPressureTracker::closeBottom() {
265 if (RequireIntervals)
266 static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
268 static_cast<RegionPressure&>(P).BottomPos = CurrPos;
270 assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
271 P.LiveOutRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
272 P.LiveOutRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
273 for (SparseSet<unsigned>::const_iterator I =
274 LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
275 P.LiveOutRegs.push_back(*I);
276 std::sort(P.LiveOutRegs.begin(), P.LiveOutRegs.end());
277 P.LiveOutRegs.erase(std::unique(P.LiveOutRegs.begin(), P.LiveOutRegs.end()),
278 P.LiveOutRegs.end());
281 /// Finalize the region boundaries and record live ins and live outs.
282 void RegPressureTracker::closeRegion() {
283 if (!isTopClosed() && !isBottomClosed()) {
284 assert(LiveRegs.PhysRegs.empty() && LiveRegs.VirtRegs.empty() &&
285 "no region boundary");
288 if (!isBottomClosed())
290 else if (!isTopClosed())
292 // If both top and bottom are closed, do nothing.
295 /// The register tracker is unaware of global liveness so ignores normal
296 /// live-thru ranges. However, two-address or coalesced chains can also lead
297 /// to live ranges with no holes. Count these to inform heuristics that we
298 /// can never drop below this pressure.
299 void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
300 LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
301 assert(isBottomClosed() && "need bottom-up tracking to intialize.");
302 for (unsigned i = 0, e = P.LiveOutRegs.size(); i < e; ++i) {
303 unsigned Reg = P.LiveOutRegs[i];
304 if (TargetRegisterInfo::isVirtualRegister(Reg)
305 && !RPTracker.hasUntiedDef(Reg)) {
306 increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
311 /// \brief Convenient wrapper for checking membership in RegisterOperands.
312 /// (std::count() doesn't have an early exit).
313 static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
314 return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
318 /// Collect this instruction's unique uses and defs into SmallVectors for
319 /// processing defs and uses in order.
321 /// FIXME: always ignore tied opers
322 class RegisterOperands {
323 const TargetRegisterInfo *TRI;
324 const MachineRegisterInfo *MRI;
328 SmallVector<unsigned, 8> Uses;
329 SmallVector<unsigned, 8> Defs;
330 SmallVector<unsigned, 8> DeadDefs;
332 RegisterOperands(const TargetRegisterInfo *tri,
333 const MachineRegisterInfo *mri, bool ID = false):
334 TRI(tri), MRI(mri), IgnoreDead(ID) {}
336 /// Push this operand's register onto the correct vector.
337 void collect(const MachineOperand &MO) {
338 if (!MO.isReg() || !MO.getReg())
341 pushRegUnits(MO.getReg(), Uses);
345 pushRegUnits(MO.getReg(), DeadDefs);
348 pushRegUnits(MO.getReg(), Defs);
353 void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) {
354 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
355 if (containsReg(RegUnits, Reg))
357 RegUnits.push_back(Reg);
359 else if (MRI->isAllocatable(Reg)) {
360 for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) {
361 if (containsReg(RegUnits, *Units))
363 RegUnits.push_back(*Units);
370 /// Collect physical and virtual register operands.
371 static void collectOperands(const MachineInstr *MI,
372 RegisterOperands &RegOpers) {
373 for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
374 RegOpers.collect(*OperI);
376 // Remove redundant physreg dead defs.
377 SmallVectorImpl<unsigned>::iterator I =
378 std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
379 std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
380 RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
383 /// Initialize an array of N PressureDiffs.
384 void PressureDiffs::init(unsigned N) {
387 memset(PDiffArray, 0, N * sizeof(PressureDiff));
392 PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
395 /// Add a change in pressure to the pressure diff of a given instruction.
396 void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
397 const MachineRegisterInfo *MRI) {
398 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
399 int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
400 for (; PSetI.isValid(); ++PSetI) {
401 // Find an existing entry in the pressure diff for this PSet.
402 PressureDiff::iterator I = begin(), E = end();
403 for (; I != E && I->isValid(); ++I) {
404 if (I->getPSet() >= *PSetI)
407 // If all pressure sets are more constrained, skip the remaining PSets.
410 // Insert this PressureChange.
411 if (!I->isValid() || I->getPSet() != *PSetI) {
412 PressureChange PTmp = PressureChange(*PSetI);
413 for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
416 // Update the units for this pressure set.
417 I->setUnitInc(I->getUnitInc() + Weight);
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 /// Advance across the current instruction.
565 bool RegPressureTracker::advance() {
566 assert(!TrackUntiedDefs && "unsupported mode");
568 // Check for the bottom of the analyzable region.
569 if (CurrPos == MBB->end()) {
577 if (RequireIntervals)
578 SlotIdx = getCurrSlot();
580 // Open the bottom of the region using slot indexes.
581 if (isBottomClosed()) {
582 if (RequireIntervals)
583 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
585 static_cast<RegionPressure&>(P).openBottom(CurrPos);
588 RegisterOperands RegOpers(TRI, MRI);
589 collectOperands(CurrPos, RegOpers);
591 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
592 unsigned Reg = RegOpers.Uses[i];
593 // Discover live-ins.
594 bool isLive = LiveRegs.contains(Reg);
597 // Kill liveness at last uses.
598 bool lastUse = false;
599 if (RequireIntervals) {
600 const LiveRange *LR = getLiveRange(Reg);
601 lastUse = LR && LR->Query(SlotIdx).isKill();
604 // Allocatable physregs are always single-use before register rewriting.
605 lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
607 if (lastUse && isLive) {
609 decreaseRegPressure(Reg);
611 else if (!lastUse && !isLive)
612 increaseRegPressure(Reg);
615 // Generate liveness for defs.
616 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
617 unsigned Reg = RegOpers.Defs[i];
618 if (LiveRegs.insert(Reg))
619 increaseRegPressure(Reg);
622 // Boost pressure for all dead defs together.
623 increaseRegPressure(RegOpers.DeadDefs);
624 decreaseRegPressure(RegOpers.DeadDefs);
626 // Find the next instruction.
629 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
633 /// Find the max change in excess pressure across all sets.
634 static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
635 ArrayRef<unsigned> NewPressureVec,
636 RegPressureDelta &Delta,
637 const RegisterClassInfo *RCI,
638 ArrayRef<unsigned> LiveThruPressureVec) {
639 Delta.Excess = PressureChange();
640 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
641 unsigned POld = OldPressureVec[i];
642 unsigned PNew = NewPressureVec[i];
643 int PDiff = (int)PNew - (int)POld;
644 if (!PDiff) // No change in this set in the common case.
646 // Only consider change beyond the limit.
647 unsigned Limit = RCI->getRegPressureSetLimit(i);
648 if (!LiveThruPressureVec.empty())
649 Limit += LiveThruPressureVec[i];
653 PDiff = 0; // Under the limit
655 PDiff = PNew - Limit; // Just exceeded limit.
657 else if (Limit > PNew)
658 PDiff = Limit - POld; // Just obeyed limit.
661 Delta.Excess = PressureChange(i);
662 Delta.Excess.setUnitInc(PDiff);
668 /// Find the max change in max pressure that either surpasses a critical PSet
669 /// limit or exceeds the current MaxPressureLimit.
671 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
672 /// silly. It's done now to demonstrate the concept but will go away with a
673 /// RegPressureTracker API change to work with pressure differences.
674 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
675 ArrayRef<unsigned> NewMaxPressureVec,
676 ArrayRef<PressureChange> CriticalPSets,
677 ArrayRef<unsigned> MaxPressureLimit,
678 RegPressureDelta &Delta) {
679 Delta.CriticalMax = PressureChange();
680 Delta.CurrentMax = PressureChange();
682 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
683 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
684 unsigned POld = OldMaxPressureVec[i];
685 unsigned PNew = NewMaxPressureVec[i];
686 if (PNew == POld) // No change in this set in the common case.
689 if (!Delta.CriticalMax.isValid()) {
690 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
693 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
694 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
696 Delta.CriticalMax = PressureChange(i);
697 Delta.CriticalMax.setUnitInc(PDiff);
701 // Find the first increase above MaxPressureLimit.
702 // (Ignores negative MDiff).
703 if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
704 Delta.CurrentMax = PressureChange(i);
705 Delta.CurrentMax.setUnitInc(PNew - POld);
706 if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
712 /// Record the upward impact of a single instruction on current register
713 /// pressure. Unlike the advance/recede pressure tracking interface, this does
714 /// not discover live in/outs.
716 /// This is intended for speculative queries. It leaves pressure inconsistent
717 /// with the current position, so must be restored by the caller.
718 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
719 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
721 // Account for register pressure similar to RegPressureTracker::recede().
722 RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
723 collectOperands(MI, RegOpers);
725 // Boost max pressure for all dead defs together.
726 // Since CurrSetPressure and MaxSetPressure
727 increaseRegPressure(RegOpers.DeadDefs);
728 decreaseRegPressure(RegOpers.DeadDefs);
730 // Kill liveness at live defs.
731 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
732 unsigned Reg = RegOpers.Defs[i];
733 bool DeadDef = false;
734 if (RequireIntervals) {
735 const LiveRange *LR = getLiveRange(Reg);
737 SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
738 LiveQueryResult LRQ = LR->Query(SlotIdx);
739 DeadDef = LRQ.isDeadDef();
743 if (!containsReg(RegOpers.Uses, Reg))
744 decreaseRegPressure(Reg);
747 // Generate liveness for uses.
748 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
749 unsigned Reg = RegOpers.Uses[i];
750 if (!LiveRegs.contains(Reg))
751 increaseRegPressure(Reg);
755 /// Consider the pressure increase caused by traversing this instruction
756 /// bottom-up. Find the pressure set with the most change beyond its pressure
757 /// limit based on the tracker's current pressure, and return the change in
758 /// number of register units of that pressure set introduced by this
761 /// This assumes that the current LiveOut set is sufficient.
763 /// This is expensive for an on-the-fly query because it calls
764 /// bumpUpwardPressure to recompute the pressure sets based on current
765 /// liveness. This mainly exists to verify correctness, e.g. with
766 /// -verify-misched. getUpwardPressureDelta is the fast version of this query
767 /// that uses the per-SUnit cache of the PressureDiff.
768 void RegPressureTracker::
769 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
770 RegPressureDelta &Delta,
771 ArrayRef<PressureChange> CriticalPSets,
772 ArrayRef<unsigned> MaxPressureLimit) {
773 // Snapshot Pressure.
774 // FIXME: The snapshot heap space should persist. But I'm planning to
775 // summarize the pressure effect so we don't need to snapshot at all.
776 std::vector<unsigned> SavedPressure = CurrSetPressure;
777 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
779 bumpUpwardPressure(MI);
781 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
783 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
784 MaxPressureLimit, Delta);
785 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
786 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
788 // Restore the tracker's state.
789 P.MaxSetPressure.swap(SavedMaxPressure);
790 CurrSetPressure.swap(SavedPressure);
796 // Check if the alternate algorithm yields the same result.
797 RegPressureDelta Delta2;
798 getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
799 if (Delta != Delta2) {
802 dbgs() << "DELTA: " << *MI;
803 if (Delta.Excess.isValid())
804 dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
805 << " " << Delta.Excess.getUnitInc() << "\n";
806 if (Delta.CriticalMax.isValid())
807 dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
808 << " " << Delta.CriticalMax.getUnitInc() << "\n";
809 if (Delta.CurrentMax.isValid())
810 dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
811 << " " << Delta.CurrentMax.getUnitInc() << "\n";
812 if (Delta2.Excess.isValid())
813 dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
814 << " " << Delta2.Excess.getUnitInc() << "\n";
815 if (Delta2.CriticalMax.isValid())
816 dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
817 << " " << Delta2.CriticalMax.getUnitInc() << "\n";
818 if (Delta2.CurrentMax.isValid())
819 dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
820 << " " << Delta2.CurrentMax.getUnitInc() << "\n";
821 llvm_unreachable("RegP Delta Mismatch");
826 /// This is the fast version of querying register pressure that does not
827 /// directly depend on current liveness.
829 /// @param Delta captures information needed for heuristics.
831 /// @param CriticalPSets Are the pressure sets that are known to exceed some
832 /// limit within the region, not necessarily at the current position.
834 /// @param MaxPressureLimit Is the max pressure within the region, not
835 /// necessarily at the current position.
836 void RegPressureTracker::
837 getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
838 RegPressureDelta &Delta,
839 ArrayRef<PressureChange> CriticalPSets,
840 ArrayRef<unsigned> MaxPressureLimit) const {
841 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
842 for (PressureDiff::const_iterator
843 PDiffI = PDiff.begin(), PDiffE = PDiff.end();
844 PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
846 unsigned PSetID = PDiffI->getPSet();
847 unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
848 if (!LiveThruPressure.empty())
849 Limit += LiveThruPressure[PSetID];
851 unsigned POld = CurrSetPressure[PSetID];
852 unsigned MOld = P.MaxSetPressure[PSetID];
853 unsigned MNew = MOld;
854 // Ignore DeadDefs here because they aren't captured by PressureChange.
855 unsigned PNew = POld + PDiffI->getUnitInc();
856 assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
859 // Check if current pressure has exceeded the limit.
860 if (!Delta.Excess.isValid()) {
861 unsigned ExcessInc = 0;
863 ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
864 else if (POld > Limit)
865 ExcessInc = Limit - POld;
867 Delta.Excess = PressureChange(PSetID);
868 Delta.Excess.setUnitInc(ExcessInc);
871 // Check if max pressure has exceeded a critical pressure set max.
874 if (!Delta.CriticalMax.isValid()) {
875 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
878 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
879 int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
880 if (CritInc > 0 && CritInc <= INT16_MAX) {
881 Delta.CriticalMax = PressureChange(PSetID);
882 Delta.CriticalMax.setUnitInc(CritInc);
886 // Check if max pressure has exceeded the current max.
887 if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
888 Delta.CurrentMax = PressureChange(PSetID);
889 Delta.CurrentMax.setUnitInc(MNew - MOld);
894 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
895 static bool findUseBetween(unsigned Reg,
896 SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
897 const MachineRegisterInfo *MRI,
898 const LiveIntervals *LIS) {
899 for (MachineRegisterInfo::use_instr_nodbg_iterator
900 UI = MRI->use_instr_nodbg_begin(Reg),
901 UE = MRI->use_instr_nodbg_end(); UI != UE; ++UI) {
902 const MachineInstr* MI = &*UI;
903 if (MI->isDebugValue())
905 SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
906 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
912 /// Record the downward impact of a single instruction on current register
913 /// pressure. Unlike the advance/recede pressure tracking interface, this does
914 /// not discover live in/outs.
916 /// This is intended for speculative queries. It leaves pressure inconsistent
917 /// with the current position, so must be restored by the caller.
918 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
919 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
921 // Account for register pressure similar to RegPressureTracker::recede().
922 RegisterOperands RegOpers(TRI, MRI);
923 collectOperands(MI, RegOpers);
925 // Kill liveness at last uses. Assume allocatable physregs are single-use
926 // rather than checking LiveIntervals.
928 if (RequireIntervals)
929 SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
931 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
932 unsigned Reg = RegOpers.Uses[i];
933 if (RequireIntervals) {
934 // FIXME: allow the caller to pass in the list of vreg uses that remain
935 // to be bottom-scheduled to avoid searching uses at each query.
936 SlotIndex CurrIdx = getCurrSlot();
937 const LiveRange *LR = getLiveRange(Reg);
939 LiveQueryResult LRQ = LR->Query(SlotIdx);
940 if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
941 decreaseRegPressure(Reg);
945 else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
946 // Allocatable physregs are always single-use before register rewriting.
947 decreaseRegPressure(Reg);
951 // Generate liveness for defs.
952 increaseRegPressure(RegOpers.Defs);
954 // Boost pressure for all dead defs together.
955 increaseRegPressure(RegOpers.DeadDefs);
956 decreaseRegPressure(RegOpers.DeadDefs);
959 /// Consider the pressure increase caused by traversing this instruction
960 /// top-down. Find the register class with the most change in its pressure limit
961 /// based on the tracker's current pressure, and return the number of excess
962 /// register units of that pressure set introduced by this instruction.
964 /// This assumes that the current LiveIn set is sufficient.
966 /// This is expensive for an on-the-fly query because it calls
967 /// bumpDownwardPressure to recompute the pressure sets based on current
968 /// liveness. We don't yet have a fast version of downward pressure tracking
969 /// analagous to getUpwardPressureDelta.
970 void RegPressureTracker::
971 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
972 ArrayRef<PressureChange> CriticalPSets,
973 ArrayRef<unsigned> MaxPressureLimit) {
974 // Snapshot Pressure.
975 std::vector<unsigned> SavedPressure = CurrSetPressure;
976 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
978 bumpDownwardPressure(MI);
980 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
982 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
983 MaxPressureLimit, Delta);
984 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
985 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
987 // Restore the tracker's state.
988 P.MaxSetPressure.swap(SavedMaxPressure);
989 CurrSetPressure.swap(SavedPressure);
992 /// Get the pressure of each PSet after traversing this instruction bottom-up.
993 void RegPressureTracker::
994 getUpwardPressure(const MachineInstr *MI,
995 std::vector<unsigned> &PressureResult,
996 std::vector<unsigned> &MaxPressureResult) {
997 // Snapshot pressure.
998 PressureResult = CurrSetPressure;
999 MaxPressureResult = P.MaxSetPressure;
1001 bumpUpwardPressure(MI);
1003 // Current pressure becomes the result. Restore current pressure.
1004 P.MaxSetPressure.swap(MaxPressureResult);
1005 CurrSetPressure.swap(PressureResult);
1008 /// Get the pressure of each PSet after traversing this instruction top-down.
1009 void RegPressureTracker::
1010 getDownwardPressure(const MachineInstr *MI,
1011 std::vector<unsigned> &PressureResult,
1012 std::vector<unsigned> &MaxPressureResult) {
1013 // Snapshot pressure.
1014 PressureResult = CurrSetPressure;
1015 MaxPressureResult = P.MaxSetPressure;
1017 bumpDownwardPressure(MI);
1019 // Current pressure becomes the result. Restore current pressure.
1020 P.MaxSetPressure.swap(MaxPressureResult);
1021 CurrSetPressure.swap(PressureResult);