RegAllocGreedy.cpp revision 9efa2a263ea470caacef1c85f6ca45e32bf516d3 
1//===-- RegAllocGreedy.cpp - greedy register allocator --------------------===//
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 defines the RAGreedy function pass for register allocation in
11// optimized builds.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "regalloc"
16#include "AllocationOrder.h"
17#include "InterferenceCache.h"
18#include "LiveDebugVariables.h"
19#include "LiveRangeEdit.h"
20#include "RegAllocBase.h"
21#include "Spiller.h"
22#include "SpillPlacement.h"
23#include "SplitKit.h"
24#include "VirtRegMap.h"
25#include "llvm/ADT/Statistic.h"
26#include "llvm/Analysis/AliasAnalysis.h"
27#include "llvm/Function.h"
28#include "llvm/PassAnalysisSupport.h"
29#include "llvm/CodeGen/CalcSpillWeights.h"
30#include "llvm/CodeGen/EdgeBundles.h"
31#include "llvm/CodeGen/LiveIntervalAnalysis.h"
32#include "llvm/CodeGen/LiveStackAnalysis.h"
33#include "llvm/CodeGen/MachineDominators.h"
34#include "llvm/CodeGen/MachineFunctionPass.h"
35#include "llvm/CodeGen/MachineLoopInfo.h"
36#include "llvm/CodeGen/MachineLoopRanges.h"
37#include "llvm/CodeGen/MachineRegisterInfo.h"
38#include "llvm/CodeGen/Passes.h"
39#include "llvm/CodeGen/RegAllocRegistry.h"
40#include "llvm/CodeGen/RegisterCoalescer.h"
41#include "llvm/Target/TargetOptions.h"
42#include "llvm/Support/Debug.h"
43#include "llvm/Support/ErrorHandling.h"
44#include "llvm/Support/raw_ostream.h"
45#include "llvm/Support/Timer.h"
46
47#include <queue>
48
49using namespace llvm;
50
51STATISTIC(NumGlobalSplits, "Number of split global live ranges");
52STATISTIC(NumLocalSplits,  "Number of split local live ranges");
53STATISTIC(NumEvicted,      "Number of interferences evicted");
54
55static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
56                                       createGreedyRegisterAllocator);
57
58namespace {
59class RAGreedy : public MachineFunctionPass,
60                 public RegAllocBase,
61                 private LiveRangeEdit::Delegate {
62
63  // context
64  MachineFunction *MF;
65  BitVector ReservedRegs;
66
67  // analyses
68  SlotIndexes *Indexes;
69  LiveStacks *LS;
70  MachineDominatorTree *DomTree;
71  MachineLoopInfo *Loops;
72  MachineLoopRanges *LoopRanges;
73  EdgeBundles *Bundles;
74  SpillPlacement *SpillPlacer;
75
76  // state
77  std::auto_ptr<Spiller> SpillerInstance;
78  std::priority_queue<std::pair<unsigned, unsigned> > Queue;
79
80  // Live ranges pass through a number of stages as we try to allocate them.
81  // Some of the stages may also create new live ranges:
82  //
83  // - Region splitting.
84  // - Per-block splitting.
85  // - Local splitting.
86  // - Spilling.
87  //
88  // Ranges produced by one of the stages skip the previous stages when they are
89  // dequeued. This improves performance because we can skip interference checks
90  // that are unlikely to give any results. It also guarantees that the live
91  // range splitting algorithm terminates, something that is otherwise hard to
92  // ensure.
93  enum LiveRangeStage {
94    RS_New,      ///< Never seen before.
95    RS_First,    ///< First time in the queue.
96    RS_Second,   ///< Second time in the queue.
97    RS_Region,   ///< Produced by region splitting.
98    RS_Block,    ///< Produced by per-block splitting.
99    RS_Local,    ///< Produced by local splitting.
100    RS_Spill     ///< Produced by spilling.
101  };
102
103  IndexedMap<unsigned char, VirtReg2IndexFunctor> LRStage;
104
105  LiveRangeStage getStage(const LiveInterval &VirtReg) const {
106    return LiveRangeStage(LRStage[VirtReg.reg]);
107  }
108
109  template<typename Iterator>
110  void setStage(Iterator Begin, Iterator End, LiveRangeStage NewStage) {
111    LRStage.resize(MRI->getNumVirtRegs());
112    for (;Begin != End; ++Begin) {
113      unsigned Reg = (*Begin)->reg;
114      if (LRStage[Reg] == RS_New)
115        LRStage[Reg] = NewStage;
116    }
117  }
118
119  // splitting state.
120  std::auto_ptr<SplitAnalysis> SA;
121  std::auto_ptr<SplitEditor> SE;
122
123  /// Cached per-block interference maps
124  InterferenceCache IntfCache;
125
126  /// All basic blocks where the current register is live.
127  SmallVector<SpillPlacement::BlockConstraint, 8> SplitConstraints;
128
129  /// Global live range splitting candidate info.
130  struct GlobalSplitCandidate {
131    unsigned PhysReg;
132    BitVector LiveBundles;
133  };
134
135  /// Candidate info for for each PhysReg in AllocationOrder.
136  /// This vector never shrinks, but grows to the size of the largest register
137  /// class.
138  SmallVector<GlobalSplitCandidate, 32> GlobalCand;
139
140  /// For every instruction in SA->UseSlots, store the previous non-copy
141  /// instruction.
142  SmallVector<SlotIndex, 8> PrevSlot;
143
144public:
145  RAGreedy();
146
147  /// Return the pass name.
148  virtual const char* getPassName() const {
149    return "Greedy Register Allocator";
150  }
151
152  /// RAGreedy analysis usage.
153  virtual void getAnalysisUsage(AnalysisUsage &AU) const;
154  virtual void releaseMemory();
155  virtual Spiller &spiller() { return *SpillerInstance; }
156  virtual void enqueue(LiveInterval *LI);
157  virtual LiveInterval *dequeue();
158  virtual unsigned selectOrSplit(LiveInterval&,
159                                 SmallVectorImpl<LiveInterval*>&);
160
161  /// Perform register allocation.
162  virtual bool runOnMachineFunction(MachineFunction &mf);
163
164  static char ID;
165
166private:
167  void LRE_WillEraseInstruction(MachineInstr*);
168  bool LRE_CanEraseVirtReg(unsigned);
169  void LRE_WillShrinkVirtReg(unsigned);
170  void LRE_DidCloneVirtReg(unsigned, unsigned);
171
172  float calcSplitConstraints(unsigned);
173  float calcGlobalSplitCost(const BitVector&);
174  void splitAroundRegion(LiveInterval&, unsigned, const BitVector&,
175                         SmallVectorImpl<LiveInterval*>&);
176  void calcGapWeights(unsigned, SmallVectorImpl<float>&);
177  SlotIndex getPrevMappedIndex(const MachineInstr*);
178  void calcPrevSlots();
179  unsigned nextSplitPoint(unsigned);
180  bool canEvictInterference(LiveInterval&, unsigned, float&);
181
182  unsigned tryEvict(LiveInterval&, AllocationOrder&,
183                    SmallVectorImpl<LiveInterval*>&);
184  unsigned tryRegionSplit(LiveInterval&, AllocationOrder&,
185                          SmallVectorImpl<LiveInterval*>&);
186  unsigned tryLocalSplit(LiveInterval&, AllocationOrder&,
187    SmallVectorImpl<LiveInterval*>&);
188  unsigned trySplit(LiveInterval&, AllocationOrder&,
189                    SmallVectorImpl<LiveInterval*>&);
190};
191} // end anonymous namespace
192
193char RAGreedy::ID = 0;
194
195FunctionPass* llvm::createGreedyRegisterAllocator() {
196  return new RAGreedy();
197}
198
199RAGreedy::RAGreedy(): MachineFunctionPass(ID), LRStage(RS_New) {
200  initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
201  initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
202  initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
203  initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
204  initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
205  initializeRegisterCoalescerAnalysisGroup(*PassRegistry::getPassRegistry());
206  initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
207  initializeLiveStacksPass(*PassRegistry::getPassRegistry());
208  initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry());
209  initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
210  initializeMachineLoopRangesPass(*PassRegistry::getPassRegistry());
211  initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
212  initializeEdgeBundlesPass(*PassRegistry::getPassRegistry());
213  initializeSpillPlacementPass(*PassRegistry::getPassRegistry());
214}
215
216void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
217  AU.setPreservesCFG();
218  AU.addRequired<AliasAnalysis>();
219  AU.addPreserved<AliasAnalysis>();
220  AU.addRequired<LiveIntervals>();
221  AU.addRequired<SlotIndexes>();
222  AU.addPreserved<SlotIndexes>();
223  AU.addRequired<LiveDebugVariables>();
224  AU.addPreserved<LiveDebugVariables>();
225  if (StrongPHIElim)
226    AU.addRequiredID(StrongPHIEliminationID);
227  AU.addRequiredTransitive<RegisterCoalescer>();
228  AU.addRequired<CalculateSpillWeights>();
229  AU.addRequired<LiveStacks>();
230  AU.addPreserved<LiveStacks>();
231  AU.addRequired<MachineDominatorTree>();
232  AU.addPreserved<MachineDominatorTree>();
233  AU.addRequired<MachineLoopInfo>();
234  AU.addPreserved<MachineLoopInfo>();
235  AU.addRequired<MachineLoopRanges>();
236  AU.addPreserved<MachineLoopRanges>();
237  AU.addRequired<VirtRegMap>();
238  AU.addPreserved<VirtRegMap>();
239  AU.addRequired<EdgeBundles>();
240  AU.addRequired<SpillPlacement>();
241  MachineFunctionPass::getAnalysisUsage(AU);
242}
243
244
245//===----------------------------------------------------------------------===//
246//                     LiveRangeEdit delegate methods
247//===----------------------------------------------------------------------===//
248
249void RAGreedy::LRE_WillEraseInstruction(MachineInstr *MI) {
250  // LRE itself will remove from SlotIndexes and parent basic block.
251  VRM->RemoveMachineInstrFromMaps(MI);
252}
253
254bool RAGreedy::LRE_CanEraseVirtReg(unsigned VirtReg) {
255  if (unsigned PhysReg = VRM->getPhys(VirtReg)) {
256    unassign(LIS->getInterval(VirtReg), PhysReg);
257    return true;
258  }
259  // Unassigned virtreg is probably in the priority queue.
260  // RegAllocBase will erase it after dequeueing.
261  return false;
262}
263
264void RAGreedy::LRE_WillShrinkVirtReg(unsigned VirtReg) {
265  unsigned PhysReg = VRM->getPhys(VirtReg);
266  if (!PhysReg)
267    return;
268
269  // Register is assigned, put it back on the queue for reassignment.
270  LiveInterval &LI = LIS->getInterval(VirtReg);
271  unassign(LI, PhysReg);
272  enqueue(&LI);
273}
274
275void RAGreedy::LRE_DidCloneVirtReg(unsigned New, unsigned Old) {
276  // LRE may clone a virtual register because dead code elimination causes it to
277  // be split into connected components. Ensure that the new register gets the
278  // same stage as the parent.
279  LRStage.grow(New);
280  LRStage[New] = LRStage[Old];
281}
282
283void RAGreedy::releaseMemory() {
284  SpillerInstance.reset(0);
285  LRStage.clear();
286  RegAllocBase::releaseMemory();
287}
288
289void RAGreedy::enqueue(LiveInterval *LI) {
290  // Prioritize live ranges by size, assigning larger ranges first.
291  // The queue holds (size, reg) pairs.
292  const unsigned Size = LI->getSize();
293  const unsigned Reg = LI->reg;
294  assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
295         "Can only enqueue virtual registers");
296  unsigned Prio;
297
298  LRStage.grow(Reg);
299  if (LRStage[Reg] == RS_New)
300    LRStage[Reg] = RS_First;
301
302  if (LRStage[Reg] == RS_Second)
303    // Unsplit ranges that couldn't be allocated immediately are deferred until
304    // everything else has been allocated. Long ranges are allocated last so
305    // they are split against realistic interference.
306    Prio = (1u << 31) - Size;
307  else {
308    // Everything else is allocated in long->short order. Long ranges that don't
309    // fit should be spilled ASAP so they don't create interference.
310    Prio = (1u << 31) + Size;
311
312    // Boost ranges that have a physical register hint.
313    if (TargetRegisterInfo::isPhysicalRegister(VRM->getRegAllocPref(Reg)))
314      Prio |= (1u << 30);
315  }
316
317  Queue.push(std::make_pair(Prio, Reg));
318}
319
320LiveInterval *RAGreedy::dequeue() {
321  if (Queue.empty())
322    return 0;
323  LiveInterval *LI = &LIS->getInterval(Queue.top().second);
324  Queue.pop();
325  return LI;
326}
327
328//===----------------------------------------------------------------------===//
329//                         Interference eviction
330//===----------------------------------------------------------------------===//
331
332/// canEvict - Return true if all interferences between VirtReg and PhysReg can
333/// be evicted. Set maxWeight to the maximal spill weight of an interference.
334bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg,
335                                    float &MaxWeight) {
336  float Weight = 0;
337  for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
338    LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
339    // If there is 10 or more interferences, chances are one is smaller.
340    if (Q.collectInterferingVRegs(10) >= 10)
341      return false;
342
343    // Check if any interfering live range is heavier than VirtReg.
344    for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
345      LiveInterval *Intf = Q.interferingVRegs()[i];
346      if (TargetRegisterInfo::isPhysicalRegister(Intf->reg))
347        return false;
348      if (Intf->weight >= VirtReg.weight)
349        return false;
350      Weight = std::max(Weight, Intf->weight);
351    }
352  }
353  MaxWeight = Weight;
354  return true;
355}
356
357/// tryEvict - Try to evict all interferences for a physreg.
358/// @param  VirtReg Currently unassigned virtual register.
359/// @param  Order   Physregs to try.
360/// @return         Physreg to assign VirtReg, or 0.
361unsigned RAGreedy::tryEvict(LiveInterval &VirtReg,
362                            AllocationOrder &Order,
363                            SmallVectorImpl<LiveInterval*> &NewVRegs){
364  NamedRegionTimer T("Evict", TimerGroupName, TimePassesIsEnabled);
365
366  // Keep track of the lightest single interference seen so far.
367  float BestWeight = 0;
368  unsigned BestPhys = 0;
369
370  Order.rewind();
371  while (unsigned PhysReg = Order.next()) {
372    float Weight = 0;
373    if (!canEvictInterference(VirtReg, PhysReg, Weight))
374      continue;
375
376    // This is an eviction candidate.
377    DEBUG(dbgs() << "max " << PrintReg(PhysReg, TRI) << " interference = "
378                 << Weight << '\n');
379    if (BestPhys && Weight >= BestWeight)
380      continue;
381
382    // Best so far.
383    BestPhys = PhysReg;
384    BestWeight = Weight;
385    // Stop if the hint can be used.
386    if (Order.isHint(PhysReg))
387      break;
388  }
389
390  if (!BestPhys)
391    return 0;
392
393  DEBUG(dbgs() << "evicting " << PrintReg(BestPhys, TRI) << " interference\n");
394  for (const unsigned *AliasI = TRI->getOverlaps(BestPhys); *AliasI; ++AliasI) {
395    LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
396    assert(Q.seenAllInterferences() && "Didn't check all interfererences.");
397    for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
398      LiveInterval *Intf = Q.interferingVRegs()[i];
399      unassign(*Intf, VRM->getPhys(Intf->reg));
400      ++NumEvicted;
401      NewVRegs.push_back(Intf);
402    }
403  }
404  return BestPhys;
405}
406
407
408//===----------------------------------------------------------------------===//
409//                              Region Splitting
410//===----------------------------------------------------------------------===//
411
412/// calcSplitConstraints - Fill out the SplitConstraints vector based on the
413/// interference pattern in Physreg and its aliases. Return the static cost of
414/// this split, assuming that all preferences in SplitConstraints are met.
415float RAGreedy::calcSplitConstraints(unsigned PhysReg) {
416  InterferenceCache::Cursor Intf(IntfCache, PhysReg);
417  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
418
419  // Reset interference dependent info.
420  SplitConstraints.resize(UseBlocks.size());
421  float StaticCost = 0;
422  for (unsigned i = 0; i != UseBlocks.size(); ++i) {
423    const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
424    SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
425
426    BC.Number = BI.MBB->getNumber();
427    Intf.moveToBlock(BC.Number);
428    BC.Entry = BI.LiveIn ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
429    BC.Exit = BI.LiveOut ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
430
431    if (!Intf.hasInterference())
432      continue;
433
434    // Number of spill code instructions to insert.
435    unsigned Ins = 0;
436
437    // Interference for the live-in value.
438    if (BI.LiveIn) {
439      if (Intf.first() <= Indexes->getMBBStartIdx(BC.Number))
440        BC.Entry = SpillPlacement::MustSpill, ++Ins;
441      else if (Intf.first() < BI.FirstUse)
442        BC.Entry = SpillPlacement::PrefSpill, ++Ins;
443      else if (Intf.first() < (BI.LiveThrough ? BI.LastUse : BI.Kill))
444        ++Ins;
445    }
446
447    // Interference for the live-out value.
448    if (BI.LiveOut) {
449      if (Intf.last() >= SA->getLastSplitPoint(BC.Number))
450        BC.Exit = SpillPlacement::MustSpill, ++Ins;
451      else if (Intf.last() > BI.LastUse)
452        BC.Exit = SpillPlacement::PrefSpill, ++Ins;
453      else if (Intf.last() > (BI.LiveThrough ? BI.FirstUse : BI.Def))
454        ++Ins;
455    }
456
457    // Accumulate the total frequency of inserted spill code.
458    if (Ins)
459      StaticCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
460  }
461
462  // Now handle the live-through blocks without uses.
463  ArrayRef<unsigned> ThroughBlocks = SA->getThroughBlocks();
464  SplitConstraints.resize(UseBlocks.size() + ThroughBlocks.size());
465  for (unsigned i = 0; i != ThroughBlocks.size(); ++i) {
466    SpillPlacement::BlockConstraint &BC = SplitConstraints[UseBlocks.size()+i];
467    BC.Number = ThroughBlocks[i];
468    BC.Entry = SpillPlacement::DontCare;
469    BC.Exit = SpillPlacement::DontCare;
470
471    Intf.moveToBlock(BC.Number);
472    if (!Intf.hasInterference())
473      continue;
474
475    // Interference for the live-in value.
476    if (Intf.first() <= Indexes->getMBBStartIdx(BC.Number))
477      BC.Entry = SpillPlacement::MustSpill;
478    else
479      BC.Entry = SpillPlacement::PrefSpill;
480
481    // Interference for the live-out value.
482    if (Intf.last() >= SA->getLastSplitPoint(BC.Number))
483      BC.Exit = SpillPlacement::MustSpill;
484    else
485      BC.Exit = SpillPlacement::PrefSpill;
486  }
487
488  return StaticCost;
489}
490
491
492/// calcGlobalSplitCost - Return the global split cost of following the split
493/// pattern in LiveBundles. This cost should be added to the local cost of the
494/// interference pattern in SplitConstraints.
495///
496float RAGreedy::calcGlobalSplitCost(const BitVector &LiveBundles) {
497  float GlobalCost = 0;
498  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
499  for (unsigned i = 0; i != UseBlocks.size(); ++i) {
500    const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
501    SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
502    bool RegIn  = LiveBundles[Bundles->getBundle(BC.Number, 0)];
503    bool RegOut = LiveBundles[Bundles->getBundle(BC.Number, 1)];
504    unsigned Ins = 0;
505
506    if (BI.LiveIn)
507      Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
508    if (BI.LiveOut)
509      Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
510    if (Ins)
511      GlobalCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
512  }
513
514  ArrayRef<unsigned> ThroughBlocks = SA->getThroughBlocks();
515  SplitConstraints.resize(UseBlocks.size() + ThroughBlocks.size());
516  for (unsigned i = 0; i != ThroughBlocks.size(); ++i) {
517    unsigned Number = ThroughBlocks[i];
518    bool RegIn  = LiveBundles[Bundles->getBundle(Number, 0)];
519    bool RegOut = LiveBundles[Bundles->getBundle(Number, 1)];
520    if (RegIn != RegOut)
521      GlobalCost += SpillPlacer->getBlockFrequency(Number);
522  }
523  return GlobalCost;
524}
525
526/// splitAroundRegion - Split VirtReg around the region determined by
527/// LiveBundles. Make an effort to avoid interference from PhysReg.
528///
529/// The 'register' interval is going to contain as many uses as possible while
530/// avoiding interference. The 'stack' interval is the complement constructed by
531/// SplitEditor. It will contain the rest.
532///
533void RAGreedy::splitAroundRegion(LiveInterval &VirtReg, unsigned PhysReg,
534                                 const BitVector &LiveBundles,
535                                 SmallVectorImpl<LiveInterval*> &NewVRegs) {
536  DEBUG({
537    dbgs() << "Splitting around region for " << PrintReg(PhysReg, TRI)
538           << " with bundles";
539    for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
540      dbgs() << " EB#" << i;
541    dbgs() << ".\n";
542  });
543
544  InterferenceCache::Cursor Intf(IntfCache, PhysReg);
545  LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
546  SE->reset(LREdit);
547
548  // Create the main cross-block interval.
549  SE->openIntv();
550
551  // First add all defs that are live out of a block.
552  ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
553  for (unsigned i = 0; i != UseBlocks.size(); ++i) {
554    const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
555    bool RegIn  = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
556    bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
557
558    // Should the register be live out?
559    if (!BI.LiveOut || !RegOut)
560      continue;
561
562    SlotIndex Start, Stop;
563    tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
564    Intf.moveToBlock(BI.MBB->getNumber());
565    DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " -> EB#"
566                 << Bundles->getBundle(BI.MBB->getNumber(), 1)
567                 << " [" << Start << ';'
568                 << SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
569                 << ") intf [" << Intf.first() << ';' << Intf.last() << ')');
570
571    // The interference interval should either be invalid or overlap MBB.
572    assert((!Intf.hasInterference() || Intf.first() < Stop)
573           && "Bad interference");
574    assert((!Intf.hasInterference() || Intf.last() > Start)
575           && "Bad interference");
576
577    // Check interference leaving the block.
578    if (!Intf.hasInterference()) {
579      // Block is interference-free.
580      DEBUG(dbgs() << ", no interference");
581      if (!BI.LiveThrough) {
582        DEBUG(dbgs() << ", not live-through.\n");
583        SE->useIntv(SE->enterIntvBefore(BI.Def), Stop);
584        continue;
585      }
586      if (!RegIn) {
587        // Block is live-through, but entry bundle is on the stack.
588        // Reload just before the first use.
589        DEBUG(dbgs() << ", not live-in, enter before first use.\n");
590        SE->useIntv(SE->enterIntvBefore(BI.FirstUse), Stop);
591        continue;
592      }
593      DEBUG(dbgs() << ", live-through.\n");
594      continue;
595    }
596
597    // Block has interference.
598    DEBUG(dbgs() << ", interference to " << Intf.last());
599
600    if (!BI.LiveThrough && Intf.last() <= BI.Def) {
601      // The interference doesn't reach the outgoing segment.
602      DEBUG(dbgs() << " doesn't affect def from " << BI.Def << '\n');
603      SE->useIntv(BI.Def, Stop);
604      continue;
605    }
606
607    SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
608    if (Intf.last().getBoundaryIndex() < BI.LastUse) {
609      // There are interference-free uses at the end of the block.
610      // Find the first use that can get the live-out register.
611      SmallVectorImpl<SlotIndex>::const_iterator UI =
612        std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
613                         Intf.last().getBoundaryIndex());
614      assert(UI != SA->UseSlots.end() && "Couldn't find last use");
615      SlotIndex Use = *UI;
616      assert(Use <= BI.LastUse && "Couldn't find last use");
617      // Only attempt a split befroe the last split point.
618      if (Use.getBaseIndex() <= LastSplitPoint) {
619        DEBUG(dbgs() << ", free use at " << Use << ".\n");
620        SlotIndex SegStart = SE->enterIntvBefore(Use);
621        assert(SegStart >= Intf.last() && "Couldn't avoid interference");
622        assert(SegStart < LastSplitPoint && "Impossible split point");
623        SE->useIntv(SegStart, Stop);
624        continue;
625      }
626    }
627
628    // Interference is after the last use.
629    DEBUG(dbgs() << " after last use.\n");
630    SlotIndex SegStart = SE->enterIntvAtEnd(*BI.MBB);
631    assert(SegStart >= Intf.last() && "Couldn't avoid interference");
632  }
633
634  // Now all defs leading to live bundles are handled, do everything else.
635  for (unsigned i = 0; i != UseBlocks.size(); ++i) {
636    const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
637    bool RegIn  = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
638    bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
639
640    // Is the register live-in?
641    if (!BI.LiveIn || !RegIn)
642      continue;
643
644    // We have an incoming register. Check for interference.
645    SlotIndex Start, Stop;
646    tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
647    Intf.moveToBlock(BI.MBB->getNumber());
648    DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
649                 << " -> BB#" << BI.MBB->getNumber() << " [" << Start << ';'
650                 << SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
651                 << ')');
652
653    // Check interference entering the block.
654    if (!Intf.hasInterference()) {
655      // Block is interference-free.
656      DEBUG(dbgs() << ", no interference");
657      if (!BI.LiveThrough) {
658        DEBUG(dbgs() << ", killed in block.\n");
659        SE->useIntv(Start, SE->leaveIntvAfter(BI.Kill));
660        continue;
661      }
662      if (!RegOut) {
663        SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
664        // Block is live-through, but exit bundle is on the stack.
665        // Spill immediately after the last use.
666        if (BI.LastUse < LastSplitPoint) {
667          DEBUG(dbgs() << ", uses, stack-out.\n");
668          SE->useIntv(Start, SE->leaveIntvAfter(BI.LastUse));
669          continue;
670        }
671        // The last use is after the last split point, it is probably an
672        // indirect jump.
673        DEBUG(dbgs() << ", uses at " << BI.LastUse << " after split point "
674                     << LastSplitPoint << ", stack-out.\n");
675        SlotIndex SegEnd = SE->leaveIntvBefore(LastSplitPoint);
676        SE->useIntv(Start, SegEnd);
677        // Run a double interval from the split to the last use.
678        // This makes it possible to spill the complement without affecting the
679        // indirect branch.
680        SE->overlapIntv(SegEnd, BI.LastUse);
681        continue;
682      }
683      // Register is live-through.
684      DEBUG(dbgs() << ", uses, live-through.\n");
685      SE->useIntv(Start, Stop);
686      continue;
687    }
688
689    // Block has interference.
690    DEBUG(dbgs() << ", interference from " << Intf.first());
691
692    if (!BI.LiveThrough && Intf.first() >= BI.Kill) {
693      // The interference doesn't reach the outgoing segment.
694      DEBUG(dbgs() << " doesn't affect kill at " << BI.Kill << '\n');
695      SE->useIntv(Start, BI.Kill);
696      continue;
697    }
698
699    if (Intf.first().getBaseIndex() > BI.FirstUse) {
700      // There are interference-free uses at the beginning of the block.
701      // Find the last use that can get the register.
702      SmallVectorImpl<SlotIndex>::const_iterator UI =
703        std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
704                         Intf.first().getBaseIndex());
705      assert(UI != SA->UseSlots.begin() && "Couldn't find first use");
706      SlotIndex Use = (--UI)->getBoundaryIndex();
707      DEBUG(dbgs() << ", free use at " << *UI << ".\n");
708      SlotIndex SegEnd = SE->leaveIntvAfter(Use);
709      assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
710      SE->useIntv(Start, SegEnd);
711      continue;
712    }
713
714    // Interference is before the first use.
715    DEBUG(dbgs() << " before first use.\n");
716    SlotIndex SegEnd = SE->leaveIntvAtTop(*BI.MBB);
717    assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
718  }
719
720  // Handle live-through blocks.
721  ArrayRef<unsigned> ThroughBlocks = SA->getThroughBlocks();
722  for (unsigned i = 0; i != ThroughBlocks.size(); ++i) {
723    unsigned Number = ThroughBlocks[i];
724    bool RegIn  = LiveBundles[Bundles->getBundle(Number, 0)];
725    bool RegOut = LiveBundles[Bundles->getBundle(Number, 1)];
726    DEBUG(dbgs() << "Live through BB#" << Number << '\n');
727    if (RegIn && RegOut) {
728      Intf.moveToBlock(Number);
729      if (!Intf.hasInterference()) {
730        SE->useIntv(Indexes->getMBBStartIdx(Number),
731                    Indexes->getMBBEndIdx(Number));
732        continue;
733      }
734    }
735    MachineBasicBlock *MBB = MF->getBlockNumbered(Number);
736    if (RegIn)
737      SE->leaveIntvAtTop(*MBB);
738    if (RegOut)
739      SE->enterIntvAtEnd(*MBB);
740  }
741
742  SE->closeIntv();
743
744  // FIXME: Should we be more aggressive about splitting the stack region into
745  // per-block segments? The current approach allows the stack region to
746  // separate into connected components. Some components may be allocatable.
747  SE->finish();
748  ++NumGlobalSplits;
749
750  if (VerifyEnabled)
751    MF->verify(this, "After splitting live range around region");
752}
753
754unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
755                                  SmallVectorImpl<LiveInterval*> &NewVRegs) {
756  BitVector LiveBundles, BestBundles;
757  float BestCost = 0;
758  unsigned BestReg = 0;
759
760  Order.rewind();
761  for (unsigned Cand = 0; unsigned PhysReg = Order.next(); ++Cand) {
762    if (GlobalCand.size() <= Cand)
763      GlobalCand.resize(Cand+1);
764    GlobalCand[Cand].PhysReg = PhysReg;
765
766    float Cost = calcSplitConstraints(PhysReg);
767    DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tstatic = " << Cost);
768    if (BestReg && Cost >= BestCost) {
769      DEBUG(dbgs() << " higher.\n");
770      continue;
771    }
772
773    SpillPlacer->prepare(LiveBundles);
774    SpillPlacer->addConstraints(SplitConstraints);
775    SpillPlacer->finish();
776
777    // No live bundles, defer to splitSingleBlocks().
778    if (!LiveBundles.any()) {
779      DEBUG(dbgs() << " no bundles.\n");
780      continue;
781    }
782
783    Cost += calcGlobalSplitCost(LiveBundles);
784    DEBUG({
785      dbgs() << ", total = " << Cost << " with bundles";
786      for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
787        dbgs() << " EB#" << i;
788      dbgs() << ".\n";
789    });
790    if (!BestReg || Cost < BestCost) {
791      BestReg = PhysReg;
792      BestCost = 0.98f * Cost; // Prevent rounding effects.
793      BestBundles.swap(LiveBundles);
794    }
795  }
796
797  if (!BestReg)
798    return 0;
799
800  splitAroundRegion(VirtReg, BestReg, BestBundles, NewVRegs);
801  setStage(NewVRegs.begin(), NewVRegs.end(), RS_Region);
802  return 0;
803}
804
805
806//===----------------------------------------------------------------------===//
807//                             Local Splitting
808//===----------------------------------------------------------------------===//
809
810
811/// calcGapWeights - Compute the maximum spill weight that needs to be evicted
812/// in order to use PhysReg between two entries in SA->UseSlots.
813///
814/// GapWeight[i] represents the gap between UseSlots[i] and UseSlots[i+1].
815///
816void RAGreedy::calcGapWeights(unsigned PhysReg,
817                              SmallVectorImpl<float> &GapWeight) {
818  assert(SA->getUseBlocks().size() == 1 && "Not a local interval");
819  const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front();
820  const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
821  const unsigned NumGaps = Uses.size()-1;
822
823  // Start and end points for the interference check.
824  SlotIndex StartIdx = BI.LiveIn ? BI.FirstUse.getBaseIndex() : BI.FirstUse;
825  SlotIndex StopIdx = BI.LiveOut ? BI.LastUse.getBoundaryIndex() : BI.LastUse;
826
827  GapWeight.assign(NumGaps, 0.0f);
828
829  // Add interference from each overlapping register.
830  for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
831    if (!query(const_cast<LiveInterval&>(SA->getParent()), *AI)
832           .checkInterference())
833      continue;
834
835    // We know that VirtReg is a continuous interval from FirstUse to LastUse,
836    // so we don't need InterferenceQuery.
837    //
838    // Interference that overlaps an instruction is counted in both gaps
839    // surrounding the instruction. The exception is interference before
840    // StartIdx and after StopIdx.
841    //
842    LiveIntervalUnion::SegmentIter IntI = PhysReg2LiveUnion[*AI].find(StartIdx);
843    for (unsigned Gap = 0; IntI.valid() && IntI.start() < StopIdx; ++IntI) {
844      // Skip the gaps before IntI.
845      while (Uses[Gap+1].getBoundaryIndex() < IntI.start())
846        if (++Gap == NumGaps)
847          break;
848      if (Gap == NumGaps)
849        break;
850
851      // Update the gaps covered by IntI.
852      const float weight = IntI.value()->weight;
853      for (; Gap != NumGaps; ++Gap) {
854        GapWeight[Gap] = std::max(GapWeight[Gap], weight);
855        if (Uses[Gap+1].getBaseIndex() >= IntI.stop())
856          break;
857      }
858      if (Gap == NumGaps)
859        break;
860    }
861  }
862}
863
864/// getPrevMappedIndex - Return the slot index of the last non-copy instruction
865/// before MI that has a slot index. If MI is the first mapped instruction in
866/// its block, return the block start index instead.
867///
868SlotIndex RAGreedy::getPrevMappedIndex(const MachineInstr *MI) {
869  assert(MI && "Missing MachineInstr");
870  const MachineBasicBlock *MBB = MI->getParent();
871  MachineBasicBlock::const_iterator B = MBB->begin(), I = MI;
872  while (I != B)
873    if (!(--I)->isDebugValue() && !I->isCopy())
874      return Indexes->getInstructionIndex(I);
875  return Indexes->getMBBStartIdx(MBB);
876}
877
878/// calcPrevSlots - Fill in the PrevSlot array with the index of the previous
879/// real non-copy instruction for each instruction in SA->UseSlots.
880///
881void RAGreedy::calcPrevSlots() {
882  const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
883  PrevSlot.clear();
884  PrevSlot.reserve(Uses.size());
885  for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
886    const MachineInstr *MI = Indexes->getInstructionFromIndex(Uses[i]);
887    PrevSlot.push_back(getPrevMappedIndex(MI).getDefIndex());
888  }
889}
890
891/// nextSplitPoint - Find the next index into SA->UseSlots > i such that it may
892/// be beneficial to split before UseSlots[i].
893///
894/// 0 is always a valid split point
895unsigned RAGreedy::nextSplitPoint(unsigned i) {
896  const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
897  const unsigned Size = Uses.size();
898  assert(i != Size && "No split points after the end");
899  // Allow split before i when Uses[i] is not adjacent to the previous use.
900  while (++i != Size && PrevSlot[i].getBaseIndex() <= Uses[i-1].getBaseIndex())
901    ;
902  return i;
903}
904
905/// tryLocalSplit - Try to split VirtReg into smaller intervals inside its only
906/// basic block.
907///
908unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order,
909                                 SmallVectorImpl<LiveInterval*> &NewVRegs) {
910  assert(SA->getUseBlocks().size() == 1 && "Not a local interval");
911  const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front();
912
913  // Note that it is possible to have an interval that is live-in or live-out
914  // while only covering a single block - A phi-def can use undef values from
915  // predecessors, and the block could be a single-block loop.
916  // We don't bother doing anything clever about such a case, we simply assume
917  // that the interval is continuous from FirstUse to LastUse. We should make
918  // sure that we don't do anything illegal to such an interval, though.
919
920  const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
921  if (Uses.size() <= 2)
922    return 0;
923  const unsigned NumGaps = Uses.size()-1;
924
925  DEBUG({
926    dbgs() << "tryLocalSplit: ";
927    for (unsigned i = 0, e = Uses.size(); i != e; ++i)
928      dbgs() << ' ' << SA->UseSlots[i];
929    dbgs() << '\n';
930  });
931
932  // For every use, find the previous mapped non-copy instruction.
933  // We use this to detect valid split points, and to estimate new interval
934  // sizes.
935  calcPrevSlots();
936
937  unsigned BestBefore = NumGaps;
938  unsigned BestAfter = 0;
939  float BestDiff = 0;
940
941  const float blockFreq = SpillPlacer->getBlockFrequency(BI.MBB->getNumber());
942  SmallVector<float, 8> GapWeight;
943
944  Order.rewind();
945  while (unsigned PhysReg = Order.next()) {
946    // Keep track of the largest spill weight that would need to be evicted in
947    // order to make use of PhysReg between UseSlots[i] and UseSlots[i+1].
948    calcGapWeights(PhysReg, GapWeight);
949
950    // Try to find the best sequence of gaps to close.
951    // The new spill weight must be larger than any gap interference.
952
953    // We will split before Uses[SplitBefore] and after Uses[SplitAfter].
954    unsigned SplitBefore = 0, SplitAfter = nextSplitPoint(1) - 1;
955
956    // MaxGap should always be max(GapWeight[SplitBefore..SplitAfter-1]).
957    // It is the spill weight that needs to be evicted.
958    float MaxGap = GapWeight[0];
959    for (unsigned i = 1; i != SplitAfter; ++i)
960      MaxGap = std::max(MaxGap, GapWeight[i]);
961
962    for (;;) {
963      // Live before/after split?
964      const bool LiveBefore = SplitBefore != 0 || BI.LiveIn;
965      const bool LiveAfter = SplitAfter != NumGaps || BI.LiveOut;
966
967      DEBUG(dbgs() << PrintReg(PhysReg, TRI) << ' '
968                   << Uses[SplitBefore] << '-' << Uses[SplitAfter]
969                   << " i=" << MaxGap);
970
971      // Stop before the interval gets so big we wouldn't be making progress.
972      if (!LiveBefore && !LiveAfter) {
973        DEBUG(dbgs() << " all\n");
974        break;
975      }
976      // Should the interval be extended or shrunk?
977      bool Shrink = true;
978      if (MaxGap < HUGE_VALF) {
979        // Estimate the new spill weight.
980        //
981        // Each instruction reads and writes the register, except the first
982        // instr doesn't read when !FirstLive, and the last instr doesn't write
983        // when !LastLive.
984        //
985        // We will be inserting copies before and after, so the total number of
986        // reads and writes is 2 * EstUses.
987        //
988        const unsigned EstUses = 2*(SplitAfter - SplitBefore) +
989                                 2*(LiveBefore + LiveAfter);
990
991        // Try to guess the size of the new interval. This should be trivial,
992        // but the slot index of an inserted copy can be a lot smaller than the
993        // instruction it is inserted before if there are many dead indexes
994        // between them.
995        //
996        // We measure the distance from the instruction before SplitBefore to
997        // get a conservative estimate.
998        //
999        // The final distance can still be different if inserting copies
1000        // triggers a slot index renumbering.
1001        //
1002        const float EstWeight = normalizeSpillWeight(blockFreq * EstUses,
1003                              PrevSlot[SplitBefore].distance(Uses[SplitAfter]));
1004        // Would this split be possible to allocate?
1005        // Never allocate all gaps, we wouldn't be making progress.
1006        float Diff = EstWeight - MaxGap;
1007        DEBUG(dbgs() << " w=" << EstWeight << " d=" << Diff);
1008        if (Diff > 0) {
1009          Shrink = false;
1010          if (Diff > BestDiff) {
1011            DEBUG(dbgs() << " (best)");
1012            BestDiff = Diff;
1013            BestBefore = SplitBefore;
1014            BestAfter = SplitAfter;
1015          }
1016        }
1017      }
1018
1019      // Try to shrink.
1020      if (Shrink) {
1021        SplitBefore = nextSplitPoint(SplitBefore);
1022        if (SplitBefore < SplitAfter) {
1023          DEBUG(dbgs() << " shrink\n");
1024          // Recompute the max when necessary.
1025          if (GapWeight[SplitBefore - 1] >= MaxGap) {
1026            MaxGap = GapWeight[SplitBefore];
1027            for (unsigned i = SplitBefore + 1; i != SplitAfter; ++i)
1028              MaxGap = std::max(MaxGap, GapWeight[i]);
1029          }
1030          continue;
1031        }
1032        MaxGap = 0;
1033      }
1034
1035      // Try to extend the interval.
1036      if (SplitAfter >= NumGaps) {
1037        DEBUG(dbgs() << " end\n");
1038        break;
1039      }
1040
1041      DEBUG(dbgs() << " extend\n");
1042      for (unsigned e = nextSplitPoint(SplitAfter + 1) - 1;
1043           SplitAfter != e; ++SplitAfter)
1044        MaxGap = std::max(MaxGap, GapWeight[SplitAfter]);
1045          continue;
1046    }
1047  }
1048
1049  // Didn't find any candidates?
1050  if (BestBefore == NumGaps)
1051    return 0;
1052
1053  DEBUG(dbgs() << "Best local split range: " << Uses[BestBefore]
1054               << '-' << Uses[BestAfter] << ", " << BestDiff
1055               << ", " << (BestAfter - BestBefore + 1) << " instrs\n");
1056
1057  LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
1058  SE->reset(LREdit);
1059
1060  SE->openIntv();
1061  SlotIndex SegStart = SE->enterIntvBefore(Uses[BestBefore]);
1062  SlotIndex SegStop  = SE->leaveIntvAfter(Uses[BestAfter]);
1063  SE->useIntv(SegStart, SegStop);
1064  SE->closeIntv();
1065  SE->finish();
1066  setStage(NewVRegs.begin(), NewVRegs.end(), RS_Local);
1067  ++NumLocalSplits;
1068
1069  return 0;
1070}
1071
1072//===----------------------------------------------------------------------===//
1073//                          Live Range Splitting
1074//===----------------------------------------------------------------------===//
1075
1076/// trySplit - Try to split VirtReg or one of its interferences, making it
1077/// assignable.
1078/// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
1079unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
1080                            SmallVectorImpl<LiveInterval*>&NewVRegs) {
1081  // Local intervals are handled separately.
1082  if (LIS->intervalIsInOneMBB(VirtReg)) {
1083    NamedRegionTimer T("Local Splitting", TimerGroupName, TimePassesIsEnabled);
1084    SA->analyze(&VirtReg);
1085    return tryLocalSplit(VirtReg, Order, NewVRegs);
1086  }
1087
1088  NamedRegionTimer T("Global Splitting", TimerGroupName, TimePassesIsEnabled);
1089
1090  // Don't iterate global splitting.
1091  // Move straight to spilling if this range was produced by a global split.
1092  LiveRangeStage Stage = getStage(VirtReg);
1093  if (Stage >= RS_Block)
1094    return 0;
1095
1096  SA->analyze(&VirtReg);
1097
1098  // First try to split around a region spanning multiple blocks.
1099  if (Stage < RS_Region) {
1100    unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
1101    if (PhysReg || !NewVRegs.empty())
1102      return PhysReg;
1103  }
1104
1105  // Then isolate blocks with multiple uses.
1106  if (Stage < RS_Block) {
1107    SplitAnalysis::BlockPtrSet Blocks;
1108    if (SA->getMultiUseBlocks(Blocks)) {
1109      LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
1110      SE->reset(LREdit);
1111      SE->splitSingleBlocks(Blocks);
1112      setStage(NewVRegs.begin(), NewVRegs.end(), RS_Block);
1113      if (VerifyEnabled)
1114        MF->verify(this, "After splitting live range around basic blocks");
1115    }
1116  }
1117
1118  // Don't assign any physregs.
1119  return 0;
1120}
1121
1122
1123//===----------------------------------------------------------------------===//
1124//                            Main Entry Point
1125//===----------------------------------------------------------------------===//
1126
1127unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
1128                                 SmallVectorImpl<LiveInterval*> &NewVRegs) {
1129  // First try assigning a free register.
1130  AllocationOrder Order(VirtReg.reg, *VRM, ReservedRegs);
1131  while (unsigned PhysReg = Order.next()) {
1132    if (!checkPhysRegInterference(VirtReg, PhysReg))
1133      return PhysReg;
1134  }
1135
1136  if (unsigned PhysReg = tryEvict(VirtReg, Order, NewVRegs))
1137    return PhysReg;
1138
1139  assert(NewVRegs.empty() && "Cannot append to existing NewVRegs");
1140
1141  // The first time we see a live range, don't try to split or spill.
1142  // Wait until the second time, when all smaller ranges have been allocated.
1143  // This gives a better picture of the interference to split around.
1144  LiveRangeStage Stage = getStage(VirtReg);
1145  if (Stage == RS_First) {
1146    LRStage[VirtReg.reg] = RS_Second;
1147    DEBUG(dbgs() << "wait for second round\n");
1148    NewVRegs.push_back(&VirtReg);
1149    return 0;
1150  }
1151
1152  assert(Stage < RS_Spill && "Cannot allocate after spilling");
1153
1154  // Try splitting VirtReg or interferences.
1155  unsigned PhysReg = trySplit(VirtReg, Order, NewVRegs);
1156  if (PhysReg || !NewVRegs.empty())
1157    return PhysReg;
1158
1159  // Finally spill VirtReg itself.
1160  NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
1161  LiveRangeEdit LRE(VirtReg, NewVRegs, this);
1162  spiller().spill(LRE);
1163  setStage(NewVRegs.begin(), NewVRegs.end(), RS_Spill);
1164
1165  if (VerifyEnabled)
1166    MF->verify(this, "After spilling");
1167
1168  // The live virtual register requesting allocation was spilled, so tell
1169  // the caller not to allocate anything during this round.
1170  return 0;
1171}
1172
1173bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
1174  DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n"
1175               << "********** Function: "
1176               << ((Value*)mf.getFunction())->getName() << '\n');
1177
1178  MF = &mf;
1179  if (VerifyEnabled)
1180    MF->verify(this, "Before greedy register allocator");
1181
1182  RegAllocBase::init(getAnalysis<VirtRegMap>(), getAnalysis<LiveIntervals>());
1183  Indexes = &getAnalysis<SlotIndexes>();
1184  DomTree = &getAnalysis<MachineDominatorTree>();
1185  ReservedRegs = TRI->getReservedRegs(*MF);
1186  SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
1187  Loops = &getAnalysis<MachineLoopInfo>();
1188  LoopRanges = &getAnalysis<MachineLoopRanges>();
1189  Bundles = &getAnalysis<EdgeBundles>();
1190  SpillPlacer = &getAnalysis<SpillPlacement>();
1191
1192  SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops));
1193  SE.reset(new SplitEditor(*SA, *LIS, *VRM, *DomTree));
1194  LRStage.clear();
1195  LRStage.resize(MRI->getNumVirtRegs());
1196  IntfCache.init(MF, &PhysReg2LiveUnion[0], Indexes, TRI);
1197
1198  allocatePhysRegs();
1199  addMBBLiveIns(MF);
1200  LIS->addKillFlags();
1201
1202  // Run rewriter
1203  {
1204    NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
1205    VRM->rewrite(Indexes);
1206  }
1207
1208  // Write out new DBG_VALUE instructions.
1209  getAnalysis<LiveDebugVariables>().emitDebugValues(VRM);
1210
1211  // The pass output is in VirtRegMap. Release all the transient data.
1212  releaseMemory();
1213
1214  return true;
1215}
1216