RegisterPressure.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
1//===-- RegisterPressure.cpp - Dynamic Register Pressure ------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the RegisterPressure class which can be used to track
11// MachineInstr level register pressure.
12//
13//===----------------------------------------------------------------------===//
14
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"
23
24using namespace llvm;
25
26/// Increase pressure for each pressure set provided by TargetRegisterInfo.
27static void increaseSetPressure(std::vector<unsigned> &CurrSetPressure,
28                                PSetIterator PSetI) {
29  unsigned Weight = PSetI.getWeight();
30  for (; PSetI.isValid(); ++PSetI)
31    CurrSetPressure[*PSetI] += Weight;
32}
33
34/// Decrease pressure for each pressure set provided by TargetRegisterInfo.
35static void decreaseSetPressure(std::vector<unsigned> &CurrSetPressure,
36                                PSetIterator PSetI) {
37  unsigned Weight = PSetI.getWeight();
38  for (; PSetI.isValid(); ++PSetI) {
39    assert(CurrSetPressure[*PSetI] >= Weight && "register pressure underflow");
40    CurrSetPressure[*PSetI] -= Weight;
41  }
42}
43
44#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
45void llvm::dumpRegSetPressure(ArrayRef<unsigned> SetPressure,
46                              const TargetRegisterInfo *TRI) {
47  bool Empty = true;
48  for (unsigned i = 0, e = SetPressure.size(); i < e; ++i) {
49    if (SetPressure[i] != 0) {
50      dbgs() << TRI->getRegPressureSetName(i) << "=" << SetPressure[i] << '\n';
51      Empty = false;
52    }
53  }
54  if (Empty)
55    dbgs() << "\n";
56}
57
58void 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) << " ";
64  dbgs() << '\n';
65  dbgs() << "Live Out: ";
66  for (unsigned i = 0, e = LiveOutRegs.size(); i < e; ++i)
67    dbgs() << PrintReg(LiveOutRegs[i], TRI) << " ";
68  dbgs() << '\n';
69}
70
71void RegPressureTracker::dump() const {
72  if (!isTopClosed() || !isBottomClosed()) {
73    dbgs() << "Curr Pressure: ";
74    dumpRegSetPressure(CurrSetPressure, TRI);
75  }
76  P.dump(TRI);
77}
78#endif
79
80/// Increase the current pressure as impacted by these registers and bump
81/// the high water mark if needed.
82void 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];
90      }
91    }
92  }
93}
94
95/// Simply decrease the current pressure as impacted by these registers.
96void RegPressureTracker::decreaseRegPressure(ArrayRef<unsigned> RegUnits) {
97  for (unsigned I = 0, E = RegUnits.size(); I != E; ++I)
98    decreaseSetPressure(CurrSetPressure, MRI->getPressureSets(RegUnits[I]));
99}
100
101/// Clear the result so it can be used for another round of pressure tracking.
102void IntervalPressure::reset() {
103  TopIdx = BottomIdx = SlotIndex();
104  MaxSetPressure.clear();
105  LiveInRegs.clear();
106  LiveOutRegs.clear();
107}
108
109/// Clear the result so it can be used for another round of pressure tracking.
110void RegionPressure::reset() {
111  TopPos = BottomPos = MachineBasicBlock::const_iterator();
112  MaxSetPressure.clear();
113  LiveInRegs.clear();
114  LiveOutRegs.clear();
115}
116
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.
119void IntervalPressure::openTop(SlotIndex NextTop) {
120  if (TopIdx <= NextTop)
121    return;
122  TopIdx = SlotIndex();
123  LiveInRegs.clear();
124}
125
126/// If the current top is the previous instruction (before receding), open it.
127void RegionPressure::openTop(MachineBasicBlock::const_iterator PrevTop) {
128  if (TopPos != PrevTop)
129    return;
130  TopPos = MachineBasicBlock::const_iterator();
131  LiveInRegs.clear();
132}
133
134/// If the current bottom is not greater than the previous index, open it.
135void IntervalPressure::openBottom(SlotIndex PrevBottom) {
136  if (BottomIdx > PrevBottom)
137    return;
138  BottomIdx = SlotIndex();
139  LiveInRegs.clear();
140}
141
142/// If the current bottom is the previous instr (before advancing), open it.
143void RegionPressure::openBottom(MachineBasicBlock::const_iterator PrevBottom) {
144  if (BottomPos != PrevBottom)
145    return;
146  BottomPos = MachineBasicBlock::const_iterator();
147  LiveInRegs.clear();
148}
149
150const LiveRange *RegPressureTracker::getLiveRange(unsigned Reg) const {
151  if (TargetRegisterInfo::isVirtualRegister(Reg))
152    return &LIS->getInterval(Reg);
153  return LIS->getCachedRegUnit(Reg);
154}
155
156void RegPressureTracker::reset() {
157  MBB = 0;
158  LIS = 0;
159
160  CurrSetPressure.clear();
161  LiveThruPressure.clear();
162  P.MaxSetPressure.clear();
163
164  if (RequireIntervals)
165    static_cast<IntervalPressure&>(P).reset();
166  else
167    static_cast<RegionPressure&>(P).reset();
168
169  LiveRegs.PhysRegs.clear();
170  LiveRegs.VirtRegs.clear();
171  UntiedDefs.clear();
172}
173
174/// Setup the RegPressureTracker.
175///
176/// TODO: Add support for pressure without LiveIntervals.
177void RegPressureTracker::init(const MachineFunction *mf,
178                              const RegisterClassInfo *rci,
179                              const LiveIntervals *lis,
180                              const MachineBasicBlock *mbb,
181                              MachineBasicBlock::const_iterator pos,
182                              bool ShouldTrackUntiedDefs)
183{
184  reset();
185
186  MF = mf;
187  TRI = MF->getTarget().getRegisterInfo();
188  RCI = rci;
189  MRI = &MF->getRegInfo();
190  MBB = mbb;
191  TrackUntiedDefs = ShouldTrackUntiedDefs;
192
193  if (RequireIntervals) {
194    assert(lis && "IntervalPressure requires LiveIntervals");
195    LIS = lis;
196  }
197
198  CurrPos = pos;
199  CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
200
201  P.MaxSetPressure = CurrSetPressure;
202
203  LiveRegs.PhysRegs.setUniverse(TRI->getNumRegs());
204  LiveRegs.VirtRegs.setUniverse(MRI->getNumVirtRegs());
205  if (TrackUntiedDefs)
206    UntiedDefs.setUniverse(MRI->getNumVirtRegs());
207}
208
209/// Does this pressure result have a valid top position and live ins.
210bool RegPressureTracker::isTopClosed() const {
211  if (RequireIntervals)
212    return static_cast<IntervalPressure&>(P).TopIdx.isValid();
213  return (static_cast<RegionPressure&>(P).TopPos ==
214          MachineBasicBlock::const_iterator());
215}
216
217/// Does this pressure result have a valid bottom position and live outs.
218bool RegPressureTracker::isBottomClosed() const {
219  if (RequireIntervals)
220    return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
221  return (static_cast<RegionPressure&>(P).BottomPos ==
222          MachineBasicBlock::const_iterator());
223}
224
225
226SlotIndex RegPressureTracker::getCurrSlot() const {
227  MachineBasicBlock::const_iterator IdxPos = CurrPos;
228  while (IdxPos != MBB->end() && IdxPos->isDebugValue())
229    ++IdxPos;
230  if (IdxPos == MBB->end())
231    return LIS->getMBBEndIdx(MBB);
232  return LIS->getInstructionIndex(IdxPos).getRegSlot();
233}
234
235/// Set the boundary for the top of the region and summarize live ins.
236void RegPressureTracker::closeTop() {
237  if (RequireIntervals)
238    static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
239  else
240    static_cast<RegionPressure&>(P).TopPos = CurrPos;
241
242  assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
243  P.LiveInRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
244  P.LiveInRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
245  for (SparseSet<unsigned>::const_iterator I =
246         LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
247    P.LiveInRegs.push_back(*I);
248  std::sort(P.LiveInRegs.begin(), P.LiveInRegs.end());
249  P.LiveInRegs.erase(std::unique(P.LiveInRegs.begin(), P.LiveInRegs.end()),
250                     P.LiveInRegs.end());
251}
252
253/// Set the boundary for the bottom of the region and summarize live outs.
254void RegPressureTracker::closeBottom() {
255  if (RequireIntervals)
256    static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
257  else
258    static_cast<RegionPressure&>(P).BottomPos = CurrPos;
259
260  assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
261  P.LiveOutRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
262  P.LiveOutRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
263  for (SparseSet<unsigned>::const_iterator I =
264         LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
265    P.LiveOutRegs.push_back(*I);
266  std::sort(P.LiveOutRegs.begin(), P.LiveOutRegs.end());
267  P.LiveOutRegs.erase(std::unique(P.LiveOutRegs.begin(), P.LiveOutRegs.end()),
268                      P.LiveOutRegs.end());
269}
270
271/// Finalize the region boundaries and record live ins and live outs.
272void RegPressureTracker::closeRegion() {
273  if (!isTopClosed() && !isBottomClosed()) {
274    assert(LiveRegs.PhysRegs.empty() && LiveRegs.VirtRegs.empty() &&
275           "no region boundary");
276    return;
277  }
278  if (!isBottomClosed())
279    closeBottom();
280  else if (!isTopClosed())
281    closeTop();
282  // If both top and bottom are closed, do nothing.
283}
284
285/// The register tracker is unaware of global liveness so ignores normal
286/// live-thru ranges. However, two-address or coalesced chains can also lead
287/// to live ranges with no holes. Count these to inform heuristics that we
288/// can never drop below this pressure.
289void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
290  LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
291  assert(isBottomClosed() && "need bottom-up tracking to intialize.");
292  for (unsigned i = 0, e = P.LiveOutRegs.size(); i < e; ++i) {
293    unsigned Reg = P.LiveOutRegs[i];
294    if (TargetRegisterInfo::isVirtualRegister(Reg)
295        && !RPTracker.hasUntiedDef(Reg)) {
296      increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
297    }
298  }
299}
300
301/// \brief Convenient wrapper for checking membership in RegisterOperands.
302/// (std::count() doesn't have an early exit).
303static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
304  return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
305}
306
307/// Collect this instruction's unique uses and defs into SmallVectors for
308/// processing defs and uses in order.
309///
310/// FIXME: always ignore tied opers
311class RegisterOperands {
312  const TargetRegisterInfo *TRI;
313  const MachineRegisterInfo *MRI;
314  bool IgnoreDead;
315
316public:
317  SmallVector<unsigned, 8> Uses;
318  SmallVector<unsigned, 8> Defs;
319  SmallVector<unsigned, 8> DeadDefs;
320
321  RegisterOperands(const TargetRegisterInfo *tri,
322                   const MachineRegisterInfo *mri, bool ID = false):
323    TRI(tri), MRI(mri), IgnoreDead(ID) {}
324
325  /// Push this operand's register onto the correct vector.
326  void collect(const MachineOperand &MO) {
327    if (!MO.isReg() || !MO.getReg())
328      return;
329    if (MO.readsReg())
330      pushRegUnits(MO.getReg(), Uses);
331    if (MO.isDef()) {
332      if (MO.isDead()) {
333        if (!IgnoreDead)
334          pushRegUnits(MO.getReg(), DeadDefs);
335      }
336      else
337        pushRegUnits(MO.getReg(), Defs);
338    }
339  }
340
341protected:
342  void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) {
343    if (TargetRegisterInfo::isVirtualRegister(Reg)) {
344      if (containsReg(RegUnits, Reg))
345        return;
346      RegUnits.push_back(Reg);
347    }
348    else if (MRI->isAllocatable(Reg)) {
349      for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) {
350        if (containsReg(RegUnits, *Units))
351          continue;
352        RegUnits.push_back(*Units);
353      }
354    }
355  }
356};
357
358/// Collect physical and virtual register operands.
359static void collectOperands(const MachineInstr *MI,
360                            RegisterOperands &RegOpers) {
361  for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
362    RegOpers.collect(*OperI);
363
364  // Remove redundant physreg dead defs.
365  SmallVectorImpl<unsigned>::iterator I =
366    std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
367                   std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
368  RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
369}
370
371/// Initialize an array of N PressureDiffs.
372void PressureDiffs::init(unsigned N) {
373  Size = N;
374  if (N <= Max) {
375    memset(PDiffArray, 0, N * sizeof(PressureDiff));
376    return;
377  }
378  Max = Size;
379  free(PDiffArray);
380  PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
381}
382
383/// Add a change in pressure to the pressure diff of a given instruction.
384void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
385                                     const MachineRegisterInfo *MRI) {
386  PSetIterator PSetI = MRI->getPressureSets(RegUnit);
387  int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
388  for (; PSetI.isValid(); ++PSetI) {
389    // Find an existing entry in the pressure diff for this PSet.
390    PressureDiff::iterator I = begin(), E = end();
391    for (; I != E && I->isValid(); ++I) {
392      if (I->getPSet() >= *PSetI)
393        break;
394    }
395    // If all pressure sets are more constrained, skip the remaining PSets.
396    if (I == E)
397      break;
398    // Insert this PressureChange.
399    if (!I->isValid() || I->getPSet() != *PSetI) {
400      PressureChange PTmp = PressureChange(*PSetI);
401      for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
402        std::swap(*J,PTmp);
403    }
404    // Update the units for this pressure set.
405    I->setUnitInc(I->getUnitInc() + Weight);
406  }
407}
408
409/// Record the pressure difference induced by the given operand list.
410static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
411                         const MachineRegisterInfo *MRI) {
412  assert(!PDiff.begin()->isValid() && "stale PDiff");
413
414  for (unsigned i = 0, e = RegOpers.Defs.size(); i != e; ++i)
415    PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
416
417  for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
418    PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
419}
420
421/// Force liveness of registers.
422void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
423  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
424    if (LiveRegs.insert(Regs[i]))
425      increaseRegPressure(Regs[i]);
426  }
427}
428
429/// Add Reg to the live in set and increase max pressure.
430void RegPressureTracker::discoverLiveIn(unsigned Reg) {
431  assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
432  if (containsReg(P.LiveInRegs, Reg))
433    return;
434
435  // At live in discovery, unconditionally increase the high water mark.
436  P.LiveInRegs.push_back(Reg);
437  increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
438}
439
440/// Add Reg to the live out set and increase max pressure.
441void RegPressureTracker::discoverLiveOut(unsigned Reg) {
442  assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
443  if (containsReg(P.LiveOutRegs, Reg))
444    return;
445
446  // At live out discovery, unconditionally increase the high water mark.
447  P.LiveOutRegs.push_back(Reg);
448  increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
449}
450
451/// Recede across the previous instruction. If LiveUses is provided, record any
452/// RegUnits that are made live by the current instruction's uses. This includes
453/// registers that are both defined and used by the instruction.  If a pressure
454/// difference pointer is provided record the changes is pressure caused by this
455/// instruction independent of liveness.
456bool RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
457                                PressureDiff *PDiff) {
458  // Check for the top of the analyzable region.
459  if (CurrPos == MBB->begin()) {
460    closeRegion();
461    return false;
462  }
463  if (!isBottomClosed())
464    closeBottom();
465
466  // Open the top of the region using block iterators.
467  if (!RequireIntervals && isTopClosed())
468    static_cast<RegionPressure&>(P).openTop(CurrPos);
469
470  // Find the previous instruction.
471  do
472    --CurrPos;
473  while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
474
475  if (CurrPos->isDebugValue()) {
476    closeRegion();
477    return false;
478  }
479  SlotIndex SlotIdx;
480  if (RequireIntervals)
481    SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
482
483  // Open the top of the region using slot indexes.
484  if (RequireIntervals && isTopClosed())
485    static_cast<IntervalPressure&>(P).openTop(SlotIdx);
486
487  RegisterOperands RegOpers(TRI, MRI);
488  collectOperands(CurrPos, RegOpers);
489
490  if (PDiff)
491    collectPDiff(*PDiff, RegOpers, MRI);
492
493  // Boost pressure for all dead defs together.
494  increaseRegPressure(RegOpers.DeadDefs);
495  decreaseRegPressure(RegOpers.DeadDefs);
496
497  // Kill liveness at live defs.
498  // TODO: consider earlyclobbers?
499  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
500    unsigned Reg = RegOpers.Defs[i];
501    bool DeadDef = false;
502    if (RequireIntervals) {
503      const LiveRange *LR = getLiveRange(Reg);
504      if (LR) {
505        LiveQueryResult LRQ = LR->Query(SlotIdx);
506        DeadDef = LRQ.isDeadDef();
507      }
508    }
509    if (DeadDef) {
510      // LiveIntervals knows this is a dead even though it's MachineOperand is
511      // not flagged as such. Since this register will not be recorded as
512      // live-out, increase its PDiff value to avoid underflowing pressure.
513      if (PDiff)
514        PDiff->addPressureChange(Reg, false, MRI);
515    } else {
516      if (LiveRegs.erase(Reg))
517        decreaseRegPressure(Reg);
518      else
519        discoverLiveOut(Reg);
520    }
521  }
522
523  // Generate liveness for uses.
524  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
525    unsigned Reg = RegOpers.Uses[i];
526    if (!LiveRegs.contains(Reg)) {
527      // Adjust liveouts if LiveIntervals are available.
528      if (RequireIntervals) {
529        const LiveRange *LR = getLiveRange(Reg);
530        if (LR) {
531          LiveQueryResult LRQ = LR->Query(SlotIdx);
532          if (!LRQ.isKill() && !LRQ.valueDefined())
533            discoverLiveOut(Reg);
534        }
535      }
536      increaseRegPressure(Reg);
537      LiveRegs.insert(Reg);
538      if (LiveUses && !containsReg(*LiveUses, Reg))
539        LiveUses->push_back(Reg);
540    }
541  }
542  if (TrackUntiedDefs) {
543    for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
544      unsigned Reg = RegOpers.Defs[i];
545      if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
546        UntiedDefs.insert(Reg);
547    }
548  }
549  return true;
550}
551
552/// Advance across the current instruction.
553bool RegPressureTracker::advance() {
554  assert(!TrackUntiedDefs && "unsupported mode");
555
556  // Check for the bottom of the analyzable region.
557  if (CurrPos == MBB->end()) {
558    closeRegion();
559    return false;
560  }
561  if (!isTopClosed())
562    closeTop();
563
564  SlotIndex SlotIdx;
565  if (RequireIntervals)
566    SlotIdx = getCurrSlot();
567
568  // Open the bottom of the region using slot indexes.
569  if (isBottomClosed()) {
570    if (RequireIntervals)
571      static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
572    else
573      static_cast<RegionPressure&>(P).openBottom(CurrPos);
574  }
575
576  RegisterOperands RegOpers(TRI, MRI);
577  collectOperands(CurrPos, RegOpers);
578
579  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
580    unsigned Reg = RegOpers.Uses[i];
581    // Discover live-ins.
582    bool isLive = LiveRegs.contains(Reg);
583    if (!isLive)
584      discoverLiveIn(Reg);
585    // Kill liveness at last uses.
586    bool lastUse = false;
587    if (RequireIntervals) {
588      const LiveRange *LR = getLiveRange(Reg);
589      lastUse = LR && LR->Query(SlotIdx).isKill();
590    }
591    else {
592      // Allocatable physregs are always single-use before register rewriting.
593      lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
594    }
595    if (lastUse && isLive) {
596      LiveRegs.erase(Reg);
597      decreaseRegPressure(Reg);
598    }
599    else if (!lastUse && !isLive)
600      increaseRegPressure(Reg);
601  }
602
603  // Generate liveness for defs.
604  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
605    unsigned Reg = RegOpers.Defs[i];
606    if (LiveRegs.insert(Reg))
607      increaseRegPressure(Reg);
608  }
609
610  // Boost pressure for all dead defs together.
611  increaseRegPressure(RegOpers.DeadDefs);
612  decreaseRegPressure(RegOpers.DeadDefs);
613
614  // Find the next instruction.
615  do
616    ++CurrPos;
617  while (CurrPos != MBB->end() && CurrPos->isDebugValue());
618  return true;
619}
620
621/// Find the max change in excess pressure across all sets.
622static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
623                                       ArrayRef<unsigned> NewPressureVec,
624                                       RegPressureDelta &Delta,
625                                       const RegisterClassInfo *RCI,
626                                       ArrayRef<unsigned> LiveThruPressureVec) {
627  Delta.Excess = PressureChange();
628  for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
629    unsigned POld = OldPressureVec[i];
630    unsigned PNew = NewPressureVec[i];
631    int PDiff = (int)PNew - (int)POld;
632    if (!PDiff) // No change in this set in the common case.
633      continue;
634    // Only consider change beyond the limit.
635    unsigned Limit = RCI->getRegPressureSetLimit(i);
636    if (!LiveThruPressureVec.empty())
637      Limit += LiveThruPressureVec[i];
638
639    if (Limit > POld) {
640      if (Limit > PNew)
641        PDiff = 0;            // Under the limit
642      else
643        PDiff = PNew - Limit; // Just exceeded limit.
644    }
645    else if (Limit > PNew)
646      PDiff = Limit - POld;   // Just obeyed limit.
647
648    if (PDiff) {
649      Delta.Excess = PressureChange(i);
650      Delta.Excess.setUnitInc(PDiff);
651      break;
652    }
653  }
654}
655
656/// Find the max change in max pressure that either surpasses a critical PSet
657/// limit or exceeds the current MaxPressureLimit.
658///
659/// FIXME: comparing each element of the old and new MaxPressure vectors here is
660/// silly. It's done now to demonstrate the concept but will go away with a
661/// RegPressureTracker API change to work with pressure differences.
662static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
663                                    ArrayRef<unsigned> NewMaxPressureVec,
664                                    ArrayRef<PressureChange> CriticalPSets,
665                                    ArrayRef<unsigned> MaxPressureLimit,
666                                    RegPressureDelta &Delta) {
667  Delta.CriticalMax = PressureChange();
668  Delta.CurrentMax = PressureChange();
669
670  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
671  for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
672    unsigned POld = OldMaxPressureVec[i];
673    unsigned PNew = NewMaxPressureVec[i];
674    if (PNew == POld) // No change in this set in the common case.
675      continue;
676
677    if (!Delta.CriticalMax.isValid()) {
678      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
679        ++CritIdx;
680
681      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
682        int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
683        if (PDiff > 0) {
684          Delta.CriticalMax = PressureChange(i);
685          Delta.CriticalMax.setUnitInc(PDiff);
686        }
687      }
688    }
689    // Find the first increase above MaxPressureLimit.
690    // (Ignores negative MDiff).
691    if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
692      Delta.CurrentMax = PressureChange(i);
693      Delta.CurrentMax.setUnitInc(PNew - POld);
694      if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
695        break;
696    }
697  }
698}
699
700/// Record the upward impact of a single instruction on current register
701/// pressure. Unlike the advance/recede pressure tracking interface, this does
702/// not discover live in/outs.
703///
704/// This is intended for speculative queries. It leaves pressure inconsistent
705/// with the current position, so must be restored by the caller.
706void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
707  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
708
709  // Account for register pressure similar to RegPressureTracker::recede().
710  RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
711  collectOperands(MI, RegOpers);
712
713  // Boost max pressure for all dead defs together.
714  // Since CurrSetPressure and MaxSetPressure
715  increaseRegPressure(RegOpers.DeadDefs);
716  decreaseRegPressure(RegOpers.DeadDefs);
717
718  // Kill liveness at live defs.
719  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
720    unsigned Reg = RegOpers.Defs[i];
721    bool DeadDef = false;
722    if (RequireIntervals) {
723      const LiveRange *LR = getLiveRange(Reg);
724      if (LR) {
725        SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
726        LiveQueryResult LRQ = LR->Query(SlotIdx);
727        DeadDef = LRQ.isDeadDef();
728      }
729    }
730    if (!DeadDef) {
731      if (!containsReg(RegOpers.Uses, Reg))
732        decreaseRegPressure(Reg);
733    }
734  }
735  // Generate liveness for uses.
736  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
737    unsigned Reg = RegOpers.Uses[i];
738    if (!LiveRegs.contains(Reg))
739      increaseRegPressure(Reg);
740  }
741}
742
743/// Consider the pressure increase caused by traversing this instruction
744/// bottom-up. Find the pressure set with the most change beyond its pressure
745/// limit based on the tracker's current pressure, and return the change in
746/// number of register units of that pressure set introduced by this
747/// instruction.
748///
749/// This assumes that the current LiveOut set is sufficient.
750///
751/// FIXME: This is expensive for an on-the-fly query. We need to cache the
752/// result per-SUnit with enough information to adjust for the current
753/// scheduling position. But this works as a proof of concept.
754void RegPressureTracker::
755getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
756                          RegPressureDelta &Delta,
757                          ArrayRef<PressureChange> CriticalPSets,
758                          ArrayRef<unsigned> MaxPressureLimit) {
759  // Snapshot Pressure.
760  // FIXME: The snapshot heap space should persist. But I'm planning to
761  // summarize the pressure effect so we don't need to snapshot at all.
762  std::vector<unsigned> SavedPressure = CurrSetPressure;
763  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
764
765  bumpUpwardPressure(MI);
766
767  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
768                             LiveThruPressure);
769  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
770                          MaxPressureLimit, Delta);
771  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
772         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
773
774  // Restore the tracker's state.
775  P.MaxSetPressure.swap(SavedMaxPressure);
776  CurrSetPressure.swap(SavedPressure);
777
778#ifndef NDEBUG
779  if (!PDiff)
780    return;
781
782  // Check if the alternate algorithm yields the same result.
783  RegPressureDelta Delta2;
784  getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
785  if (Delta != Delta2) {
786    dbgs() << "DELTA: " << *MI;
787    if (Delta.Excess.isValid())
788      dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
789             << " " << Delta.Excess.getUnitInc() << "\n";
790    if (Delta.CriticalMax.isValid())
791      dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
792             << " " << Delta.CriticalMax.getUnitInc() << "\n";
793    if (Delta.CurrentMax.isValid())
794      dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
795             << " " << Delta.CurrentMax.getUnitInc() << "\n";
796    if (Delta2.Excess.isValid())
797      dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
798             << " " << Delta2.Excess.getUnitInc() << "\n";
799    if (Delta2.CriticalMax.isValid())
800      dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
801             << " " << Delta2.CriticalMax.getUnitInc() << "\n";
802    if (Delta2.CurrentMax.isValid())
803      dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
804             << " " << Delta2.CurrentMax.getUnitInc() << "\n";
805    llvm_unreachable("RegP Delta Mismatch");
806  }
807#endif
808}
809
810/// This is a prototype of the fast version of querying register pressure that
811/// does not directly depend on current liveness. It's still slow because we
812/// recompute pressure change on-the-fly. This implementation only exists to
813/// prove correctness.
814///
815/// @param Delta captures information needed for heuristics.
816///
817/// @param CriticalPSets Are the pressure sets that are known to exceed some
818/// limit within the region, not necessarily at the current position.
819///
820/// @param MaxPressureLimit Is the max pressure within the region, not
821/// necessarily at the current position.
822void RegPressureTracker::
823getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
824                       RegPressureDelta &Delta,
825                       ArrayRef<PressureChange> CriticalPSets,
826                       ArrayRef<unsigned> MaxPressureLimit) const {
827  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
828  for (PressureDiff::const_iterator
829         PDiffI = PDiff.begin(), PDiffE = PDiff.end();
830       PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
831
832    unsigned PSetID = PDiffI->getPSet();
833    unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
834    if (!LiveThruPressure.empty())
835      Limit += LiveThruPressure[PSetID];
836
837    unsigned POld = CurrSetPressure[PSetID];
838    unsigned MOld = P.MaxSetPressure[PSetID];
839    unsigned MNew = MOld;
840    // Ignore DeadDefs here because they aren't captured by PressureChange.
841    unsigned PNew = POld + PDiffI->getUnitInc();
842    assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
843    if (PNew > MOld)
844      MNew = PNew;
845    // Check if current pressure has exceeded the limit.
846    if (!Delta.Excess.isValid()) {
847      unsigned ExcessInc = 0;
848      if (PNew > Limit)
849        ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
850      else if (POld > Limit)
851        ExcessInc = Limit - POld;
852      if (ExcessInc) {
853        Delta.Excess = PressureChange(PSetID);
854        Delta.Excess.setUnitInc(ExcessInc);
855      }
856    }
857    // Check if max pressure has exceeded a critical pressure set max.
858    if (MNew == MOld)
859      continue;
860    if (!Delta.CriticalMax.isValid()) {
861      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
862        ++CritIdx;
863
864      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
865        int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
866        if (CritInc > 0 && CritInc <= INT16_MAX) {
867          Delta.CriticalMax = PressureChange(PSetID);
868          Delta.CriticalMax.setUnitInc(CritInc);
869        }
870      }
871    }
872    // Check if max pressure has exceeded the current max.
873    if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
874      Delta.CurrentMax = PressureChange(PSetID);
875      Delta.CurrentMax.setUnitInc(MNew - MOld);
876    }
877  }
878}
879
880/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
881static bool findUseBetween(unsigned Reg,
882                           SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
883                           const MachineRegisterInfo *MRI,
884                           const LiveIntervals *LIS) {
885  for (MachineRegisterInfo::use_instr_nodbg_iterator
886       UI = MRI->use_instr_nodbg_begin(Reg),
887       UE = MRI->use_instr_nodbg_end(); UI != UE; ++UI) {
888      const MachineInstr* MI = &*UI;
889      if (MI->isDebugValue())
890        continue;
891      SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
892      if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
893        return true;
894  }
895  return false;
896}
897
898/// Record the downward impact of a single instruction on current register
899/// pressure. Unlike the advance/recede pressure tracking interface, this does
900/// not discover live in/outs.
901///
902/// This is intended for speculative queries. It leaves pressure inconsistent
903/// with the current position, so must be restored by the caller.
904void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
905  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
906
907  // Account for register pressure similar to RegPressureTracker::recede().
908  RegisterOperands RegOpers(TRI, MRI);
909  collectOperands(MI, RegOpers);
910
911  // Kill liveness at last uses. Assume allocatable physregs are single-use
912  // rather than checking LiveIntervals.
913  SlotIndex SlotIdx;
914  if (RequireIntervals)
915    SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
916
917  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
918    unsigned Reg = RegOpers.Uses[i];
919    if (RequireIntervals) {
920      // FIXME: allow the caller to pass in the list of vreg uses that remain
921      // to be bottom-scheduled to avoid searching uses at each query.
922      SlotIndex CurrIdx = getCurrSlot();
923      const LiveRange *LR = getLiveRange(Reg);
924      if (LR) {
925        LiveQueryResult LRQ = LR->Query(SlotIdx);
926        if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
927          decreaseRegPressure(Reg);
928        }
929      }
930    }
931    else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
932      // Allocatable physregs are always single-use before register rewriting.
933      decreaseRegPressure(Reg);
934    }
935  }
936
937  // Generate liveness for defs.
938  increaseRegPressure(RegOpers.Defs);
939
940  // Boost pressure for all dead defs together.
941  increaseRegPressure(RegOpers.DeadDefs);
942  decreaseRegPressure(RegOpers.DeadDefs);
943}
944
945/// Consider the pressure increase caused by traversing this instruction
946/// top-down. Find the register class with the most change in its pressure limit
947/// based on the tracker's current pressure, and return the number of excess
948/// register units of that pressure set introduced by this instruction.
949///
950/// This assumes that the current LiveIn set is sufficient.
951void RegPressureTracker::
952getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
953                            ArrayRef<PressureChange> CriticalPSets,
954                            ArrayRef<unsigned> MaxPressureLimit) {
955  // Snapshot Pressure.
956  std::vector<unsigned> SavedPressure = CurrSetPressure;
957  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
958
959  bumpDownwardPressure(MI);
960
961  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
962                             LiveThruPressure);
963  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
964                          MaxPressureLimit, Delta);
965  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
966         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
967
968  // Restore the tracker's state.
969  P.MaxSetPressure.swap(SavedMaxPressure);
970  CurrSetPressure.swap(SavedPressure);
971}
972
973/// Get the pressure of each PSet after traversing this instruction bottom-up.
974void RegPressureTracker::
975getUpwardPressure(const MachineInstr *MI,
976                  std::vector<unsigned> &PressureResult,
977                  std::vector<unsigned> &MaxPressureResult) {
978  // Snapshot pressure.
979  PressureResult = CurrSetPressure;
980  MaxPressureResult = P.MaxSetPressure;
981
982  bumpUpwardPressure(MI);
983
984  // Current pressure becomes the result. Restore current pressure.
985  P.MaxSetPressure.swap(MaxPressureResult);
986  CurrSetPressure.swap(PressureResult);
987}
988
989/// Get the pressure of each PSet after traversing this instruction top-down.
990void RegPressureTracker::
991getDownwardPressure(const MachineInstr *MI,
992                    std::vector<unsigned> &PressureResult,
993                    std::vector<unsigned> &MaxPressureResult) {
994  // Snapshot pressure.
995  PressureResult = CurrSetPressure;
996  MaxPressureResult = P.MaxSetPressure;
997
998  bumpDownwardPressure(MI);
999
1000  // Current pressure becomes the result. Restore current pressure.
1001  P.MaxSetPressure.swap(MaxPressureResult);
1002  CurrSetPressure.swap(PressureResult);
1003}
1004