RegisterPressure.cpp revision 1362dcb5899bc88f0e567dd10e2e9003a79ace21 
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 LiveInterval *RegPressureTracker::getInterval(unsigned Reg) const {
151  if (TargetRegisterInfo::isVirtualRegister(Reg))
152    return &LIS->getInterval(Reg);
153  return LIS->getCachedRegUnit(Reg);
154}
155
156/// Setup the RegPressureTracker.
157///
158/// TODO: Add support for pressure without LiveIntervals.
159void RegPressureTracker::init(const MachineFunction *mf,
160                              const RegisterClassInfo *rci,
161                              const LiveIntervals *lis,
162                              const MachineBasicBlock *mbb,
163                              MachineBasicBlock::const_iterator pos,
164                              bool ShouldTrackUntiedDefs)
165{
166  MF = mf;
167  TRI = MF->getTarget().getRegisterInfo();
168  RCI = rci;
169  MRI = &MF->getRegInfo();
170  MBB = mbb;
171  TrackUntiedDefs = ShouldTrackUntiedDefs;
172
173  if (RequireIntervals) {
174    assert(lis && "IntervalPressure requires LiveIntervals");
175    LIS = lis;
176  }
177
178  CurrPos = pos;
179  CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
180  LiveThruPressure.clear();
181
182  if (RequireIntervals)
183    static_cast<IntervalPressure&>(P).reset();
184  else
185    static_cast<RegionPressure&>(P).reset();
186  P.MaxSetPressure = CurrSetPressure;
187
188  LiveRegs.PhysRegs.clear();
189  LiveRegs.PhysRegs.setUniverse(TRI->getNumRegs());
190  LiveRegs.VirtRegs.clear();
191  LiveRegs.VirtRegs.setUniverse(MRI->getNumVirtRegs());
192  UntiedDefs.clear();
193  if (TrackUntiedDefs)
194    UntiedDefs.setUniverse(MRI->getNumVirtRegs());
195}
196
197/// Does this pressure result have a valid top position and live ins.
198bool RegPressureTracker::isTopClosed() const {
199  if (RequireIntervals)
200    return static_cast<IntervalPressure&>(P).TopIdx.isValid();
201  return (static_cast<RegionPressure&>(P).TopPos ==
202          MachineBasicBlock::const_iterator());
203}
204
205/// Does this pressure result have a valid bottom position and live outs.
206bool RegPressureTracker::isBottomClosed() const {
207  if (RequireIntervals)
208    return static_cast<IntervalPressure&>(P).BottomIdx.isValid();
209  return (static_cast<RegionPressure&>(P).BottomPos ==
210          MachineBasicBlock::const_iterator());
211}
212
213
214SlotIndex RegPressureTracker::getCurrSlot() const {
215  MachineBasicBlock::const_iterator IdxPos = CurrPos;
216  while (IdxPos != MBB->end() && IdxPos->isDebugValue())
217    ++IdxPos;
218  if (IdxPos == MBB->end())
219    return LIS->getMBBEndIdx(MBB);
220  return LIS->getInstructionIndex(IdxPos).getRegSlot();
221}
222
223/// Set the boundary for the top of the region and summarize live ins.
224void RegPressureTracker::closeTop() {
225  if (RequireIntervals)
226    static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
227  else
228    static_cast<RegionPressure&>(P).TopPos = CurrPos;
229
230  assert(P.LiveInRegs.empty() && "inconsistent max pressure result");
231  P.LiveInRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
232  P.LiveInRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
233  for (SparseSet<unsigned>::const_iterator I =
234         LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
235    P.LiveInRegs.push_back(*I);
236  std::sort(P.LiveInRegs.begin(), P.LiveInRegs.end());
237  P.LiveInRegs.erase(std::unique(P.LiveInRegs.begin(), P.LiveInRegs.end()),
238                     P.LiveInRegs.end());
239}
240
241/// Set the boundary for the bottom of the region and summarize live outs.
242void RegPressureTracker::closeBottom() {
243  if (RequireIntervals)
244    static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
245  else
246    static_cast<RegionPressure&>(P).BottomPos = CurrPos;
247
248  assert(P.LiveOutRegs.empty() && "inconsistent max pressure result");
249  P.LiveOutRegs.reserve(LiveRegs.PhysRegs.size() + LiveRegs.VirtRegs.size());
250  P.LiveOutRegs.append(LiveRegs.PhysRegs.begin(), LiveRegs.PhysRegs.end());
251  for (SparseSet<unsigned>::const_iterator I =
252         LiveRegs.VirtRegs.begin(), E = LiveRegs.VirtRegs.end(); I != E; ++I)
253    P.LiveOutRegs.push_back(*I);
254  std::sort(P.LiveOutRegs.begin(), P.LiveOutRegs.end());
255  P.LiveOutRegs.erase(std::unique(P.LiveOutRegs.begin(), P.LiveOutRegs.end()),
256                      P.LiveOutRegs.end());
257}
258
259/// Finalize the region boundaries and record live ins and live outs.
260void RegPressureTracker::closeRegion() {
261  if (!isTopClosed() && !isBottomClosed()) {
262    assert(LiveRegs.PhysRegs.empty() && LiveRegs.VirtRegs.empty() &&
263           "no region boundary");
264    return;
265  }
266  if (!isBottomClosed())
267    closeBottom();
268  else if (!isTopClosed())
269    closeTop();
270  // If both top and bottom are closed, do nothing.
271}
272
273/// The register tracker is unaware of global liveness so ignores normal
274/// live-thru ranges. However, two-address or coalesced chains can also lead
275/// to live ranges with no holes. Count these to inform heuristics that we
276/// can never drop below this pressure.
277void RegPressureTracker::initLiveThru(const RegPressureTracker &RPTracker) {
278  LiveThruPressure.assign(TRI->getNumRegPressureSets(), 0);
279  assert(isBottomClosed() && "need bottom-up tracking to intialize.");
280  for (unsigned i = 0, e = P.LiveOutRegs.size(); i < e; ++i) {
281    unsigned Reg = P.LiveOutRegs[i];
282    if (TargetRegisterInfo::isVirtualRegister(Reg)
283        && !RPTracker.hasUntiedDef(Reg)) {
284      increaseSetPressure(LiveThruPressure, MRI->getPressureSets(Reg));
285    }
286  }
287}
288
289/// \brief Convenient wrapper for checking membership in RegisterOperands.
290/// (std::count() doesn't have an early exit).
291static bool containsReg(ArrayRef<unsigned> RegUnits, unsigned RegUnit) {
292  return std::find(RegUnits.begin(), RegUnits.end(), RegUnit) != RegUnits.end();
293}
294
295/// Collect this instruction's unique uses and defs into SmallVectors for
296/// processing defs and uses in order.
297///
298/// FIXME: always ignore tied opers
299class RegisterOperands {
300  const TargetRegisterInfo *TRI;
301  const MachineRegisterInfo *MRI;
302  bool IgnoreDead;
303
304public:
305  SmallVector<unsigned, 8> Uses;
306  SmallVector<unsigned, 8> Defs;
307  SmallVector<unsigned, 8> DeadDefs;
308
309  RegisterOperands(const TargetRegisterInfo *tri,
310                   const MachineRegisterInfo *mri, bool ID = false):
311    TRI(tri), MRI(mri), IgnoreDead(ID) {}
312
313  /// Push this operand's register onto the correct vector.
314  void collect(const MachineOperand &MO) {
315    if (!MO.isReg() || !MO.getReg())
316      return;
317    if (MO.readsReg())
318      pushRegUnits(MO.getReg(), Uses);
319    if (MO.isDef()) {
320      if (MO.isDead()) {
321        if (!IgnoreDead)
322          pushRegUnits(MO.getReg(), DeadDefs);
323      }
324      else
325        pushRegUnits(MO.getReg(), Defs);
326    }
327  }
328
329protected:
330  void pushRegUnits(unsigned Reg, SmallVectorImpl<unsigned> &RegUnits) {
331    if (TargetRegisterInfo::isVirtualRegister(Reg)) {
332      if (containsReg(RegUnits, Reg))
333        return;
334      RegUnits.push_back(Reg);
335    }
336    else if (MRI->isAllocatable(Reg)) {
337      for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units) {
338        if (containsReg(RegUnits, *Units))
339          continue;
340        RegUnits.push_back(*Units);
341      }
342    }
343  }
344};
345
346/// Collect physical and virtual register operands.
347static void collectOperands(const MachineInstr *MI,
348                            RegisterOperands &RegOpers) {
349  for (ConstMIBundleOperands OperI(MI); OperI.isValid(); ++OperI)
350    RegOpers.collect(*OperI);
351
352  // Remove redundant physreg dead defs.
353  SmallVectorImpl<unsigned>::iterator I =
354    std::remove_if(RegOpers.DeadDefs.begin(), RegOpers.DeadDefs.end(),
355                   std::bind1st(std::ptr_fun(containsReg), RegOpers.Defs));
356  RegOpers.DeadDefs.erase(I, RegOpers.DeadDefs.end());
357}
358
359/// Initialize an array of N PressureDiffs.
360void PressureDiffs::init(unsigned N) {
361  Size = N;
362  if (N <= Max) {
363    memset(PDiffArray, 0, N * sizeof(PressureDiff));
364    return;
365  }
366  Max = Size;
367  free(PDiffArray);
368  PDiffArray = reinterpret_cast<PressureDiff*>(calloc(N, sizeof(PressureDiff)));
369}
370
371/// Add a change in pressure to the pressure diff of a given instruction.
372void PressureDiff::addPressureChange(unsigned RegUnit, bool IsDec,
373                                     const MachineRegisterInfo *MRI) {
374  PSetIterator PSetI = MRI->getPressureSets(RegUnit);
375  int Weight = IsDec ? -PSetI.getWeight() : PSetI.getWeight();
376  for (; PSetI.isValid(); ++PSetI) {
377    // Find an existing entry in the pressure diff for this PSet.
378    PressureDiff::iterator I = begin(), E = end();
379    for (; I != E && I->isValid(); ++I) {
380      if (I->getPSet() >= *PSetI)
381        break;
382    }
383    // If all pressure sets are more constrained, skip the remaining PSets.
384    if (I == E)
385      break;
386    // Insert this PressureChange.
387    if (!I->isValid() || I->getPSet() != *PSetI) {
388      PressureChange PTmp = PressureChange(*PSetI);
389      for (PressureDiff::iterator J = I; J != E && PTmp.isValid(); ++J)
390        std::swap(*J,PTmp);
391    }
392    // Update the units for this pressure set.
393    I->setUnitInc(I->getUnitInc() + Weight);
394  }
395}
396
397/// Record the pressure difference induced by the given operand list.
398static void collectPDiff(PressureDiff &PDiff, RegisterOperands &RegOpers,
399                         const MachineRegisterInfo *MRI) {
400  assert(!PDiff.begin()->isValid() && "stale PDiff");
401
402  for (unsigned i = 0, e = RegOpers.Defs.size(); i != e; ++i) {
403    if (!containsReg(RegOpers.Uses, RegOpers.Defs[i]))
404      PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
405  }
406  for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
407    PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
408}
409
410/// Force liveness of registers.
411void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
412  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
413    if (LiveRegs.insert(Regs[i]))
414      increaseRegPressure(Regs[i]);
415  }
416}
417
418/// Add Reg to the live in set and increase max pressure.
419void RegPressureTracker::discoverLiveIn(unsigned Reg) {
420  assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
421  if (containsReg(P.LiveInRegs, Reg))
422    return;
423
424  // At live in discovery, unconditionally increase the high water mark.
425  P.LiveInRegs.push_back(Reg);
426  increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
427}
428
429/// Add Reg to the live out set and increase max pressure.
430void RegPressureTracker::discoverLiveOut(unsigned Reg) {
431  assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
432  if (containsReg(P.LiveOutRegs, Reg))
433    return;
434
435  // At live out discovery, unconditionally increase the high water mark.
436  P.LiveOutRegs.push_back(Reg);
437  increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
438}
439
440/// Recede across the previous instruction.
441/// Record the pressure difference if it is provided.
442bool RegPressureTracker::recede(PressureDiff *PDiff) {
443  // Check for the top of the analyzable region.
444  if (CurrPos == MBB->begin()) {
445    closeRegion();
446    return false;
447  }
448  if (!isBottomClosed())
449    closeBottom();
450
451  // Open the top of the region using block iterators.
452  if (!RequireIntervals && isTopClosed())
453    static_cast<RegionPressure&>(P).openTop(CurrPos);
454
455  // Find the previous instruction.
456  do
457    --CurrPos;
458  while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
459
460  if (CurrPos->isDebugValue()) {
461    closeRegion();
462    return false;
463  }
464  SlotIndex SlotIdx;
465  if (RequireIntervals)
466    SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
467
468  // Open the top of the region using slot indexes.
469  if (RequireIntervals && isTopClosed())
470    static_cast<IntervalPressure&>(P).openTop(SlotIdx);
471
472  RegisterOperands RegOpers(TRI, MRI);
473  collectOperands(CurrPos, RegOpers);
474
475  if (PDiff)
476    collectPDiff(*PDiff, RegOpers, MRI);
477
478  // Boost pressure for all dead defs together.
479  increaseRegPressure(RegOpers.DeadDefs);
480  decreaseRegPressure(RegOpers.DeadDefs);
481
482  // Kill liveness at live defs.
483  // TODO: consider earlyclobbers?
484  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
485    unsigned Reg = RegOpers.Defs[i];
486    if (LiveRegs.erase(Reg))
487      decreaseRegPressure(Reg);
488    else
489      discoverLiveOut(Reg);
490  }
491
492  // Generate liveness for uses.
493  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
494    unsigned Reg = RegOpers.Uses[i];
495    if (!LiveRegs.contains(Reg)) {
496      // Adjust liveouts if LiveIntervals are available.
497      if (RequireIntervals) {
498        const LiveInterval *LI = getInterval(Reg);
499        if (LI && !LI->isKilledAtInstr(SlotIdx))
500          discoverLiveOut(Reg);
501      }
502      increaseRegPressure(Reg);
503      LiveRegs.insert(Reg);
504    }
505  }
506  if (TrackUntiedDefs) {
507    for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
508      unsigned Reg = RegOpers.Defs[i];
509      if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
510        UntiedDefs.insert(Reg);
511    }
512  }
513  return true;
514}
515
516/// Advance across the current instruction.
517bool RegPressureTracker::advance() {
518  assert(!TrackUntiedDefs && "unsupported mode");
519
520  // Check for the bottom of the analyzable region.
521  if (CurrPos == MBB->end()) {
522    closeRegion();
523    return false;
524  }
525  if (!isTopClosed())
526    closeTop();
527
528  SlotIndex SlotIdx;
529  if (RequireIntervals)
530    SlotIdx = getCurrSlot();
531
532  // Open the bottom of the region using slot indexes.
533  if (isBottomClosed()) {
534    if (RequireIntervals)
535      static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
536    else
537      static_cast<RegionPressure&>(P).openBottom(CurrPos);
538  }
539
540  RegisterOperands RegOpers(TRI, MRI);
541  collectOperands(CurrPos, RegOpers);
542
543  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
544    unsigned Reg = RegOpers.Uses[i];
545    // Discover live-ins.
546    bool isLive = LiveRegs.contains(Reg);
547    if (!isLive)
548      discoverLiveIn(Reg);
549    // Kill liveness at last uses.
550    bool lastUse = false;
551    if (RequireIntervals) {
552      const LiveInterval *LI = getInterval(Reg);
553      lastUse = LI && LI->isKilledAtInstr(SlotIdx);
554    }
555    else {
556      // Allocatable physregs are always single-use before register rewriting.
557      lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
558    }
559    if (lastUse && isLive) {
560      LiveRegs.erase(Reg);
561      decreaseRegPressure(Reg);
562    }
563    else if (!lastUse && !isLive)
564      increaseRegPressure(Reg);
565  }
566
567  // Generate liveness for defs.
568  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
569    unsigned Reg = RegOpers.Defs[i];
570    if (LiveRegs.insert(Reg))
571      increaseRegPressure(Reg);
572  }
573
574  // Boost pressure for all dead defs together.
575  increaseRegPressure(RegOpers.DeadDefs);
576  decreaseRegPressure(RegOpers.DeadDefs);
577
578  // Find the next instruction.
579  do
580    ++CurrPos;
581  while (CurrPos != MBB->end() && CurrPos->isDebugValue());
582  return true;
583}
584
585/// Find the max change in excess pressure across all sets.
586static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
587                                       ArrayRef<unsigned> NewPressureVec,
588                                       RegPressureDelta &Delta,
589                                       const RegisterClassInfo *RCI,
590                                       ArrayRef<unsigned> LiveThruPressureVec) {
591  Delta.Excess = PressureChange();
592  for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
593    unsigned POld = OldPressureVec[i];
594    unsigned PNew = NewPressureVec[i];
595    int PDiff = (int)PNew - (int)POld;
596    if (!PDiff) // No change in this set in the common case.
597      continue;
598    // Only consider change beyond the limit.
599    unsigned Limit = RCI->getRegPressureSetLimit(i);
600    if (!LiveThruPressureVec.empty())
601      Limit += LiveThruPressureVec[i];
602
603    if (Limit > POld) {
604      if (Limit > PNew)
605        PDiff = 0;            // Under the limit
606      else
607        PDiff = PNew - Limit; // Just exceeded limit.
608    }
609    else if (Limit > PNew)
610      PDiff = Limit - POld;   // Just obeyed limit.
611
612    if (PDiff) {
613      Delta.Excess = PressureChange(i);
614      Delta.Excess.setUnitInc(PDiff);
615      break;
616    }
617  }
618}
619
620/// Find the max change in max pressure that either surpasses a critical PSet
621/// limit or exceeds the current MaxPressureLimit.
622///
623/// FIXME: comparing each element of the old and new MaxPressure vectors here is
624/// silly. It's done now to demonstrate the concept but will go away with a
625/// RegPressureTracker API change to work with pressure differences.
626static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
627                                    ArrayRef<unsigned> NewMaxPressureVec,
628                                    ArrayRef<PressureChange> CriticalPSets,
629                                    ArrayRef<unsigned> MaxPressureLimit,
630                                    RegPressureDelta &Delta) {
631  Delta.CriticalMax = PressureChange();
632  Delta.CurrentMax = PressureChange();
633
634  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
635  for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
636    unsigned POld = OldMaxPressureVec[i];
637    unsigned PNew = NewMaxPressureVec[i];
638    if (PNew == POld) // No change in this set in the common case.
639      continue;
640
641    if (!Delta.CriticalMax.isValid()) {
642      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
643        ++CritIdx;
644
645      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
646        int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
647        if (PDiff > 0) {
648          Delta.CriticalMax = PressureChange(i);
649          Delta.CriticalMax.setUnitInc(PDiff);
650        }
651      }
652    }
653    // Find the first increase above MaxPressureLimit.
654    // (Ignores negative MDiff).
655    if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
656      Delta.CurrentMax = PressureChange(i);
657      Delta.CurrentMax.setUnitInc(PNew - POld);
658      if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
659        break;
660    }
661  }
662}
663
664/// Record the upward impact of a single instruction on current register
665/// pressure. Unlike the advance/recede pressure tracking interface, this does
666/// not discover live in/outs.
667///
668/// This is intended for speculative queries. It leaves pressure inconsistent
669/// with the current position, so must be restored by the caller.
670void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
671  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
672
673  // Account for register pressure similar to RegPressureTracker::recede().
674  RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
675  collectOperands(MI, RegOpers);
676
677  // Boost max pressure for all dead defs together.
678  // Since CurrSetPressure and MaxSetPressure
679  increaseRegPressure(RegOpers.DeadDefs);
680  decreaseRegPressure(RegOpers.DeadDefs);
681
682  // Kill liveness at live defs.
683  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
684    unsigned Reg = RegOpers.Defs[i];
685    if (!containsReg(RegOpers.Uses, Reg))
686      decreaseRegPressure(Reg);
687  }
688  // Generate liveness for uses.
689  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
690    unsigned Reg = RegOpers.Uses[i];
691    if (!LiveRegs.contains(Reg))
692      increaseRegPressure(Reg);
693  }
694}
695
696/// Consider the pressure increase caused by traversing this instruction
697/// bottom-up. Find the pressure set with the most change beyond its pressure
698/// limit based on the tracker's current pressure, and return the change in
699/// number of register units of that pressure set introduced by this
700/// instruction.
701///
702/// This assumes that the current LiveOut set is sufficient.
703///
704/// FIXME: This is expensive for an on-the-fly query. We need to cache the
705/// result per-SUnit with enough information to adjust for the current
706/// scheduling position. But this works as a proof of concept.
707void RegPressureTracker::
708getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
709                          RegPressureDelta &Delta,
710                          ArrayRef<PressureChange> CriticalPSets,
711                          ArrayRef<unsigned> MaxPressureLimit) {
712  // Snapshot Pressure.
713  // FIXME: The snapshot heap space should persist. But I'm planning to
714  // summarize the pressure effect so we don't need to snapshot at all.
715  std::vector<unsigned> SavedPressure = CurrSetPressure;
716  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
717
718  bumpUpwardPressure(MI);
719
720  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
721                             LiveThruPressure);
722  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
723                          MaxPressureLimit, Delta);
724  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
725         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
726
727  // Restore the tracker's state.
728  P.MaxSetPressure.swap(SavedMaxPressure);
729  CurrSetPressure.swap(SavedPressure);
730
731#ifndef NDEBUG
732  if (!PDiff)
733    return;
734
735  // Check if the alternate algorithm yields the same result.
736  RegPressureDelta Delta2;
737  getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
738  if (Delta != Delta2) {
739    dbgs() << "DELTA: " << *MI;
740    if (Delta.Excess.isValid())
741      dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
742             << " " << Delta.Excess.getUnitInc() << "\n";
743    if (Delta.CriticalMax.isValid())
744      dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
745             << " " << Delta.CriticalMax.getUnitInc() << "\n";
746    if (Delta.CurrentMax.isValid())
747      dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
748             << " " << Delta.CurrentMax.getUnitInc() << "\n";
749    if (Delta2.Excess.isValid())
750      dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
751             << " " << Delta2.Excess.getUnitInc() << "\n";
752    if (Delta2.CriticalMax.isValid())
753      dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
754             << " " << Delta2.CriticalMax.getUnitInc() << "\n";
755    if (Delta2.CurrentMax.isValid())
756      dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
757             << " " << Delta2.CurrentMax.getUnitInc() << "\n";
758    llvm_unreachable("RegP Delta Mismatch");
759  }
760#endif
761}
762
763/// This is a prototype of the fast version of querying register pressure that
764/// does not directly depend on current liveness. It's still slow because we
765/// recompute pressure change on-the-fly. This implementation only exists to
766/// prove correctness.
767///
768/// @param Delta captures information needed for heuristics.
769///
770/// @param CriticalPSets Are the pressure sets that are known to exceed some
771/// limit within the region, not necessarily at the current position.
772///
773/// @param MaxPressureLimit Is the max pressure within the region, not
774/// necessarily at the current position.
775void RegPressureTracker::
776getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff1,
777                       RegPressureDelta &Delta,
778                       ArrayRef<PressureChange> CriticalPSets,
779                       ArrayRef<unsigned> MaxPressureLimit) const {
780  RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
781  collectOperands(MI, RegOpers);
782
783  // Decrease the pressure change for live uses.
784  PressureDiff PDiff = PDiff1;
785  for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i) {
786    if (LiveRegs.contains(RegOpers.Uses[i]))
787      PDiff.addPressureChange(RegOpers.Uses[i], true, MRI);
788  }
789
790  // Now directly query pressure from PDiff. Everything above this can be
791  // cached and updated independent of the query.
792  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
793  for (PressureDiff::const_iterator
794         PDiffI = PDiff.begin(), PDiffE = PDiff.end();
795       PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
796
797    unsigned PSetID = PDiffI->getPSet();
798    unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
799    if (!LiveThruPressure.empty())
800      Limit += LiveThruPressure[PSetID];
801
802    unsigned POld = CurrSetPressure[PSetID];
803    unsigned MOld = P.MaxSetPressure[PSetID];
804    unsigned MNew = MOld;
805    // Ignore DeadDefs here because they aren't captured by PressureChange.
806    unsigned PNew = POld + PDiffI->getUnitInc();
807    assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
808    if (PNew > MOld)
809      MNew = PNew;
810    // Check if current pressure has exceeded the limit.
811    if (!Delta.Excess.isValid()) {
812      unsigned ExcessInc = 0;
813      if (PNew > Limit)
814        ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
815      else if (POld > Limit)
816        ExcessInc = Limit - POld;
817      if (ExcessInc) {
818        Delta.Excess = PressureChange(PSetID);
819        Delta.Excess.setUnitInc(ExcessInc);
820      }
821    }
822    // Check if max pressure has exceeded a critical pressure set max.
823    if (MNew == MOld)
824      continue;
825    if (!Delta.CriticalMax.isValid()) {
826      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
827        ++CritIdx;
828
829      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
830        int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
831        if (CritInc > 0 && CritInc <= INT16_MAX) {
832          Delta.CriticalMax = PressureChange(PSetID);
833          Delta.CriticalMax.setUnitInc(CritInc);
834        }
835      }
836    }
837    // Check if max pressure has exceeded the current max.
838    if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
839      Delta.CurrentMax = PressureChange(PSetID);
840      Delta.CurrentMax.setUnitInc(MNew - MOld);
841    }
842  }
843}
844
845/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
846static bool findUseBetween(unsigned Reg,
847                           SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
848                           const MachineRegisterInfo *MRI,
849                           const LiveIntervals *LIS) {
850  for (MachineRegisterInfo::use_nodbg_iterator
851         UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
852         UI != UE; UI.skipInstruction()) {
853      const MachineInstr* MI = &*UI;
854      if (MI->isDebugValue())
855        continue;
856      SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
857      if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
858        return true;
859  }
860  return false;
861}
862
863/// Record the downward impact of a single instruction on current register
864/// pressure. Unlike the advance/recede pressure tracking interface, this does
865/// not discover live in/outs.
866///
867/// This is intended for speculative queries. It leaves pressure inconsistent
868/// with the current position, so must be restored by the caller.
869void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
870  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
871
872  // Account for register pressure similar to RegPressureTracker::recede().
873  RegisterOperands RegOpers(TRI, MRI);
874  collectOperands(MI, RegOpers);
875
876  // Kill liveness at last uses. Assume allocatable physregs are single-use
877  // rather than checking LiveIntervals.
878  SlotIndex SlotIdx;
879  if (RequireIntervals)
880    SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
881
882  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
883    unsigned Reg = RegOpers.Uses[i];
884    if (RequireIntervals) {
885      // FIXME: allow the caller to pass in the list of vreg uses that remain
886      // to be bottom-scheduled to avoid searching uses at each query.
887      SlotIndex CurrIdx = getCurrSlot();
888      const LiveInterval *LI = getInterval(Reg);
889      if (LI && LI->isKilledAtInstr(SlotIdx)
890          && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
891        decreaseRegPressure(Reg);
892      }
893    }
894    else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
895      // Allocatable physregs are always single-use before register rewriting.
896      decreaseRegPressure(Reg);
897    }
898  }
899
900  // Generate liveness for defs.
901  increaseRegPressure(RegOpers.Defs);
902
903  // Boost pressure for all dead defs together.
904  increaseRegPressure(RegOpers.DeadDefs);
905  decreaseRegPressure(RegOpers.DeadDefs);
906}
907
908/// Consider the pressure increase caused by traversing this instruction
909/// top-down. Find the register class with the most change in its pressure limit
910/// based on the tracker's current pressure, and return the number of excess
911/// register units of that pressure set introduced by this instruction.
912///
913/// This assumes that the current LiveIn set is sufficient.
914void RegPressureTracker::
915getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
916                            ArrayRef<PressureChange> CriticalPSets,
917                            ArrayRef<unsigned> MaxPressureLimit) {
918  // Snapshot Pressure.
919  std::vector<unsigned> SavedPressure = CurrSetPressure;
920  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
921
922  bumpDownwardPressure(MI);
923
924  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
925                             LiveThruPressure);
926  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
927                          MaxPressureLimit, Delta);
928  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
929         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
930
931  // Restore the tracker's state.
932  P.MaxSetPressure.swap(SavedMaxPressure);
933  CurrSetPressure.swap(SavedPressure);
934}
935
936/// Get the pressure of each PSet after traversing this instruction bottom-up.
937void RegPressureTracker::
938getUpwardPressure(const MachineInstr *MI,
939                  std::vector<unsigned> &PressureResult,
940                  std::vector<unsigned> &MaxPressureResult) {
941  // Snapshot pressure.
942  PressureResult = CurrSetPressure;
943  MaxPressureResult = P.MaxSetPressure;
944
945  bumpUpwardPressure(MI);
946
947  // Current pressure becomes the result. Restore current pressure.
948  P.MaxSetPressure.swap(MaxPressureResult);
949  CurrSetPressure.swap(PressureResult);
950}
951
952/// Get the pressure of each PSet after traversing this instruction top-down.
953void RegPressureTracker::
954getDownwardPressure(const MachineInstr *MI,
955                    std::vector<unsigned> &PressureResult,
956                    std::vector<unsigned> &MaxPressureResult) {
957  // Snapshot pressure.
958  PressureResult = CurrSetPressure;
959  MaxPressureResult = P.MaxSetPressure;
960
961  bumpDownwardPressure(MI);
962
963  // Current pressure becomes the result. Restore current pressure.
964  P.MaxSetPressure.swap(MaxPressureResult);
965  CurrSetPressure.swap(PressureResult);
966}
967