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/LiveInterval.h"
16 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
17 #include "llvm/CodeGen/MachineRegisterInfo.h"
18 #include "llvm/CodeGen/RegisterClassInfo.h"
19 #include "llvm/CodeGen/RegisterPressure.h"
20 #include "llvm/Target/TargetMachine.h"
21 #include "llvm/Support/Debug.h"
22 #include "llvm/Support/raw_ostream.h"
26 /// Increase register pressure for each set impacted by this register class.
27 static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
28 std::vector<unsigned> &MaxSetPressure,
29 const TargetRegisterClass *RC,
30 const TargetRegisterInfo *TRI) {
31 unsigned Weight = TRI->getRegClassWeight(RC).RegWeight;
32 for (const int *PSet = TRI->getRegClassPressureSets(RC);
33 *PSet != -1; ++PSet) {
34 CurrSetPressure[*PSet] += Weight;
35 if (&CurrSetPressure != &MaxSetPressure
36 && CurrSetPressure[*PSet] > MaxSetPressure[*PSet]) {
37 MaxSetPressure[*PSet] = CurrSetPressure[*PSet];
42 /// Decrease register pressure for each set impacted by this register class.
43 static void decreaseSetPressure(std::vector<unsigned> &CurrSetPressure,
44 const TargetRegisterClass *RC,
45 const TargetRegisterInfo *TRI) {
46 unsigned Weight = TRI->getRegClassWeight(RC).RegWeight;
47 for (const int *PSet = TRI->getRegClassPressureSets(RC);
48 *PSet != -1; ++PSet) {
49 assert(CurrSetPressure[*PSet] >= Weight && "register pressure underflow");
50 CurrSetPressure[*PSet] -= Weight;
54 /// Directly increase pressure only within this RegisterPressure result.
55 void RegisterPressure::increase(const TargetRegisterClass *RC,
56 const TargetRegisterInfo *TRI) {
57 increaseSetPressure(MaxSetPressure, MaxSetPressure, RC, TRI);
60 /// Directly decrease pressure only within this RegisterPressure result.
61 void RegisterPressure::decrease(const TargetRegisterClass *RC,
62 const TargetRegisterInfo *TRI) {
63 decreaseSetPressure(MaxSetPressure, RC, TRI);
66 void RegisterPressure::dump(const TargetRegisterInfo *TRI) {
67 dbgs() << "Live In: ";
68 for (unsigned i = 0, e = LiveInRegs.size(); i < e; ++i)
69 dbgs() << PrintReg(LiveInRegs[i], TRI) << " ";
71 dbgs() << "Live Out: ";
72 for (unsigned i = 0, e = LiveOutRegs.size(); i < e; ++i)
73 dbgs() << PrintReg(LiveOutRegs[i], TRI) << " ";
75 for (unsigned i = 0, e = MaxSetPressure.size(); i < e; ++i) {
76 if (MaxSetPressure[i] != 0)
77 dbgs() << TRI->getRegPressureSetName(i) << "=" << MaxSetPressure[i]
82 /// Increase the current pressure as impacted by these physical registers and
83 /// bump the high water mark if needed.
84 void RegPressureTracker::increasePhysRegPressure(ArrayRef<unsigned> Regs) {
85 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
86 increaseSetPressure(CurrSetPressure, P.MaxSetPressure,
87 TRI->getMinimalPhysRegClass(Regs[I]), TRI);
90 /// Simply decrease the current pressure as impacted by these physcial
92 void RegPressureTracker::decreasePhysRegPressure(ArrayRef<unsigned> Regs) {
93 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
94 decreaseSetPressure(CurrSetPressure, TRI->getMinimalPhysRegClass(Regs[I]),
98 /// Increase the current pressure as impacted by these virtual registers and
99 /// bump the high water mark if needed.
100 void RegPressureTracker::increaseVirtRegPressure(ArrayRef<unsigned> Regs) {
101 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
102 increaseSetPressure(CurrSetPressure, P.MaxSetPressure,
103 MRI->getRegClass(Regs[I]), TRI);
106 /// Simply decrease the current pressure as impacted by these virtual registers.
107 void RegPressureTracker::decreaseVirtRegPressure(ArrayRef<unsigned> Regs) {
108 for (unsigned I = 0, E = Regs.size(); I != E; ++I)
109 decreaseSetPressure(CurrSetPressure, MRI->getRegClass(Regs[I]), TRI);
112 /// Clear the result so it can be used for another round of pressure tracking.
113 void IntervalPressure::reset() {
114 TopIdx = BottomIdx = SlotIndex();
115 MaxSetPressure.clear();
120 /// Clear the result so it can be used for another round of pressure tracking.
121 void RegionPressure::reset() {
122 TopPos = BottomPos = MachineBasicBlock::const_iterator();
123 MaxSetPressure.clear();
128 /// If the current top is not less than or equal to the next index, open it.
129 /// We happen to need the SlotIndex for the next top for pressure update.
130 void IntervalPressure::openTop(SlotIndex NextTop) {
131 if (TopIdx <= NextTop)
133 TopIdx = SlotIndex();
137 /// If the current top is the previous instruction (before receding), open it.
138 void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
139 if (TopPos != PrevTop)
141 TopPos = MachineBasicBlock::const_iterator();
145 /// If the current bottom is not greater than the previous index, open it.
146 void IntervalPressure::openBottom(SlotIndex PrevBottom) {
147 if (BottomIdx > PrevBottom)
149 BottomIdx = SlotIndex();
153 /// If the current bottom is the previous instr (before advancing), open it.
154 void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
155 if (BottomPos != PrevBottom)
157 BottomPos = MachineBasicBlock::const_iterator();
161 /// Setup the RegPressureTracker.
163 /// TODO: Add support for pressure without LiveIntervals.
164 void RegPressureTracker::init(const MachineFunction *mf,
165 const RegisterClassInfo *rci,
166 const LiveIntervals *lis,
167 const MachineBasicBlock *mbb,
168 MachineBasicBlock::const_iterator pos)
171 TRI = MF->getTarget().getRegisterInfo();
173 MRI = &MF->getRegInfo();
176 if (RequireIntervals) {
177 assert(lis && "IntervalPressure requires LiveIntervals");
182 while (CurrPos != MBB->end() && CurrPos->isDebugValue())
185 CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
187 if (RequireIntervals)
188 static_cast<IntervalPressure&>(P).reset();
190 static_cast<RegionPressure&>(P).reset();
191 P.MaxSetPressure = CurrSetPressure;
193 LivePhysRegs.clear();
194 LivePhysRegs.setUniverse(TRI->getNumRegs());
195 LiveVirtRegs.clear();
196 LiveVirtRegs.setUniverse(MRI->getNumVirtRegs());
199 /// Does this pressure result have a valid top position and live ins.
200 bool RegPressureTracker::isTopClosed() const {
201 if (RequireIntervals)
202 return static_cast<IntervalPressure&>(P).TopIdx.isValid();
203 return (static_cast<RegionPressure&>(P).TopPos ==
204 MachineBasicBlock::const_iterator());
207 /// Does this pressure result have a valid bottom position and live outs.
208 bool RegPressureTracker::isBottomClosed() const {
209 if (RequireIntervals)
210 return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
211 return (static_cast<RegionPressure&>(P).BottomPos ==
212 MachineBasicBlock::const_iterator());
215 /// Set the boundary for the top of the region and summarize live ins.
216 void RegPressureTracker::closeTop() {
217 if (RequireIntervals)
218 static_cast<IntervalPressure&>(P).TopIdx =
219 LIS->getInstructionIndex(CurrPos).getRegSlot();
221 static_cast<RegionPressure&>(P).TopPos = CurrPos;
223 assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
224 P.LiveInRegs.reserve(LivePhysRegs.size() + LiveVirtRegs.size());
225 P.LiveInRegs.append(LivePhysRegs.begin(), LivePhysRegs.end());
226 for (SparseSet<unsigned>::const_iterator I =
227 LiveVirtRegs.begin(), E = LiveVirtRegs.end(); I != E; ++I)
228 P.LiveInRegs.push_back(*I);
229 std::sort(P.LiveInRegs.begin(), P.LiveInRegs.end());
230 P.LiveInRegs.erase(std::unique(P.LiveInRegs.begin(), P.LiveInRegs.end()),
234 /// Set the boundary for the bottom of the region and summarize live outs.
235 void RegPressureTracker::closeBottom() {
236 if (RequireIntervals)
237 if (CurrPos == MBB->end())
238 static_cast<IntervalPressure&>(P).BottomIdx = LIS->getMBBEndIdx(MBB);
240 static_cast<IntervalPressure&>(P).BottomIdx =
241 LIS->getInstructionIndex(CurrPos).getRegSlot();
243 static_cast<RegionPressure&>(P).BottomPos = CurrPos;
245 assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
246 P.LiveOutRegs.reserve(LivePhysRegs.size() + LiveVirtRegs.size());
247 P.LiveOutRegs.append(LivePhysRegs.begin(), LivePhysRegs.end());
248 for (SparseSet<unsigned>::const_iterator I =
249 LiveVirtRegs.begin(), E = LiveVirtRegs.end(); I != E; ++I)
250 P.LiveOutRegs.push_back(*I);
251 std::sort(P.LiveOutRegs.begin(), P.LiveOutRegs.end());
252 P.LiveOutRegs.erase(std::unique(P.LiveOutRegs.begin(), P.LiveOutRegs.end()),
253 P.LiveOutRegs.end());
256 /// Finalize the region boundaries and record live ins and live outs.
257 void RegPressureTracker::closeRegion() {
258 if (!isTopClosed() && !isBottomClosed()) {
259 assert(LivePhysRegs.empty() && LiveVirtRegs.empty() &&
260 "no region boundary");
263 if (!isBottomClosed())
265 else if (!isTopClosed())
267 // If both top and bottom are closed, do nothing.
270 /// Return true if Reg aliases a register in Regs SparseSet.
271 static bool hasRegAlias(unsigned Reg, SparseSet<unsigned> &Regs,
272 const TargetRegisterInfo *TRI) {
273 assert(!TargetRegisterInfo::isVirtualRegister(Reg) && "only for physregs");
274 for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI)
280 /// Return true if Reg aliases a register in unsorted Regs SmallVector.
281 /// This is only valid for physical registers.
282 static SmallVectorImpl<unsigned>::iterator
283 findRegAlias(unsigned Reg, SmallVectorImpl<unsigned> &Regs,
284 const TargetRegisterInfo *TRI) {
285 for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
286 SmallVectorImpl<unsigned>::iterator I =
287 std::find(Regs.begin(), Regs.end(), *AI);
294 /// Return true if Reg can be inserted into Regs SmallVector. For virtual
295 /// register, do a linear search. For physical registers check for aliases.
296 static SmallVectorImpl<unsigned>::iterator
297 findReg(unsigned Reg, bool isVReg, SmallVectorImpl<unsigned> &Regs,
298 const TargetRegisterInfo *TRI) {
300 return std::find(Regs.begin(), Regs.end(), Reg);
301 return findRegAlias(Reg, Regs, TRI);
304 /// Collect this instruction's unique uses and defs into SmallVectors for
305 /// processing defs and uses in order.
306 template<bool isVReg>
307 struct RegisterOperands {
308 SmallVector<unsigned, 8> Uses;
309 SmallVector<unsigned, 8> Defs;
310 SmallVector<unsigned, 8> DeadDefs;
312 /// Push this operand's register onto the correct vector.
313 void collect(const MachineOperand &MO, const TargetRegisterInfo *TRI) {
315 if (findReg(MO.getReg(), isVReg, Uses, TRI) == Uses.end())
316 Uses.push_back(MO.getReg());
320 if (findReg(MO.getReg(), isVReg, DeadDefs, TRI) == DeadDefs.end())
321 DeadDefs.push_back(MO.getReg());
324 if (findReg(MO.getReg(), isVReg, Defs, TRI) == Defs.end())
325 Defs.push_back(MO.getReg());
330 typedef RegisterOperands<false> PhysRegOperands;
331 typedef RegisterOperands<true> VirtRegOperands;
333 /// Collect physical and virtual register operands.
334 static void collectOperands(const MachineInstr *MI,
335 PhysRegOperands &PhysRegOpers,
336 VirtRegOperands &VirtRegOpers,
337 const TargetRegisterInfo *TRI,
338 const RegisterClassInfo *RCI) {
339 for(ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI) {
340 const MachineOperand &MO = *OperI;
341 if (!MO.isReg() || !MO.getReg())
344 if (TargetRegisterInfo::isVirtualRegister(MO.getReg()))
345 VirtRegOpers.collect(MO, TRI);
346 else if (RCI->isAllocatable(MO.getReg()))
347 PhysRegOpers.collect(MO, TRI);
349 // Remove redundant physreg dead defs.
350 for (unsigned i = PhysRegOpers.DeadDefs.size(); i > 0; --i) {
351 unsigned Reg = PhysRegOpers.DeadDefs[i-1];
352 if (findRegAlias(Reg, PhysRegOpers.Defs, TRI) != PhysRegOpers.Defs.end())
353 PhysRegOpers.DeadDefs.erase(&PhysRegOpers.DeadDefs[i-1]);
357 /// Force liveness of registers.
358 void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
359 for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
360 if (TargetRegisterInfo::isVirtualRegister(Regs[i])) {
361 if (LiveVirtRegs.insert(Regs[i]).second)
362 increaseVirtRegPressure(Regs[i]);
365 if (!hasRegAlias(Regs[i], LivePhysRegs, TRI)) {
366 LivePhysRegs.insert(Regs[i]);
367 increasePhysRegPressure(Regs[i]);
373 /// Add PhysReg to the live in set and increase max pressure.
374 void RegPressureTracker::discoverPhysLiveIn(unsigned Reg) {
375 assert(!LivePhysRegs.count(Reg) && "avoid bumping max pressure twice");
376 if (findRegAlias(Reg, P.LiveInRegs, TRI) != P.LiveInRegs.end())
379 // At live in discovery, unconditionally increase the high water mark.
380 P.LiveInRegs.push_back(Reg);
381 P.increase(TRI->getMinimalPhysRegClass(Reg), TRI);
384 /// Add PhysReg to the live out set and increase max pressure.
385 void RegPressureTracker::discoverPhysLiveOut(unsigned Reg) {
386 assert(!LivePhysRegs.count(Reg) && "avoid bumping max pressure twice");
387 if (findRegAlias(Reg, P.LiveOutRegs, TRI) != P.LiveOutRegs.end())
390 // At live out discovery, unconditionally increase the high water mark.
391 P.LiveOutRegs.push_back(Reg);
392 P.increase(TRI->getMinimalPhysRegClass(Reg), TRI);
395 /// Add VirtReg to the live in set and increase max pressure.
396 void RegPressureTracker::discoverVirtLiveIn(unsigned Reg) {
397 assert(!LiveVirtRegs.count(Reg) && "avoid bumping max pressure twice");
398 if (std::find(P.LiveInRegs.begin(), P.LiveInRegs.end(), Reg) !=
402 // At live in discovery, unconditionally increase the high water mark.
403 P.LiveInRegs.push_back(Reg);
404 P.increase(MRI->getRegClass(Reg), TRI);
407 /// Add VirtReg to the live out set and increase max pressure.
408 void RegPressureTracker::discoverVirtLiveOut(unsigned Reg) {
409 assert(!LiveVirtRegs.count(Reg) && "avoid bumping max pressure twice");
410 if (std::find(P.LiveOutRegs.begin(), P.LiveOutRegs.end(), Reg) !=
414 // At live out discovery, unconditionally increase the high water mark.
415 P.LiveOutRegs.push_back(Reg);
416 P.increase(MRI->getRegClass(Reg), TRI);
419 /// Recede across the previous instruction.
420 bool RegPressureTracker::recede() {
421 // Check for the top of the analyzable region.
422 if (CurrPos == MBB->begin()) {
426 if (!isBottomClosed())
429 // Open the top of the region using block iterators.
430 if (!RequireIntervals && isTopClosed())
431 static_cast<RegionPressure&>(P).openTop(CurrPos);
433 // Find the previous instruction.
436 while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
438 if (CurrPos->isDebugValue()) {
443 if (RequireIntervals)
444 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
446 // Open the top of the region using slot indexes.
447 if (RequireIntervals && isTopClosed())
448 static_cast<IntervalPressure&>(P).openTop(SlotIdx);
450 PhysRegOperands PhysRegOpers;
451 VirtRegOperands VirtRegOpers;
452 collectOperands(CurrPos, PhysRegOpers, VirtRegOpers, TRI, RCI);
454 // Boost pressure for all dead defs together.
455 increasePhysRegPressure(PhysRegOpers.DeadDefs);
456 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
457 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
458 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
460 // Kill liveness at live defs.
461 // TODO: consider earlyclobbers?
462 for (unsigned i = 0, e = PhysRegOpers.Defs.size(); i < e; ++i) {
463 unsigned Reg = PhysRegOpers.Defs[i];
464 if (LivePhysRegs.erase(Reg))
465 decreasePhysRegPressure(Reg);
467 discoverPhysLiveOut(Reg);
469 for (unsigned i = 0, e = VirtRegOpers.Defs.size(); i < e; ++i) {
470 unsigned Reg = VirtRegOpers.Defs[i];
471 if (LiveVirtRegs.erase(Reg))
472 decreaseVirtRegPressure(Reg);
474 discoverVirtLiveOut(Reg);
477 // Generate liveness for uses.
478 for (unsigned i = 0, e = PhysRegOpers.Uses.size(); i < e; ++i) {
479 unsigned Reg = PhysRegOpers.Uses[i];
480 if (!hasRegAlias(Reg, LivePhysRegs, TRI)) {
481 increasePhysRegPressure(Reg);
482 LivePhysRegs.insert(Reg);
485 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
486 unsigned Reg = VirtRegOpers.Uses[i];
487 if (!LiveVirtRegs.count(Reg)) {
488 // Adjust liveouts if LiveIntervals are available.
489 if (RequireIntervals) {
490 const LiveInterval *LI = &LIS->getInterval(Reg);
491 if (!LI->killedAt(SlotIdx))
492 discoverVirtLiveOut(Reg);
494 increaseVirtRegPressure(Reg);
495 LiveVirtRegs.insert(Reg);
501 /// Advance across the current instruction.
502 bool RegPressureTracker::advance() {
503 // Check for the bottom of the analyzable region.
504 if (CurrPos == MBB->end()) {
512 if (RequireIntervals)
513 SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
515 // Open the bottom of the region using slot indexes.
516 if (isBottomClosed()) {
517 if (RequireIntervals)
518 static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
520 static_cast<RegionPressure&>(P).openBottom(CurrPos);
523 PhysRegOperands PhysRegOpers;
524 VirtRegOperands VirtRegOpers;
525 collectOperands(CurrPos, PhysRegOpers, VirtRegOpers, TRI, RCI);
527 // Kill liveness at last uses.
528 for (unsigned i = 0, e = PhysRegOpers.Uses.size(); i < e; ++i) {
529 unsigned Reg = PhysRegOpers.Uses[i];
530 if (!hasRegAlias(Reg, LivePhysRegs, TRI))
531 discoverPhysLiveIn(Reg);
533 // Allocatable physregs are always single-use before regalloc.
534 decreasePhysRegPressure(Reg);
535 LivePhysRegs.erase(Reg);
538 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
539 unsigned Reg = VirtRegOpers.Uses[i];
540 if (RequireIntervals) {
541 const LiveInterval *LI = &LIS->getInterval(Reg);
542 if (LI->killedAt(SlotIdx)) {
543 if (LiveVirtRegs.erase(Reg))
544 decreaseVirtRegPressure(Reg);
546 discoverVirtLiveIn(Reg);
549 else if (!LiveVirtRegs.count(Reg)) {
550 discoverVirtLiveIn(Reg);
551 increaseVirtRegPressure(Reg);
555 // Generate liveness for defs.
556 for (unsigned i = 0, e = PhysRegOpers.Defs.size(); i < e; ++i) {
557 unsigned Reg = PhysRegOpers.Defs[i];
558 if (!hasRegAlias(Reg, LivePhysRegs, TRI)) {
559 increasePhysRegPressure(Reg);
560 LivePhysRegs.insert(Reg);
563 for (unsigned i = 0, e = VirtRegOpers.Defs.size(); i < e; ++i) {
564 unsigned Reg = VirtRegOpers.Defs[i];
565 if (LiveVirtRegs.insert(Reg).second)
566 increaseVirtRegPressure(Reg);
569 // Boost pressure for all dead defs together.
570 increasePhysRegPressure(PhysRegOpers.DeadDefs);
571 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
572 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
573 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
575 // Find the next instruction.
578 while (CurrPos != MBB->end() && CurrPos->isDebugValue());
582 /// Find the max change in excess pressure across all sets.
583 static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
584 ArrayRef<unsigned> NewPressureVec,
585 RegPressureDelta &Delta,
586 const TargetRegisterInfo *TRI) {
588 unsigned PSetID = ~0U;
589 for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
590 unsigned POld = OldPressureVec[i];
591 unsigned PNew = NewPressureVec[i];
592 int PDiff = (int)PNew - (int)POld;
593 if (!PDiff) // No change in this set in the common case.
595 // Only consider change beyond the limit.
596 unsigned Limit = TRI->getRegPressureSetLimit(i);
599 PDiff = 0; // Under the limit
601 PDiff = PNew - Limit; // Just exceeded limit.
603 else if (Limit > PNew)
604 PDiff = Limit - POld; // Just obeyed limit.
606 if (std::abs(PDiff) > std::abs(ExcessUnits)) {
611 Delta.Excess.PSetID = PSetID;
612 Delta.Excess.UnitIncrease = ExcessUnits;
615 /// Find the max change in max pressure that either surpasses a critical PSet
616 /// limit or exceeds the current MaxPressureLimit.
618 /// FIXME: comparing each element of the old and new MaxPressure vectors here is
619 /// silly. It's done now to demonstrate the concept but will go away with a
620 /// RegPressureTracker API change to work with pressure differences.
621 static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
622 ArrayRef<unsigned> NewMaxPressureVec,
623 ArrayRef<PressureElement> CriticalPSets,
624 ArrayRef<unsigned> MaxPressureLimit,
625 RegPressureDelta &Delta) {
626 Delta.CriticalMax = PressureElement();
627 Delta.CurrentMax = PressureElement();
629 unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
630 for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
631 unsigned POld = OldMaxPressureVec[i];
632 unsigned PNew = NewMaxPressureVec[i];
633 if (PNew == POld) // No change in this set in the common case.
636 while (CritIdx != CritEnd && CriticalPSets[CritIdx].PSetID < i)
639 if (CritIdx != CritEnd && CriticalPSets[CritIdx].PSetID == i) {
640 int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].UnitIncrease;
641 if (PDiff > Delta.CriticalMax.UnitIncrease) {
642 Delta.CriticalMax.PSetID = i;
643 Delta.CriticalMax.UnitIncrease = PDiff;
647 // Find the greatest increase above MaxPressureLimit.
648 // (Ignores negative MDiff).
649 int MDiff = (int)PNew - (int)MaxPressureLimit[i];
650 if (MDiff > Delta.CurrentMax.UnitIncrease) {
651 Delta.CurrentMax.PSetID = i;
652 Delta.CurrentMax.UnitIncrease = PNew;
657 /// Record the upward impact of a single instruction on current register
658 /// pressure. Unlike the advance/recede pressure tracking interface, this does
659 /// not discover live in/outs.
661 /// This is intended for speculative queries. It leaves pressure inconsistent
662 /// with the current position, so must be restored by the caller.
663 void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
664 // Account for register pressure similar to RegPressureTracker::recede().
665 PhysRegOperands PhysRegOpers;
666 VirtRegOperands VirtRegOpers;
667 collectOperands(MI, PhysRegOpers, VirtRegOpers, TRI, RCI);
669 // Boost max pressure for all dead defs together.
670 // Since CurrSetPressure and MaxSetPressure
671 increasePhysRegPressure(PhysRegOpers.DeadDefs);
672 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
673 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
674 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
676 // Kill liveness at live defs.
677 decreasePhysRegPressure(PhysRegOpers.Defs);
678 decreaseVirtRegPressure(VirtRegOpers.Defs);
680 // Generate liveness for uses.
681 for (unsigned i = 0, e = PhysRegOpers.Uses.size(); i < e; ++i) {
682 unsigned Reg = PhysRegOpers.Uses[i];
683 if (!hasRegAlias(Reg, LivePhysRegs, TRI))
684 increasePhysRegPressure(Reg);
686 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
687 unsigned Reg = VirtRegOpers.Uses[i];
688 if (!LiveVirtRegs.count(Reg))
689 increaseVirtRegPressure(Reg);
693 /// Consider the pressure increase caused by traversing this instruction
694 /// bottom-up. Find the pressure set with the most change beyond its pressure
695 /// limit based on the tracker's current pressure, and return the change in
696 /// number of register units of that pressure set introduced by this
699 /// This assumes that the current LiveOut set is sufficient.
701 /// FIXME: This is expensive for an on-the-fly query. We need to cache the
702 /// result per-SUnit with enough information to adjust for the current
703 /// scheduling position. But this works as a proof of concept.
704 void RegPressureTracker::
705 getMaxUpwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
706 ArrayRef<PressureElement> CriticalPSets,
707 ArrayRef<unsigned> MaxPressureLimit) {
708 // Snapshot Pressure.
709 // FIXME: The snapshot heap space should persist. But I'm planning to
710 // summarize the pressure effect so we don't need to snapshot at all.
711 std::vector<unsigned> SavedPressure = CurrSetPressure;
712 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
714 bumpUpwardPressure(MI);
716 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, TRI);
717 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
718 MaxPressureLimit, Delta);
719 assert(Delta.CriticalMax.UnitIncrease >= 0 &&
720 Delta.CurrentMax.UnitIncrease >= 0 && "cannot decrease max pressure");
722 // Restore the tracker's state.
723 P.MaxSetPressure.swap(SavedMaxPressure);
724 CurrSetPressure.swap(SavedPressure);
727 /// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
728 static bool findUseBetween(unsigned Reg,
729 SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
730 const MachineRegisterInfo *MRI,
731 const LiveIntervals *LIS) {
732 for (MachineRegisterInfo::use_nodbg_iterator
733 UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
734 UI != UE; UI.skipInstruction()) {
735 const MachineInstr* MI = &*UI;
736 SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
737 if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
743 /// Record the downward impact of a single instruction on current register
744 /// pressure. Unlike the advance/recede pressure tracking interface, this does
745 /// not discover live in/outs.
747 /// This is intended for speculative queries. It leaves pressure inconsistent
748 /// with the current position, so must be restored by the caller.
749 void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
750 // Account for register pressure similar to RegPressureTracker::recede().
751 PhysRegOperands PhysRegOpers;
752 VirtRegOperands VirtRegOpers;
753 collectOperands(MI, PhysRegOpers, VirtRegOpers, TRI, RCI);
755 // Kill liveness at last uses. Assume allocatable physregs are single-use
756 // rather than checking LiveIntervals.
757 decreasePhysRegPressure(PhysRegOpers.Uses);
758 if (RequireIntervals) {
759 SlotIndex SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
760 for (unsigned i = 0, e = VirtRegOpers.Uses.size(); i < e; ++i) {
761 unsigned Reg = VirtRegOpers.Uses[i];
762 const LiveInterval *LI = &LIS->getInterval(Reg);
763 // FIXME: allow the caller to pass in the list of vreg uses that remain to
764 // be bottom-scheduled to avoid searching uses at each query.
765 SlotIndex CurrIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
766 if (LI->killedAt(SlotIdx)
767 && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
768 decreaseVirtRegPressure(Reg);
773 // Generate liveness for defs.
774 increasePhysRegPressure(PhysRegOpers.Defs);
775 increaseVirtRegPressure(VirtRegOpers.Defs);
777 // Boost pressure for all dead defs together.
778 increasePhysRegPressure(PhysRegOpers.DeadDefs);
779 increaseVirtRegPressure(VirtRegOpers.DeadDefs);
780 decreasePhysRegPressure(PhysRegOpers.DeadDefs);
781 decreaseVirtRegPressure(VirtRegOpers.DeadDefs);
784 /// Consider the pressure increase caused by traversing this instruction
785 /// top-down. Find the register class with the most change in its pressure limit
786 /// based on the tracker's current pressure, and return the number of excess
787 /// register units of that pressure set introduced by this instruction.
789 /// This assumes that the current LiveIn set is sufficient.
790 void RegPressureTracker::
791 getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
792 ArrayRef<PressureElement> CriticalPSets,
793 ArrayRef<unsigned> MaxPressureLimit) {
794 // Snapshot Pressure.
795 std::vector<unsigned> SavedPressure = CurrSetPressure;
796 std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
798 bumpDownwardPressure(MI);
800 computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, TRI);
801 computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
802 MaxPressureLimit, Delta);
803 assert(Delta.CriticalMax.UnitIncrease >= 0 &&
804 Delta.CurrentMax.UnitIncrease >= 0 && "cannot decrease max pressure");
806 // Restore the tracker's state.
807 P.MaxSetPressure.swap(SavedMaxPressure);
808 CurrSetPressure.swap(SavedPressure);
811 /// Get the pressure of each PSet after traversing this instruction bottom-up.
812 void RegPressureTracker::
813 getUpwardPressure(const MachineInstr *MI,
814 std::vector<unsigned> &PressureResult,
815 std::vector<unsigned> &MaxPressureResult) {
816 // Snapshot pressure.
817 PressureResult = CurrSetPressure;
818 MaxPressureResult = P.MaxSetPressure;
820 bumpUpwardPressure(MI);
822 // Current pressure becomes the result. Restore current pressure.
823 P.MaxSetPressure.swap(MaxPressureResult);
824 CurrSetPressure.swap(PressureResult);
827 /// Get the pressure of each PSet after traversing this instruction top-down.
828 void RegPressureTracker::
829 getDownwardPressure(const MachineInstr *MI,
830 std::vector<unsigned> &PressureResult,
831 std::vector<unsigned> &MaxPressureResult) {
832 // Snapshot pressure.
833 PressureResult = CurrSetPressure;
834 MaxPressureResult = P.MaxSetPressure;
836 bumpDownwardPressure(MI);
838 // Current pressure becomes the result. Restore current pressure.
839 P.MaxSetPressure.swap(MaxPressureResult);
840 CurrSetPressure.swap(PressureResult);