1// Copyright 2012 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "src/crankshaft/lithium-allocator.h"
6
7#include "src/crankshaft/hydrogen.h"
8#include "src/crankshaft/lithium-inl.h"
9#include "src/crankshaft/lithium-allocator-inl.h"
10#include "src/register-configuration.h"
11#include "src/string-stream.h"
12
13namespace v8 {
14namespace internal {
15
16static inline LifetimePosition Min(LifetimePosition a, LifetimePosition b) {
17  return a.Value() < b.Value() ? a : b;
18}
19
20
21static inline LifetimePosition Max(LifetimePosition a, LifetimePosition b) {
22  return a.Value() > b.Value() ? a : b;
23}
24
25
26UsePosition::UsePosition(LifetimePosition pos,
27                         LOperand* operand,
28                         LOperand* hint)
29    : operand_(operand),
30      hint_(hint),
31      pos_(pos),
32      next_(NULL),
33      requires_reg_(false),
34      register_beneficial_(true) {
35  if (operand_ != NULL && operand_->IsUnallocated()) {
36    LUnallocated* unalloc = LUnallocated::cast(operand_);
37    requires_reg_ = unalloc->HasRegisterPolicy() ||
38        unalloc->HasDoubleRegisterPolicy();
39    register_beneficial_ = !unalloc->HasAnyPolicy();
40  }
41  DCHECK(pos_.IsValid());
42}
43
44
45bool UsePosition::HasHint() const {
46  return hint_ != NULL && !hint_->IsUnallocated();
47}
48
49
50bool UsePosition::RequiresRegister() const {
51  return requires_reg_;
52}
53
54
55bool UsePosition::RegisterIsBeneficial() const {
56  return register_beneficial_;
57}
58
59
60void UseInterval::SplitAt(LifetimePosition pos, Zone* zone) {
61  DCHECK(Contains(pos) && pos.Value() != start().Value());
62  UseInterval* after = new(zone) UseInterval(pos, end_);
63  after->next_ = next_;
64  next_ = after;
65  end_ = pos;
66}
67
68
69#ifdef DEBUG
70
71
72void LiveRange::Verify() const {
73  UsePosition* cur = first_pos_;
74  while (cur != NULL) {
75    DCHECK(Start().Value() <= cur->pos().Value() &&
76           cur->pos().Value() <= End().Value());
77    cur = cur->next();
78  }
79}
80
81
82bool LiveRange::HasOverlap(UseInterval* target) const {
83  UseInterval* current_interval = first_interval_;
84  while (current_interval != NULL) {
85    // Intervals overlap if the start of one is contained in the other.
86    if (current_interval->Contains(target->start()) ||
87        target->Contains(current_interval->start())) {
88      return true;
89    }
90    current_interval = current_interval->next();
91  }
92  return false;
93}
94
95
96#endif
97
98
99LiveRange::LiveRange(int id, Zone* zone)
100    : id_(id),
101      spilled_(false),
102      kind_(UNALLOCATED_REGISTERS),
103      assigned_register_(kInvalidAssignment),
104      last_interval_(NULL),
105      first_interval_(NULL),
106      first_pos_(NULL),
107      parent_(NULL),
108      next_(NULL),
109      current_interval_(NULL),
110      last_processed_use_(NULL),
111      current_hint_operand_(NULL),
112      spill_operand_(new (zone) LOperand()),
113      spill_start_index_(kMaxInt) {}
114
115
116void LiveRange::set_assigned_register(int reg, Zone* zone) {
117  DCHECK(!HasRegisterAssigned() && !IsSpilled());
118  assigned_register_ = reg;
119  ConvertOperands(zone);
120}
121
122
123void LiveRange::MakeSpilled(Zone* zone) {
124  DCHECK(!IsSpilled());
125  DCHECK(TopLevel()->HasAllocatedSpillOperand());
126  spilled_ = true;
127  assigned_register_ = kInvalidAssignment;
128  ConvertOperands(zone);
129}
130
131
132bool LiveRange::HasAllocatedSpillOperand() const {
133  DCHECK(spill_operand_ != NULL);
134  return !spill_operand_->IsIgnored();
135}
136
137
138void LiveRange::SetSpillOperand(LOperand* operand) {
139  DCHECK(!operand->IsUnallocated());
140  DCHECK(spill_operand_ != NULL);
141  DCHECK(spill_operand_->IsIgnored());
142  spill_operand_->ConvertTo(operand->kind(), operand->index());
143}
144
145
146UsePosition* LiveRange::NextUsePosition(LifetimePosition start) {
147  UsePosition* use_pos = last_processed_use_;
148  if (use_pos == NULL) use_pos = first_pos();
149  while (use_pos != NULL && use_pos->pos().Value() < start.Value()) {
150    use_pos = use_pos->next();
151  }
152  last_processed_use_ = use_pos;
153  return use_pos;
154}
155
156
157UsePosition* LiveRange::NextUsePositionRegisterIsBeneficial(
158    LifetimePosition start) {
159  UsePosition* pos = NextUsePosition(start);
160  while (pos != NULL && !pos->RegisterIsBeneficial()) {
161    pos = pos->next();
162  }
163  return pos;
164}
165
166
167UsePosition* LiveRange::PreviousUsePositionRegisterIsBeneficial(
168    LifetimePosition start) {
169  UsePosition* pos = first_pos();
170  UsePosition* prev = NULL;
171  while (pos != NULL && pos->pos().Value() < start.Value()) {
172    if (pos->RegisterIsBeneficial()) prev = pos;
173    pos = pos->next();
174  }
175  return prev;
176}
177
178
179UsePosition* LiveRange::NextRegisterPosition(LifetimePosition start) {
180  UsePosition* pos = NextUsePosition(start);
181  while (pos != NULL && !pos->RequiresRegister()) {
182    pos = pos->next();
183  }
184  return pos;
185}
186
187
188bool LiveRange::CanBeSpilled(LifetimePosition pos) {
189  // We cannot spill a live range that has a use requiring a register
190  // at the current or the immediate next position.
191  UsePosition* use_pos = NextRegisterPosition(pos);
192  if (use_pos == NULL) return true;
193  return
194      use_pos->pos().Value() > pos.NextInstruction().InstructionEnd().Value();
195}
196
197
198LOperand* LiveRange::CreateAssignedOperand(Zone* zone) {
199  LOperand* op = NULL;
200  if (HasRegisterAssigned()) {
201    DCHECK(!IsSpilled());
202    switch (Kind()) {
203      case GENERAL_REGISTERS:
204        op = LRegister::Create(assigned_register(), zone);
205        break;
206      case DOUBLE_REGISTERS:
207        op = LDoubleRegister::Create(assigned_register(), zone);
208        break;
209      default:
210        UNREACHABLE();
211    }
212  } else if (IsSpilled()) {
213    DCHECK(!HasRegisterAssigned());
214    op = TopLevel()->GetSpillOperand();
215    DCHECK(!op->IsUnallocated());
216  } else {
217    LUnallocated* unalloc = new(zone) LUnallocated(LUnallocated::NONE);
218    unalloc->set_virtual_register(id_);
219    op = unalloc;
220  }
221  return op;
222}
223
224
225UseInterval* LiveRange::FirstSearchIntervalForPosition(
226    LifetimePosition position) const {
227  if (current_interval_ == NULL) return first_interval_;
228  if (current_interval_->start().Value() > position.Value()) {
229    current_interval_ = NULL;
230    return first_interval_;
231  }
232  return current_interval_;
233}
234
235
236void LiveRange::AdvanceLastProcessedMarker(
237    UseInterval* to_start_of, LifetimePosition but_not_past) const {
238  if (to_start_of == NULL) return;
239  if (to_start_of->start().Value() > but_not_past.Value()) return;
240  LifetimePosition start =
241      current_interval_ == NULL ? LifetimePosition::Invalid()
242                                : current_interval_->start();
243  if (to_start_of->start().Value() > start.Value()) {
244    current_interval_ = to_start_of;
245  }
246}
247
248
249void LiveRange::SplitAt(LifetimePosition position,
250                        LiveRange* result,
251                        Zone* zone) {
252  DCHECK(Start().Value() < position.Value());
253  DCHECK(result->IsEmpty());
254  // Find the last interval that ends before the position. If the
255  // position is contained in one of the intervals in the chain, we
256  // split that interval and use the first part.
257  UseInterval* current = FirstSearchIntervalForPosition(position);
258
259  // If the split position coincides with the beginning of a use interval
260  // we need to split use positons in a special way.
261  bool split_at_start = false;
262
263  if (current->start().Value() == position.Value()) {
264    // When splitting at start we need to locate the previous use interval.
265    current = first_interval_;
266  }
267
268  while (current != NULL) {
269    if (current->Contains(position)) {
270      current->SplitAt(position, zone);
271      break;
272    }
273    UseInterval* next = current->next();
274    if (next->start().Value() >= position.Value()) {
275      split_at_start = (next->start().Value() == position.Value());
276      break;
277    }
278    current = next;
279  }
280
281  // Partition original use intervals to the two live ranges.
282  UseInterval* before = current;
283  UseInterval* after = before->next();
284  result->last_interval_ = (last_interval_ == before)
285      ? after            // Only interval in the range after split.
286      : last_interval_;  // Last interval of the original range.
287  result->first_interval_ = after;
288  last_interval_ = before;
289
290  // Find the last use position before the split and the first use
291  // position after it.
292  UsePosition* use_after = first_pos_;
293  UsePosition* use_before = NULL;
294  if (split_at_start) {
295    // The split position coincides with the beginning of a use interval (the
296    // end of a lifetime hole). Use at this position should be attributed to
297    // the split child because split child owns use interval covering it.
298    while (use_after != NULL && use_after->pos().Value() < position.Value()) {
299      use_before = use_after;
300      use_after = use_after->next();
301    }
302  } else {
303    while (use_after != NULL && use_after->pos().Value() <= position.Value()) {
304      use_before = use_after;
305      use_after = use_after->next();
306    }
307  }
308
309  // Partition original use positions to the two live ranges.
310  if (use_before != NULL) {
311    use_before->next_ = NULL;
312  } else {
313    first_pos_ = NULL;
314  }
315  result->first_pos_ = use_after;
316
317  // Discard cached iteration state. It might be pointing
318  // to the use that no longer belongs to this live range.
319  last_processed_use_ = NULL;
320  current_interval_ = NULL;
321
322  // Link the new live range in the chain before any of the other
323  // ranges linked from the range before the split.
324  result->parent_ = (parent_ == NULL) ? this : parent_;
325  result->kind_ = result->parent_->kind_;
326  result->next_ = next_;
327  next_ = result;
328
329#ifdef DEBUG
330  Verify();
331  result->Verify();
332#endif
333}
334
335
336// This implements an ordering on live ranges so that they are ordered by their
337// start positions.  This is needed for the correctness of the register
338// allocation algorithm.  If two live ranges start at the same offset then there
339// is a tie breaker based on where the value is first used.  This part of the
340// ordering is merely a heuristic.
341bool LiveRange::ShouldBeAllocatedBefore(const LiveRange* other) const {
342  LifetimePosition start = Start();
343  LifetimePosition other_start = other->Start();
344  if (start.Value() == other_start.Value()) {
345    UsePosition* pos = first_pos();
346    if (pos == NULL) return false;
347    UsePosition* other_pos = other->first_pos();
348    if (other_pos == NULL) return true;
349    return pos->pos().Value() < other_pos->pos().Value();
350  }
351  return start.Value() < other_start.Value();
352}
353
354
355void LiveRange::ShortenTo(LifetimePosition start) {
356  LAllocator::TraceAlloc("Shorten live range %d to [%d\n", id_, start.Value());
357  DCHECK(first_interval_ != NULL);
358  DCHECK(first_interval_->start().Value() <= start.Value());
359  DCHECK(start.Value() < first_interval_->end().Value());
360  first_interval_->set_start(start);
361}
362
363
364void LiveRange::EnsureInterval(LifetimePosition start,
365                               LifetimePosition end,
366                               Zone* zone) {
367  LAllocator::TraceAlloc("Ensure live range %d in interval [%d %d[\n",
368                         id_,
369                         start.Value(),
370                         end.Value());
371  LifetimePosition new_end = end;
372  while (first_interval_ != NULL &&
373         first_interval_->start().Value() <= end.Value()) {
374    if (first_interval_->end().Value() > end.Value()) {
375      new_end = first_interval_->end();
376    }
377    first_interval_ = first_interval_->next();
378  }
379
380  UseInterval* new_interval = new(zone) UseInterval(start, new_end);
381  new_interval->next_ = first_interval_;
382  first_interval_ = new_interval;
383  if (new_interval->next() == NULL) {
384    last_interval_ = new_interval;
385  }
386}
387
388
389void LiveRange::AddUseInterval(LifetimePosition start,
390                               LifetimePosition end,
391                               Zone* zone) {
392  LAllocator::TraceAlloc("Add to live range %d interval [%d %d[\n",
393                         id_,
394                         start.Value(),
395                         end.Value());
396  if (first_interval_ == NULL) {
397    UseInterval* interval = new(zone) UseInterval(start, end);
398    first_interval_ = interval;
399    last_interval_ = interval;
400  } else {
401    if (end.Value() == first_interval_->start().Value()) {
402      first_interval_->set_start(start);
403    } else if (end.Value() < first_interval_->start().Value()) {
404      UseInterval* interval = new(zone) UseInterval(start, end);
405      interval->set_next(first_interval_);
406      first_interval_ = interval;
407    } else {
408      // Order of instruction's processing (see ProcessInstructions) guarantees
409      // that each new use interval either precedes or intersects with
410      // last added interval.
411      DCHECK(start.Value() < first_interval_->end().Value());
412      first_interval_->start_ = Min(start, first_interval_->start_);
413      first_interval_->end_ = Max(end, first_interval_->end_);
414    }
415  }
416}
417
418
419void LiveRange::AddUsePosition(LifetimePosition pos,
420                               LOperand* operand,
421                               LOperand* hint,
422                               Zone* zone) {
423  LAllocator::TraceAlloc("Add to live range %d use position %d\n",
424                         id_,
425                         pos.Value());
426  UsePosition* use_pos = new(zone) UsePosition(pos, operand, hint);
427  UsePosition* prev_hint = NULL;
428  UsePosition* prev = NULL;
429  UsePosition* current = first_pos_;
430  while (current != NULL && current->pos().Value() < pos.Value()) {
431    prev_hint = current->HasHint() ? current : prev_hint;
432    prev = current;
433    current = current->next();
434  }
435
436  if (prev == NULL) {
437    use_pos->set_next(first_pos_);
438    first_pos_ = use_pos;
439  } else {
440    use_pos->next_ = prev->next_;
441    prev->next_ = use_pos;
442  }
443
444  if (prev_hint == NULL && use_pos->HasHint()) {
445    current_hint_operand_ = hint;
446  }
447}
448
449
450void LiveRange::ConvertOperands(Zone* zone) {
451  LOperand* op = CreateAssignedOperand(zone);
452  UsePosition* use_pos = first_pos();
453  while (use_pos != NULL) {
454    DCHECK(Start().Value() <= use_pos->pos().Value() &&
455           use_pos->pos().Value() <= End().Value());
456
457    if (use_pos->HasOperand()) {
458      DCHECK(op->IsRegister() || op->IsDoubleRegister() ||
459             !use_pos->RequiresRegister());
460      use_pos->operand()->ConvertTo(op->kind(), op->index());
461    }
462    use_pos = use_pos->next();
463  }
464}
465
466
467bool LiveRange::CanCover(LifetimePosition position) const {
468  if (IsEmpty()) return false;
469  return Start().Value() <= position.Value() &&
470         position.Value() < End().Value();
471}
472
473
474bool LiveRange::Covers(LifetimePosition position) {
475  if (!CanCover(position)) return false;
476  UseInterval* start_search = FirstSearchIntervalForPosition(position);
477  for (UseInterval* interval = start_search;
478       interval != NULL;
479       interval = interval->next()) {
480    DCHECK(interval->next() == NULL ||
481           interval->next()->start().Value() >= interval->start().Value());
482    AdvanceLastProcessedMarker(interval, position);
483    if (interval->Contains(position)) return true;
484    if (interval->start().Value() > position.Value()) return false;
485  }
486  return false;
487}
488
489
490LifetimePosition LiveRange::FirstIntersection(LiveRange* other) {
491  UseInterval* b = other->first_interval();
492  if (b == NULL) return LifetimePosition::Invalid();
493  LifetimePosition advance_last_processed_up_to = b->start();
494  UseInterval* a = FirstSearchIntervalForPosition(b->start());
495  while (a != NULL && b != NULL) {
496    if (a->start().Value() > other->End().Value()) break;
497    if (b->start().Value() > End().Value()) break;
498    LifetimePosition cur_intersection = a->Intersect(b);
499    if (cur_intersection.IsValid()) {
500      return cur_intersection;
501    }
502    if (a->start().Value() < b->start().Value()) {
503      a = a->next();
504      if (a == NULL || a->start().Value() > other->End().Value()) break;
505      AdvanceLastProcessedMarker(a, advance_last_processed_up_to);
506    } else {
507      b = b->next();
508    }
509  }
510  return LifetimePosition::Invalid();
511}
512
513
514LAllocator::LAllocator(int num_values, HGraph* graph)
515    : chunk_(NULL),
516      live_in_sets_(graph->blocks()->length(), zone()),
517      live_ranges_(num_values * 2, zone()),
518      fixed_live_ranges_(NULL),
519      fixed_double_live_ranges_(NULL),
520      unhandled_live_ranges_(num_values * 2, zone()),
521      active_live_ranges_(8, zone()),
522      inactive_live_ranges_(8, zone()),
523      reusable_slots_(8, zone()),
524      next_virtual_register_(num_values),
525      first_artificial_register_(num_values),
526      mode_(UNALLOCATED_REGISTERS),
527      num_registers_(-1),
528      graph_(graph),
529      has_osr_entry_(false),
530      allocation_ok_(true) {}
531
532
533void LAllocator::InitializeLivenessAnalysis() {
534  // Initialize the live_in sets for each block to NULL.
535  int block_count = graph_->blocks()->length();
536  live_in_sets_.Initialize(block_count, zone());
537  live_in_sets_.AddBlock(NULL, block_count, zone());
538}
539
540
541BitVector* LAllocator::ComputeLiveOut(HBasicBlock* block) {
542  // Compute live out for the given block, except not including backward
543  // successor edges.
544  BitVector* live_out = new(zone()) BitVector(next_virtual_register_, zone());
545
546  // Process all successor blocks.
547  for (HSuccessorIterator it(block->end()); !it.Done(); it.Advance()) {
548    // Add values live on entry to the successor. Note the successor's
549    // live_in will not be computed yet for backwards edges.
550    HBasicBlock* successor = it.Current();
551    BitVector* live_in = live_in_sets_[successor->block_id()];
552    if (live_in != NULL) live_out->Union(*live_in);
553
554    // All phi input operands corresponding to this successor edge are live
555    // out from this block.
556    int index = successor->PredecessorIndexOf(block);
557    const ZoneList<HPhi*>* phis = successor->phis();
558    for (int i = 0; i < phis->length(); ++i) {
559      HPhi* phi = phis->at(i);
560      if (!phi->OperandAt(index)->IsConstant()) {
561        live_out->Add(phi->OperandAt(index)->id());
562      }
563    }
564  }
565
566  return live_out;
567}
568
569
570void LAllocator::AddInitialIntervals(HBasicBlock* block,
571                                     BitVector* live_out) {
572  // Add an interval that includes the entire block to the live range for
573  // each live_out value.
574  LifetimePosition start = LifetimePosition::FromInstructionIndex(
575      block->first_instruction_index());
576  LifetimePosition end = LifetimePosition::FromInstructionIndex(
577      block->last_instruction_index()).NextInstruction();
578  BitVector::Iterator iterator(live_out);
579  while (!iterator.Done()) {
580    int operand_index = iterator.Current();
581    LiveRange* range = LiveRangeFor(operand_index);
582    range->AddUseInterval(start, end, zone());
583    iterator.Advance();
584  }
585}
586
587
588int LAllocator::FixedDoubleLiveRangeID(int index) {
589  return -index - 1 - Register::kNumRegisters;
590}
591
592
593LOperand* LAllocator::AllocateFixed(LUnallocated* operand,
594                                    int pos,
595                                    bool is_tagged) {
596  TraceAlloc("Allocating fixed reg for op %d\n", operand->virtual_register());
597  DCHECK(operand->HasFixedPolicy());
598  if (operand->HasFixedSlotPolicy()) {
599    operand->ConvertTo(LOperand::STACK_SLOT, operand->fixed_slot_index());
600  } else if (operand->HasFixedRegisterPolicy()) {
601    int reg_index = operand->fixed_register_index();
602    operand->ConvertTo(LOperand::REGISTER, reg_index);
603  } else if (operand->HasFixedDoubleRegisterPolicy()) {
604    int reg_index = operand->fixed_register_index();
605    operand->ConvertTo(LOperand::DOUBLE_REGISTER, reg_index);
606  } else {
607    UNREACHABLE();
608  }
609  if (is_tagged) {
610    TraceAlloc("Fixed reg is tagged at %d\n", pos);
611    LInstruction* instr = InstructionAt(pos);
612    if (instr->HasPointerMap()) {
613      instr->pointer_map()->RecordPointer(operand, chunk()->zone());
614    }
615  }
616  return operand;
617}
618
619
620LiveRange* LAllocator::FixedLiveRangeFor(int index) {
621  DCHECK(index < Register::kNumRegisters);
622  LiveRange* result = fixed_live_ranges_[index];
623  if (result == NULL) {
624    result = new(zone()) LiveRange(FixedLiveRangeID(index), chunk()->zone());
625    DCHECK(result->IsFixed());
626    result->kind_ = GENERAL_REGISTERS;
627    SetLiveRangeAssignedRegister(result, index);
628    fixed_live_ranges_[index] = result;
629  }
630  return result;
631}
632
633
634LiveRange* LAllocator::FixedDoubleLiveRangeFor(int index) {
635  DCHECK(index < DoubleRegister::kMaxNumRegisters);
636  LiveRange* result = fixed_double_live_ranges_[index];
637  if (result == NULL) {
638    result = new(zone()) LiveRange(FixedDoubleLiveRangeID(index),
639                                   chunk()->zone());
640    DCHECK(result->IsFixed());
641    result->kind_ = DOUBLE_REGISTERS;
642    SetLiveRangeAssignedRegister(result, index);
643    fixed_double_live_ranges_[index] = result;
644  }
645  return result;
646}
647
648
649LiveRange* LAllocator::LiveRangeFor(int index) {
650  if (index >= live_ranges_.length()) {
651    live_ranges_.AddBlock(NULL, index - live_ranges_.length() + 1, zone());
652  }
653  LiveRange* result = live_ranges_[index];
654  if (result == NULL) {
655    result = new(zone()) LiveRange(index, chunk()->zone());
656    live_ranges_[index] = result;
657  }
658  return result;
659}
660
661
662LGap* LAllocator::GetLastGap(HBasicBlock* block) {
663  int last_instruction = block->last_instruction_index();
664  int index = chunk_->NearestGapPos(last_instruction);
665  return GapAt(index);
666}
667
668
669HPhi* LAllocator::LookupPhi(LOperand* operand) const {
670  if (!operand->IsUnallocated()) return NULL;
671  int index = LUnallocated::cast(operand)->virtual_register();
672  HValue* instr = graph_->LookupValue(index);
673  if (instr != NULL && instr->IsPhi()) {
674    return HPhi::cast(instr);
675  }
676  return NULL;
677}
678
679
680LiveRange* LAllocator::LiveRangeFor(LOperand* operand) {
681  if (operand->IsUnallocated()) {
682    return LiveRangeFor(LUnallocated::cast(operand)->virtual_register());
683  } else if (operand->IsRegister()) {
684    return FixedLiveRangeFor(operand->index());
685  } else if (operand->IsDoubleRegister()) {
686    return FixedDoubleLiveRangeFor(operand->index());
687  } else {
688    return NULL;
689  }
690}
691
692
693void LAllocator::Define(LifetimePosition position,
694                        LOperand* operand,
695                        LOperand* hint) {
696  LiveRange* range = LiveRangeFor(operand);
697  if (range == NULL) return;
698
699  if (range->IsEmpty() || range->Start().Value() > position.Value()) {
700    // Can happen if there is a definition without use.
701    range->AddUseInterval(position, position.NextInstruction(), zone());
702    range->AddUsePosition(position.NextInstruction(), NULL, NULL, zone());
703  } else {
704    range->ShortenTo(position);
705  }
706
707  if (operand->IsUnallocated()) {
708    LUnallocated* unalloc_operand = LUnallocated::cast(operand);
709    range->AddUsePosition(position, unalloc_operand, hint, zone());
710  }
711}
712
713
714void LAllocator::Use(LifetimePosition block_start,
715                     LifetimePosition position,
716                     LOperand* operand,
717                     LOperand* hint) {
718  LiveRange* range = LiveRangeFor(operand);
719  if (range == NULL) return;
720  if (operand->IsUnallocated()) {
721    LUnallocated* unalloc_operand = LUnallocated::cast(operand);
722    range->AddUsePosition(position, unalloc_operand, hint, zone());
723  }
724  range->AddUseInterval(block_start, position, zone());
725}
726
727
728void LAllocator::AddConstraintsGapMove(int index,
729                                       LOperand* from,
730                                       LOperand* to) {
731  LGap* gap = GapAt(index);
732  LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START,
733                                                     chunk()->zone());
734  if (from->IsUnallocated()) {
735    const ZoneList<LMoveOperands>* move_operands = move->move_operands();
736    for (int i = 0; i < move_operands->length(); ++i) {
737      LMoveOperands cur = move_operands->at(i);
738      LOperand* cur_to = cur.destination();
739      if (cur_to->IsUnallocated()) {
740        if (LUnallocated::cast(cur_to)->virtual_register() ==
741            LUnallocated::cast(from)->virtual_register()) {
742          move->AddMove(cur.source(), to, chunk()->zone());
743          return;
744        }
745      }
746    }
747  }
748  move->AddMove(from, to, chunk()->zone());
749}
750
751
752void LAllocator::MeetRegisterConstraints(HBasicBlock* block) {
753  int start = block->first_instruction_index();
754  int end = block->last_instruction_index();
755  if (start == -1) return;
756  for (int i = start; i <= end; ++i) {
757    if (IsGapAt(i)) {
758      LInstruction* instr = NULL;
759      LInstruction* prev_instr = NULL;
760      if (i < end) instr = InstructionAt(i + 1);
761      if (i > start) prev_instr = InstructionAt(i - 1);
762      MeetConstraintsBetween(prev_instr, instr, i);
763      if (!AllocationOk()) return;
764    }
765  }
766}
767
768
769void LAllocator::MeetConstraintsBetween(LInstruction* first,
770                                        LInstruction* second,
771                                        int gap_index) {
772  // Handle fixed temporaries.
773  if (first != NULL) {
774    for (TempIterator it(first); !it.Done(); it.Advance()) {
775      LUnallocated* temp = LUnallocated::cast(it.Current());
776      if (temp->HasFixedPolicy()) {
777        AllocateFixed(temp, gap_index - 1, false);
778      }
779    }
780  }
781
782  // Handle fixed output operand.
783  if (first != NULL && first->Output() != NULL) {
784    LUnallocated* first_output = LUnallocated::cast(first->Output());
785    LiveRange* range = LiveRangeFor(first_output->virtual_register());
786    bool assigned = false;
787    if (first_output->HasFixedPolicy()) {
788      LUnallocated* output_copy = first_output->CopyUnconstrained(
789          chunk()->zone());
790      bool is_tagged = HasTaggedValue(first_output->virtual_register());
791      AllocateFixed(first_output, gap_index, is_tagged);
792
793      // This value is produced on the stack, we never need to spill it.
794      if (first_output->IsStackSlot()) {
795        range->SetSpillOperand(first_output);
796        range->SetSpillStartIndex(gap_index - 1);
797        assigned = true;
798      }
799      chunk_->AddGapMove(gap_index, first_output, output_copy);
800    }
801
802    if (!assigned) {
803      range->SetSpillStartIndex(gap_index);
804
805      // This move to spill operand is not a real use. Liveness analysis
806      // and splitting of live ranges do not account for it.
807      // Thus it should be inserted to a lifetime position corresponding to
808      // the instruction end.
809      LGap* gap = GapAt(gap_index);
810      LParallelMove* move = gap->GetOrCreateParallelMove(LGap::BEFORE,
811                                                         chunk()->zone());
812      move->AddMove(first_output, range->GetSpillOperand(),
813                    chunk()->zone());
814    }
815  }
816
817  // Handle fixed input operands of second instruction.
818  if (second != NULL) {
819    for (UseIterator it(second); !it.Done(); it.Advance()) {
820      LUnallocated* cur_input = LUnallocated::cast(it.Current());
821      if (cur_input->HasFixedPolicy()) {
822        LUnallocated* input_copy = cur_input->CopyUnconstrained(
823            chunk()->zone());
824        bool is_tagged = HasTaggedValue(cur_input->virtual_register());
825        AllocateFixed(cur_input, gap_index + 1, is_tagged);
826        AddConstraintsGapMove(gap_index, input_copy, cur_input);
827      } else if (cur_input->HasWritableRegisterPolicy()) {
828        // The live range of writable input registers always goes until the end
829        // of the instruction.
830        DCHECK(!cur_input->IsUsedAtStart());
831
832        LUnallocated* input_copy = cur_input->CopyUnconstrained(
833            chunk()->zone());
834        int vreg = GetVirtualRegister();
835        if (!AllocationOk()) return;
836        cur_input->set_virtual_register(vreg);
837
838        if (RequiredRegisterKind(input_copy->virtual_register()) ==
839            DOUBLE_REGISTERS) {
840          double_artificial_registers_.Add(
841              cur_input->virtual_register() - first_artificial_register_,
842              zone());
843        }
844
845        AddConstraintsGapMove(gap_index, input_copy, cur_input);
846      }
847    }
848  }
849
850  // Handle "output same as input" for second instruction.
851  if (second != NULL && second->Output() != NULL) {
852    LUnallocated* second_output = LUnallocated::cast(second->Output());
853    if (second_output->HasSameAsInputPolicy()) {
854      LUnallocated* cur_input = LUnallocated::cast(second->FirstInput());
855      int output_vreg = second_output->virtual_register();
856      int input_vreg = cur_input->virtual_register();
857
858      LUnallocated* input_copy = cur_input->CopyUnconstrained(
859          chunk()->zone());
860      cur_input->set_virtual_register(second_output->virtual_register());
861      AddConstraintsGapMove(gap_index, input_copy, cur_input);
862
863      if (HasTaggedValue(input_vreg) && !HasTaggedValue(output_vreg)) {
864        int index = gap_index + 1;
865        LInstruction* instr = InstructionAt(index);
866        if (instr->HasPointerMap()) {
867          instr->pointer_map()->RecordPointer(input_copy, chunk()->zone());
868        }
869      } else if (!HasTaggedValue(input_vreg) && HasTaggedValue(output_vreg)) {
870        // The input is assumed to immediately have a tagged representation,
871        // before the pointer map can be used. I.e. the pointer map at the
872        // instruction will include the output operand (whose value at the
873        // beginning of the instruction is equal to the input operand). If
874        // this is not desired, then the pointer map at this instruction needs
875        // to be adjusted manually.
876      }
877    }
878  }
879}
880
881
882void LAllocator::ProcessInstructions(HBasicBlock* block, BitVector* live) {
883  int block_start = block->first_instruction_index();
884  int index = block->last_instruction_index();
885
886  LifetimePosition block_start_position =
887      LifetimePosition::FromInstructionIndex(block_start);
888
889  while (index >= block_start) {
890    LifetimePosition curr_position =
891        LifetimePosition::FromInstructionIndex(index);
892
893    if (IsGapAt(index)) {
894      // We have a gap at this position.
895      LGap* gap = GapAt(index);
896      LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START,
897                                                         chunk()->zone());
898      const ZoneList<LMoveOperands>* move_operands = move->move_operands();
899      for (int i = 0; i < move_operands->length(); ++i) {
900        LMoveOperands* cur = &move_operands->at(i);
901        if (cur->IsIgnored()) continue;
902        LOperand* from = cur->source();
903        LOperand* to = cur->destination();
904        HPhi* phi = LookupPhi(to);
905        LOperand* hint = to;
906        if (phi != NULL) {
907          // This is a phi resolving move.
908          if (!phi->block()->IsLoopHeader()) {
909            hint = LiveRangeFor(phi->id())->current_hint_operand();
910          }
911        } else {
912          if (to->IsUnallocated()) {
913            if (live->Contains(LUnallocated::cast(to)->virtual_register())) {
914              Define(curr_position, to, from);
915              live->Remove(LUnallocated::cast(to)->virtual_register());
916            } else {
917              cur->Eliminate();
918              continue;
919            }
920          } else {
921            Define(curr_position, to, from);
922          }
923        }
924        Use(block_start_position, curr_position, from, hint);
925        if (from->IsUnallocated()) {
926          live->Add(LUnallocated::cast(from)->virtual_register());
927        }
928      }
929    } else {
930      DCHECK(!IsGapAt(index));
931      LInstruction* instr = InstructionAt(index);
932
933      if (instr != NULL) {
934        LOperand* output = instr->Output();
935        if (output != NULL) {
936          if (output->IsUnallocated()) {
937            live->Remove(LUnallocated::cast(output)->virtual_register());
938          }
939          Define(curr_position, output, NULL);
940        }
941
942        if (instr->ClobbersRegisters()) {
943          for (int i = 0; i < Register::kNumRegisters; ++i) {
944            if (Register::from_code(i).IsAllocatable()) {
945              if (output == NULL || !output->IsRegister() ||
946                  output->index() != i) {
947                LiveRange* range = FixedLiveRangeFor(i);
948                range->AddUseInterval(curr_position,
949                                      curr_position.InstructionEnd(), zone());
950              }
951            }
952          }
953        }
954
955        if (instr->ClobbersDoubleRegisters(isolate())) {
956          for (int i = 0; i < DoubleRegister::kMaxNumRegisters; ++i) {
957            if (DoubleRegister::from_code(i).IsAllocatable()) {
958              if (output == NULL || !output->IsDoubleRegister() ||
959                  output->index() != i) {
960                LiveRange* range = FixedDoubleLiveRangeFor(i);
961                range->AddUseInterval(curr_position,
962                                      curr_position.InstructionEnd(), zone());
963              }
964            }
965          }
966        }
967
968        for (UseIterator it(instr); !it.Done(); it.Advance()) {
969          LOperand* input = it.Current();
970
971          LifetimePosition use_pos;
972          if (input->IsUnallocated() &&
973              LUnallocated::cast(input)->IsUsedAtStart()) {
974            use_pos = curr_position;
975          } else {
976            use_pos = curr_position.InstructionEnd();
977          }
978
979          Use(block_start_position, use_pos, input, NULL);
980          if (input->IsUnallocated()) {
981            live->Add(LUnallocated::cast(input)->virtual_register());
982          }
983        }
984
985        for (TempIterator it(instr); !it.Done(); it.Advance()) {
986          LOperand* temp = it.Current();
987          if (instr->ClobbersTemps()) {
988            if (temp->IsRegister()) continue;
989            if (temp->IsUnallocated()) {
990              LUnallocated* temp_unalloc = LUnallocated::cast(temp);
991              if (temp_unalloc->HasFixedPolicy()) {
992                continue;
993              }
994            }
995          }
996          Use(block_start_position, curr_position.InstructionEnd(), temp, NULL);
997          Define(curr_position, temp, NULL);
998
999          if (temp->IsUnallocated()) {
1000            LUnallocated* temp_unalloc = LUnallocated::cast(temp);
1001            if (temp_unalloc->HasDoubleRegisterPolicy()) {
1002              double_artificial_registers_.Add(
1003                  temp_unalloc->virtual_register() - first_artificial_register_,
1004                  zone());
1005            }
1006          }
1007        }
1008      }
1009    }
1010
1011    index = index - 1;
1012  }
1013}
1014
1015
1016void LAllocator::ResolvePhis(HBasicBlock* block) {
1017  const ZoneList<HPhi*>* phis = block->phis();
1018  for (int i = 0; i < phis->length(); ++i) {
1019    HPhi* phi = phis->at(i);
1020    LUnallocated* phi_operand =
1021        new (chunk()->zone()) LUnallocated(LUnallocated::NONE);
1022    phi_operand->set_virtual_register(phi->id());
1023    for (int j = 0; j < phi->OperandCount(); ++j) {
1024      HValue* op = phi->OperandAt(j);
1025      LOperand* operand = NULL;
1026      if (op->IsConstant() && op->EmitAtUses()) {
1027        HConstant* constant = HConstant::cast(op);
1028        operand = chunk_->DefineConstantOperand(constant);
1029      } else {
1030        DCHECK(!op->EmitAtUses());
1031        LUnallocated* unalloc =
1032            new(chunk()->zone()) LUnallocated(LUnallocated::ANY);
1033        unalloc->set_virtual_register(op->id());
1034        operand = unalloc;
1035      }
1036      HBasicBlock* cur_block = block->predecessors()->at(j);
1037      // The gap move must be added without any special processing as in
1038      // the AddConstraintsGapMove.
1039      chunk_->AddGapMove(cur_block->last_instruction_index() - 1,
1040                         operand,
1041                         phi_operand);
1042
1043      // We are going to insert a move before the branch instruction.
1044      // Some branch instructions (e.g. loops' back edges)
1045      // can potentially cause a GC so they have a pointer map.
1046      // By inserting a move we essentially create a copy of a
1047      // value which is invisible to PopulatePointerMaps(), because we store
1048      // it into a location different from the operand of a live range
1049      // covering a branch instruction.
1050      // Thus we need to manually record a pointer.
1051      LInstruction* branch =
1052          InstructionAt(cur_block->last_instruction_index());
1053      if (branch->HasPointerMap()) {
1054        if (phi->representation().IsTagged() && !phi->type().IsSmi()) {
1055          branch->pointer_map()->RecordPointer(phi_operand, chunk()->zone());
1056        } else if (!phi->representation().IsDouble()) {
1057          branch->pointer_map()->RecordUntagged(phi_operand, chunk()->zone());
1058        }
1059      }
1060    }
1061
1062    LiveRange* live_range = LiveRangeFor(phi->id());
1063    LLabel* label = chunk_->GetLabel(phi->block()->block_id());
1064    label->GetOrCreateParallelMove(LGap::START, chunk()->zone())->
1065        AddMove(phi_operand, live_range->GetSpillOperand(), chunk()->zone());
1066    live_range->SetSpillStartIndex(phi->block()->first_instruction_index());
1067  }
1068}
1069
1070
1071bool LAllocator::Allocate(LChunk* chunk) {
1072  DCHECK(chunk_ == NULL);
1073  chunk_ = static_cast<LPlatformChunk*>(chunk);
1074  assigned_registers_ =
1075      new (chunk->zone()) BitVector(Register::kNumRegisters, chunk->zone());
1076  assigned_double_registers_ = new (chunk->zone())
1077      BitVector(DoubleRegister::kMaxNumRegisters, chunk->zone());
1078  MeetRegisterConstraints();
1079  if (!AllocationOk()) return false;
1080  ResolvePhis();
1081  BuildLiveRanges();
1082  AllocateGeneralRegisters();
1083  if (!AllocationOk()) return false;
1084  AllocateDoubleRegisters();
1085  if (!AllocationOk()) return false;
1086  PopulatePointerMaps();
1087  ConnectRanges();
1088  ResolveControlFlow();
1089  return true;
1090}
1091
1092
1093void LAllocator::MeetRegisterConstraints() {
1094  LAllocatorPhase phase("L_Register constraints", this);
1095  const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1096  for (int i = 0; i < blocks->length(); ++i) {
1097    HBasicBlock* block = blocks->at(i);
1098    MeetRegisterConstraints(block);
1099    if (!AllocationOk()) return;
1100  }
1101}
1102
1103
1104void LAllocator::ResolvePhis() {
1105  LAllocatorPhase phase("L_Resolve phis", this);
1106
1107  // Process the blocks in reverse order.
1108  const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1109  for (int block_id = blocks->length() - 1; block_id >= 0; --block_id) {
1110    HBasicBlock* block = blocks->at(block_id);
1111    ResolvePhis(block);
1112  }
1113}
1114
1115
1116void LAllocator::ResolveControlFlow(LiveRange* range,
1117                                    HBasicBlock* block,
1118                                    HBasicBlock* pred) {
1119  LifetimePosition pred_end =
1120      LifetimePosition::FromInstructionIndex(pred->last_instruction_index());
1121  LifetimePosition cur_start =
1122      LifetimePosition::FromInstructionIndex(block->first_instruction_index());
1123  LiveRange* pred_cover = NULL;
1124  LiveRange* cur_cover = NULL;
1125  LiveRange* cur_range = range;
1126  while (cur_range != NULL && (cur_cover == NULL || pred_cover == NULL)) {
1127    if (cur_range->CanCover(cur_start)) {
1128      DCHECK(cur_cover == NULL);
1129      cur_cover = cur_range;
1130    }
1131    if (cur_range->CanCover(pred_end)) {
1132      DCHECK(pred_cover == NULL);
1133      pred_cover = cur_range;
1134    }
1135    cur_range = cur_range->next();
1136  }
1137
1138  if (cur_cover->IsSpilled()) return;
1139  DCHECK(pred_cover != NULL && cur_cover != NULL);
1140  if (pred_cover != cur_cover) {
1141    LOperand* pred_op = pred_cover->CreateAssignedOperand(chunk()->zone());
1142    LOperand* cur_op = cur_cover->CreateAssignedOperand(chunk()->zone());
1143    if (!pred_op->Equals(cur_op)) {
1144      LGap* gap = NULL;
1145      if (block->predecessors()->length() == 1) {
1146        gap = GapAt(block->first_instruction_index());
1147      } else {
1148        DCHECK(pred->end()->SecondSuccessor() == NULL);
1149        gap = GetLastGap(pred);
1150
1151        // We are going to insert a move before the branch instruction.
1152        // Some branch instructions (e.g. loops' back edges)
1153        // can potentially cause a GC so they have a pointer map.
1154        // By inserting a move we essentially create a copy of a
1155        // value which is invisible to PopulatePointerMaps(), because we store
1156        // it into a location different from the operand of a live range
1157        // covering a branch instruction.
1158        // Thus we need to manually record a pointer.
1159        LInstruction* branch = InstructionAt(pred->last_instruction_index());
1160        if (branch->HasPointerMap()) {
1161          if (HasTaggedValue(range->id())) {
1162            branch->pointer_map()->RecordPointer(cur_op, chunk()->zone());
1163          } else if (!cur_op->IsDoubleStackSlot() &&
1164                     !cur_op->IsDoubleRegister()) {
1165            branch->pointer_map()->RemovePointer(cur_op);
1166          }
1167        }
1168      }
1169      gap->GetOrCreateParallelMove(
1170          LGap::START, chunk()->zone())->AddMove(pred_op, cur_op,
1171                                                 chunk()->zone());
1172    }
1173  }
1174}
1175
1176
1177LParallelMove* LAllocator::GetConnectingParallelMove(LifetimePosition pos) {
1178  int index = pos.InstructionIndex();
1179  if (IsGapAt(index)) {
1180    LGap* gap = GapAt(index);
1181    return gap->GetOrCreateParallelMove(
1182        pos.IsInstructionStart() ? LGap::START : LGap::END, chunk()->zone());
1183  }
1184  int gap_pos = pos.IsInstructionStart() ? (index - 1) : (index + 1);
1185  return GapAt(gap_pos)->GetOrCreateParallelMove(
1186      (gap_pos < index) ? LGap::AFTER : LGap::BEFORE, chunk()->zone());
1187}
1188
1189
1190HBasicBlock* LAllocator::GetBlock(LifetimePosition pos) {
1191  LGap* gap = GapAt(chunk_->NearestGapPos(pos.InstructionIndex()));
1192  return gap->block();
1193}
1194
1195
1196void LAllocator::ConnectRanges() {
1197  LAllocatorPhase phase("L_Connect ranges", this);
1198  for (int i = 0; i < live_ranges()->length(); ++i) {
1199    LiveRange* first_range = live_ranges()->at(i);
1200    if (first_range == NULL || first_range->parent() != NULL) continue;
1201
1202    LiveRange* second_range = first_range->next();
1203    while (second_range != NULL) {
1204      LifetimePosition pos = second_range->Start();
1205
1206      if (!second_range->IsSpilled()) {
1207        // Add gap move if the two live ranges touch and there is no block
1208        // boundary.
1209        if (first_range->End().Value() == pos.Value()) {
1210          bool should_insert = true;
1211          if (IsBlockBoundary(pos)) {
1212            should_insert = CanEagerlyResolveControlFlow(GetBlock(pos));
1213          }
1214          if (should_insert) {
1215            LParallelMove* move = GetConnectingParallelMove(pos);
1216            LOperand* prev_operand = first_range->CreateAssignedOperand(
1217                chunk()->zone());
1218            LOperand* cur_operand = second_range->CreateAssignedOperand(
1219                chunk()->zone());
1220            move->AddMove(prev_operand, cur_operand,
1221                          chunk()->zone());
1222          }
1223        }
1224      }
1225
1226      first_range = second_range;
1227      second_range = second_range->next();
1228    }
1229  }
1230}
1231
1232
1233bool LAllocator::CanEagerlyResolveControlFlow(HBasicBlock* block) const {
1234  if (block->predecessors()->length() != 1) return false;
1235  return block->predecessors()->first()->block_id() == block->block_id() - 1;
1236}
1237
1238
1239void LAllocator::ResolveControlFlow() {
1240  LAllocatorPhase phase("L_Resolve control flow", this);
1241  const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1242  for (int block_id = 1; block_id < blocks->length(); ++block_id) {
1243    HBasicBlock* block = blocks->at(block_id);
1244    if (CanEagerlyResolveControlFlow(block)) continue;
1245    BitVector* live = live_in_sets_[block->block_id()];
1246    BitVector::Iterator iterator(live);
1247    while (!iterator.Done()) {
1248      int operand_index = iterator.Current();
1249      for (int i = 0; i < block->predecessors()->length(); ++i) {
1250        HBasicBlock* cur = block->predecessors()->at(i);
1251        LiveRange* cur_range = LiveRangeFor(operand_index);
1252        ResolveControlFlow(cur_range, block, cur);
1253      }
1254      iterator.Advance();
1255    }
1256  }
1257}
1258
1259
1260void LAllocator::BuildLiveRanges() {
1261  LAllocatorPhase phase("L_Build live ranges", this);
1262  InitializeLivenessAnalysis();
1263  // Process the blocks in reverse order.
1264  const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1265  for (int block_id = blocks->length() - 1; block_id >= 0; --block_id) {
1266    HBasicBlock* block = blocks->at(block_id);
1267    BitVector* live = ComputeLiveOut(block);
1268    // Initially consider all live_out values live for the entire block. We
1269    // will shorten these intervals if necessary.
1270    AddInitialIntervals(block, live);
1271
1272    // Process the instructions in reverse order, generating and killing
1273    // live values.
1274    ProcessInstructions(block, live);
1275    // All phi output operands are killed by this block.
1276    const ZoneList<HPhi*>* phis = block->phis();
1277    for (int i = 0; i < phis->length(); ++i) {
1278      // The live range interval already ends at the first instruction of the
1279      // block.
1280      HPhi* phi = phis->at(i);
1281      live->Remove(phi->id());
1282
1283      LOperand* hint = NULL;
1284      LOperand* phi_operand = NULL;
1285      LGap* gap = GetLastGap(phi->block()->predecessors()->at(0));
1286      LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START,
1287                                                         chunk()->zone());
1288      for (int j = 0; j < move->move_operands()->length(); ++j) {
1289        LOperand* to = move->move_operands()->at(j).destination();
1290        if (to->IsUnallocated() &&
1291            LUnallocated::cast(to)->virtual_register() == phi->id()) {
1292          hint = move->move_operands()->at(j).source();
1293          phi_operand = to;
1294          break;
1295        }
1296      }
1297      DCHECK(hint != NULL);
1298
1299      LifetimePosition block_start = LifetimePosition::FromInstructionIndex(
1300              block->first_instruction_index());
1301      Define(block_start, phi_operand, hint);
1302    }
1303
1304    // Now live is live_in for this block except not including values live
1305    // out on backward successor edges.
1306    live_in_sets_[block_id] = live;
1307
1308    // If this block is a loop header go back and patch up the necessary
1309    // predecessor blocks.
1310    if (block->IsLoopHeader()) {
1311      // TODO(kmillikin): Need to be able to get the last block of the loop
1312      // in the loop information. Add a live range stretching from the first
1313      // loop instruction to the last for each value live on entry to the
1314      // header.
1315      HBasicBlock* back_edge = block->loop_information()->GetLastBackEdge();
1316      BitVector::Iterator iterator(live);
1317      LifetimePosition start = LifetimePosition::FromInstructionIndex(
1318          block->first_instruction_index());
1319      LifetimePosition end = LifetimePosition::FromInstructionIndex(
1320          back_edge->last_instruction_index()).NextInstruction();
1321      while (!iterator.Done()) {
1322        int operand_index = iterator.Current();
1323        LiveRange* range = LiveRangeFor(operand_index);
1324        range->EnsureInterval(start, end, zone());
1325        iterator.Advance();
1326      }
1327
1328      for (int i = block->block_id() + 1; i <= back_edge->block_id(); ++i) {
1329        live_in_sets_[i]->Union(*live);
1330      }
1331    }
1332
1333#ifdef DEBUG
1334    if (block_id == 0) {
1335      BitVector::Iterator iterator(live);
1336      bool found = false;
1337      while (!iterator.Done()) {
1338        found = true;
1339        int operand_index = iterator.Current();
1340        {
1341          AllowHandleDereference allow_deref;
1342          PrintF("Function: %s\n", chunk_->info()->GetDebugName().get());
1343        }
1344        PrintF("Value %d used before first definition!\n", operand_index);
1345        LiveRange* range = LiveRangeFor(operand_index);
1346        PrintF("First use is at %d\n", range->first_pos()->pos().Value());
1347        iterator.Advance();
1348      }
1349      DCHECK(!found);
1350    }
1351#endif
1352  }
1353
1354  for (int i = 0; i < live_ranges_.length(); ++i) {
1355    if (live_ranges_[i] != NULL) {
1356      live_ranges_[i]->kind_ = RequiredRegisterKind(live_ranges_[i]->id());
1357    }
1358  }
1359}
1360
1361
1362bool LAllocator::SafePointsAreInOrder() const {
1363  const ZoneList<LPointerMap*>* pointer_maps = chunk_->pointer_maps();
1364  int safe_point = 0;
1365  for (int i = 0; i < pointer_maps->length(); ++i) {
1366    LPointerMap* map = pointer_maps->at(i);
1367    if (safe_point > map->lithium_position()) return false;
1368    safe_point = map->lithium_position();
1369  }
1370  return true;
1371}
1372
1373
1374void LAllocator::PopulatePointerMaps() {
1375  LAllocatorPhase phase("L_Populate pointer maps", this);
1376  const ZoneList<LPointerMap*>* pointer_maps = chunk_->pointer_maps();
1377
1378  DCHECK(SafePointsAreInOrder());
1379
1380  // Iterate over all safe point positions and record a pointer
1381  // for all spilled live ranges at this point.
1382  int first_safe_point_index = 0;
1383  int last_range_start = 0;
1384  for (int range_idx = 0; range_idx < live_ranges()->length(); ++range_idx) {
1385    LiveRange* range = live_ranges()->at(range_idx);
1386    if (range == NULL) continue;
1387    // Iterate over the first parts of multi-part live ranges.
1388    if (range->parent() != NULL) continue;
1389    // Skip non-pointer values.
1390    if (!HasTaggedValue(range->id())) continue;
1391    // Skip empty live ranges.
1392    if (range->IsEmpty()) continue;
1393
1394    // Find the extent of the range and its children.
1395    int start = range->Start().InstructionIndex();
1396    int end = 0;
1397    for (LiveRange* cur = range; cur != NULL; cur = cur->next()) {
1398      LifetimePosition this_end = cur->End();
1399      if (this_end.InstructionIndex() > end) end = this_end.InstructionIndex();
1400      DCHECK(cur->Start().InstructionIndex() >= start);
1401    }
1402
1403    // Most of the ranges are in order, but not all.  Keep an eye on when
1404    // they step backwards and reset the first_safe_point_index so we don't
1405    // miss any safe points.
1406    if (start < last_range_start) {
1407      first_safe_point_index = 0;
1408    }
1409    last_range_start = start;
1410
1411    // Step across all the safe points that are before the start of this range,
1412    // recording how far we step in order to save doing this for the next range.
1413    while (first_safe_point_index < pointer_maps->length()) {
1414      LPointerMap* map = pointer_maps->at(first_safe_point_index);
1415      int safe_point = map->lithium_position();
1416      if (safe_point >= start) break;
1417      first_safe_point_index++;
1418    }
1419
1420    // Step through the safe points to see whether they are in the range.
1421    for (int safe_point_index = first_safe_point_index;
1422         safe_point_index < pointer_maps->length();
1423         ++safe_point_index) {
1424      LPointerMap* map = pointer_maps->at(safe_point_index);
1425      int safe_point = map->lithium_position();
1426
1427      // The safe points are sorted so we can stop searching here.
1428      if (safe_point - 1 > end) break;
1429
1430      // Advance to the next active range that covers the current
1431      // safe point position.
1432      LifetimePosition safe_point_pos =
1433          LifetimePosition::FromInstructionIndex(safe_point);
1434      LiveRange* cur = range;
1435      while (cur != NULL && !cur->Covers(safe_point_pos)) {
1436        cur = cur->next();
1437      }
1438      if (cur == NULL) continue;
1439
1440      // Check if the live range is spilled and the safe point is after
1441      // the spill position.
1442      if (range->HasAllocatedSpillOperand() &&
1443          safe_point >= range->spill_start_index()) {
1444        TraceAlloc("Pointer for range %d (spilled at %d) at safe point %d\n",
1445                   range->id(), range->spill_start_index(), safe_point);
1446        map->RecordPointer(range->GetSpillOperand(), chunk()->zone());
1447      }
1448
1449      if (!cur->IsSpilled()) {
1450        TraceAlloc("Pointer in register for range %d (start at %d) "
1451                   "at safe point %d\n",
1452                   cur->id(), cur->Start().Value(), safe_point);
1453        LOperand* operand = cur->CreateAssignedOperand(chunk()->zone());
1454        DCHECK(!operand->IsStackSlot());
1455        map->RecordPointer(operand, chunk()->zone());
1456      }
1457    }
1458  }
1459}
1460
1461
1462void LAllocator::AllocateGeneralRegisters() {
1463  LAllocatorPhase phase("L_Allocate general registers", this);
1464  num_registers_ =
1465      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
1466          ->num_allocatable_general_registers();
1467  allocatable_register_codes_ =
1468      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
1469          ->allocatable_general_codes();
1470  mode_ = GENERAL_REGISTERS;
1471  AllocateRegisters();
1472}
1473
1474
1475void LAllocator::AllocateDoubleRegisters() {
1476  LAllocatorPhase phase("L_Allocate double registers", this);
1477  num_registers_ =
1478      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
1479          ->num_allocatable_double_registers();
1480  allocatable_register_codes_ =
1481      RegisterConfiguration::ArchDefault(RegisterConfiguration::CRANKSHAFT)
1482          ->allocatable_double_codes();
1483  mode_ = DOUBLE_REGISTERS;
1484  AllocateRegisters();
1485}
1486
1487
1488void LAllocator::AllocateRegisters() {
1489  DCHECK(unhandled_live_ranges_.is_empty());
1490
1491  for (int i = 0; i < live_ranges_.length(); ++i) {
1492    if (live_ranges_[i] != NULL) {
1493      if (live_ranges_[i]->Kind() == mode_) {
1494        AddToUnhandledUnsorted(live_ranges_[i]);
1495      }
1496    }
1497  }
1498  SortUnhandled();
1499  DCHECK(UnhandledIsSorted());
1500
1501  DCHECK(reusable_slots_.is_empty());
1502  DCHECK(active_live_ranges_.is_empty());
1503  DCHECK(inactive_live_ranges_.is_empty());
1504
1505  if (mode_ == DOUBLE_REGISTERS) {
1506    for (int i = 0; i < fixed_double_live_ranges_.length(); ++i) {
1507      LiveRange* current = fixed_double_live_ranges_.at(i);
1508      if (current != NULL) {
1509        AddToInactive(current);
1510      }
1511    }
1512  } else {
1513    DCHECK(mode_ == GENERAL_REGISTERS);
1514    for (int i = 0; i < fixed_live_ranges_.length(); ++i) {
1515      LiveRange* current = fixed_live_ranges_.at(i);
1516      if (current != NULL) {
1517        AddToInactive(current);
1518      }
1519    }
1520  }
1521
1522  while (!unhandled_live_ranges_.is_empty()) {
1523    DCHECK(UnhandledIsSorted());
1524    LiveRange* current = unhandled_live_ranges_.RemoveLast();
1525    DCHECK(UnhandledIsSorted());
1526    LifetimePosition position = current->Start();
1527#ifdef DEBUG
1528    allocation_finger_ = position;
1529#endif
1530    TraceAlloc("Processing interval %d start=%d\n",
1531               current->id(),
1532               position.Value());
1533
1534    if (current->HasAllocatedSpillOperand()) {
1535      TraceAlloc("Live range %d already has a spill operand\n", current->id());
1536      LifetimePosition next_pos = position;
1537      if (IsGapAt(next_pos.InstructionIndex())) {
1538        next_pos = next_pos.NextInstruction();
1539      }
1540      UsePosition* pos = current->NextUsePositionRegisterIsBeneficial(next_pos);
1541      // If the range already has a spill operand and it doesn't need a
1542      // register immediately, split it and spill the first part of the range.
1543      if (pos == NULL) {
1544        Spill(current);
1545        continue;
1546      } else if (pos->pos().Value() >
1547                 current->Start().NextInstruction().Value()) {
1548        // Do not spill live range eagerly if use position that can benefit from
1549        // the register is too close to the start of live range.
1550        SpillBetween(current, current->Start(), pos->pos());
1551        if (!AllocationOk()) return;
1552        DCHECK(UnhandledIsSorted());
1553        continue;
1554      }
1555    }
1556
1557    for (int i = 0; i < active_live_ranges_.length(); ++i) {
1558      LiveRange* cur_active = active_live_ranges_.at(i);
1559      if (cur_active->End().Value() <= position.Value()) {
1560        ActiveToHandled(cur_active);
1561        --i;  // The live range was removed from the list of active live ranges.
1562      } else if (!cur_active->Covers(position)) {
1563        ActiveToInactive(cur_active);
1564        --i;  // The live range was removed from the list of active live ranges.
1565      }
1566    }
1567
1568    for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1569      LiveRange* cur_inactive = inactive_live_ranges_.at(i);
1570      if (cur_inactive->End().Value() <= position.Value()) {
1571        InactiveToHandled(cur_inactive);
1572        --i;  // Live range was removed from the list of inactive live ranges.
1573      } else if (cur_inactive->Covers(position)) {
1574        InactiveToActive(cur_inactive);
1575        --i;  // Live range was removed from the list of inactive live ranges.
1576      }
1577    }
1578
1579    DCHECK(!current->HasRegisterAssigned() && !current->IsSpilled());
1580
1581    bool result = TryAllocateFreeReg(current);
1582    if (!AllocationOk()) return;
1583
1584    if (!result) AllocateBlockedReg(current);
1585    if (!AllocationOk()) return;
1586
1587    if (current->HasRegisterAssigned()) {
1588      AddToActive(current);
1589    }
1590  }
1591
1592  reusable_slots_.Rewind(0);
1593  active_live_ranges_.Rewind(0);
1594  inactive_live_ranges_.Rewind(0);
1595}
1596
1597
1598const char* LAllocator::RegisterName(int allocation_index) {
1599  if (mode_ == GENERAL_REGISTERS) {
1600    return Register::from_code(allocation_index).ToString();
1601  } else {
1602    return DoubleRegister::from_code(allocation_index).ToString();
1603  }
1604}
1605
1606
1607void LAllocator::TraceAlloc(const char* msg, ...) {
1608  if (FLAG_trace_alloc) {
1609    va_list arguments;
1610    va_start(arguments, msg);
1611    base::OS::VPrint(msg, arguments);
1612    va_end(arguments);
1613  }
1614}
1615
1616
1617bool LAllocator::HasTaggedValue(int virtual_register) const {
1618  HValue* value = graph_->LookupValue(virtual_register);
1619  if (value == NULL) return false;
1620  return value->representation().IsTagged() && !value->type().IsSmi();
1621}
1622
1623
1624RegisterKind LAllocator::RequiredRegisterKind(int virtual_register) const {
1625  if (virtual_register < first_artificial_register_) {
1626    HValue* value = graph_->LookupValue(virtual_register);
1627    if (value != NULL && value->representation().IsDouble()) {
1628      return DOUBLE_REGISTERS;
1629    }
1630  } else if (double_artificial_registers_.Contains(
1631      virtual_register - first_artificial_register_)) {
1632    return DOUBLE_REGISTERS;
1633  }
1634
1635  return GENERAL_REGISTERS;
1636}
1637
1638
1639void LAllocator::AddToActive(LiveRange* range) {
1640  TraceAlloc("Add live range %d to active\n", range->id());
1641  active_live_ranges_.Add(range, zone());
1642}
1643
1644
1645void LAllocator::AddToInactive(LiveRange* range) {
1646  TraceAlloc("Add live range %d to inactive\n", range->id());
1647  inactive_live_ranges_.Add(range, zone());
1648}
1649
1650
1651void LAllocator::AddToUnhandledSorted(LiveRange* range) {
1652  if (range == NULL || range->IsEmpty()) return;
1653  DCHECK(!range->HasRegisterAssigned() && !range->IsSpilled());
1654  DCHECK(allocation_finger_.Value() <= range->Start().Value());
1655  for (int i = unhandled_live_ranges_.length() - 1; i >= 0; --i) {
1656    LiveRange* cur_range = unhandled_live_ranges_.at(i);
1657    if (range->ShouldBeAllocatedBefore(cur_range)) {
1658      TraceAlloc("Add live range %d to unhandled at %d\n", range->id(), i + 1);
1659      unhandled_live_ranges_.InsertAt(i + 1, range, zone());
1660      DCHECK(UnhandledIsSorted());
1661      return;
1662    }
1663  }
1664  TraceAlloc("Add live range %d to unhandled at start\n", range->id());
1665  unhandled_live_ranges_.InsertAt(0, range, zone());
1666  DCHECK(UnhandledIsSorted());
1667}
1668
1669
1670void LAllocator::AddToUnhandledUnsorted(LiveRange* range) {
1671  if (range == NULL || range->IsEmpty()) return;
1672  DCHECK(!range->HasRegisterAssigned() && !range->IsSpilled());
1673  TraceAlloc("Add live range %d to unhandled unsorted at end\n", range->id());
1674  unhandled_live_ranges_.Add(range, zone());
1675}
1676
1677
1678static int UnhandledSortHelper(LiveRange* const* a, LiveRange* const* b) {
1679  DCHECK(!(*a)->ShouldBeAllocatedBefore(*b) ||
1680         !(*b)->ShouldBeAllocatedBefore(*a));
1681  if ((*a)->ShouldBeAllocatedBefore(*b)) return 1;
1682  if ((*b)->ShouldBeAllocatedBefore(*a)) return -1;
1683  return (*a)->id() - (*b)->id();
1684}
1685
1686
1687// Sort the unhandled live ranges so that the ranges to be processed first are
1688// at the end of the array list.  This is convenient for the register allocation
1689// algorithm because it is efficient to remove elements from the end.
1690void LAllocator::SortUnhandled() {
1691  TraceAlloc("Sort unhandled\n");
1692  unhandled_live_ranges_.Sort(&UnhandledSortHelper);
1693}
1694
1695
1696bool LAllocator::UnhandledIsSorted() {
1697  int len = unhandled_live_ranges_.length();
1698  for (int i = 1; i < len; i++) {
1699    LiveRange* a = unhandled_live_ranges_.at(i - 1);
1700    LiveRange* b = unhandled_live_ranges_.at(i);
1701    if (a->Start().Value() < b->Start().Value()) return false;
1702  }
1703  return true;
1704}
1705
1706
1707void LAllocator::FreeSpillSlot(LiveRange* range) {
1708  // Check that we are the last range.
1709  if (range->next() != NULL) return;
1710
1711  if (!range->TopLevel()->HasAllocatedSpillOperand()) return;
1712
1713  int index = range->TopLevel()->GetSpillOperand()->index();
1714  if (index >= 0) {
1715    reusable_slots_.Add(range, zone());
1716  }
1717}
1718
1719
1720LOperand* LAllocator::TryReuseSpillSlot(LiveRange* range) {
1721  if (reusable_slots_.is_empty()) return NULL;
1722  if (reusable_slots_.first()->End().Value() >
1723      range->TopLevel()->Start().Value()) {
1724    return NULL;
1725  }
1726  LOperand* result = reusable_slots_.first()->TopLevel()->GetSpillOperand();
1727  reusable_slots_.Remove(0);
1728  return result;
1729}
1730
1731
1732void LAllocator::ActiveToHandled(LiveRange* range) {
1733  DCHECK(active_live_ranges_.Contains(range));
1734  active_live_ranges_.RemoveElement(range);
1735  TraceAlloc("Moving live range %d from active to handled\n", range->id());
1736  FreeSpillSlot(range);
1737}
1738
1739
1740void LAllocator::ActiveToInactive(LiveRange* range) {
1741  DCHECK(active_live_ranges_.Contains(range));
1742  active_live_ranges_.RemoveElement(range);
1743  inactive_live_ranges_.Add(range, zone());
1744  TraceAlloc("Moving live range %d from active to inactive\n", range->id());
1745}
1746
1747
1748void LAllocator::InactiveToHandled(LiveRange* range) {
1749  DCHECK(inactive_live_ranges_.Contains(range));
1750  inactive_live_ranges_.RemoveElement(range);
1751  TraceAlloc("Moving live range %d from inactive to handled\n", range->id());
1752  FreeSpillSlot(range);
1753}
1754
1755
1756void LAllocator::InactiveToActive(LiveRange* range) {
1757  DCHECK(inactive_live_ranges_.Contains(range));
1758  inactive_live_ranges_.RemoveElement(range);
1759  active_live_ranges_.Add(range, zone());
1760  TraceAlloc("Moving live range %d from inactive to active\n", range->id());
1761}
1762
1763
1764bool LAllocator::TryAllocateFreeReg(LiveRange* current) {
1765  DCHECK(DoubleRegister::kMaxNumRegisters >= Register::kNumRegisters);
1766
1767  LifetimePosition free_until_pos[DoubleRegister::kMaxNumRegisters];
1768
1769  for (int i = 0; i < DoubleRegister::kMaxNumRegisters; i++) {
1770    free_until_pos[i] = LifetimePosition::MaxPosition();
1771  }
1772
1773  for (int i = 0; i < active_live_ranges_.length(); ++i) {
1774    LiveRange* cur_active = active_live_ranges_.at(i);
1775    free_until_pos[cur_active->assigned_register()] =
1776        LifetimePosition::FromInstructionIndex(0);
1777  }
1778
1779  for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1780    LiveRange* cur_inactive = inactive_live_ranges_.at(i);
1781    DCHECK(cur_inactive->End().Value() > current->Start().Value());
1782    LifetimePosition next_intersection =
1783        cur_inactive->FirstIntersection(current);
1784    if (!next_intersection.IsValid()) continue;
1785    int cur_reg = cur_inactive->assigned_register();
1786    free_until_pos[cur_reg] = Min(free_until_pos[cur_reg], next_intersection);
1787  }
1788
1789  LOperand* hint = current->FirstHint();
1790  if (hint != NULL && (hint->IsRegister() || hint->IsDoubleRegister())) {
1791    int register_index = hint->index();
1792    TraceAlloc(
1793        "Found reg hint %s (free until [%d) for live range %d (end %d[).\n",
1794        RegisterName(register_index),
1795        free_until_pos[register_index].Value(),
1796        current->id(),
1797        current->End().Value());
1798
1799    // The desired register is free until the end of the current live range.
1800    if (free_until_pos[register_index].Value() >= current->End().Value()) {
1801      TraceAlloc("Assigning preferred reg %s to live range %d\n",
1802                 RegisterName(register_index),
1803                 current->id());
1804      SetLiveRangeAssignedRegister(current, register_index);
1805      return true;
1806    }
1807  }
1808
1809  // Find the register which stays free for the longest time.
1810  int reg = allocatable_register_codes_[0];
1811  for (int i = 1; i < RegisterCount(); ++i) {
1812    int code = allocatable_register_codes_[i];
1813    if (free_until_pos[code].Value() > free_until_pos[reg].Value()) {
1814      reg = code;
1815    }
1816  }
1817
1818  LifetimePosition pos = free_until_pos[reg];
1819
1820  if (pos.Value() <= current->Start().Value()) {
1821    // All registers are blocked.
1822    return false;
1823  }
1824
1825  if (pos.Value() < current->End().Value()) {
1826    // Register reg is available at the range start but becomes blocked before
1827    // the range end. Split current at position where it becomes blocked.
1828    LiveRange* tail = SplitRangeAt(current, pos);
1829    if (!AllocationOk()) return false;
1830    AddToUnhandledSorted(tail);
1831  }
1832
1833
1834  // Register reg is available at the range start and is free until
1835  // the range end.
1836  DCHECK(pos.Value() >= current->End().Value());
1837  TraceAlloc("Assigning free reg %s to live range %d\n",
1838             RegisterName(reg),
1839             current->id());
1840  SetLiveRangeAssignedRegister(current, reg);
1841
1842  return true;
1843}
1844
1845
1846void LAllocator::AllocateBlockedReg(LiveRange* current) {
1847  UsePosition* register_use = current->NextRegisterPosition(current->Start());
1848  if (register_use == NULL) {
1849    // There is no use in the current live range that requires a register.
1850    // We can just spill it.
1851    Spill(current);
1852    return;
1853  }
1854
1855
1856  LifetimePosition use_pos[DoubleRegister::kMaxNumRegisters];
1857  LifetimePosition block_pos[DoubleRegister::kMaxNumRegisters];
1858
1859  for (int i = 0; i < DoubleRegister::kMaxNumRegisters; i++) {
1860    use_pos[i] = block_pos[i] = LifetimePosition::MaxPosition();
1861  }
1862
1863  for (int i = 0; i < active_live_ranges_.length(); ++i) {
1864    LiveRange* range = active_live_ranges_[i];
1865    int cur_reg = range->assigned_register();
1866    if (range->IsFixed() || !range->CanBeSpilled(current->Start())) {
1867      block_pos[cur_reg] = use_pos[cur_reg] =
1868          LifetimePosition::FromInstructionIndex(0);
1869    } else {
1870      UsePosition* next_use = range->NextUsePositionRegisterIsBeneficial(
1871          current->Start());
1872      if (next_use == NULL) {
1873        use_pos[cur_reg] = range->End();
1874      } else {
1875        use_pos[cur_reg] = next_use->pos();
1876      }
1877    }
1878  }
1879
1880  for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1881    LiveRange* range = inactive_live_ranges_.at(i);
1882    DCHECK(range->End().Value() > current->Start().Value());
1883    LifetimePosition next_intersection = range->FirstIntersection(current);
1884    if (!next_intersection.IsValid()) continue;
1885    int cur_reg = range->assigned_register();
1886    if (range->IsFixed()) {
1887      block_pos[cur_reg] = Min(block_pos[cur_reg], next_intersection);
1888      use_pos[cur_reg] = Min(block_pos[cur_reg], use_pos[cur_reg]);
1889    } else {
1890      use_pos[cur_reg] = Min(use_pos[cur_reg], next_intersection);
1891    }
1892  }
1893
1894  int reg = allocatable_register_codes_[0];
1895  for (int i = 1; i < RegisterCount(); ++i) {
1896    int code = allocatable_register_codes_[i];
1897    if (use_pos[code].Value() > use_pos[reg].Value()) {
1898      reg = code;
1899    }
1900  }
1901
1902  LifetimePosition pos = use_pos[reg];
1903
1904  if (pos.Value() < register_use->pos().Value()) {
1905    // All registers are blocked before the first use that requires a register.
1906    // Spill starting part of live range up to that use.
1907    SpillBetween(current, current->Start(), register_use->pos());
1908    return;
1909  }
1910
1911  if (block_pos[reg].Value() < current->End().Value()) {
1912    // Register becomes blocked before the current range end. Split before that
1913    // position.
1914    LiveRange* tail = SplitBetween(current,
1915                                   current->Start(),
1916                                   block_pos[reg].InstructionStart());
1917    if (!AllocationOk()) return;
1918    AddToUnhandledSorted(tail);
1919  }
1920
1921  // Register reg is not blocked for the whole range.
1922  DCHECK(block_pos[reg].Value() >= current->End().Value());
1923  TraceAlloc("Assigning blocked reg %s to live range %d\n",
1924             RegisterName(reg),
1925             current->id());
1926  SetLiveRangeAssignedRegister(current, reg);
1927
1928  // This register was not free. Thus we need to find and spill
1929  // parts of active and inactive live regions that use the same register
1930  // at the same lifetime positions as current.
1931  SplitAndSpillIntersecting(current);
1932}
1933
1934
1935LifetimePosition LAllocator::FindOptimalSpillingPos(LiveRange* range,
1936                                                    LifetimePosition pos) {
1937  HBasicBlock* block = GetBlock(pos.InstructionStart());
1938  HBasicBlock* loop_header =
1939      block->IsLoopHeader() ? block : block->parent_loop_header();
1940
1941  if (loop_header == NULL) return pos;
1942
1943  UsePosition* prev_use =
1944    range->PreviousUsePositionRegisterIsBeneficial(pos);
1945
1946  while (loop_header != NULL) {
1947    // We are going to spill live range inside the loop.
1948    // If possible try to move spilling position backwards to loop header.
1949    // This will reduce number of memory moves on the back edge.
1950    LifetimePosition loop_start = LifetimePosition::FromInstructionIndex(
1951        loop_header->first_instruction_index());
1952
1953    if (range->Covers(loop_start)) {
1954      if (prev_use == NULL || prev_use->pos().Value() < loop_start.Value()) {
1955        // No register beneficial use inside the loop before the pos.
1956        pos = loop_start;
1957      }
1958    }
1959
1960    // Try hoisting out to an outer loop.
1961    loop_header = loop_header->parent_loop_header();
1962  }
1963
1964  return pos;
1965}
1966
1967
1968void LAllocator::SplitAndSpillIntersecting(LiveRange* current) {
1969  DCHECK(current->HasRegisterAssigned());
1970  int reg = current->assigned_register();
1971  LifetimePosition split_pos = current->Start();
1972  for (int i = 0; i < active_live_ranges_.length(); ++i) {
1973    LiveRange* range = active_live_ranges_[i];
1974    if (range->assigned_register() == reg) {
1975      UsePosition* next_pos = range->NextRegisterPosition(current->Start());
1976      LifetimePosition spill_pos = FindOptimalSpillingPos(range, split_pos);
1977      if (next_pos == NULL) {
1978        SpillAfter(range, spill_pos);
1979      } else {
1980        // When spilling between spill_pos and next_pos ensure that the range
1981        // remains spilled at least until the start of the current live range.
1982        // This guarantees that we will not introduce new unhandled ranges that
1983        // start before the current range as this violates allocation invariant
1984        // and will lead to an inconsistent state of active and inactive
1985        // live-ranges: ranges are allocated in order of their start positions,
1986        // ranges are retired from active/inactive when the start of the
1987        // current live-range is larger than their end.
1988        SpillBetweenUntil(range, spill_pos, current->Start(), next_pos->pos());
1989      }
1990      if (!AllocationOk()) return;
1991      ActiveToHandled(range);
1992      --i;
1993    }
1994  }
1995
1996  for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1997    LiveRange* range = inactive_live_ranges_[i];
1998    DCHECK(range->End().Value() > current->Start().Value());
1999    if (range->assigned_register() == reg && !range->IsFixed()) {
2000      LifetimePosition next_intersection = range->FirstIntersection(current);
2001      if (next_intersection.IsValid()) {
2002        UsePosition* next_pos = range->NextRegisterPosition(current->Start());
2003        if (next_pos == NULL) {
2004          SpillAfter(range, split_pos);
2005        } else {
2006          next_intersection = Min(next_intersection, next_pos->pos());
2007          SpillBetween(range, split_pos, next_intersection);
2008        }
2009        if (!AllocationOk()) return;
2010        InactiveToHandled(range);
2011        --i;
2012      }
2013    }
2014  }
2015}
2016
2017
2018bool LAllocator::IsBlockBoundary(LifetimePosition pos) {
2019  return pos.IsInstructionStart() &&
2020      InstructionAt(pos.InstructionIndex())->IsLabel();
2021}
2022
2023
2024LiveRange* LAllocator::SplitRangeAt(LiveRange* range, LifetimePosition pos) {
2025  DCHECK(!range->IsFixed());
2026  TraceAlloc("Splitting live range %d at %d\n", range->id(), pos.Value());
2027
2028  if (pos.Value() <= range->Start().Value()) return range;
2029
2030  // We can't properly connect liveranges if split occured at the end
2031  // of control instruction.
2032  DCHECK(pos.IsInstructionStart() ||
2033         !chunk_->instructions()->at(pos.InstructionIndex())->IsControl());
2034
2035  int vreg = GetVirtualRegister();
2036  if (!AllocationOk()) return NULL;
2037  LiveRange* result = LiveRangeFor(vreg);
2038  range->SplitAt(pos, result, zone());
2039  return result;
2040}
2041
2042
2043LiveRange* LAllocator::SplitBetween(LiveRange* range,
2044                                    LifetimePosition start,
2045                                    LifetimePosition end) {
2046  DCHECK(!range->IsFixed());
2047  TraceAlloc("Splitting live range %d in position between [%d, %d]\n",
2048             range->id(),
2049             start.Value(),
2050             end.Value());
2051
2052  LifetimePosition split_pos = FindOptimalSplitPos(start, end);
2053  DCHECK(split_pos.Value() >= start.Value());
2054  return SplitRangeAt(range, split_pos);
2055}
2056
2057
2058LifetimePosition LAllocator::FindOptimalSplitPos(LifetimePosition start,
2059                                                 LifetimePosition end) {
2060  int start_instr = start.InstructionIndex();
2061  int end_instr = end.InstructionIndex();
2062  DCHECK(start_instr <= end_instr);
2063
2064  // We have no choice
2065  if (start_instr == end_instr) return end;
2066
2067  HBasicBlock* start_block = GetBlock(start);
2068  HBasicBlock* end_block = GetBlock(end);
2069
2070  if (end_block == start_block) {
2071    // The interval is split in the same basic block. Split at the latest
2072    // possible position.
2073    return end;
2074  }
2075
2076  HBasicBlock* block = end_block;
2077  // Find header of outermost loop.
2078  while (block->parent_loop_header() != NULL &&
2079      block->parent_loop_header()->block_id() > start_block->block_id()) {
2080    block = block->parent_loop_header();
2081  }
2082
2083  // We did not find any suitable outer loop. Split at the latest possible
2084  // position unless end_block is a loop header itself.
2085  if (block == end_block && !end_block->IsLoopHeader()) return end;
2086
2087  return LifetimePosition::FromInstructionIndex(
2088      block->first_instruction_index());
2089}
2090
2091
2092void LAllocator::SpillAfter(LiveRange* range, LifetimePosition pos) {
2093  LiveRange* second_part = SplitRangeAt(range, pos);
2094  if (!AllocationOk()) return;
2095  Spill(second_part);
2096}
2097
2098
2099void LAllocator::SpillBetween(LiveRange* range,
2100                              LifetimePosition start,
2101                              LifetimePosition end) {
2102  SpillBetweenUntil(range, start, start, end);
2103}
2104
2105
2106void LAllocator::SpillBetweenUntil(LiveRange* range,
2107                                   LifetimePosition start,
2108                                   LifetimePosition until,
2109                                   LifetimePosition end) {
2110  CHECK(start.Value() < end.Value());
2111  LiveRange* second_part = SplitRangeAt(range, start);
2112  if (!AllocationOk()) return;
2113
2114  if (second_part->Start().Value() < end.Value()) {
2115    // The split result intersects with [start, end[.
2116    // Split it at position between ]start+1, end[, spill the middle part
2117    // and put the rest to unhandled.
2118    LiveRange* third_part = SplitBetween(
2119        second_part,
2120        Max(second_part->Start().InstructionEnd(), until),
2121        end.PrevInstruction().InstructionEnd());
2122    if (!AllocationOk()) return;
2123
2124    DCHECK(third_part != second_part);
2125
2126    Spill(second_part);
2127    AddToUnhandledSorted(third_part);
2128  } else {
2129    // The split result does not intersect with [start, end[.
2130    // Nothing to spill. Just put it to unhandled as whole.
2131    AddToUnhandledSorted(second_part);
2132  }
2133}
2134
2135
2136void LAllocator::Spill(LiveRange* range) {
2137  DCHECK(!range->IsSpilled());
2138  TraceAlloc("Spilling live range %d\n", range->id());
2139  LiveRange* first = range->TopLevel();
2140
2141  if (!first->HasAllocatedSpillOperand()) {
2142    LOperand* op = TryReuseSpillSlot(range);
2143    if (op == NULL) op = chunk_->GetNextSpillSlot(range->Kind());
2144    first->SetSpillOperand(op);
2145  }
2146  range->MakeSpilled(chunk()->zone());
2147}
2148
2149
2150int LAllocator::RegisterCount() const {
2151  return num_registers_;
2152}
2153
2154
2155#ifdef DEBUG
2156
2157
2158void LAllocator::Verify() const {
2159  for (int i = 0; i < live_ranges()->length(); ++i) {
2160    LiveRange* current = live_ranges()->at(i);
2161    if (current != NULL) current->Verify();
2162  }
2163}
2164
2165
2166#endif
2167
2168
2169LAllocatorPhase::LAllocatorPhase(const char* name, LAllocator* allocator)
2170    : CompilationPhase(name, allocator->graph()->info()),
2171      allocator_(allocator) {
2172  if (FLAG_hydrogen_stats) {
2173    allocator_zone_start_allocation_size_ =
2174        allocator->zone()->allocation_size();
2175  }
2176}
2177
2178
2179LAllocatorPhase::~LAllocatorPhase() {
2180  if (FLAG_hydrogen_stats) {
2181    size_t size = allocator_->zone()->allocation_size() -
2182                  allocator_zone_start_allocation_size_;
2183    isolate()->GetHStatistics()->SaveTiming(name(), base::TimeDelta(), size);
2184  }
2185
2186  if (ShouldProduceTraceOutput()) {
2187    isolate()->GetHTracer()->TraceLithium(name(), allocator_->chunk());
2188    isolate()->GetHTracer()->TraceLiveRanges(name(), allocator_);
2189  }
2190
2191#ifdef DEBUG
2192  if (allocator_ != NULL) allocator_->Verify();
2193#endif
2194}
2195
2196
2197}  // namespace internal
2198}  // namespace v8
2199