RegisterPressure.cpp revision 846b31d74aa673a178f57f9d47f366d8ddb756d3 
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    PDiff.addPressureChange(RegOpers.Defs[i], true, MRI);
404
405  for (unsigned i = 0, e = RegOpers.Uses.size(); i != e; ++i)
406    PDiff.addPressureChange(RegOpers.Uses[i], false, MRI);
407}
408
409/// Force liveness of registers.
410void RegPressureTracker::addLiveRegs(ArrayRef<unsigned> Regs) {
411  for (unsigned i = 0, e = Regs.size(); i != e; ++i) {
412    if (LiveRegs.insert(Regs[i]))
413      increaseRegPressure(Regs[i]);
414  }
415}
416
417/// Add Reg to the live in set and increase max pressure.
418void RegPressureTracker::discoverLiveIn(unsigned Reg) {
419  assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
420  if (containsReg(P.LiveInRegs, Reg))
421    return;
422
423  // At live in discovery, unconditionally increase the high water mark.
424  P.LiveInRegs.push_back(Reg);
425  increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
426}
427
428/// Add Reg to the live out set and increase max pressure.
429void RegPressureTracker::discoverLiveOut(unsigned Reg) {
430  assert(!LiveRegs.contains(Reg) && "avoid bumping max pressure twice");
431  if (containsReg(P.LiveOutRegs, Reg))
432    return;
433
434  // At live out discovery, unconditionally increase the high water mark.
435  P.LiveOutRegs.push_back(Reg);
436  increaseSetPressure(P.MaxSetPressure, MRI->getPressureSets(Reg));
437}
438
439/// Recede across the previous instruction. If LiveUses is provided, record any
440/// RegUnits that are made live by the current instruction's uses. This includes
441/// registers that are both defined and used by the instruction.  If a pressure
442/// difference pointer is provided record the changes is pressure caused by this
443/// instruction independent of liveness.
444bool RegPressureTracker::recede(SmallVectorImpl<unsigned> *LiveUses,
445                                PressureDiff *PDiff) {
446  // Check for the top of the analyzable region.
447  if (CurrPos == MBB->begin()) {
448    closeRegion();
449    return false;
450  }
451  if (!isBottomClosed())
452    closeBottom();
453
454  // Open the top of the region using block iterators.
455  if (!RequireIntervals && isTopClosed())
456    static_cast<RegionPressure&>(P).openTop(CurrPos);
457
458  // Find the previous instruction.
459  do
460    --CurrPos;
461  while (CurrPos != MBB->begin() && CurrPos->isDebugValue());
462
463  if (CurrPos->isDebugValue()) {
464    closeRegion();
465    return false;
466  }
467  SlotIndex SlotIdx;
468  if (RequireIntervals)
469    SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
470
471  // Open the top of the region using slot indexes.
472  if (RequireIntervals && isTopClosed())
473    static_cast<IntervalPressure&>(P).openTop(SlotIdx);
474
475  RegisterOperands RegOpers(TRI, MRI);
476  collectOperands(CurrPos, RegOpers);
477
478  if (PDiff)
479    collectPDiff(*PDiff, RegOpers, MRI);
480
481  // Boost pressure for all dead defs together.
482  increaseRegPressure(RegOpers.DeadDefs);
483  decreaseRegPressure(RegOpers.DeadDefs);
484
485  // Kill liveness at live defs.
486  // TODO: consider earlyclobbers?
487  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
488    unsigned Reg = RegOpers.Defs[i];
489    if (LiveRegs.erase(Reg))
490      decreaseRegPressure(Reg);
491    else
492      discoverLiveOut(Reg);
493  }
494
495  // Generate liveness for uses.
496  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
497    unsigned Reg = RegOpers.Uses[i];
498    if (!LiveRegs.contains(Reg)) {
499      // Adjust liveouts if LiveIntervals are available.
500      if (RequireIntervals) {
501        const LiveInterval *LI = getInterval(Reg);
502        // Check if this LR is killed and not redefined here.
503        if (LI) {
504          LiveRangeQuery LRQ(*LI, SlotIdx);
505          if (!LRQ.isKill() && !LRQ.valueDefined())
506            discoverLiveOut(Reg);
507        }
508      }
509      increaseRegPressure(Reg);
510      LiveRegs.insert(Reg);
511      if (LiveUses && !containsReg(*LiveUses, Reg))
512        LiveUses->push_back(Reg);
513    }
514  }
515  if (TrackUntiedDefs) {
516    for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
517      unsigned Reg = RegOpers.Defs[i];
518      if (TargetRegisterInfo::isVirtualRegister(Reg) && !LiveRegs.contains(Reg))
519        UntiedDefs.insert(Reg);
520    }
521  }
522  return true;
523}
524
525/// Advance across the current instruction.
526bool RegPressureTracker::advance() {
527  assert(!TrackUntiedDefs && "unsupported mode");
528
529  // Check for the bottom of the analyzable region.
530  if (CurrPos == MBB->end()) {
531    closeRegion();
532    return false;
533  }
534  if (!isTopClosed())
535    closeTop();
536
537  SlotIndex SlotIdx;
538  if (RequireIntervals)
539    SlotIdx = getCurrSlot();
540
541  // Open the bottom of the region using slot indexes.
542  if (isBottomClosed()) {
543    if (RequireIntervals)
544      static_cast<IntervalPressure&>(P).openBottom(SlotIdx);
545    else
546      static_cast<RegionPressure&>(P).openBottom(CurrPos);
547  }
548
549  RegisterOperands RegOpers(TRI, MRI);
550  collectOperands(CurrPos, RegOpers);
551
552  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
553    unsigned Reg = RegOpers.Uses[i];
554    // Discover live-ins.
555    bool isLive = LiveRegs.contains(Reg);
556    if (!isLive)
557      discoverLiveIn(Reg);
558    // Kill liveness at last uses.
559    bool lastUse = false;
560    if (RequireIntervals) {
561      const LiveInterval *LI = getInterval(Reg);
562      lastUse = LI && LiveRangeQuery(*LI, SlotIdx).isKill();
563    }
564    else {
565      // Allocatable physregs are always single-use before register rewriting.
566      lastUse = !TargetRegisterInfo::isVirtualRegister(Reg);
567    }
568    if (lastUse && isLive) {
569      LiveRegs.erase(Reg);
570      decreaseRegPressure(Reg);
571    }
572    else if (!lastUse && !isLive)
573      increaseRegPressure(Reg);
574  }
575
576  // Generate liveness for defs.
577  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
578    unsigned Reg = RegOpers.Defs[i];
579    if (LiveRegs.insert(Reg))
580      increaseRegPressure(Reg);
581  }
582
583  // Boost pressure for all dead defs together.
584  increaseRegPressure(RegOpers.DeadDefs);
585  decreaseRegPressure(RegOpers.DeadDefs);
586
587  // Find the next instruction.
588  do
589    ++CurrPos;
590  while (CurrPos != MBB->end() && CurrPos->isDebugValue());
591  return true;
592}
593
594/// Find the max change in excess pressure across all sets.
595static void computeExcessPressureDelta(ArrayRef<unsigned> OldPressureVec,
596                                       ArrayRef<unsigned> NewPressureVec,
597                                       RegPressureDelta &Delta,
598                                       const RegisterClassInfo *RCI,
599                                       ArrayRef<unsigned> LiveThruPressureVec) {
600  Delta.Excess = PressureChange();
601  for (unsigned i = 0, e = OldPressureVec.size(); i < e; ++i) {
602    unsigned POld = OldPressureVec[i];
603    unsigned PNew = NewPressureVec[i];
604    int PDiff = (int)PNew - (int)POld;
605    if (!PDiff) // No change in this set in the common case.
606      continue;
607    // Only consider change beyond the limit.
608    unsigned Limit = RCI->getRegPressureSetLimit(i);
609    if (!LiveThruPressureVec.empty())
610      Limit += LiveThruPressureVec[i];
611
612    if (Limit > POld) {
613      if (Limit > PNew)
614        PDiff = 0;            // Under the limit
615      else
616        PDiff = PNew - Limit; // Just exceeded limit.
617    }
618    else if (Limit > PNew)
619      PDiff = Limit - POld;   // Just obeyed limit.
620
621    if (PDiff) {
622      Delta.Excess = PressureChange(i);
623      Delta.Excess.setUnitInc(PDiff);
624      break;
625    }
626  }
627}
628
629/// Find the max change in max pressure that either surpasses a critical PSet
630/// limit or exceeds the current MaxPressureLimit.
631///
632/// FIXME: comparing each element of the old and new MaxPressure vectors here is
633/// silly. It's done now to demonstrate the concept but will go away with a
634/// RegPressureTracker API change to work with pressure differences.
635static void computeMaxPressureDelta(ArrayRef<unsigned> OldMaxPressureVec,
636                                    ArrayRef<unsigned> NewMaxPressureVec,
637                                    ArrayRef<PressureChange> CriticalPSets,
638                                    ArrayRef<unsigned> MaxPressureLimit,
639                                    RegPressureDelta &Delta) {
640  Delta.CriticalMax = PressureChange();
641  Delta.CurrentMax = PressureChange();
642
643  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
644  for (unsigned i = 0, e = OldMaxPressureVec.size(); i < e; ++i) {
645    unsigned POld = OldMaxPressureVec[i];
646    unsigned PNew = NewMaxPressureVec[i];
647    if (PNew == POld) // No change in this set in the common case.
648      continue;
649
650    if (!Delta.CriticalMax.isValid()) {
651      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < i)
652        ++CritIdx;
653
654      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == i) {
655        int PDiff = (int)PNew - (int)CriticalPSets[CritIdx].getUnitInc();
656        if (PDiff > 0) {
657          Delta.CriticalMax = PressureChange(i);
658          Delta.CriticalMax.setUnitInc(PDiff);
659        }
660      }
661    }
662    // Find the first increase above MaxPressureLimit.
663    // (Ignores negative MDiff).
664    if (!Delta.CurrentMax.isValid() && PNew > MaxPressureLimit[i]) {
665      Delta.CurrentMax = PressureChange(i);
666      Delta.CurrentMax.setUnitInc(PNew - POld);
667      if (CritIdx == CritEnd || Delta.CriticalMax.isValid())
668        break;
669    }
670  }
671}
672
673/// Record the upward impact of a single instruction on current register
674/// pressure. Unlike the advance/recede pressure tracking interface, this does
675/// not discover live in/outs.
676///
677/// This is intended for speculative queries. It leaves pressure inconsistent
678/// with the current position, so must be restored by the caller.
679void RegPressureTracker::bumpUpwardPressure(const MachineInstr *MI) {
680  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
681
682  // Account for register pressure similar to RegPressureTracker::recede().
683  RegisterOperands RegOpers(TRI, MRI, /*IgnoreDead=*/true);
684  collectOperands(MI, RegOpers);
685
686  // Boost max pressure for all dead defs together.
687  // Since CurrSetPressure and MaxSetPressure
688  increaseRegPressure(RegOpers.DeadDefs);
689  decreaseRegPressure(RegOpers.DeadDefs);
690
691  // Kill liveness at live defs.
692  for (unsigned i = 0, e = RegOpers.Defs.size(); i < e; ++i) {
693    unsigned Reg = RegOpers.Defs[i];
694    if (!containsReg(RegOpers.Uses, Reg))
695      decreaseRegPressure(Reg);
696  }
697  // Generate liveness for uses.
698  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
699    unsigned Reg = RegOpers.Uses[i];
700    if (!LiveRegs.contains(Reg))
701      increaseRegPressure(Reg);
702  }
703}
704
705/// Consider the pressure increase caused by traversing this instruction
706/// bottom-up. Find the pressure set with the most change beyond its pressure
707/// limit based on the tracker's current pressure, and return the change in
708/// number of register units of that pressure set introduced by this
709/// instruction.
710///
711/// This assumes that the current LiveOut set is sufficient.
712///
713/// FIXME: This is expensive for an on-the-fly query. We need to cache the
714/// result per-SUnit with enough information to adjust for the current
715/// scheduling position. But this works as a proof of concept.
716void RegPressureTracker::
717getMaxUpwardPressureDelta(const MachineInstr *MI, PressureDiff *PDiff,
718                          RegPressureDelta &Delta,
719                          ArrayRef<PressureChange> CriticalPSets,
720                          ArrayRef<unsigned> MaxPressureLimit) {
721  // Snapshot Pressure.
722  // FIXME: The snapshot heap space should persist. But I'm planning to
723  // summarize the pressure effect so we don't need to snapshot at all.
724  std::vector<unsigned> SavedPressure = CurrSetPressure;
725  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
726
727  bumpUpwardPressure(MI);
728
729  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
730                             LiveThruPressure);
731  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
732                          MaxPressureLimit, Delta);
733  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
734         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
735
736  // Restore the tracker's state.
737  P.MaxSetPressure.swap(SavedMaxPressure);
738  CurrSetPressure.swap(SavedPressure);
739
740#ifndef NDEBUG
741  if (!PDiff)
742    return;
743
744  // Check if the alternate algorithm yields the same result.
745  RegPressureDelta Delta2;
746  getUpwardPressureDelta(MI, *PDiff, Delta2, CriticalPSets, MaxPressureLimit);
747  if (Delta != Delta2) {
748    dbgs() << "DELTA: " << *MI;
749    if (Delta.Excess.isValid())
750      dbgs() << "Excess1 " << TRI->getRegPressureSetName(Delta.Excess.getPSet())
751             << " " << Delta.Excess.getUnitInc() << "\n";
752    if (Delta.CriticalMax.isValid())
753      dbgs() << "Critic1 " << TRI->getRegPressureSetName(Delta.CriticalMax.getPSet())
754             << " " << Delta.CriticalMax.getUnitInc() << "\n";
755    if (Delta.CurrentMax.isValid())
756      dbgs() << "CurrMx1 " << TRI->getRegPressureSetName(Delta.CurrentMax.getPSet())
757             << " " << Delta.CurrentMax.getUnitInc() << "\n";
758    if (Delta2.Excess.isValid())
759      dbgs() << "Excess2 " << TRI->getRegPressureSetName(Delta2.Excess.getPSet())
760             << " " << Delta2.Excess.getUnitInc() << "\n";
761    if (Delta2.CriticalMax.isValid())
762      dbgs() << "Critic2 " << TRI->getRegPressureSetName(Delta2.CriticalMax.getPSet())
763             << " " << Delta2.CriticalMax.getUnitInc() << "\n";
764    if (Delta2.CurrentMax.isValid())
765      dbgs() << "CurrMx2 " << TRI->getRegPressureSetName(Delta2.CurrentMax.getPSet())
766             << " " << Delta2.CurrentMax.getUnitInc() << "\n";
767    llvm_unreachable("RegP Delta Mismatch");
768  }
769#endif
770}
771
772/// This is a prototype of the fast version of querying register pressure that
773/// does not directly depend on current liveness. It's still slow because we
774/// recompute pressure change on-the-fly. This implementation only exists to
775/// prove correctness.
776///
777/// @param Delta captures information needed for heuristics.
778///
779/// @param CriticalPSets Are the pressure sets that are known to exceed some
780/// limit within the region, not necessarily at the current position.
781///
782/// @param MaxPressureLimit Is the max pressure within the region, not
783/// necessarily at the current position.
784void RegPressureTracker::
785getUpwardPressureDelta(const MachineInstr *MI, /*const*/ PressureDiff &PDiff,
786                       RegPressureDelta &Delta,
787                       ArrayRef<PressureChange> CriticalPSets,
788                       ArrayRef<unsigned> MaxPressureLimit) const {
789  unsigned CritIdx = 0, CritEnd = CriticalPSets.size();
790  for (PressureDiff::const_iterator
791         PDiffI = PDiff.begin(), PDiffE = PDiff.end();
792       PDiffI != PDiffE && PDiffI->isValid(); ++PDiffI) {
793
794    unsigned PSetID = PDiffI->getPSet();
795    unsigned Limit = RCI->getRegPressureSetLimit(PSetID);
796    if (!LiveThruPressure.empty())
797      Limit += LiveThruPressure[PSetID];
798
799    unsigned POld = CurrSetPressure[PSetID];
800    unsigned MOld = P.MaxSetPressure[PSetID];
801    unsigned MNew = MOld;
802    // Ignore DeadDefs here because they aren't captured by PressureChange.
803    unsigned PNew = POld + PDiffI->getUnitInc();
804    assert((PDiffI->getUnitInc() >= 0) == (PNew >= POld) && "PSet overflow");
805    if (PNew > MOld)
806      MNew = PNew;
807    // Check if current pressure has exceeded the limit.
808    if (!Delta.Excess.isValid()) {
809      unsigned ExcessInc = 0;
810      if (PNew > Limit)
811        ExcessInc = POld > Limit ? PNew - POld : PNew - Limit;
812      else if (POld > Limit)
813        ExcessInc = Limit - POld;
814      if (ExcessInc) {
815        Delta.Excess = PressureChange(PSetID);
816        Delta.Excess.setUnitInc(ExcessInc);
817      }
818    }
819    // Check if max pressure has exceeded a critical pressure set max.
820    if (MNew == MOld)
821      continue;
822    if (!Delta.CriticalMax.isValid()) {
823      while (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() < PSetID)
824        ++CritIdx;
825
826      if (CritIdx != CritEnd && CriticalPSets[CritIdx].getPSet() == PSetID) {
827        int CritInc = (int)MNew - (int)CriticalPSets[CritIdx].getUnitInc();
828        if (CritInc > 0 && CritInc <= INT16_MAX) {
829          Delta.CriticalMax = PressureChange(PSetID);
830          Delta.CriticalMax.setUnitInc(CritInc);
831        }
832      }
833    }
834    // Check if max pressure has exceeded the current max.
835    if (!Delta.CurrentMax.isValid() && MNew > MaxPressureLimit[PSetID]) {
836      Delta.CurrentMax = PressureChange(PSetID);
837      Delta.CurrentMax.setUnitInc(MNew - MOld);
838    }
839  }
840}
841
842/// Helper to find a vreg use between two indices [PriorUseIdx, NextUseIdx).
843static bool findUseBetween(unsigned Reg,
844                           SlotIndex PriorUseIdx, SlotIndex NextUseIdx,
845                           const MachineRegisterInfo *MRI,
846                           const LiveIntervals *LIS) {
847  for (MachineRegisterInfo::use_nodbg_iterator
848         UI = MRI->use_nodbg_begin(Reg), UE = MRI->use_nodbg_end();
849         UI != UE; UI.skipInstruction()) {
850      const MachineInstr* MI = &*UI;
851      if (MI->isDebugValue())
852        continue;
853      SlotIndex InstSlot = LIS->getInstructionIndex(MI).getRegSlot();
854      if (InstSlot >= PriorUseIdx && InstSlot < NextUseIdx)
855        return true;
856  }
857  return false;
858}
859
860/// Record the downward impact of a single instruction on current register
861/// pressure. Unlike the advance/recede pressure tracking interface, this does
862/// not discover live in/outs.
863///
864/// This is intended for speculative queries. It leaves pressure inconsistent
865/// with the current position, so must be restored by the caller.
866void RegPressureTracker::bumpDownwardPressure(const MachineInstr *MI) {
867  assert(!MI->isDebugValue() && "Expect a nondebug instruction.");
868
869  // Account for register pressure similar to RegPressureTracker::recede().
870  RegisterOperands RegOpers(TRI, MRI);
871  collectOperands(MI, RegOpers);
872
873  // Kill liveness at last uses. Assume allocatable physregs are single-use
874  // rather than checking LiveIntervals.
875  SlotIndex SlotIdx;
876  if (RequireIntervals)
877    SlotIdx = LIS->getInstructionIndex(MI).getRegSlot();
878
879  for (unsigned i = 0, e = RegOpers.Uses.size(); i < e; ++i) {
880    unsigned Reg = RegOpers.Uses[i];
881    if (RequireIntervals) {
882      // FIXME: allow the caller to pass in the list of vreg uses that remain
883      // to be bottom-scheduled to avoid searching uses at each query.
884      SlotIndex CurrIdx = getCurrSlot();
885      const LiveInterval *LI = getInterval(Reg);
886      if (LI) {
887        LiveRangeQuery LRQ(*LI, SlotIdx);
888        if (LRQ.isKill() && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS))
889          decreaseRegPressure(Reg);
890      }
891    }
892    else if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
893      // Allocatable physregs are always single-use before register rewriting.
894      decreaseRegPressure(Reg);
895    }
896  }
897
898  // Generate liveness for defs.
899  increaseRegPressure(RegOpers.Defs);
900
901  // Boost pressure for all dead defs together.
902  increaseRegPressure(RegOpers.DeadDefs);
903  decreaseRegPressure(RegOpers.DeadDefs);
904}
905
906/// Consider the pressure increase caused by traversing this instruction
907/// top-down. Find the register class with the most change in its pressure limit
908/// based on the tracker's current pressure, and return the number of excess
909/// register units of that pressure set introduced by this instruction.
910///
911/// This assumes that the current LiveIn set is sufficient.
912void RegPressureTracker::
913getMaxDownwardPressureDelta(const MachineInstr *MI, RegPressureDelta &Delta,
914                            ArrayRef<PressureChange> CriticalPSets,
915                            ArrayRef<unsigned> MaxPressureLimit) {
916  // Snapshot Pressure.
917  std::vector<unsigned> SavedPressure = CurrSetPressure;
918  std::vector<unsigned> SavedMaxPressure = P.MaxSetPressure;
919
920  bumpDownwardPressure(MI);
921
922  computeExcessPressureDelta(SavedPressure, CurrSetPressure, Delta, RCI,
923                             LiveThruPressure);
924  computeMaxPressureDelta(SavedMaxPressure, P.MaxSetPressure, CriticalPSets,
925                          MaxPressureLimit, Delta);
926  assert(Delta.CriticalMax.getUnitInc() >= 0 &&
927         Delta.CurrentMax.getUnitInc() >= 0 && "cannot decrease max pressure");
928
929  // Restore the tracker's state.
930  P.MaxSetPressure.swap(SavedMaxPressure);
931  CurrSetPressure.swap(SavedPressure);
932}
933
934/// Get the pressure of each PSet after traversing this instruction bottom-up.
935void RegPressureTracker::
936getUpwardPressure(const MachineInstr *MI,
937                  std::vector<unsigned> &PressureResult,
938                  std::vector<unsigned> &MaxPressureResult) {
939  // Snapshot pressure.
940  PressureResult = CurrSetPressure;
941  MaxPressureResult = P.MaxSetPressure;
942
943  bumpUpwardPressure(MI);
944
945  // Current pressure becomes the result. Restore current pressure.
946  P.MaxSetPressure.swap(MaxPressureResult);
947  CurrSetPressure.swap(PressureResult);
948}
949
950/// Get the pressure of each PSet after traversing this instruction top-down.
951void RegPressureTracker::
952getDownwardPressure(const MachineInstr *MI,
953                    std::vector<unsigned> &PressureResult,
954                    std::vector<unsigned> &MaxPressureResult) {
955  // Snapshot pressure.
956  PressureResult = CurrSetPressure;
957  MaxPressureResult = P.MaxSetPressure;
958
959  bumpDownwardPressure(MI);
960
961  // Current pressure becomes the result. Restore current pressure.
962  P.MaxSetPressure.swap(MaxPressureResult);
963  CurrSetPressure.swap(PressureResult);
964}
965