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"
22 #include "llvm/Target/TargetMachine.h"
26 /// Increase pressure for each pressure set provided by TargetRegisterInfo.
27 static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
29 unsigned Weight = PSetI.getWeight();
30 for (; PSetI.isValid(); ++PSetI)
31 CurrSetPressure[*PSetI] += Weight;
34 /// Decrease pressure for each pressure set provided by TargetRegisterInfo.
35 static void decreaseSetPressure(std::vector<unsigned> &CurrSetPressure,
37 unsigned Weight = PSetI.getWeight();
38 for (; PSetI.isValid(); ++PSetI) {
39 assert(CurrSetPressure[*PSetI] >= Weight && "register pressure underflow");
40 CurrSetPressure[*PSetI] -= Weight;
44 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
45 void llvm::dumpRegSetPressure(ArrayRef<unsigned> SetPressure,
46 const TargetRegisterInfo *TRI) {
48 for (unsigned i = 0, e = SetPressure.size(); i < e; ++i) {
49 if (SetPressure[i] != 0) {
50 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() << PrintReg(LiveInRegs[i], TRI) << " ";
65 dbgs() << "Live Out: ";
66 for (unsigned i = 0, e = LiveOutRegs.size(); i < e; ++i)
67 dbgs() << PrintReg(LiveOutRegs[i], TRI) << " ";
71 void RegPressureTracker::dump() const {
72 if (!isTopClosed() || !isBottomClosed()) {
73 dbgs() << "Curr Pressure: ";
74 dumpRegSetPressure(CurrSetPressure, TRI);
80 /// Increase the current pressure as impacted by these registers and bump
81 /// the high water mark if needed.
82 void RegPressureTracker::increaseRegPressure(ArrayRef<unsigned> RegUnits) {
83 for (unsigned i = 0, e = RegUnits.size(); i != e; ++i) {
84 PSetIterator PSetI = MRI->getPressureSets(RegUnits[i]);
85 unsigned Weight = PSetI.getWeight();
86 for (; PSetI.isValid(); ++PSetI) {
87 CurrSetPressure[*PSetI] += Weight;
88 if (CurrSetPressure[*PSetI] > P.MaxSetPressure[*PSetI]) {
89 P.MaxSetPressure[*PSetI] = CurrSetPressure[*PSetI];
95 /// Simply decrease the current pressure as impacted by these registers.
96 void RegPressureTracker::decreaseRegPressure(ArrayRef<unsigned> RegUnits) {
97 for (unsigned I = 0, E = RegUnits.size(); I != E; ++I)
98 decreaseSetPressure(CurrSetPressure, MRI->getPressureSets(RegUnits[I]));
101 /// Clear the result so it can be used for another round of pressure tracking.
102 void IntervalPressure::reset() {
103 TopIdx = BottomIdx = SlotIndex();
104 MaxSetPressure.clear();
109 /// Clear the result so it can be used for another round of pressure tracking.
110 void RegionPressure::reset() {
111 TopPos = BottomPos = MachineBasicBlock::const_iterator();
112 MaxSetPressure.clear();
117 /// If the current top is not less than or equal to the next index, open it.
118 /// We happen to need the SlotIndex for the next top for pressure update.
119 void IntervalPressure::openTop(SlotIndex NextTop) {
120 if (TopIdx <= NextTop)
122 TopIdx = SlotIndex();
126 /// If the current top is the previous instruction (before receding), open it.
127 void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
128 if (TopPos != PrevTop)
130 TopPos = MachineBasicBlock::const_iterator();
134 /// If the current bottom is not greater than the previous index, open it.
135 void IntervalPressure::openBottom(SlotIndex PrevBottom) {
136 if (BottomIdx > PrevBottom)
138 BottomIdx = SlotIndex();
142 /// If the current bottom is the previous instr (before advancing), open it.
143 void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
144 if (BottomPos != PrevBottom)
146 BottomPos = MachineBasicBlock::const_iterator();
150 const LiveInterval *RegPressureTracker::getInterval(unsigned Reg) const {
151 if (TargetRegisterInfo::isVirtualRegister(Reg))
152 return &LIS->getInterval(Reg);
153 return LIS->getCachedRegUnit(Reg);
156 /// Setup the RegPressureTracker.
158 /// TODO: Add support for pressure without LiveIntervals.
159 void RegPressureTracker::init(const MachineFunction *mf,
160 const RegisterClassInfo *rci,
161 const LiveIntervals *lis,
162 const MachineBasicBlock *mbb,
163 MachineBasicBlock::const_iterator pos,
164 bool ShouldTrackUntiedDefs)
167 TRI = MF->getTarget().getRegisterInfo();
169 MRI = &MF->getRegInfo();
171 TrackUntiedDefs = ShouldTrackUntiedDefs;
173 if (RequireIntervals) {
174 assert(lis && "IntervalPressure requires LiveIntervals");
179 CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
180 LiveThruPressure.clear();
182 if (RequireIntervals)
183 static_cast<IntervalPressure&>(P).reset();
185 static_cast<RegionPressure&>(P).reset();
186 P.MaxSetPressure = CurrSetPressure;
188 LiveRegs.PhysRegs.clear();
189 LiveRegs.PhysRegs.setUniverse(TRI->getNumRegs());
190 LiveRegs.VirtRegs.clear();
191 LiveRegs.VirtRegs.setUniverse(MRI->getNumVirtRegs());
194 UntiedDefs.setUniverse(MRI->getNumVirtRegs());
197 /// Does this pressure result have a valid top position and live ins.
198 bool RegPressureTracker::isTopClosed() const {
199 if (RequireIntervals)
200 return static_cast<IntervalPressure&>(P).TopIdx.isValid();
201 return (static_cast<RegionPressure&>(P).TopPos ==
202 MachineBasicBlock::const_iterator());
205 /// Does this pressure result have a valid bottom position and live outs.
206 bool RegPressureTracker::isBottomClosed() const {
207 if (RequireIntervals)
208 return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
209 return (static_cast<RegionPressure&>(P).BottomPos ==
210 MachineBasicBlock::const_iterator());
214 SlotIndex RegPressureTracker::getCurrSlot() const {
215 MachineBasicBlock::const_iterator IdxPos = CurrPos;
216 while (IdxPos != MBB->end() && IdxPos->isDebugValue())
218 if (IdxPos == MBB->end())
219 return LIS->getMBBEndIdx(MBB);
220 return LIS->getInstructionIndex(IdxPos).getRegSlot();
223 /// Set the boundary for the top of the region and summarize live ins.
224 void RegPressureTracker::closeTop() {
225 if (RequireIntervals)
226 static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
228 static_cast<RegionPressure&>(P).TopPos = CurrPos;
230 assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
231 P.LiveInRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
232 P.LiveInRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
233 for (SparseSet<unsigned>::const_iterator I =
234 LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
235 P.LiveInRegs.push_back(*I);
236 std::sort(P.LiveInRegs.begin(), P.LiveInRegs.end());
237 P.LiveInRegs.erase(std::unique(P.LiveInRegs.begin(), P.LiveInRegs.end()),
241 /// Set the boundary for the bottom of the region and summarize live outs.
242 void RegPressureTracker::closeBottom() {
243 if (RequireIntervals)
244 static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
246 static_cast<RegionPressure&>(P).BottomPos = CurrPos;
248 assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
249 P.LiveOutRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
250 P.LiveOutRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
251 for (SparseSet<unsigned>::const_iterator I =
252 LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
253 P.LiveOutRegs.push_back(*I);
254 std::sort(P.LiveOutRegs.begin(), P.LiveOutRegs.end());
255 P.LiveOutRegs.erase(std::unique(P.LiveOutRegs.begin(), P.LiveOutRegs.end()),
256 P.LiveOutRegs.end());
259 /// Finalize the region boundaries and record live ins and live outs.
260 void RegPressureTracker::closeRegion() {
261 if (!isTopClosed() && !isBottomClosed()) {
262 assert(LiveRegs.PhysRegs.empty() && LiveRegs.VirtRegs.empty() &&
263 "no region boundary");
266 if (!isBottomClosed())
268 else if (!isTopClosed())
270 // If both top and bottom are closed, do nothing.
273 /// The register tracker is unaware of global liveness so ignores normal
274 /// live-thru ranges. However, two-address or coalesced chains can also lead
275 /// to live ranges with no holes. Count these to inform heuristics that we
276 /// can never drop below this pressure.
277 void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
278 LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
279 assert(isBottomClosed() && "need bottom-up tracking to intialize.");
280 for (unsigned i = 0, e = P.LiveOutRegs.size(); i < e; ++i) {
281 unsigned Reg = P.LiveOutRegs[i];
282 if (TargetRegisterInfo::isVirtualRegister(Reg)
283 && !RPTracker.hasUntiedDef(Reg)) {
284 increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
289 /// \brief Convenient wrapper for checking membership in RegisterOperands.
290 /// (std::count() doesn't have an early exit).
291 static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
292 return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
295 /// Collect this instruction's unique uses and defs into SmallVectors for
296 /// processing defs and uses in order.
298 /// FIXME: always ignore tied opers
299 class RegisterOperands {
300 const TargetRegisterInfo *TRI;
301 const MachineRegisterInfo *MRI;
305 SmallVector<unsigned, 8> Uses;
306 SmallVector<unsigned, 8> Defs;
307 SmallVector<unsigned, 8> DeadDefs;
309 RegisterOperands(const TargetRegisterInfo *tri,
310 const MachineRegisterInfo *mri, bool ID = false):
311 TRI(tri), MRI(mri), IgnoreDead(ID) {}
313 /// Push this operand's register onto the correct vector.
314 void collect(const MachineOperand &MO) {
315 if (!MO.isReg() || !MO.getReg())
318 pushRegUnits(MO.getReg(), Uses);
322 pushRegUnits(MO.getReg(), DeadDefs);
325 pushRegUnits(MO.getReg(), Defs);
330 void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) {
331 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
332 if (containsReg(RegUnits, Reg))
334 RegUnits.push_back(Reg);
336 else if (MRI->isAllocatable(Reg)) {
337 for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) {
338 if (containsReg(RegUnits, *Units))
340 RegUnits.push_back(*Units);
346 /// Collect physical and virtual register operands.
347 static void collectOperands(const MachineInstr *MI,
348 RegisterOperands &RegOpers) {
349 for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
350 RegOpers.collect(*OperI);
352 // Remove redundant physreg dead defs.
353 SmallVectorImpl<unsigned>::iterator I =
354 std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
355 std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
356 RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
359 /// Initialize an array of N PressureDiffs.
360 void PressureDiffs::init(unsigned N) {
363 memset(PDiffArray, 0, N * sizeof(PressureDiff));
368 PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
371 /// Add a change in pressure to the pressure diff of a given instruction.
372 void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
373 const MachineRegisterInfo *MRI) {
374 PSetIterator PSetI = MRI->getPressureSets(RegUnit);
375 int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
376 for (; PSetI.isValid(); ++PSetI) {
377 // Find an existing entry in the pressure diff for this PSet.
378 PressureDiff::iterator I = begin(), E = end();
379 for (; I != E && I->isValid(); ++I) {
380 if (I->getPSet() >= *PSetI)
383 // If all pressure sets are more constrained, skip the remaining PSets.
386 // Insert this PressureChange.
387 if (!I->isValid() || I->getPSet() != *PSetI) {
388 PressureChange PTmp = PressureChange(*PSetI);
389 for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
392 // Update the units for this pressure set.
393 I->setUnitInc(I->getUnitInc() + Weight);
397 /// Record the pressure difference induced by the given operand list.
398 static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
399 const MachineRegisterInfo *MRI) {
400 assert(!PDiff.begin()->isValid() && "stale PDiff");
402 for (unsigned i = 0, e = RegOpers.Defs.size(); i != e; ++i)
403 PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
405 for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
406 PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
409 /// Force liveness of registers.
410 void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
411 for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
412 if (LiveRegs.insert(Regs[i]))
413 increaseRegPressure(Regs[i]);
417 /// Add Reg to the live in set and increase max pressure.
418 void RegPressureTracker::discoverLiveIn(unsigned Reg) {
419 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
420 if (containsReg(P.LiveInRegs, Reg))
423 // At live in discovery, unconditionally increase the high water mark.
424 P.LiveInRegs.push_back(Reg);
425 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
428 /// Add Reg to the live out set and increase max pressure.
429 void RegPressureTracker::discoverLiveOut(unsigned Reg) {
430 assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
431 if (containsReg(P.LiveOutRegs, Reg))
434 // At live out discovery, unconditionally increase the high water mark.
435 P.LiveOutRegs.push_back(Reg);
436 increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
439 /// Recede across the previous instruction. If LiveUses is provided, record any
440 /// RegUnits that are made live by the current instruction's uses. This includes
441 /// registers that are both defined and used by the instruction. If a pressure
442 /// difference pointer is provided record the changes is pressure caused by this
443 /// instruction independent of liveness.
444 bool RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
445 PressureDiff *PDiff) {
446 // Check for the top of the analyzable region.
447 if (CurrPos == MBB->begin()) {
451 if (!isBottomClosed())
454 // Open the top of the region using block iterators.
455 if (!RequireIntervals && isTopClosed())
456 static_cast<RegionPressure&>(P).openTop(CurrPos);
458 // Find the previous instruction.
461 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
463 if (CurrPos->isDebugValue()) {
468 if (RequireIntervals)
469 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
471 // Open the top of the region using slot indexes.
472 if (RequireIntervals && isTopClosed())
473 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
475 RegisterOperands RegOpers(TRI, MRI);
476 collectOperands(CurrPos, RegOpers);
479 collectPDiff(*PDiff, RegOpers, MRI);
481 // Boost pressure for all dead defs together.
482 increaseRegPressure(RegOpers.DeadDefs);
483 decreaseRegPressure(RegOpers.DeadDefs);
485 // Kill liveness at live defs.
486 // TODO: consider earlyclobbers?
487 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
488 unsigned Reg = RegOpers.Defs[i];
489 if (LiveRegs.erase(Reg))
490 decreaseRegPressure(Reg);
492 discoverLiveOut(Reg);
495 // Generate liveness for uses.
496 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
497 unsigned Reg = RegOpers.Uses[i];
498 if (!LiveRegs.contains(Reg)) {
499 // Adjust liveouts if LiveIntervals are available.
500 if (RequireIntervals) {
501 const LiveInterval *LI = getInterval(Reg);
502 // Check if this LR is killed and not redefined here.
503 if (LI && !LI->isKilledAtInstr(SlotIdx)
504 && !LI->isDefinedByInstr(SlotIdx)) {
505 discoverLiveOut(Reg);
508 increaseRegPressure(Reg);
509 LiveRegs.insert(Reg);
510 if (LiveUses && !containsReg(*LiveUses, Reg))
511 LiveUses->push_back(Reg);
514 if (TrackUntiedDefs) {
515 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
516 unsigned Reg = RegOpers.Defs[i];
517 if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
518 UntiedDefs.insert(Reg);
524 /// Advance across the current instruction.
525 bool RegPressureTracker::advance() {
526 assert(!TrackUntiedDefs && "unsupported mode");
528 // Check for the bottom of the analyzable region.
529 if (CurrPos == MBB->end()) {
537 if (RequireIntervals)
538 SlotIdx = getCurrSlot();
540 // Open the bottom of the region using slot indexes.
541 if (isBottomClosed()) {
542 if (RequireIntervals)
543 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
545 static_cast<RegionPressure&>(P).openBottom(CurrPos);
548 RegisterOperands RegOpers(TRI, MRI);
549 collectOperands(CurrPos, RegOpers);
551 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
552 unsigned Reg = RegOpers.Uses[i];
553 // Discover live-ins.
554 bool isLive = LiveRegs.contains(Reg);
557 // Kill liveness at last uses.
558 bool lastUse = false;
559 if (RequireIntervals) {
560 const LiveInterval *LI = getInterval(Reg);
561 lastUse = LI && LI->isKilledAtInstr(SlotIdx);
564 // Allocatable physregs are always single-use before register rewriting.
565 lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
567 if (lastUse && isLive) {
569 decreaseRegPressure(Reg);
571 else if (!lastUse && !isLive)
572 increaseRegPressure(Reg);
575 // Generate liveness for defs.
576 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
577 unsigned Reg = RegOpers.Defs[i];
578 if (LiveRegs.insert(Reg))
579 increaseRegPressure(Reg);
582 // Boost pressure for all dead defs together.
583 increaseRegPressure(RegOpers.DeadDefs);
584 decreaseRegPressure(RegOpers.DeadDefs);
586 // Find the next instruction.
589 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
593 /// Find the max change in excess pressure across all sets.
594 static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
595 ArrayRef<unsigned> NewPressureVec,
596 RegPressureDelta &Delta,
597 const RegisterClassInfo *RCI,
598 ArrayRef<unsigned> LiveThruPressureVec) {
599 Delta.Excess = PressureChange();
600 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
601 unsigned POld = OldPressureVec[i];
602 unsigned PNew = NewPressureVec[i];
603 int PDiff = (int)PNew - (int)POld;
604 if (!PDiff) // No change in this set in the common case.
606 // Only consider change beyond the limit.
607 unsigned Limit = RCI->getRegPressureSetLimit(i);
608 if (!LiveThruPressureVec.empty())
609 Limit += LiveThruPressureVec[i];
613 PDiff = 0; // Under the limit
615 PDiff = PNew - Limit; // Just exceeded limit.
617 else if (Limit > PNew)
618 PDiff = Limit - POld; // Just obeyed limit.
621 Delta.Excess = PressureChange(i);
622 Delta.Excess.setUnitInc(PDiff);
628 /// Find the max change in max pressure that either surpasses a critical PSet
629 /// limit or exceeds the current MaxPressureLimit.
631 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
632 /// silly. It's done now to demonstrate the concept but will go away with a
633 /// RegPressureTracker API change to work with pressure differences.
634 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
635 ArrayRef<unsigned> NewMaxPressureVec,
636 ArrayRef<PressureChange> CriticalPSets,
637 ArrayRef<unsigned> MaxPressureLimit,
638 RegPressureDelta &Delta) {
639 Delta.CriticalMax = PressureChange();
640 Delta.CurrentMax = PressureChange();
642 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
643 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
644 unsigned POld = OldMaxPressureVec[i];
645 unsigned PNew = NewMaxPressureVec[i];
646 if (PNew == POld) // No change in this set in the common case.
649 if (!Delta.CriticalMax.isValid()) {
650 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
653 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
654 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
656 Delta.CriticalMax = PressureChange(i);
657 Delta.CriticalMax.setUnitInc(PDiff);
661 // Find the first increase above MaxPressureLimit.
662 // (Ignores negative MDiff).
663 if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
664 Delta.CurrentMax = PressureChange(i);
665 Delta.CurrentMax.setUnitInc(PNew - POld);
666 if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
672 /// Record the upward impact of a single instruction on current register
673 /// pressure. Unlike the advance/recede pressure tracking interface, this does
674 /// not discover live in/outs.
676 /// This is intended for speculative queries. It leaves pressure inconsistent
677 /// with the current position, so must be restored by the caller.
678 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
679 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
681 // Account for register pressure similar to RegPressureTracker::recede().
682 RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
683 collectOperands(MI, RegOpers);
685 // Boost max pressure for all dead defs together.
686 // Since CurrSetPressure and MaxSetPressure
687 increaseRegPressure(RegOpers.DeadDefs);
688 decreaseRegPressure(RegOpers.DeadDefs);
690 // Kill liveness at live defs.
691 for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
692 unsigned Reg = RegOpers.Defs[i];
693 if (!containsReg(RegOpers.Uses, Reg))
694 decreaseRegPressure(Reg);
696 // Generate liveness for uses.
697 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
698 unsigned Reg = RegOpers.Uses[i];
699 if (!LiveRegs.contains(Reg))
700 increaseRegPressure(Reg);
704 /// Consider the pressure increase caused by traversing this instruction
705 /// bottom-up. Find the pressure set with the most change beyond its pressure
706 /// limit based on the tracker's current pressure, and return the change in
707 /// number of register units of that pressure set introduced by this
710 /// This assumes that the current LiveOut set is sufficient.
712 /// FIXME: This is expensive for an on-the-fly query. We need to cache the
713 /// result per-SUnit with enough information to adjust for the current
714 /// scheduling position. But this works as a proof of concept.
715 void RegPressureTracker::
716 getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
717 RegPressureDelta &Delta,
718 ArrayRef<PressureChange> CriticalPSets,
719 ArrayRef<unsigned> MaxPressureLimit) {
720 // Snapshot Pressure.
721 // FIXME: The snapshot heap space should persist. But I'm planning to
722 // summarize the pressure effect so we don't need to snapshot at all.
723 std::vector<unsigned> SavedPressure = CurrSetPressure;
724 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
726 bumpUpwardPressure(MI);
728 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
730 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
731 MaxPressureLimit, Delta);
732 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
733 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
735 // Restore the tracker's state.
736 P.MaxSetPressure.swap(SavedMaxPressure);
737 CurrSetPressure.swap(SavedPressure);
743 // Check if the alternate algorithm yields the same result.
744 RegPressureDelta Delta2;
745 getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
746 if (Delta != Delta2) {
747 dbgs() << "DELTA: " << *MI;
748 if (Delta.Excess.isValid())
749 dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
750 << " " << Delta.Excess.getUnitInc() << "\n";
751 if (Delta.CriticalMax.isValid())
752 dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
753 << " " << Delta.CriticalMax.getUnitInc() << "\n";
754 if (Delta.CurrentMax.isValid())
755 dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
756 << " " << Delta.CurrentMax.getUnitInc() << "\n";
757 if (Delta2.Excess.isValid())
758 dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
759 << " " << Delta2.Excess.getUnitInc() << "\n";
760 if (Delta2.CriticalMax.isValid())
761 dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
762 << " " << Delta2.CriticalMax.getUnitInc() << "\n";
763 if (Delta2.CurrentMax.isValid())
764 dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
765 << " " << Delta2.CurrentMax.getUnitInc() << "\n";
766 llvm_unreachable("RegP Delta Mismatch");
771 /// This is a prototype of the fast version of querying register pressure that
772 /// does not directly depend on current liveness. It's still slow because we
773 /// recompute pressure change on-the-fly. This implementation only exists to
774 /// prove correctness.
776 /// @param Delta captures information needed for heuristics.
778 /// @param CriticalPSets Are the pressure sets that are known to exceed some
779 /// limit within the region, not necessarily at the current position.
781 /// @param MaxPressureLimit Is the max pressure within the region, not
782 /// necessarily at the current position.
783 void RegPressureTracker::
784 getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
785 RegPressureDelta &Delta,
786 ArrayRef<PressureChange> CriticalPSets,
787 ArrayRef<unsigned> MaxPressureLimit) const {
788 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
789 for (PressureDiff::const_iterator
790 PDiffI = PDiff.begin(), PDiffE = PDiff.end();
791 PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
793 unsigned PSetID = PDiffI->getPSet();
794 unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
795 if (!LiveThruPressure.empty())
796 Limit += LiveThruPressure[PSetID];
798 unsigned POld = CurrSetPressure[PSetID];
799 unsigned MOld = P.MaxSetPressure[PSetID];
800 unsigned MNew = MOld;
801 // Ignore DeadDefs here because they aren't captured by PressureChange.
802 unsigned PNew = POld + PDiffI->getUnitInc();
803 assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
806 // Check if current pressure has exceeded the limit.
807 if (!Delta.Excess.isValid()) {
808 unsigned ExcessInc = 0;
810 ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
811 else if (POld > Limit)
812 ExcessInc = Limit - POld;
814 Delta.Excess = PressureChange(PSetID);
815 Delta.Excess.setUnitInc(ExcessInc);
818 // Check if max pressure has exceeded a critical pressure set max.
821 if (!Delta.CriticalMax.isValid()) {
822 while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
825 if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
826 int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
827 if (CritInc > 0 && CritInc <= INT16_MAX) {
828 Delta.CriticalMax = PressureChange(PSetID);
829 Delta.CriticalMax.setUnitInc(CritInc);
833 // Check if max pressure has exceeded the current max.
834 if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
835 Delta.CurrentMax = PressureChange(PSetID);
836 Delta.CurrentMax.setUnitInc(MNew - MOld);
841 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
842 static bool findUseBetween(unsigned Reg,
843 SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
844 const MachineRegisterInfo *MRI,
845 const LiveIntervals *LIS) {
846 for (MachineRegisterInfo::use_nodbg_iterator
847 UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
848 UI != UE; UI.skipInstruction()) {
849 const MachineInstr* MI = &*UI;
850 if (MI->isDebugValue())
852 SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
853 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
859 /// Record the downward impact of a single instruction on current register
860 /// pressure. Unlike the advance/recede pressure tracking interface, this does
861 /// not discover live in/outs.
863 /// This is intended for speculative queries. It leaves pressure inconsistent
864 /// with the current position, so must be restored by the caller.
865 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
866 assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
868 // Account for register pressure similar to RegPressureTracker::recede().
869 RegisterOperands RegOpers(TRI, MRI);
870 collectOperands(MI, RegOpers);
872 // Kill liveness at last uses. Assume allocatable physregs are single-use
873 // rather than checking LiveIntervals.
875 if (RequireIntervals)
876 SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
878 for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
879 unsigned Reg = RegOpers.Uses[i];
880 if (RequireIntervals) {
881 // FIXME: allow the caller to pass in the list of vreg uses that remain
882 // to be bottom-scheduled to avoid searching uses at each query.
883 SlotIndex CurrIdx = getCurrSlot();
884 const LiveInterval *LI = getInterval(Reg);
885 if (LI && LI->isKilledAtInstr(SlotIdx)
886 && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
887 decreaseRegPressure(Reg);
890 else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
891 // Allocatable physregs are always single-use before register rewriting.
892 decreaseRegPressure(Reg);
896 // Generate liveness for defs.
897 increaseRegPressure(RegOpers.Defs);
899 // Boost pressure for all dead defs together.
900 increaseRegPressure(RegOpers.DeadDefs);
901 decreaseRegPressure(RegOpers.DeadDefs);
904 /// Consider the pressure increase caused by traversing this instruction
905 /// top-down. Find the register class with the most change in its pressure limit
906 /// based on the tracker's current pressure, and return the number of excess
907 /// register units of that pressure set introduced by this instruction.
909 /// This assumes that the current LiveIn set is sufficient.
910 void RegPressureTracker::
911 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
912 ArrayRef<PressureChange> CriticalPSets,
913 ArrayRef<unsigned> MaxPressureLimit) {
914 // Snapshot Pressure.
915 std::vector<unsigned> SavedPressure = CurrSetPressure;
916 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
918 bumpDownwardPressure(MI);
920 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
922 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
923 MaxPressureLimit, Delta);
924 assert(Delta.CriticalMax.getUnitInc() >= 0 &&
925 Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
927 // Restore the tracker's state.
928 P.MaxSetPressure.swap(SavedMaxPressure);
929 CurrSetPressure.swap(SavedPressure);
932 /// Get the pressure of each PSet after traversing this instruction bottom-up.
933 void RegPressureTracker::
934 getUpwardPressure(const MachineInstr *MI,
935 std::vector<unsigned> &PressureResult,
936 std::vector<unsigned> &MaxPressureResult) {
937 // Snapshot pressure.
938 PressureResult = CurrSetPressure;
939 MaxPressureResult = P.MaxSetPressure;
941 bumpUpwardPressure(MI);
943 // Current pressure becomes the result. Restore current pressure.
944 P.MaxSetPressure.swap(MaxPressureResult);
945 CurrSetPressure.swap(PressureResult);
948 /// Get the pressure of each PSet after traversing this instruction top-down.
949 void RegPressureTracker::
950 getDownwardPressure(const MachineInstr *MI,
951 std::vector<unsigned> &PressureResult,
952 std::vector<unsigned> &MaxPressureResult) {
953 // Snapshot pressure.
954 PressureResult = CurrSetPressure;
955 MaxPressureResult = P.MaxSetPressure;
957 bumpDownwardPressure(MI);
959 // Current pressure becomes the result. Restore current pressure.
960 P.MaxSetPressure.swap(MaxPressureResult);
961 CurrSetPressure.swap(PressureResult);