RegisterPressure.cpp revision 4f3b5e8c9232e43d1291aab8db5f5698d7ee0ea4 
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    if (LiveRegs.erase(Reg))
502      decreaseRegPressure(Reg);
503    else
504      discoverLiveOut(Reg);
505  }
506
507  // Generate liveness for uses.
508  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
509    unsigned Reg = RegOpers.Uses[i];
510    if (!LiveRegs.contains(Reg)) {
511      // Adjust liveouts if LiveIntervals are available.
512      if (RequireIntervals) {
513        const LiveRange *LR = getLiveRange(Reg);
514        if (LR) {
515          LiveQueryResult LRQ = LR->Query(SlotIdx);
516          if (!LRQ.isKill() && !LRQ.valueDefined())
517            discoverLiveOut(Reg);
518        }
519      }
520      increaseRegPressure(Reg);
521      LiveRegs.insert(Reg);
522      if (LiveUses && !containsReg(*LiveUses, Reg))
523        LiveUses->push_back(Reg);
524    }
525  }
526  if (TrackUntiedDefs) {
527    for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
528      unsigned Reg = RegOpers.Defs[i];
529      if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
530        UntiedDefs.insert(Reg);
531    }
532  }
533  return true;
534}
535
536/// Advance across the current instruction.
537bool RegPressureTracker::advance() {
538  assert(!TrackUntiedDefs && "unsupported mode");
539
540  // Check for the bottom of the analyzable region.
541  if (CurrPos == MBB->end()) {
542    closeRegion();
543    return false;
544  }
545  if (!isTopClosed())
546    closeTop();
547
548  SlotIndex SlotIdx;
549  if (RequireIntervals)
550    SlotIdx = getCurrSlot();
551
552  // Open the bottom of the region using slot indexes.
553  if (isBottomClosed()) {
554    if (RequireIntervals)
555      static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
556    else
557      static_cast<RegionPressure&>(P).openBottom(CurrPos);
558  }
559
560  RegisterOperands RegOpers(TRI, MRI);
561  collectOperands(CurrPos, RegOpers);
562
563  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
564    unsigned Reg = RegOpers.Uses[i];
565    // Discover live-ins.
566    bool isLive = LiveRegs.contains(Reg);
567    if (!isLive)
568      discoverLiveIn(Reg);
569    // Kill liveness at last uses.
570    bool lastUse = false;
571    if (RequireIntervals) {
572      const LiveRange *LR = getLiveRange(Reg);
573      lastUse = LR && LR->Query(SlotIdx).isKill();
574    }
575    else {
576      // Allocatable physregs are always single-use before register rewriting.
577      lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
578    }
579    if (lastUse && isLive) {
580      LiveRegs.erase(Reg);
581      decreaseRegPressure(Reg);
582    }
583    else if (!lastUse && !isLive)
584      increaseRegPressure(Reg);
585  }
586
587  // Generate liveness for defs.
588  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
589    unsigned Reg = RegOpers.Defs[i];
590    if (LiveRegs.insert(Reg))
591      increaseRegPressure(Reg);
592  }
593
594  // Boost pressure for all dead defs together.
595  increaseRegPressure(RegOpers.DeadDefs);
596  decreaseRegPressure(RegOpers.DeadDefs);
597
598  // Find the next instruction.
599  do
600    ++CurrPos;
601  while (CurrPos != MBB->end() && CurrPos->isDebugValue());
602  return true;
603}
604
605/// Find the max change in excess pressure across all sets.
606static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
607                                       ArrayRef<unsigned> NewPressureVec,
608                                       RegPressureDelta &Delta,
609                                       const RegisterClassInfo *RCI,
610                                       ArrayRef<unsigned> LiveThruPressureVec) {
611  Delta.Excess = PressureChange();
612  for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
613    unsigned POld = OldPressureVec[i];
614    unsigned PNew = NewPressureVec[i];
615    int PDiff = (int)PNew - (int)POld;
616    if (!PDiff) // No change in this set in the common case.
617      continue;
618    // Only consider change beyond the limit.
619    unsigned Limit = RCI->getRegPressureSetLimit(i);
620    if (!LiveThruPressureVec.empty())
621      Limit += LiveThruPressureVec[i];
622
623    if (Limit > POld) {
624      if (Limit > PNew)
625        PDiff = 0;            // Under the limit
626      else
627        PDiff = PNew - Limit; // Just exceeded limit.
628    }
629    else if (Limit > PNew)
630      PDiff = Limit - POld;   // Just obeyed limit.
631
632    if (PDiff) {
633      Delta.Excess = PressureChange(i);
634      Delta.Excess.setUnitInc(PDiff);
635      break;
636    }
637  }
638}
639
640/// Find the max change in max pressure that either surpasses a critical PSet
641/// limit or exceeds the current MaxPressureLimit.
642///
643/// FIXME: comparing each element of the old and new MaxPressure vectors here is
644/// silly. It's done now to demonstrate the concept but will go away with a
645/// RegPressureTracker API change to work with pressure differences.
646static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
647                                    ArrayRef<unsigned> NewMaxPressureVec,
648                                    ArrayRef<PressureChange> CriticalPSets,
649                                    ArrayRef<unsigned> MaxPressureLimit,
650                                    RegPressureDelta &Delta) {
651  Delta.CriticalMax = PressureChange();
652  Delta.CurrentMax = PressureChange();
653
654  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
655  for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
656    unsigned POld = OldMaxPressureVec[i];
657    unsigned PNew = NewMaxPressureVec[i];
658    if (PNew == POld) // No change in this set in the common case.
659      continue;
660
661    if (!Delta.CriticalMax.isValid()) {
662      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
663        ++CritIdx;
664
665      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
666        int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
667        if (PDiff > 0) {
668          Delta.CriticalMax = PressureChange(i);
669          Delta.CriticalMax.setUnitInc(PDiff);
670        }
671      }
672    }
673    // Find the first increase above MaxPressureLimit.
674    // (Ignores negative MDiff).
675    if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
676      Delta.CurrentMax = PressureChange(i);
677      Delta.CurrentMax.setUnitInc(PNew - POld);
678      if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
679        break;
680    }
681  }
682}
683
684/// Record the upward impact of a single instruction on current register
685/// pressure. Unlike the advance/recede pressure tracking interface, this does
686/// not discover live in/outs.
687///
688/// This is intended for speculative queries. It leaves pressure inconsistent
689/// with the current position, so must be restored by the caller.
690void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
691  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
692
693  // Account for register pressure similar to RegPressureTracker::recede().
694  RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
695  collectOperands(MI, RegOpers);
696
697  // Boost max pressure for all dead defs together.
698  // Since CurrSetPressure and MaxSetPressure
699  increaseRegPressure(RegOpers.DeadDefs);
700  decreaseRegPressure(RegOpers.DeadDefs);
701
702  // Kill liveness at live defs.
703  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
704    unsigned Reg = RegOpers.Defs[i];
705    if (!containsReg(RegOpers.Uses, Reg))
706      decreaseRegPressure(Reg);
707  }
708  // Generate liveness for uses.
709  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
710    unsigned Reg = RegOpers.Uses[i];
711    if (!LiveRegs.contains(Reg))
712      increaseRegPressure(Reg);
713  }
714}
715
716/// Consider the pressure increase caused by traversing this instruction
717/// bottom-up. Find the pressure set with the most change beyond its pressure
718/// limit based on the tracker's current pressure, and return the change in
719/// number of register units of that pressure set introduced by this
720/// instruction.
721///
722/// This assumes that the current LiveOut set is sufficient.
723///
724/// FIXME: This is expensive for an on-the-fly query. We need to cache the
725/// result per-SUnit with enough information to adjust for the current
726/// scheduling position. But this works as a proof of concept.
727void RegPressureTracker::
728getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
729                          RegPressureDelta &Delta,
730                          ArrayRef<PressureChange> CriticalPSets,
731                          ArrayRef<unsigned> MaxPressureLimit) {
732  // Snapshot Pressure.
733  // FIXME: The snapshot heap space should persist. But I'm planning to
734  // summarize the pressure effect so we don't need to snapshot at all.
735  std::vector<unsigned> SavedPressure = CurrSetPressure;
736  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
737
738  bumpUpwardPressure(MI);
739
740  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
741                             LiveThruPressure);
742  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
743                          MaxPressureLimit, Delta);
744  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
745         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
746
747  // Restore the tracker's state.
748  P.MaxSetPressure.swap(SavedMaxPressure);
749  CurrSetPressure.swap(SavedPressure);
750
751#ifndef NDEBUG
752  if (!PDiff)
753    return;
754
755  // Check if the alternate algorithm yields the same result.
756  RegPressureDelta Delta2;
757  getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
758  if (Delta != Delta2) {
759    dbgs() << "DELTA: " << *MI;
760    if (Delta.Excess.isValid())
761      dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
762             << " " << Delta.Excess.getUnitInc() << "\n";
763    if (Delta.CriticalMax.isValid())
764      dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
765             << " " << Delta.CriticalMax.getUnitInc() << "\n";
766    if (Delta.CurrentMax.isValid())
767      dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
768             << " " << Delta.CurrentMax.getUnitInc() << "\n";
769    if (Delta2.Excess.isValid())
770      dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
771             << " " << Delta2.Excess.getUnitInc() << "\n";
772    if (Delta2.CriticalMax.isValid())
773      dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
774             << " " << Delta2.CriticalMax.getUnitInc() << "\n";
775    if (Delta2.CurrentMax.isValid())
776      dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
777             << " " << Delta2.CurrentMax.getUnitInc() << "\n";
778    llvm_unreachable("RegP Delta Mismatch");
779  }
780#endif
781}
782
783/// This is a prototype of the fast version of querying register pressure that
784/// does not directly depend on current liveness. It's still slow because we
785/// recompute pressure change on-the-fly. This implementation only exists to
786/// prove correctness.
787///
788/// @param Delta captures information needed for heuristics.
789///
790/// @param CriticalPSets Are the pressure sets that are known to exceed some
791/// limit within the region, not necessarily at the current position.
792///
793/// @param MaxPressureLimit Is the max pressure within the region, not
794/// necessarily at the current position.
795void RegPressureTracker::
796getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
797                       RegPressureDelta &Delta,
798                       ArrayRef<PressureChange> CriticalPSets,
799                       ArrayRef<unsigned> MaxPressureLimit) const {
800  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
801  for (PressureDiff::const_iterator
802         PDiffI = PDiff.begin(), PDiffE = PDiff.end();
803       PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
804
805    unsigned PSetID = PDiffI->getPSet();
806    unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
807    if (!LiveThruPressure.empty())
808      Limit += LiveThruPressure[PSetID];
809
810    unsigned POld = CurrSetPressure[PSetID];
811    unsigned MOld = P.MaxSetPressure[PSetID];
812    unsigned MNew = MOld;
813    // Ignore DeadDefs here because they aren't captured by PressureChange.
814    unsigned PNew = POld + PDiffI->getUnitInc();
815    assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
816    if (PNew > MOld)
817      MNew = PNew;
818    // Check if current pressure has exceeded the limit.
819    if (!Delta.Excess.isValid()) {
820      unsigned ExcessInc = 0;
821      if (PNew > Limit)
822        ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
823      else if (POld > Limit)
824        ExcessInc = Limit - POld;
825      if (ExcessInc) {
826        Delta.Excess = PressureChange(PSetID);
827        Delta.Excess.setUnitInc(ExcessInc);
828      }
829    }
830    // Check if max pressure has exceeded a critical pressure set max.
831    if (MNew == MOld)
832      continue;
833    if (!Delta.CriticalMax.isValid()) {
834      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
835        ++CritIdx;
836
837      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
838        int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
839        if (CritInc > 0 && CritInc <= INT16_MAX) {
840          Delta.CriticalMax = PressureChange(PSetID);
841          Delta.CriticalMax.setUnitInc(CritInc);
842        }
843      }
844    }
845    // Check if max pressure has exceeded the current max.
846    if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
847      Delta.CurrentMax = PressureChange(PSetID);
848      Delta.CurrentMax.setUnitInc(MNew - MOld);
849    }
850  }
851}
852
853/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
854static bool findUseBetween(unsigned Reg,
855                           SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
856                           const MachineRegisterInfo *MRI,
857                           const LiveIntervals *LIS) {
858  for (MachineRegisterInfo::use_nodbg_iterator
859         UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
860         UI != UE; UI.skipInstruction()) {
861      const MachineInstr* MI = &*UI;
862      if (MI->isDebugValue())
863        continue;
864      SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
865      if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
866        return true;
867  }
868  return false;
869}
870
871/// Record the downward impact of a single instruction on current register
872/// pressure. Unlike the advance/recede pressure tracking interface, this does
873/// not discover live in/outs.
874///
875/// This is intended for speculative queries. It leaves pressure inconsistent
876/// with the current position, so must be restored by the caller.
877void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
878  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
879
880  // Account for register pressure similar to RegPressureTracker::recede().
881  RegisterOperands RegOpers(TRI, MRI);
882  collectOperands(MI, RegOpers);
883
884  // Kill liveness at last uses. Assume allocatable physregs are single-use
885  // rather than checking LiveIntervals.
886  SlotIndex SlotIdx;
887  if (RequireIntervals)
888    SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
889
890  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
891    unsigned Reg = RegOpers.Uses[i];
892    if (RequireIntervals) {
893      // FIXME: allow the caller to pass in the list of vreg uses that remain
894      // to be bottom-scheduled to avoid searching uses at each query.
895      SlotIndex CurrIdx = getCurrSlot();
896      const LiveRange *LR = getLiveRange(Reg);
897      if (LR) {
898        LiveQueryResult LRQ = LR->Query(SlotIdx);
899        if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
900          decreaseRegPressure(Reg);
901        }
902      }
903    }
904    else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
905      // Allocatable physregs are always single-use before register rewriting.
906      decreaseRegPressure(Reg);
907    }
908  }
909
910  // Generate liveness for defs.
911  increaseRegPressure(RegOpers.Defs);
912
913  // Boost pressure for all dead defs together.
914  increaseRegPressure(RegOpers.DeadDefs);
915  decreaseRegPressure(RegOpers.DeadDefs);
916}
917
918/// Consider the pressure increase caused by traversing this instruction
919/// top-down. Find the register class with the most change in its pressure limit
920/// based on the tracker's current pressure, and return the number of excess
921/// register units of that pressure set introduced by this instruction.
922///
923/// This assumes that the current LiveIn set is sufficient.
924void RegPressureTracker::
925getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
926                            ArrayRef<PressureChange> CriticalPSets,
927                            ArrayRef<unsigned> MaxPressureLimit) {
928  // Snapshot Pressure.
929  std::vector<unsigned> SavedPressure = CurrSetPressure;
930  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
931
932  bumpDownwardPressure(MI);
933
934  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
935                             LiveThruPressure);
936  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
937                          MaxPressureLimit, Delta);
938  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
939         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
940
941  // Restore the tracker's state.
942  P.MaxSetPressure.swap(SavedMaxPressure);
943  CurrSetPressure.swap(SavedPressure);
944}
945
946/// Get the pressure of each PSet after traversing this instruction bottom-up.
947void RegPressureTracker::
948getUpwardPressure(const MachineInstr *MI,
949                  std::vector<unsigned> &PressureResult,
950                  std::vector<unsigned> &MaxPressureResult) {
951  // Snapshot pressure.
952  PressureResult = CurrSetPressure;
953  MaxPressureResult = P.MaxSetPressure;
954
955  bumpUpwardPressure(MI);
956
957  // Current pressure becomes the result. Restore current pressure.
958  P.MaxSetPressure.swap(MaxPressureResult);
959  CurrSetPressure.swap(PressureResult);
960}
961
962/// Get the pressure of each PSet after traversing this instruction top-down.
963void RegPressureTracker::
964getDownwardPressure(const MachineInstr *MI,
965                    std::vector<unsigned> &PressureResult,
966                    std::vector<unsigned> &MaxPressureResult) {
967  // Snapshot pressure.
968  PressureResult = CurrSetPressure;
969  MaxPressureResult = P.MaxSetPressure;
970
971  bumpDownwardPressure(MI);
972
973  // Current pressure becomes the result. Restore current pressure.
974  P.MaxSetPressure.swap(MaxPressureResult);
975  CurrSetPressure.swap(PressureResult);
976}
977