RegisterPressure.cpp revision d900b1179535298510490030a5d2ecce93f79eb0 
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      if (LiveRegs.erase(Reg))
511        decreaseRegPressure(Reg);
512      else
513        discoverLiveOut(Reg);
514    }
515  }
516
517  // Generate liveness for uses.
518  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
519    unsigned Reg = RegOpers.Uses[i];
520    if (!LiveRegs.contains(Reg)) {
521      // Adjust liveouts if LiveIntervals are available.
522      if (RequireIntervals) {
523        const LiveRange *LR = getLiveRange(Reg);
524        if (LR) {
525          LiveQueryResult LRQ = LR->Query(SlotIdx);
526          if (!LRQ.isKill() && !LRQ.valueDefined())
527            discoverLiveOut(Reg);
528        }
529      }
530      increaseRegPressure(Reg);
531      LiveRegs.insert(Reg);
532      if (LiveUses && !containsReg(*LiveUses, Reg))
533        LiveUses->push_back(Reg);
534    }
535  }
536  if (TrackUntiedDefs) {
537    for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
538      unsigned Reg = RegOpers.Defs[i];
539      if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
540        UntiedDefs.insert(Reg);
541    }
542  }
543  return true;
544}
545
546/// Advance across the current instruction.
547bool RegPressureTracker::advance() {
548  assert(!TrackUntiedDefs && "unsupported mode");
549
550  // Check for the bottom of the analyzable region.
551  if (CurrPos == MBB->end()) {
552    closeRegion();
553    return false;
554  }
555  if (!isTopClosed())
556    closeTop();
557
558  SlotIndex SlotIdx;
559  if (RequireIntervals)
560    SlotIdx = getCurrSlot();
561
562  // Open the bottom of the region using slot indexes.
563  if (isBottomClosed()) {
564    if (RequireIntervals)
565      static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
566    else
567      static_cast<RegionPressure&>(P).openBottom(CurrPos);
568  }
569
570  RegisterOperands RegOpers(TRI, MRI);
571  collectOperands(CurrPos, RegOpers);
572
573  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
574    unsigned Reg = RegOpers.Uses[i];
575    // Discover live-ins.
576    bool isLive = LiveRegs.contains(Reg);
577    if (!isLive)
578      discoverLiveIn(Reg);
579    // Kill liveness at last uses.
580    bool lastUse = false;
581    if (RequireIntervals) {
582      const LiveRange *LR = getLiveRange(Reg);
583      lastUse = LR && LR->Query(SlotIdx).isKill();
584    }
585    else {
586      // Allocatable physregs are always single-use before register rewriting.
587      lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
588    }
589    if (lastUse && isLive) {
590      LiveRegs.erase(Reg);
591      decreaseRegPressure(Reg);
592    }
593    else if (!lastUse && !isLive)
594      increaseRegPressure(Reg);
595  }
596
597  // Generate liveness for defs.
598  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
599    unsigned Reg = RegOpers.Defs[i];
600    if (LiveRegs.insert(Reg))
601      increaseRegPressure(Reg);
602  }
603
604  // Boost pressure for all dead defs together.
605  increaseRegPressure(RegOpers.DeadDefs);
606  decreaseRegPressure(RegOpers.DeadDefs);
607
608  // Find the next instruction.
609  do
610    ++CurrPos;
611  while (CurrPos != MBB->end() && CurrPos->isDebugValue());
612  return true;
613}
614
615/// Find the max change in excess pressure across all sets.
616static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
617                                       ArrayRef<unsigned> NewPressureVec,
618                                       RegPressureDelta &Delta,
619                                       const RegisterClassInfo *RCI,
620                                       ArrayRef<unsigned> LiveThruPressureVec) {
621  Delta.Excess = PressureChange();
622  for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
623    unsigned POld = OldPressureVec[i];
624    unsigned PNew = NewPressureVec[i];
625    int PDiff = (int)PNew - (int)POld;
626    if (!PDiff) // No change in this set in the common case.
627      continue;
628    // Only consider change beyond the limit.
629    unsigned Limit = RCI->getRegPressureSetLimit(i);
630    if (!LiveThruPressureVec.empty())
631      Limit += LiveThruPressureVec[i];
632
633    if (Limit > POld) {
634      if (Limit > PNew)
635        PDiff = 0;            // Under the limit
636      else
637        PDiff = PNew - Limit; // Just exceeded limit.
638    }
639    else if (Limit > PNew)
640      PDiff = Limit - POld;   // Just obeyed limit.
641
642    if (PDiff) {
643      Delta.Excess = PressureChange(i);
644      Delta.Excess.setUnitInc(PDiff);
645      break;
646    }
647  }
648}
649
650/// Find the max change in max pressure that either surpasses a critical PSet
651/// limit or exceeds the current MaxPressureLimit.
652///
653/// FIXME: comparing each element of the old and new MaxPressure vectors here is
654/// silly. It's done now to demonstrate the concept but will go away with a
655/// RegPressureTracker API change to work with pressure differences.
656static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
657                                    ArrayRef<unsigned> NewMaxPressureVec,
658                                    ArrayRef<PressureChange> CriticalPSets,
659                                    ArrayRef<unsigned> MaxPressureLimit,
660                                    RegPressureDelta &Delta) {
661  Delta.CriticalMax = PressureChange();
662  Delta.CurrentMax = PressureChange();
663
664  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
665  for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
666    unsigned POld = OldMaxPressureVec[i];
667    unsigned PNew = NewMaxPressureVec[i];
668    if (PNew == POld) // No change in this set in the common case.
669      continue;
670
671    if (!Delta.CriticalMax.isValid()) {
672      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
673        ++CritIdx;
674
675      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
676        int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
677        if (PDiff > 0) {
678          Delta.CriticalMax = PressureChange(i);
679          Delta.CriticalMax.setUnitInc(PDiff);
680        }
681      }
682    }
683    // Find the first increase above MaxPressureLimit.
684    // (Ignores negative MDiff).
685    if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
686      Delta.CurrentMax = PressureChange(i);
687      Delta.CurrentMax.setUnitInc(PNew - POld);
688      if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
689        break;
690    }
691  }
692}
693
694/// Record the upward impact of a single instruction on current register
695/// pressure. Unlike the advance/recede pressure tracking interface, this does
696/// not discover live in/outs.
697///
698/// This is intended for speculative queries. It leaves pressure inconsistent
699/// with the current position, so must be restored by the caller.
700void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
701  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
702
703  // Account for register pressure similar to RegPressureTracker::recede().
704  RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
705  collectOperands(MI, RegOpers);
706
707  // Boost max pressure for all dead defs together.
708  // Since CurrSetPressure and MaxSetPressure
709  increaseRegPressure(RegOpers.DeadDefs);
710  decreaseRegPressure(RegOpers.DeadDefs);
711
712  // Kill liveness at live defs.
713  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
714    unsigned Reg = RegOpers.Defs[i];
715    bool DeadDef = false;
716    if (RequireIntervals) {
717      const LiveRange *LR = getLiveRange(Reg);
718      if (LR) {
719        SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
720        LiveQueryResult LRQ = LR->Query(SlotIdx);
721        DeadDef = LRQ.isDeadDef();
722      }
723    }
724    if (!DeadDef) {
725      if (!containsReg(RegOpers.Uses, Reg))
726        decreaseRegPressure(Reg);
727    }
728  }
729  // Generate liveness for uses.
730  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
731    unsigned Reg = RegOpers.Uses[i];
732    if (!LiveRegs.contains(Reg))
733      increaseRegPressure(Reg);
734  }
735}
736
737/// Consider the pressure increase caused by traversing this instruction
738/// bottom-up. Find the pressure set with the most change beyond its pressure
739/// limit based on the tracker's current pressure, and return the change in
740/// number of register units of that pressure set introduced by this
741/// instruction.
742///
743/// This assumes that the current LiveOut set is sufficient.
744///
745/// FIXME: This is expensive for an on-the-fly query. We need to cache the
746/// result per-SUnit with enough information to adjust for the current
747/// scheduling position. But this works as a proof of concept.
748void RegPressureTracker::
749getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
750                          RegPressureDelta &Delta,
751                          ArrayRef<PressureChange> CriticalPSets,
752                          ArrayRef<unsigned> MaxPressureLimit) {
753  // Snapshot Pressure.
754  // FIXME: The snapshot heap space should persist. But I'm planning to
755  // summarize the pressure effect so we don't need to snapshot at all.
756  std::vector<unsigned> SavedPressure = CurrSetPressure;
757  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
758
759  bumpUpwardPressure(MI);
760
761  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
762                             LiveThruPressure);
763  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
764                          MaxPressureLimit, Delta);
765  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
766         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
767
768  // Restore the tracker's state.
769  P.MaxSetPressure.swap(SavedMaxPressure);
770  CurrSetPressure.swap(SavedPressure);
771
772#ifndef NDEBUG
773  if (!PDiff)
774    return;
775
776  // Check if the alternate algorithm yields the same result.
777  RegPressureDelta Delta2;
778  getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
779  if (Delta != Delta2) {
780    dbgs() << "DELTA: " << *MI;
781    if (Delta.Excess.isValid())
782      dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
783             << " " << Delta.Excess.getUnitInc() << "\n";
784    if (Delta.CriticalMax.isValid())
785      dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
786             << " " << Delta.CriticalMax.getUnitInc() << "\n";
787    if (Delta.CurrentMax.isValid())
788      dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
789             << " " << Delta.CurrentMax.getUnitInc() << "\n";
790    if (Delta2.Excess.isValid())
791      dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
792             << " " << Delta2.Excess.getUnitInc() << "\n";
793    if (Delta2.CriticalMax.isValid())
794      dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
795             << " " << Delta2.CriticalMax.getUnitInc() << "\n";
796    if (Delta2.CurrentMax.isValid())
797      dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
798             << " " << Delta2.CurrentMax.getUnitInc() << "\n";
799    llvm_unreachable("RegP Delta Mismatch");
800  }
801#endif
802}
803
804/// This is a prototype of the fast version of querying register pressure that
805/// does not directly depend on current liveness. It's still slow because we
806/// recompute pressure change on-the-fly. This implementation only exists to
807/// prove correctness.
808///
809/// @param Delta captures information needed for heuristics.
810///
811/// @param CriticalPSets Are the pressure sets that are known to exceed some
812/// limit within the region, not necessarily at the current position.
813///
814/// @param MaxPressureLimit Is the max pressure within the region, not
815/// necessarily at the current position.
816void RegPressureTracker::
817getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
818                       RegPressureDelta &Delta,
819                       ArrayRef<PressureChange> CriticalPSets,
820                       ArrayRef<unsigned> MaxPressureLimit) const {
821  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
822  for (PressureDiff::const_iterator
823         PDiffI = PDiff.begin(), PDiffE = PDiff.end();
824       PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
825
826    unsigned PSetID = PDiffI->getPSet();
827    unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
828    if (!LiveThruPressure.empty())
829      Limit += LiveThruPressure[PSetID];
830
831    unsigned POld = CurrSetPressure[PSetID];
832    unsigned MOld = P.MaxSetPressure[PSetID];
833    unsigned MNew = MOld;
834    // Ignore DeadDefs here because they aren't captured by PressureChange.
835    unsigned PNew = POld + PDiffI->getUnitInc();
836    assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
837    if (PNew > MOld)
838      MNew = PNew;
839    // Check if current pressure has exceeded the limit.
840    if (!Delta.Excess.isValid()) {
841      unsigned ExcessInc = 0;
842      if (PNew > Limit)
843        ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
844      else if (POld > Limit)
845        ExcessInc = Limit - POld;
846      if (ExcessInc) {
847        Delta.Excess = PressureChange(PSetID);
848        Delta.Excess.setUnitInc(ExcessInc);
849      }
850    }
851    // Check if max pressure has exceeded a critical pressure set max.
852    if (MNew == MOld)
853      continue;
854    if (!Delta.CriticalMax.isValid()) {
855      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
856        ++CritIdx;
857
858      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
859        int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
860        if (CritInc > 0 && CritInc <= INT16_MAX) {
861          Delta.CriticalMax = PressureChange(PSetID);
862          Delta.CriticalMax.setUnitInc(CritInc);
863        }
864      }
865    }
866    // Check if max pressure has exceeded the current max.
867    if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
868      Delta.CurrentMax = PressureChange(PSetID);
869      Delta.CurrentMax.setUnitInc(MNew - MOld);
870    }
871  }
872}
873
874/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
875static bool findUseBetween(unsigned Reg,
876                           SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
877                           const MachineRegisterInfo *MRI,
878                           const LiveIntervals *LIS) {
879  for (MachineRegisterInfo::use_nodbg_iterator
880         UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
881         UI != UE; UI.skipInstruction()) {
882      const MachineInstr* MI = &*UI;
883      if (MI->isDebugValue())
884        continue;
885      SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
886      if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
887        return true;
888  }
889  return false;
890}
891
892/// Record the downward impact of a single instruction on current register
893/// pressure. Unlike the advance/recede pressure tracking interface, this does
894/// not discover live in/outs.
895///
896/// This is intended for speculative queries. It leaves pressure inconsistent
897/// with the current position, so must be restored by the caller.
898void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
899  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
900
901  // Account for register pressure similar to RegPressureTracker::recede().
902  RegisterOperands RegOpers(TRI, MRI);
903  collectOperands(MI, RegOpers);
904
905  // Kill liveness at last uses. Assume allocatable physregs are single-use
906  // rather than checking LiveIntervals.
907  SlotIndex SlotIdx;
908  if (RequireIntervals)
909    SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
910
911  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
912    unsigned Reg = RegOpers.Uses[i];
913    if (RequireIntervals) {
914      // FIXME: allow the caller to pass in the list of vreg uses that remain
915      // to be bottom-scheduled to avoid searching uses at each query.
916      SlotIndex CurrIdx = getCurrSlot();
917      const LiveRange *LR = getLiveRange(Reg);
918      if (LR) {
919        LiveQueryResult LRQ = LR->Query(SlotIdx);
920        if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
921          decreaseRegPressure(Reg);
922        }
923      }
924    }
925    else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
926      // Allocatable physregs are always single-use before register rewriting.
927      decreaseRegPressure(Reg);
928    }
929  }
930
931  // Generate liveness for defs.
932  increaseRegPressure(RegOpers.Defs);
933
934  // Boost pressure for all dead defs together.
935  increaseRegPressure(RegOpers.DeadDefs);
936  decreaseRegPressure(RegOpers.DeadDefs);
937}
938
939/// Consider the pressure increase caused by traversing this instruction
940/// top-down. Find the register class with the most change in its pressure limit
941/// based on the tracker's current pressure, and return the number of excess
942/// register units of that pressure set introduced by this instruction.
943///
944/// This assumes that the current LiveIn set is sufficient.
945void RegPressureTracker::
946getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
947                            ArrayRef<PressureChange> CriticalPSets,
948                            ArrayRef<unsigned> MaxPressureLimit) {
949  // Snapshot Pressure.
950  std::vector<unsigned> SavedPressure = CurrSetPressure;
951  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
952
953  bumpDownwardPressure(MI);
954
955  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
956                             LiveThruPressure);
957  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
958                          MaxPressureLimit, Delta);
959  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
960         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
961
962  // Restore the tracker's state.
963  P.MaxSetPressure.swap(SavedMaxPressure);
964  CurrSetPressure.swap(SavedPressure);
965}
966
967/// Get the pressure of each PSet after traversing this instruction bottom-up.
968void RegPressureTracker::
969getUpwardPressure(const MachineInstr *MI,
970                  std::vector<unsigned> &PressureResult,
971                  std::vector<unsigned> &MaxPressureResult) {
972  // Snapshot pressure.
973  PressureResult = CurrSetPressure;
974  MaxPressureResult = P.MaxSetPressure;
975
976  bumpUpwardPressure(MI);
977
978  // Current pressure becomes the result. Restore current pressure.
979  P.MaxSetPressure.swap(MaxPressureResult);
980  CurrSetPressure.swap(PressureResult);
981}
982
983/// Get the pressure of each PSet after traversing this instruction top-down.
984void RegPressureTracker::
985getDownwardPressure(const MachineInstr *MI,
986                    std::vector<unsigned> &PressureResult,
987                    std::vector<unsigned> &MaxPressureResult) {
988  // Snapshot pressure.
989  PressureResult = CurrSetPressure;
990  MaxPressureResult = P.MaxSetPressure;
991
992  bumpDownwardPressure(MI);
993
994  // Current pressure becomes the result. Restore current pressure.
995  P.MaxSetPressure.swap(MaxPressureResult);
996  CurrSetPressure.swap(PressureResult);
997}
998