1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Redistribution and use in source and binary forms, with or without
3 // modification, are permitted provided that the following conditions are
4 // met:
5 //
6 // * Redistributions of source code must retain the above copyright
7 // notice, this list of conditions and the following disclaimer.
8 // * Redistributions in binary form must reproduce the above
9 // copyright notice, this list of conditions and the following
10 // disclaimer in the documentation and/or other materials provided
11 // with the distribution.
12 // * Neither the name of Google Inc. nor the names of its
13 // contributors may be used to endorse or promote products derived
14 // from this software without specific prior written permission.
15 //
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28 #include "v8.h"
29 #include "lithium-allocator-inl.h"
30
31 #include "hydrogen.h"
32 #include "string-stream.h"
33
34 #if V8_TARGET_ARCH_IA32
35 #include "ia32/lithium-ia32.h"
36 #elif V8_TARGET_ARCH_X64
37 #include "x64/lithium-x64.h"
38 #elif V8_TARGET_ARCH_ARM
39 #include "arm/lithium-arm.h"
40 #elif V8_TARGET_ARCH_MIPS
41 #include "mips/lithium-mips.h"
42 #else
43 #error "Unknown architecture."
44 #endif
45
46 namespace v8 {
47 namespace internal {
48
Min(LifetimePosition a,LifetimePosition b)49 static inline LifetimePosition Min(LifetimePosition a, LifetimePosition b) {
50 return a.Value() < b.Value() ? a : b;
51 }
52
53
Max(LifetimePosition a,LifetimePosition b)54 static inline LifetimePosition Max(LifetimePosition a, LifetimePosition b) {
55 return a.Value() > b.Value() ? a : b;
56 }
57
58
UsePosition(LifetimePosition pos,LOperand * operand)59 UsePosition::UsePosition(LifetimePosition pos, LOperand* operand)
60 : operand_(operand),
61 hint_(NULL),
62 pos_(pos),
63 next_(NULL),
64 requires_reg_(false),
65 register_beneficial_(true) {
66 if (operand_ != NULL && operand_->IsUnallocated()) {
67 LUnallocated* unalloc = LUnallocated::cast(operand_);
68 requires_reg_ = unalloc->HasRegisterPolicy();
69 register_beneficial_ = !unalloc->HasAnyPolicy();
70 }
71 ASSERT(pos_.IsValid());
72 }
73
74
HasHint() const75 bool UsePosition::HasHint() const {
76 return hint_ != NULL && !hint_->IsUnallocated();
77 }
78
79
RequiresRegister() const80 bool UsePosition::RequiresRegister() const {
81 return requires_reg_;
82 }
83
84
RegisterIsBeneficial() const85 bool UsePosition::RegisterIsBeneficial() const {
86 return register_beneficial_;
87 }
88
89
SplitAt(LifetimePosition pos,Zone * zone)90 void UseInterval::SplitAt(LifetimePosition pos, Zone* zone) {
91 ASSERT(Contains(pos) && pos.Value() != start().Value());
92 UseInterval* after = new(zone) UseInterval(pos, end_);
93 after->next_ = next_;
94 next_ = after;
95 end_ = pos;
96 }
97
98
99 #ifdef DEBUG
100
101
Verify() const102 void LiveRange::Verify() const {
103 UsePosition* cur = first_pos_;
104 while (cur != NULL) {
105 ASSERT(Start().Value() <= cur->pos().Value() &&
106 cur->pos().Value() <= End().Value());
107 cur = cur->next();
108 }
109 }
110
111
HasOverlap(UseInterval * target) const112 bool LiveRange::HasOverlap(UseInterval* target) const {
113 UseInterval* current_interval = first_interval_;
114 while (current_interval != NULL) {
115 // Intervals overlap if the start of one is contained in the other.
116 if (current_interval->Contains(target->start()) ||
117 target->Contains(current_interval->start())) {
118 return true;
119 }
120 current_interval = current_interval->next();
121 }
122 return false;
123 }
124
125
126 #endif
127
128
LiveRange(int id,Zone * zone)129 LiveRange::LiveRange(int id, Zone* zone)
130 : id_(id),
131 spilled_(false),
132 is_double_(false),
133 assigned_register_(kInvalidAssignment),
134 last_interval_(NULL),
135 first_interval_(NULL),
136 first_pos_(NULL),
137 parent_(NULL),
138 next_(NULL),
139 current_interval_(NULL),
140 last_processed_use_(NULL),
141 spill_operand_(new(zone) LOperand()),
142 spill_start_index_(kMaxInt) { }
143
144
set_assigned_register(int reg,RegisterKind register_kind,Zone * zone)145 void LiveRange::set_assigned_register(int reg,
146 RegisterKind register_kind,
147 Zone* zone) {
148 ASSERT(!HasRegisterAssigned() && !IsSpilled());
149 assigned_register_ = reg;
150 is_double_ = (register_kind == DOUBLE_REGISTERS);
151 ConvertOperands(zone);
152 }
153
154
MakeSpilled(Zone * zone)155 void LiveRange::MakeSpilled(Zone* zone) {
156 ASSERT(!IsSpilled());
157 ASSERT(TopLevel()->HasAllocatedSpillOperand());
158 spilled_ = true;
159 assigned_register_ = kInvalidAssignment;
160 ConvertOperands(zone);
161 }
162
163
HasAllocatedSpillOperand() const164 bool LiveRange::HasAllocatedSpillOperand() const {
165 ASSERT(spill_operand_ != NULL);
166 return !spill_operand_->IsIgnored();
167 }
168
169
SetSpillOperand(LOperand * operand)170 void LiveRange::SetSpillOperand(LOperand* operand) {
171 ASSERT(!operand->IsUnallocated());
172 ASSERT(spill_operand_ != NULL);
173 ASSERT(spill_operand_->IsIgnored());
174 spill_operand_->ConvertTo(operand->kind(), operand->index());
175 }
176
177
NextUsePosition(LifetimePosition start)178 UsePosition* LiveRange::NextUsePosition(LifetimePosition start) {
179 UsePosition* use_pos = last_processed_use_;
180 if (use_pos == NULL) use_pos = first_pos();
181 while (use_pos != NULL && use_pos->pos().Value() < start.Value()) {
182 use_pos = use_pos->next();
183 }
184 last_processed_use_ = use_pos;
185 return use_pos;
186 }
187
188
NextUsePositionRegisterIsBeneficial(LifetimePosition start)189 UsePosition* LiveRange::NextUsePositionRegisterIsBeneficial(
190 LifetimePosition start) {
191 UsePosition* pos = NextUsePosition(start);
192 while (pos != NULL && !pos->RegisterIsBeneficial()) {
193 pos = pos->next();
194 }
195 return pos;
196 }
197
198
NextRegisterPosition(LifetimePosition start)199 UsePosition* LiveRange::NextRegisterPosition(LifetimePosition start) {
200 UsePosition* pos = NextUsePosition(start);
201 while (pos != NULL && !pos->RequiresRegister()) {
202 pos = pos->next();
203 }
204 return pos;
205 }
206
207
CanBeSpilled(LifetimePosition pos)208 bool LiveRange::CanBeSpilled(LifetimePosition pos) {
209 // TODO(kmillikin): Comment. Now.
210 if (pos.Value() <= Start().Value() && HasRegisterAssigned()) return false;
211
212 // We cannot spill a live range that has a use requiring a register
213 // at the current or the immediate next position.
214 UsePosition* use_pos = NextRegisterPosition(pos);
215 if (use_pos == NULL) return true;
216 return
217 use_pos->pos().Value() > pos.NextInstruction().InstructionEnd().Value();
218 }
219
220
FirstPosWithHint() const221 UsePosition* LiveRange::FirstPosWithHint() const {
222 UsePosition* pos = first_pos_;
223 while (pos != NULL && !pos->HasHint()) pos = pos->next();
224 return pos;
225 }
226
227
CreateAssignedOperand(Zone * zone)228 LOperand* LiveRange::CreateAssignedOperand(Zone* zone) {
229 LOperand* op = NULL;
230 if (HasRegisterAssigned()) {
231 ASSERT(!IsSpilled());
232 if (IsDouble()) {
233 op = LDoubleRegister::Create(assigned_register());
234 } else {
235 op = LRegister::Create(assigned_register());
236 }
237 } else if (IsSpilled()) {
238 ASSERT(!HasRegisterAssigned());
239 op = TopLevel()->GetSpillOperand();
240 ASSERT(!op->IsUnallocated());
241 } else {
242 LUnallocated* unalloc = new(zone) LUnallocated(LUnallocated::NONE);
243 unalloc->set_virtual_register(id_);
244 op = unalloc;
245 }
246 return op;
247 }
248
249
FirstSearchIntervalForPosition(LifetimePosition position) const250 UseInterval* LiveRange::FirstSearchIntervalForPosition(
251 LifetimePosition position) const {
252 if (current_interval_ == NULL) return first_interval_;
253 if (current_interval_->start().Value() > position.Value()) {
254 current_interval_ = NULL;
255 return first_interval_;
256 }
257 return current_interval_;
258 }
259
260
AdvanceLastProcessedMarker(UseInterval * to_start_of,LifetimePosition but_not_past) const261 void LiveRange::AdvanceLastProcessedMarker(
262 UseInterval* to_start_of, LifetimePosition but_not_past) const {
263 if (to_start_of == NULL) return;
264 if (to_start_of->start().Value() > but_not_past.Value()) return;
265 LifetimePosition start =
266 current_interval_ == NULL ? LifetimePosition::Invalid()
267 : current_interval_->start();
268 if (to_start_of->start().Value() > start.Value()) {
269 current_interval_ = to_start_of;
270 }
271 }
272
273
SplitAt(LifetimePosition position,LiveRange * result,Zone * zone)274 void LiveRange::SplitAt(LifetimePosition position,
275 LiveRange* result,
276 Zone* zone) {
277 ASSERT(Start().Value() < position.Value());
278 ASSERT(result->IsEmpty());
279 // Find the last interval that ends before the position. If the
280 // position is contained in one of the intervals in the chain, we
281 // split that interval and use the first part.
282 UseInterval* current = FirstSearchIntervalForPosition(position);
283
284 // If the split position coincides with the beginning of a use interval
285 // we need to split use positons in a special way.
286 bool split_at_start = false;
287
288 if (current->start().Value() == position.Value()) {
289 // When splitting at start we need to locate the previous use interval.
290 current = first_interval_;
291 }
292
293 while (current != NULL) {
294 if (current->Contains(position)) {
295 current->SplitAt(position, zone);
296 break;
297 }
298 UseInterval* next = current->next();
299 if (next->start().Value() >= position.Value()) {
300 split_at_start = (next->start().Value() == position.Value());
301 break;
302 }
303 current = next;
304 }
305
306 // Partition original use intervals to the two live ranges.
307 UseInterval* before = current;
308 UseInterval* after = before->next();
309 result->last_interval_ = (last_interval_ == before)
310 ? after // Only interval in the range after split.
311 : last_interval_; // Last interval of the original range.
312 result->first_interval_ = after;
313 last_interval_ = before;
314
315 // Find the last use position before the split and the first use
316 // position after it.
317 UsePosition* use_after = first_pos_;
318 UsePosition* use_before = NULL;
319 if (split_at_start) {
320 // The split position coincides with the beginning of a use interval (the
321 // end of a lifetime hole). Use at this position should be attributed to
322 // the split child because split child owns use interval covering it.
323 while (use_after != NULL && use_after->pos().Value() < position.Value()) {
324 use_before = use_after;
325 use_after = use_after->next();
326 }
327 } else {
328 while (use_after != NULL && use_after->pos().Value() <= position.Value()) {
329 use_before = use_after;
330 use_after = use_after->next();
331 }
332 }
333
334 // Partition original use positions to the two live ranges.
335 if (use_before != NULL) {
336 use_before->next_ = NULL;
337 } else {
338 first_pos_ = NULL;
339 }
340 result->first_pos_ = use_after;
341
342 // Discard cached iteration state. It might be pointing
343 // to the use that no longer belongs to this live range.
344 last_processed_use_ = NULL;
345 current_interval_ = NULL;
346
347 // Link the new live range in the chain before any of the other
348 // ranges linked from the range before the split.
349 result->parent_ = (parent_ == NULL) ? this : parent_;
350 result->next_ = next_;
351 next_ = result;
352
353 #ifdef DEBUG
354 Verify();
355 result->Verify();
356 #endif
357 }
358
359
360 // This implements an ordering on live ranges so that they are ordered by their
361 // start positions. This is needed for the correctness of the register
362 // allocation algorithm. If two live ranges start at the same offset then there
363 // is a tie breaker based on where the value is first used. This part of the
364 // ordering is merely a heuristic.
ShouldBeAllocatedBefore(const LiveRange * other) const365 bool LiveRange::ShouldBeAllocatedBefore(const LiveRange* other) const {
366 LifetimePosition start = Start();
367 LifetimePosition other_start = other->Start();
368 if (start.Value() == other_start.Value()) {
369 UsePosition* pos = FirstPosWithHint();
370 if (pos == NULL) return false;
371 UsePosition* other_pos = other->first_pos();
372 if (other_pos == NULL) return true;
373 return pos->pos().Value() < other_pos->pos().Value();
374 }
375 return start.Value() < other_start.Value();
376 }
377
378
ShortenTo(LifetimePosition start)379 void LiveRange::ShortenTo(LifetimePosition start) {
380 LAllocator::TraceAlloc("Shorten live range %d to [%d\n", id_, start.Value());
381 ASSERT(first_interval_ != NULL);
382 ASSERT(first_interval_->start().Value() <= start.Value());
383 ASSERT(start.Value() < first_interval_->end().Value());
384 first_interval_->set_start(start);
385 }
386
387
EnsureInterval(LifetimePosition start,LifetimePosition end,Zone * zone)388 void LiveRange::EnsureInterval(LifetimePosition start,
389 LifetimePosition end,
390 Zone* zone) {
391 LAllocator::TraceAlloc("Ensure live range %d in interval [%d %d[\n",
392 id_,
393 start.Value(),
394 end.Value());
395 LifetimePosition new_end = end;
396 while (first_interval_ != NULL &&
397 first_interval_->start().Value() <= end.Value()) {
398 if (first_interval_->end().Value() > end.Value()) {
399 new_end = first_interval_->end();
400 }
401 first_interval_ = first_interval_->next();
402 }
403
404 UseInterval* new_interval = new(zone) UseInterval(start, new_end);
405 new_interval->next_ = first_interval_;
406 first_interval_ = new_interval;
407 if (new_interval->next() == NULL) {
408 last_interval_ = new_interval;
409 }
410 }
411
412
AddUseInterval(LifetimePosition start,LifetimePosition end,Zone * zone)413 void LiveRange::AddUseInterval(LifetimePosition start,
414 LifetimePosition end,
415 Zone* zone) {
416 LAllocator::TraceAlloc("Add to live range %d interval [%d %d[\n",
417 id_,
418 start.Value(),
419 end.Value());
420 if (first_interval_ == NULL) {
421 UseInterval* interval = new(zone) UseInterval(start, end);
422 first_interval_ = interval;
423 last_interval_ = interval;
424 } else {
425 if (end.Value() == first_interval_->start().Value()) {
426 first_interval_->set_start(start);
427 } else if (end.Value() < first_interval_->start().Value()) {
428 UseInterval* interval = new(zone) UseInterval(start, end);
429 interval->set_next(first_interval_);
430 first_interval_ = interval;
431 } else {
432 // Order of instruction's processing (see ProcessInstructions) guarantees
433 // that each new use interval either precedes or intersects with
434 // last added interval.
435 ASSERT(start.Value() < first_interval_->end().Value());
436 first_interval_->start_ = Min(start, first_interval_->start_);
437 first_interval_->end_ = Max(end, first_interval_->end_);
438 }
439 }
440 }
441
442
AddUsePosition(LifetimePosition pos,LOperand * operand,Zone * zone)443 UsePosition* LiveRange::AddUsePosition(LifetimePosition pos,
444 LOperand* operand,
445 Zone* zone) {
446 LAllocator::TraceAlloc("Add to live range %d use position %d\n",
447 id_,
448 pos.Value());
449 UsePosition* use_pos = new(zone) UsePosition(pos, operand);
450 UsePosition* prev = NULL;
451 UsePosition* current = first_pos_;
452 while (current != NULL && current->pos().Value() < pos.Value()) {
453 prev = current;
454 current = current->next();
455 }
456
457 if (prev == NULL) {
458 use_pos->set_next(first_pos_);
459 first_pos_ = use_pos;
460 } else {
461 use_pos->next_ = prev->next_;
462 prev->next_ = use_pos;
463 }
464
465 return use_pos;
466 }
467
468
ConvertOperands(Zone * zone)469 void LiveRange::ConvertOperands(Zone* zone) {
470 LOperand* op = CreateAssignedOperand(zone);
471 UsePosition* use_pos = first_pos();
472 while (use_pos != NULL) {
473 ASSERT(Start().Value() <= use_pos->pos().Value() &&
474 use_pos->pos().Value() <= End().Value());
475
476 if (use_pos->HasOperand()) {
477 ASSERT(op->IsRegister() || op->IsDoubleRegister() ||
478 !use_pos->RequiresRegister());
479 use_pos->operand()->ConvertTo(op->kind(), op->index());
480 }
481 use_pos = use_pos->next();
482 }
483 }
484
485
CanCover(LifetimePosition position) const486 bool LiveRange::CanCover(LifetimePosition position) const {
487 if (IsEmpty()) return false;
488 return Start().Value() <= position.Value() &&
489 position.Value() < End().Value();
490 }
491
492
Covers(LifetimePosition position)493 bool LiveRange::Covers(LifetimePosition position) {
494 if (!CanCover(position)) return false;
495 UseInterval* start_search = FirstSearchIntervalForPosition(position);
496 for (UseInterval* interval = start_search;
497 interval != NULL;
498 interval = interval->next()) {
499 ASSERT(interval->next() == NULL ||
500 interval->next()->start().Value() >= interval->start().Value());
501 AdvanceLastProcessedMarker(interval, position);
502 if (interval->Contains(position)) return true;
503 if (interval->start().Value() > position.Value()) return false;
504 }
505 return false;
506 }
507
508
FirstIntersection(LiveRange * other)509 LifetimePosition LiveRange::FirstIntersection(LiveRange* other) {
510 UseInterval* b = other->first_interval();
511 if (b == NULL) return LifetimePosition::Invalid();
512 LifetimePosition advance_last_processed_up_to = b->start();
513 UseInterval* a = FirstSearchIntervalForPosition(b->start());
514 while (a != NULL && b != NULL) {
515 if (a->start().Value() > other->End().Value()) break;
516 if (b->start().Value() > End().Value()) break;
517 LifetimePosition cur_intersection = a->Intersect(b);
518 if (cur_intersection.IsValid()) {
519 return cur_intersection;
520 }
521 if (a->start().Value() < b->start().Value()) {
522 a = a->next();
523 if (a == NULL || a->start().Value() > other->End().Value()) break;
524 AdvanceLastProcessedMarker(a, advance_last_processed_up_to);
525 } else {
526 b = b->next();
527 }
528 }
529 return LifetimePosition::Invalid();
530 }
531
532
LAllocator(int num_values,HGraph * graph)533 LAllocator::LAllocator(int num_values, HGraph* graph)
534 : zone_(graph->zone()),
535 chunk_(NULL),
536 live_in_sets_(graph->blocks()->length()),
537 live_ranges_(num_values * 2),
538 fixed_live_ranges_(NULL),
539 fixed_double_live_ranges_(NULL),
540 unhandled_live_ranges_(num_values * 2),
541 active_live_ranges_(8),
542 inactive_live_ranges_(8),
543 reusable_slots_(8),
544 next_virtual_register_(num_values),
545 first_artificial_register_(num_values),
546 mode_(GENERAL_REGISTERS),
547 num_registers_(-1),
548 graph_(graph),
549 has_osr_entry_(false),
550 allocation_ok_(true) { }
551
552
InitializeLivenessAnalysis()553 void LAllocator::InitializeLivenessAnalysis() {
554 // Initialize the live_in sets for each block to NULL.
555 int block_count = graph_->blocks()->length();
556 live_in_sets_.Initialize(block_count);
557 live_in_sets_.AddBlock(NULL, block_count);
558 }
559
560
ComputeLiveOut(HBasicBlock * block)561 BitVector* LAllocator::ComputeLiveOut(HBasicBlock* block) {
562 // Compute live out for the given block, except not including backward
563 // successor edges.
564 BitVector* live_out = new(zone_) BitVector(next_virtual_register_, zone_);
565
566 // Process all successor blocks.
567 for (HSuccessorIterator it(block->end()); !it.Done(); it.Advance()) {
568 // Add values live on entry to the successor. Note the successor's
569 // live_in will not be computed yet for backwards edges.
570 HBasicBlock* successor = it.Current();
571 BitVector* live_in = live_in_sets_[successor->block_id()];
572 if (live_in != NULL) live_out->Union(*live_in);
573
574 // All phi input operands corresponding to this successor edge are live
575 // out from this block.
576 int index = successor->PredecessorIndexOf(block);
577 const ZoneList<HPhi*>* phis = successor->phis();
578 for (int i = 0; i < phis->length(); ++i) {
579 HPhi* phi = phis->at(i);
580 if (!phi->OperandAt(index)->IsConstant()) {
581 live_out->Add(phi->OperandAt(index)->id());
582 }
583 }
584 }
585
586 return live_out;
587 }
588
589
AddInitialIntervals(HBasicBlock * block,BitVector * live_out)590 void LAllocator::AddInitialIntervals(HBasicBlock* block,
591 BitVector* live_out) {
592 // Add an interval that includes the entire block to the live range for
593 // each live_out value.
594 LifetimePosition start = LifetimePosition::FromInstructionIndex(
595 block->first_instruction_index());
596 LifetimePosition end = LifetimePosition::FromInstructionIndex(
597 block->last_instruction_index()).NextInstruction();
598 BitVector::Iterator iterator(live_out);
599 while (!iterator.Done()) {
600 int operand_index = iterator.Current();
601 LiveRange* range = LiveRangeFor(operand_index);
602 range->AddUseInterval(start, end, zone_);
603 iterator.Advance();
604 }
605 }
606
607
FixedDoubleLiveRangeID(int index)608 int LAllocator::FixedDoubleLiveRangeID(int index) {
609 return -index - 1 - Register::kNumAllocatableRegisters;
610 }
611
612
AllocateFixed(LUnallocated * operand,int pos,bool is_tagged)613 LOperand* LAllocator::AllocateFixed(LUnallocated* operand,
614 int pos,
615 bool is_tagged) {
616 TraceAlloc("Allocating fixed reg for op %d\n", operand->virtual_register());
617 ASSERT(operand->HasFixedPolicy());
618 if (operand->policy() == LUnallocated::FIXED_SLOT) {
619 operand->ConvertTo(LOperand::STACK_SLOT, operand->fixed_index());
620 } else if (operand->policy() == LUnallocated::FIXED_REGISTER) {
621 int reg_index = operand->fixed_index();
622 operand->ConvertTo(LOperand::REGISTER, reg_index);
623 } else if (operand->policy() == LUnallocated::FIXED_DOUBLE_REGISTER) {
624 int reg_index = operand->fixed_index();
625 operand->ConvertTo(LOperand::DOUBLE_REGISTER, reg_index);
626 } else {
627 UNREACHABLE();
628 }
629 if (is_tagged) {
630 TraceAlloc("Fixed reg is tagged at %d\n", pos);
631 LInstruction* instr = InstructionAt(pos);
632 if (instr->HasPointerMap()) {
633 instr->pointer_map()->RecordPointer(operand);
634 }
635 }
636 return operand;
637 }
638
639
FixedLiveRangeFor(int index)640 LiveRange* LAllocator::FixedLiveRangeFor(int index) {
641 ASSERT(index < Register::kNumAllocatableRegisters);
642 LiveRange* result = fixed_live_ranges_[index];
643 if (result == NULL) {
644 result = new(zone_) LiveRange(FixedLiveRangeID(index), zone_);
645 ASSERT(result->IsFixed());
646 result->set_assigned_register(index, GENERAL_REGISTERS, zone_);
647 fixed_live_ranges_[index] = result;
648 }
649 return result;
650 }
651
652
FixedDoubleLiveRangeFor(int index)653 LiveRange* LAllocator::FixedDoubleLiveRangeFor(int index) {
654 ASSERT(index < DoubleRegister::kNumAllocatableRegisters);
655 LiveRange* result = fixed_double_live_ranges_[index];
656 if (result == NULL) {
657 result = new(zone_) LiveRange(FixedDoubleLiveRangeID(index), zone_);
658 ASSERT(result->IsFixed());
659 result->set_assigned_register(index, DOUBLE_REGISTERS, zone_);
660 fixed_double_live_ranges_[index] = result;
661 }
662 return result;
663 }
664
665
LiveRangeFor(int index)666 LiveRange* LAllocator::LiveRangeFor(int index) {
667 if (index >= live_ranges_.length()) {
668 live_ranges_.AddBlock(NULL, index - live_ranges_.length() + 1);
669 }
670 LiveRange* result = live_ranges_[index];
671 if (result == NULL) {
672 result = new(zone_) LiveRange(index, zone_);
673 live_ranges_[index] = result;
674 }
675 return result;
676 }
677
678
GetLastGap(HBasicBlock * block)679 LGap* LAllocator::GetLastGap(HBasicBlock* block) {
680 int last_instruction = block->last_instruction_index();
681 int index = chunk_->NearestGapPos(last_instruction);
682 return GapAt(index);
683 }
684
685
LookupPhi(LOperand * operand) const686 HPhi* LAllocator::LookupPhi(LOperand* operand) const {
687 if (!operand->IsUnallocated()) return NULL;
688 int index = LUnallocated::cast(operand)->virtual_register();
689 HValue* instr = graph_->LookupValue(index);
690 if (instr != NULL && instr->IsPhi()) {
691 return HPhi::cast(instr);
692 }
693 return NULL;
694 }
695
696
LiveRangeFor(LOperand * operand)697 LiveRange* LAllocator::LiveRangeFor(LOperand* operand) {
698 if (operand->IsUnallocated()) {
699 return LiveRangeFor(LUnallocated::cast(operand)->virtual_register());
700 } else if (operand->IsRegister()) {
701 return FixedLiveRangeFor(operand->index());
702 } else if (operand->IsDoubleRegister()) {
703 return FixedDoubleLiveRangeFor(operand->index());
704 } else {
705 return NULL;
706 }
707 }
708
709
Define(LifetimePosition position,LOperand * operand,LOperand * hint)710 void LAllocator::Define(LifetimePosition position,
711 LOperand* operand,
712 LOperand* hint) {
713 LiveRange* range = LiveRangeFor(operand);
714 if (range == NULL) return;
715
716 if (range->IsEmpty() || range->Start().Value() > position.Value()) {
717 // Can happen if there is a definition without use.
718 range->AddUseInterval(position, position.NextInstruction(), zone_);
719 range->AddUsePosition(position.NextInstruction(), NULL, zone_);
720 } else {
721 range->ShortenTo(position);
722 }
723
724 if (operand->IsUnallocated()) {
725 LUnallocated* unalloc_operand = LUnallocated::cast(operand);
726 range->AddUsePosition(position, unalloc_operand, zone_)->set_hint(hint);
727 }
728 }
729
730
Use(LifetimePosition block_start,LifetimePosition position,LOperand * operand,LOperand * hint)731 void LAllocator::Use(LifetimePosition block_start,
732 LifetimePosition position,
733 LOperand* operand,
734 LOperand* hint) {
735 LiveRange* range = LiveRangeFor(operand);
736 if (range == NULL) return;
737 if (operand->IsUnallocated()) {
738 LUnallocated* unalloc_operand = LUnallocated::cast(operand);
739 range->AddUsePosition(position, unalloc_operand, zone_)->set_hint(hint);
740 }
741 range->AddUseInterval(block_start, position, zone_);
742 }
743
744
AddConstraintsGapMove(int index,LOperand * from,LOperand * to)745 void LAllocator::AddConstraintsGapMove(int index,
746 LOperand* from,
747 LOperand* to) {
748 LGap* gap = GapAt(index);
749 LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START);
750 if (from->IsUnallocated()) {
751 const ZoneList<LMoveOperands>* move_operands = move->move_operands();
752 for (int i = 0; i < move_operands->length(); ++i) {
753 LMoveOperands cur = move_operands->at(i);
754 LOperand* cur_to = cur.destination();
755 if (cur_to->IsUnallocated()) {
756 if (LUnallocated::cast(cur_to)->virtual_register() ==
757 LUnallocated::cast(from)->virtual_register()) {
758 move->AddMove(cur.source(), to);
759 return;
760 }
761 }
762 }
763 }
764 move->AddMove(from, to);
765 }
766
767
MeetRegisterConstraints(HBasicBlock * block)768 void LAllocator::MeetRegisterConstraints(HBasicBlock* block) {
769 int start = block->first_instruction_index();
770 int end = block->last_instruction_index();
771 for (int i = start; i <= end; ++i) {
772 if (IsGapAt(i)) {
773 LInstruction* instr = NULL;
774 LInstruction* prev_instr = NULL;
775 if (i < end) instr = InstructionAt(i + 1);
776 if (i > start) prev_instr = InstructionAt(i - 1);
777 MeetConstraintsBetween(prev_instr, instr, i);
778 if (!AllocationOk()) return;
779 }
780 }
781 }
782
783
MeetConstraintsBetween(LInstruction * first,LInstruction * second,int gap_index)784 void LAllocator::MeetConstraintsBetween(LInstruction* first,
785 LInstruction* second,
786 int gap_index) {
787 // Handle fixed temporaries.
788 if (first != NULL) {
789 for (TempIterator it(first); !it.Done(); it.Advance()) {
790 LUnallocated* temp = LUnallocated::cast(it.Current());
791 if (temp->HasFixedPolicy()) {
792 AllocateFixed(temp, gap_index - 1, false);
793 }
794 }
795 }
796
797 // Handle fixed output operand.
798 if (first != NULL && first->Output() != NULL) {
799 LUnallocated* first_output = LUnallocated::cast(first->Output());
800 LiveRange* range = LiveRangeFor(first_output->virtual_register());
801 bool assigned = false;
802 if (first_output->HasFixedPolicy()) {
803 LUnallocated* output_copy = first_output->CopyUnconstrained();
804 bool is_tagged = HasTaggedValue(first_output->virtual_register());
805 AllocateFixed(first_output, gap_index, is_tagged);
806
807 // This value is produced on the stack, we never need to spill it.
808 if (first_output->IsStackSlot()) {
809 range->SetSpillOperand(first_output);
810 range->SetSpillStartIndex(gap_index - 1);
811 assigned = true;
812 }
813 chunk_->AddGapMove(gap_index, first_output, output_copy);
814 }
815
816 if (!assigned) {
817 range->SetSpillStartIndex(gap_index);
818
819 // This move to spill operand is not a real use. Liveness analysis
820 // and splitting of live ranges do not account for it.
821 // Thus it should be inserted to a lifetime position corresponding to
822 // the instruction end.
823 LGap* gap = GapAt(gap_index);
824 LParallelMove* move = gap->GetOrCreateParallelMove(LGap::BEFORE);
825 move->AddMove(first_output, range->GetSpillOperand());
826 }
827 }
828
829 // Handle fixed input operands of second instruction.
830 if (second != NULL) {
831 for (UseIterator it(second); !it.Done(); it.Advance()) {
832 LUnallocated* cur_input = LUnallocated::cast(it.Current());
833 if (cur_input->HasFixedPolicy()) {
834 LUnallocated* input_copy = cur_input->CopyUnconstrained();
835 bool is_tagged = HasTaggedValue(cur_input->virtual_register());
836 AllocateFixed(cur_input, gap_index + 1, is_tagged);
837 AddConstraintsGapMove(gap_index, input_copy, cur_input);
838 } else if (cur_input->policy() == LUnallocated::WRITABLE_REGISTER) {
839 // The live range of writable input registers always goes until the end
840 // of the instruction.
841 ASSERT(!cur_input->IsUsedAtStart());
842
843 LUnallocated* input_copy = cur_input->CopyUnconstrained();
844 cur_input->set_virtual_register(GetVirtualRegister());
845 if (!AllocationOk()) return;
846
847 if (RequiredRegisterKind(input_copy->virtual_register()) ==
848 DOUBLE_REGISTERS) {
849 double_artificial_registers_.Add(
850 cur_input->virtual_register() - first_artificial_register_,
851 zone_);
852 }
853
854 AddConstraintsGapMove(gap_index, input_copy, cur_input);
855 }
856 }
857 }
858
859 // Handle "output same as input" for second instruction.
860 if (second != NULL && second->Output() != NULL) {
861 LUnallocated* second_output = LUnallocated::cast(second->Output());
862 if (second_output->HasSameAsInputPolicy()) {
863 LUnallocated* cur_input = LUnallocated::cast(second->FirstInput());
864 int output_vreg = second_output->virtual_register();
865 int input_vreg = cur_input->virtual_register();
866
867 LUnallocated* input_copy = cur_input->CopyUnconstrained();
868 cur_input->set_virtual_register(second_output->virtual_register());
869 AddConstraintsGapMove(gap_index, input_copy, cur_input);
870
871 if (HasTaggedValue(input_vreg) && !HasTaggedValue(output_vreg)) {
872 int index = gap_index + 1;
873 LInstruction* instr = InstructionAt(index);
874 if (instr->HasPointerMap()) {
875 instr->pointer_map()->RecordPointer(input_copy);
876 }
877 } else if (!HasTaggedValue(input_vreg) && HasTaggedValue(output_vreg)) {
878 // The input is assumed to immediately have a tagged representation,
879 // before the pointer map can be used. I.e. the pointer map at the
880 // instruction will include the output operand (whose value at the
881 // beginning of the instruction is equal to the input operand). If
882 // this is not desired, then the pointer map at this instruction needs
883 // to be adjusted manually.
884 }
885 }
886 }
887 }
888
889
ProcessInstructions(HBasicBlock * block,BitVector * live)890 void LAllocator::ProcessInstructions(HBasicBlock* block, BitVector* live) {
891 int block_start = block->first_instruction_index();
892 int index = block->last_instruction_index();
893
894 LifetimePosition block_start_position =
895 LifetimePosition::FromInstructionIndex(block_start);
896
897 while (index >= block_start) {
898 LifetimePosition curr_position =
899 LifetimePosition::FromInstructionIndex(index);
900
901 if (IsGapAt(index)) {
902 // We have a gap at this position.
903 LGap* gap = GapAt(index);
904 LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START);
905 const ZoneList<LMoveOperands>* move_operands = move->move_operands();
906 for (int i = 0; i < move_operands->length(); ++i) {
907 LMoveOperands* cur = &move_operands->at(i);
908 if (cur->IsIgnored()) continue;
909 LOperand* from = cur->source();
910 LOperand* to = cur->destination();
911 HPhi* phi = LookupPhi(to);
912 LOperand* hint = to;
913 if (phi != NULL) {
914 // This is a phi resolving move.
915 if (!phi->block()->IsLoopHeader()) {
916 hint = LiveRangeFor(phi->id())->FirstHint();
917 }
918 } else {
919 if (to->IsUnallocated()) {
920 if (live->Contains(LUnallocated::cast(to)->virtual_register())) {
921 Define(curr_position, to, from);
922 live->Remove(LUnallocated::cast(to)->virtual_register());
923 } else {
924 cur->Eliminate();
925 continue;
926 }
927 } else {
928 Define(curr_position, to, from);
929 }
930 }
931 Use(block_start_position, curr_position, from, hint);
932 if (from->IsUnallocated()) {
933 live->Add(LUnallocated::cast(from)->virtual_register());
934 }
935 }
936 } else {
937 ASSERT(!IsGapAt(index));
938 LInstruction* instr = InstructionAt(index);
939
940 if (instr != NULL) {
941 LOperand* output = instr->Output();
942 if (output != NULL) {
943 if (output->IsUnallocated()) {
944 live->Remove(LUnallocated::cast(output)->virtual_register());
945 }
946 Define(curr_position, output, NULL);
947 }
948
949 if (instr->IsMarkedAsCall()) {
950 for (int i = 0; i < Register::kNumAllocatableRegisters; ++i) {
951 if (output == NULL || !output->IsRegister() ||
952 output->index() != i) {
953 LiveRange* range = FixedLiveRangeFor(i);
954 range->AddUseInterval(curr_position,
955 curr_position.InstructionEnd(),
956 zone_);
957 }
958 }
959 }
960
961 if (instr->IsMarkedAsCall() || instr->IsMarkedAsSaveDoubles()) {
962 for (int i = 0; i < DoubleRegister::kNumAllocatableRegisters; ++i) {
963 if (output == NULL || !output->IsDoubleRegister() ||
964 output->index() != i) {
965 LiveRange* range = FixedDoubleLiveRangeFor(i);
966 range->AddUseInterval(curr_position,
967 curr_position.InstructionEnd(),
968 zone_);
969 }
970 }
971 }
972
973 for (UseIterator it(instr); !it.Done(); it.Advance()) {
974 LOperand* input = it.Current();
975
976 LifetimePosition use_pos;
977 if (input->IsUnallocated() &&
978 LUnallocated::cast(input)->IsUsedAtStart()) {
979 use_pos = curr_position;
980 } else {
981 use_pos = curr_position.InstructionEnd();
982 }
983
984 Use(block_start_position, use_pos, input, NULL);
985 if (input->IsUnallocated()) {
986 live->Add(LUnallocated::cast(input)->virtual_register());
987 }
988 }
989
990 for (TempIterator it(instr); !it.Done(); it.Advance()) {
991 LOperand* temp = it.Current();
992 if (instr->IsMarkedAsCall()) {
993 if (temp->IsRegister()) continue;
994 if (temp->IsUnallocated()) {
995 LUnallocated* temp_unalloc = LUnallocated::cast(temp);
996 if (temp_unalloc->HasFixedPolicy()) {
997 continue;
998 }
999 }
1000 }
1001 Use(block_start_position, curr_position.InstructionEnd(), temp, NULL);
1002 Define(curr_position, temp, NULL);
1003 }
1004 }
1005 }
1006
1007 index = index - 1;
1008 }
1009 }
1010
1011
ResolvePhis(HBasicBlock * block)1012 void LAllocator::ResolvePhis(HBasicBlock* block) {
1013 const ZoneList<HPhi*>* phis = block->phis();
1014 for (int i = 0; i < phis->length(); ++i) {
1015 HPhi* phi = phis->at(i);
1016 LUnallocated* phi_operand = new(zone_) LUnallocated(LUnallocated::NONE);
1017 phi_operand->set_virtual_register(phi->id());
1018 for (int j = 0; j < phi->OperandCount(); ++j) {
1019 HValue* op = phi->OperandAt(j);
1020 LOperand* operand = NULL;
1021 if (op->IsConstant() && op->EmitAtUses()) {
1022 HConstant* constant = HConstant::cast(op);
1023 operand = chunk_->DefineConstantOperand(constant);
1024 } else {
1025 ASSERT(!op->EmitAtUses());
1026 LUnallocated* unalloc = new(zone_) LUnallocated(LUnallocated::ANY);
1027 unalloc->set_virtual_register(op->id());
1028 operand = unalloc;
1029 }
1030 HBasicBlock* cur_block = block->predecessors()->at(j);
1031 // The gap move must be added without any special processing as in
1032 // the AddConstraintsGapMove.
1033 chunk_->AddGapMove(cur_block->last_instruction_index() - 1,
1034 operand,
1035 phi_operand);
1036
1037 // We are going to insert a move before the branch instruction.
1038 // Some branch instructions (e.g. loops' back edges)
1039 // can potentially cause a GC so they have a pointer map.
1040 // By inserting a move we essentially create a copy of a
1041 // value which is invisible to PopulatePointerMaps(), because we store
1042 // it into a location different from the operand of a live range
1043 // covering a branch instruction.
1044 // Thus we need to manually record a pointer.
1045 LInstruction* branch =
1046 InstructionAt(cur_block->last_instruction_index());
1047 if (branch->HasPointerMap()) {
1048 if (phi->representation().IsTagged()) {
1049 branch->pointer_map()->RecordPointer(phi_operand);
1050 } else if (!phi->representation().IsDouble()) {
1051 branch->pointer_map()->RecordUntagged(phi_operand);
1052 }
1053 }
1054 }
1055
1056 LiveRange* live_range = LiveRangeFor(phi->id());
1057 LLabel* label = chunk_->GetLabel(phi->block()->block_id());
1058 label->GetOrCreateParallelMove(LGap::START)->
1059 AddMove(phi_operand, live_range->GetSpillOperand());
1060 live_range->SetSpillStartIndex(phi->block()->first_instruction_index());
1061 }
1062 }
1063
1064
Allocate(LChunk * chunk)1065 bool LAllocator::Allocate(LChunk* chunk) {
1066 ASSERT(chunk_ == NULL);
1067 chunk_ = chunk;
1068 MeetRegisterConstraints();
1069 if (!AllocationOk()) return false;
1070 ResolvePhis();
1071 BuildLiveRanges();
1072 AllocateGeneralRegisters();
1073 if (!AllocationOk()) return false;
1074 AllocateDoubleRegisters();
1075 if (!AllocationOk()) return false;
1076 PopulatePointerMaps();
1077 if (has_osr_entry_) ProcessOsrEntry();
1078 ConnectRanges();
1079 ResolveControlFlow();
1080 return true;
1081 }
1082
1083
MeetRegisterConstraints()1084 void LAllocator::MeetRegisterConstraints() {
1085 HPhase phase("L_Register constraints", chunk_);
1086 first_artificial_register_ = next_virtual_register_;
1087 const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1088 for (int i = 0; i < blocks->length(); ++i) {
1089 HBasicBlock* block = blocks->at(i);
1090 MeetRegisterConstraints(block);
1091 if (!AllocationOk()) return;
1092 }
1093 }
1094
1095
ResolvePhis()1096 void LAllocator::ResolvePhis() {
1097 HPhase phase("L_Resolve phis", chunk_);
1098
1099 // Process the blocks in reverse order.
1100 const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1101 for (int block_id = blocks->length() - 1; block_id >= 0; --block_id) {
1102 HBasicBlock* block = blocks->at(block_id);
1103 ResolvePhis(block);
1104 }
1105 }
1106
1107
ResolveControlFlow(LiveRange * range,HBasicBlock * block,HBasicBlock * pred)1108 void LAllocator::ResolveControlFlow(LiveRange* range,
1109 HBasicBlock* block,
1110 HBasicBlock* pred) {
1111 LifetimePosition pred_end =
1112 LifetimePosition::FromInstructionIndex(pred->last_instruction_index());
1113 LifetimePosition cur_start =
1114 LifetimePosition::FromInstructionIndex(block->first_instruction_index());
1115 LiveRange* pred_cover = NULL;
1116 LiveRange* cur_cover = NULL;
1117 LiveRange* cur_range = range;
1118 while (cur_range != NULL && (cur_cover == NULL || pred_cover == NULL)) {
1119 if (cur_range->CanCover(cur_start)) {
1120 ASSERT(cur_cover == NULL);
1121 cur_cover = cur_range;
1122 }
1123 if (cur_range->CanCover(pred_end)) {
1124 ASSERT(pred_cover == NULL);
1125 pred_cover = cur_range;
1126 }
1127 cur_range = cur_range->next();
1128 }
1129
1130 if (cur_cover->IsSpilled()) return;
1131 ASSERT(pred_cover != NULL && cur_cover != NULL);
1132 if (pred_cover != cur_cover) {
1133 LOperand* pred_op = pred_cover->CreateAssignedOperand(zone_);
1134 LOperand* cur_op = cur_cover->CreateAssignedOperand(zone_);
1135 if (!pred_op->Equals(cur_op)) {
1136 LGap* gap = NULL;
1137 if (block->predecessors()->length() == 1) {
1138 gap = GapAt(block->first_instruction_index());
1139 } else {
1140 ASSERT(pred->end()->SecondSuccessor() == NULL);
1141 gap = GetLastGap(pred);
1142
1143 // We are going to insert a move before the branch instruction.
1144 // Some branch instructions (e.g. loops' back edges)
1145 // can potentially cause a GC so they have a pointer map.
1146 // By inserting a move we essentially create a copy of a
1147 // value which is invisible to PopulatePointerMaps(), because we store
1148 // it into a location different from the operand of a live range
1149 // covering a branch instruction.
1150 // Thus we need to manually record a pointer.
1151 LInstruction* branch = InstructionAt(pred->last_instruction_index());
1152 if (branch->HasPointerMap()) {
1153 if (HasTaggedValue(range->id())) {
1154 branch->pointer_map()->RecordPointer(cur_op);
1155 } else if (!cur_op->IsDoubleStackSlot() &&
1156 !cur_op->IsDoubleRegister()) {
1157 branch->pointer_map()->RemovePointer(cur_op);
1158 }
1159 }
1160 }
1161 gap->GetOrCreateParallelMove(LGap::START)->AddMove(pred_op, cur_op);
1162 }
1163 }
1164 }
1165
1166
GetConnectingParallelMove(LifetimePosition pos)1167 LParallelMove* LAllocator::GetConnectingParallelMove(LifetimePosition pos) {
1168 int index = pos.InstructionIndex();
1169 if (IsGapAt(index)) {
1170 LGap* gap = GapAt(index);
1171 return gap->GetOrCreateParallelMove(
1172 pos.IsInstructionStart() ? LGap::START : LGap::END);
1173 }
1174 int gap_pos = pos.IsInstructionStart() ? (index - 1) : (index + 1);
1175 return GapAt(gap_pos)->GetOrCreateParallelMove(
1176 (gap_pos < index) ? LGap::AFTER : LGap::BEFORE);
1177 }
1178
1179
GetBlock(LifetimePosition pos)1180 HBasicBlock* LAllocator::GetBlock(LifetimePosition pos) {
1181 LGap* gap = GapAt(chunk_->NearestGapPos(pos.InstructionIndex()));
1182 return gap->block();
1183 }
1184
1185
ConnectRanges()1186 void LAllocator::ConnectRanges() {
1187 HPhase phase("L_Connect ranges", this);
1188 for (int i = 0; i < live_ranges()->length(); ++i) {
1189 LiveRange* first_range = live_ranges()->at(i);
1190 if (first_range == NULL || first_range->parent() != NULL) continue;
1191
1192 LiveRange* second_range = first_range->next();
1193 while (second_range != NULL) {
1194 LifetimePosition pos = second_range->Start();
1195
1196 if (!second_range->IsSpilled()) {
1197 // Add gap move if the two live ranges touch and there is no block
1198 // boundary.
1199 if (first_range->End().Value() == pos.Value()) {
1200 bool should_insert = true;
1201 if (IsBlockBoundary(pos)) {
1202 should_insert = CanEagerlyResolveControlFlow(GetBlock(pos));
1203 }
1204 if (should_insert) {
1205 LParallelMove* move = GetConnectingParallelMove(pos);
1206 LOperand* prev_operand = first_range->CreateAssignedOperand(zone_);
1207 LOperand* cur_operand = second_range->CreateAssignedOperand(zone_);
1208 move->AddMove(prev_operand, cur_operand);
1209 }
1210 }
1211 }
1212
1213 first_range = second_range;
1214 second_range = second_range->next();
1215 }
1216 }
1217 }
1218
1219
CanEagerlyResolveControlFlow(HBasicBlock * block) const1220 bool LAllocator::CanEagerlyResolveControlFlow(HBasicBlock* block) const {
1221 if (block->predecessors()->length() != 1) return false;
1222 return block->predecessors()->first()->block_id() == block->block_id() - 1;
1223 }
1224
1225
ResolveControlFlow()1226 void LAllocator::ResolveControlFlow() {
1227 HPhase phase("L_Resolve control flow", this);
1228 const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1229 for (int block_id = 1; block_id < blocks->length(); ++block_id) {
1230 HBasicBlock* block = blocks->at(block_id);
1231 if (CanEagerlyResolveControlFlow(block)) continue;
1232 BitVector* live = live_in_sets_[block->block_id()];
1233 BitVector::Iterator iterator(live);
1234 while (!iterator.Done()) {
1235 int operand_index = iterator.Current();
1236 for (int i = 0; i < block->predecessors()->length(); ++i) {
1237 HBasicBlock* cur = block->predecessors()->at(i);
1238 LiveRange* cur_range = LiveRangeFor(operand_index);
1239 ResolveControlFlow(cur_range, block, cur);
1240 }
1241 iterator.Advance();
1242 }
1243 }
1244 }
1245
1246
BuildLiveRanges()1247 void LAllocator::BuildLiveRanges() {
1248 HPhase phase("L_Build live ranges", this);
1249 InitializeLivenessAnalysis();
1250 // Process the blocks in reverse order.
1251 const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
1252 for (int block_id = blocks->length() - 1; block_id >= 0; --block_id) {
1253 HBasicBlock* block = blocks->at(block_id);
1254 BitVector* live = ComputeLiveOut(block);
1255 // Initially consider all live_out values live for the entire block. We
1256 // will shorten these intervals if necessary.
1257 AddInitialIntervals(block, live);
1258
1259 // Process the instructions in reverse order, generating and killing
1260 // live values.
1261 ProcessInstructions(block, live);
1262 // All phi output operands are killed by this block.
1263 const ZoneList<HPhi*>* phis = block->phis();
1264 for (int i = 0; i < phis->length(); ++i) {
1265 // The live range interval already ends at the first instruction of the
1266 // block.
1267 HPhi* phi = phis->at(i);
1268 live->Remove(phi->id());
1269
1270 LOperand* hint = NULL;
1271 LOperand* phi_operand = NULL;
1272 LGap* gap = GetLastGap(phi->block()->predecessors()->at(0));
1273 LParallelMove* move = gap->GetOrCreateParallelMove(LGap::START);
1274 for (int j = 0; j < move->move_operands()->length(); ++j) {
1275 LOperand* to = move->move_operands()->at(j).destination();
1276 if (to->IsUnallocated() &&
1277 LUnallocated::cast(to)->virtual_register() == phi->id()) {
1278 hint = move->move_operands()->at(j).source();
1279 phi_operand = to;
1280 break;
1281 }
1282 }
1283 ASSERT(hint != NULL);
1284
1285 LifetimePosition block_start = LifetimePosition::FromInstructionIndex(
1286 block->first_instruction_index());
1287 Define(block_start, phi_operand, hint);
1288 }
1289
1290 // Now live is live_in for this block except not including values live
1291 // out on backward successor edges.
1292 live_in_sets_[block_id] = live;
1293
1294 // If this block is a loop header go back and patch up the necessary
1295 // predecessor blocks.
1296 if (block->IsLoopHeader()) {
1297 // TODO(kmillikin): Need to be able to get the last block of the loop
1298 // in the loop information. Add a live range stretching from the first
1299 // loop instruction to the last for each value live on entry to the
1300 // header.
1301 HBasicBlock* back_edge = block->loop_information()->GetLastBackEdge();
1302 BitVector::Iterator iterator(live);
1303 LifetimePosition start = LifetimePosition::FromInstructionIndex(
1304 block->first_instruction_index());
1305 LifetimePosition end = LifetimePosition::FromInstructionIndex(
1306 back_edge->last_instruction_index()).NextInstruction();
1307 while (!iterator.Done()) {
1308 int operand_index = iterator.Current();
1309 LiveRange* range = LiveRangeFor(operand_index);
1310 range->EnsureInterval(start, end, zone_);
1311 iterator.Advance();
1312 }
1313
1314 for (int i = block->block_id() + 1; i <= back_edge->block_id(); ++i) {
1315 live_in_sets_[i]->Union(*live);
1316 }
1317 }
1318
1319 #ifdef DEBUG
1320 if (block_id == 0) {
1321 BitVector::Iterator iterator(live);
1322 bool found = false;
1323 while (!iterator.Done()) {
1324 found = true;
1325 int operand_index = iterator.Current();
1326 PrintF("Function: %s\n",
1327 *chunk_->info()->function()->debug_name()->ToCString());
1328 PrintF("Value %d used before first definition!\n", operand_index);
1329 LiveRange* range = LiveRangeFor(operand_index);
1330 PrintF("First use is at %d\n", range->first_pos()->pos().Value());
1331 iterator.Advance();
1332 }
1333 ASSERT(!found);
1334 }
1335 #endif
1336 }
1337 }
1338
1339
SafePointsAreInOrder() const1340 bool LAllocator::SafePointsAreInOrder() const {
1341 const ZoneList<LPointerMap*>* pointer_maps = chunk_->pointer_maps();
1342 int safe_point = 0;
1343 for (int i = 0; i < pointer_maps->length(); ++i) {
1344 LPointerMap* map = pointer_maps->at(i);
1345 if (safe_point > map->lithium_position()) return false;
1346 safe_point = map->lithium_position();
1347 }
1348 return true;
1349 }
1350
1351
PopulatePointerMaps()1352 void LAllocator::PopulatePointerMaps() {
1353 HPhase phase("L_Populate pointer maps", this);
1354 const ZoneList<LPointerMap*>* pointer_maps = chunk_->pointer_maps();
1355
1356 ASSERT(SafePointsAreInOrder());
1357
1358 // Iterate over all safe point positions and record a pointer
1359 // for all spilled live ranges at this point.
1360 int first_safe_point_index = 0;
1361 int last_range_start = 0;
1362 for (int range_idx = 0; range_idx < live_ranges()->length(); ++range_idx) {
1363 LiveRange* range = live_ranges()->at(range_idx);
1364 if (range == NULL) continue;
1365 // Iterate over the first parts of multi-part live ranges.
1366 if (range->parent() != NULL) continue;
1367 // Skip non-pointer values.
1368 if (!HasTaggedValue(range->id())) continue;
1369 // Skip empty live ranges.
1370 if (range->IsEmpty()) continue;
1371
1372 // Find the extent of the range and its children.
1373 int start = range->Start().InstructionIndex();
1374 int end = 0;
1375 for (LiveRange* cur = range; cur != NULL; cur = cur->next()) {
1376 LifetimePosition this_end = cur->End();
1377 if (this_end.InstructionIndex() > end) end = this_end.InstructionIndex();
1378 ASSERT(cur->Start().InstructionIndex() >= start);
1379 }
1380
1381 // Most of the ranges are in order, but not all. Keep an eye on when
1382 // they step backwards and reset the first_safe_point_index so we don't
1383 // miss any safe points.
1384 if (start < last_range_start) {
1385 first_safe_point_index = 0;
1386 }
1387 last_range_start = start;
1388
1389 // Step across all the safe points that are before the start of this range,
1390 // recording how far we step in order to save doing this for the next range.
1391 while (first_safe_point_index < pointer_maps->length()) {
1392 LPointerMap* map = pointer_maps->at(first_safe_point_index);
1393 int safe_point = map->lithium_position();
1394 if (safe_point >= start) break;
1395 first_safe_point_index++;
1396 }
1397
1398 // Step through the safe points to see whether they are in the range.
1399 for (int safe_point_index = first_safe_point_index;
1400 safe_point_index < pointer_maps->length();
1401 ++safe_point_index) {
1402 LPointerMap* map = pointer_maps->at(safe_point_index);
1403 int safe_point = map->lithium_position();
1404
1405 // The safe points are sorted so we can stop searching here.
1406 if (safe_point - 1 > end) break;
1407
1408 // Advance to the next active range that covers the current
1409 // safe point position.
1410 LifetimePosition safe_point_pos =
1411 LifetimePosition::FromInstructionIndex(safe_point);
1412 LiveRange* cur = range;
1413 while (cur != NULL && !cur->Covers(safe_point_pos.PrevInstruction())) {
1414 cur = cur->next();
1415 }
1416 if (cur == NULL) continue;
1417
1418 // Check if the live range is spilled and the safe point is after
1419 // the spill position.
1420 if (range->HasAllocatedSpillOperand() &&
1421 safe_point >= range->spill_start_index()) {
1422 TraceAlloc("Pointer for range %d (spilled at %d) at safe point %d\n",
1423 range->id(), range->spill_start_index(), safe_point);
1424 map->RecordPointer(range->GetSpillOperand());
1425 }
1426
1427 if (!cur->IsSpilled()) {
1428 TraceAlloc("Pointer in register for range %d (start at %d) "
1429 "at safe point %d\n",
1430 cur->id(), cur->Start().Value(), safe_point);
1431 LOperand* operand = cur->CreateAssignedOperand(zone_);
1432 ASSERT(!operand->IsStackSlot());
1433 map->RecordPointer(operand);
1434 }
1435 }
1436 }
1437 }
1438
1439
ProcessOsrEntry()1440 void LAllocator::ProcessOsrEntry() {
1441 const ZoneList<LInstruction*>* instrs = chunk_->instructions();
1442
1443 // Linear search for the OSR entry instruction in the chunk.
1444 int index = -1;
1445 while (++index < instrs->length() &&
1446 !instrs->at(index)->IsOsrEntry()) {
1447 }
1448 ASSERT(index < instrs->length());
1449 LOsrEntry* instruction = LOsrEntry::cast(instrs->at(index));
1450
1451 LifetimePosition position = LifetimePosition::FromInstructionIndex(index);
1452 for (int i = 0; i < live_ranges()->length(); ++i) {
1453 LiveRange* range = live_ranges()->at(i);
1454 if (range != NULL) {
1455 if (range->Covers(position) &&
1456 range->HasRegisterAssigned() &&
1457 range->TopLevel()->HasAllocatedSpillOperand()) {
1458 int reg_index = range->assigned_register();
1459 LOperand* spill_operand = range->TopLevel()->GetSpillOperand();
1460 if (range->IsDouble()) {
1461 instruction->MarkSpilledDoubleRegister(reg_index, spill_operand);
1462 } else {
1463 instruction->MarkSpilledRegister(reg_index, spill_operand);
1464 }
1465 }
1466 }
1467 }
1468 }
1469
1470
AllocateGeneralRegisters()1471 void LAllocator::AllocateGeneralRegisters() {
1472 HPhase phase("L_Allocate general registers", this);
1473 num_registers_ = Register::kNumAllocatableRegisters;
1474 AllocateRegisters();
1475 }
1476
1477
AllocateDoubleRegisters()1478 void LAllocator::AllocateDoubleRegisters() {
1479 HPhase phase("L_Allocate double registers", this);
1480 num_registers_ = DoubleRegister::kNumAllocatableRegisters;
1481 mode_ = DOUBLE_REGISTERS;
1482 AllocateRegisters();
1483 }
1484
1485
AllocateRegisters()1486 void LAllocator::AllocateRegisters() {
1487 ASSERT(unhandled_live_ranges_.is_empty());
1488
1489 for (int i = 0; i < live_ranges_.length(); ++i) {
1490 if (live_ranges_[i] != NULL) {
1491 if (RequiredRegisterKind(live_ranges_[i]->id()) == mode_) {
1492 AddToUnhandledUnsorted(live_ranges_[i]);
1493 }
1494 }
1495 }
1496 SortUnhandled();
1497 ASSERT(UnhandledIsSorted());
1498
1499 ASSERT(reusable_slots_.is_empty());
1500 ASSERT(active_live_ranges_.is_empty());
1501 ASSERT(inactive_live_ranges_.is_empty());
1502
1503 if (mode_ == DOUBLE_REGISTERS) {
1504 for (int i = 0; i < fixed_double_live_ranges_.length(); ++i) {
1505 LiveRange* current = fixed_double_live_ranges_.at(i);
1506 if (current != NULL) {
1507 AddToInactive(current);
1508 }
1509 }
1510 } else {
1511 for (int i = 0; i < fixed_live_ranges_.length(); ++i) {
1512 LiveRange* current = fixed_live_ranges_.at(i);
1513 if (current != NULL) {
1514 AddToInactive(current);
1515 }
1516 }
1517 }
1518
1519 while (!unhandled_live_ranges_.is_empty()) {
1520 ASSERT(UnhandledIsSorted());
1521 LiveRange* current = unhandled_live_ranges_.RemoveLast();
1522 ASSERT(UnhandledIsSorted());
1523 LifetimePosition position = current->Start();
1524 TraceAlloc("Processing interval %d start=%d\n",
1525 current->id(),
1526 position.Value());
1527
1528 if (current->HasAllocatedSpillOperand()) {
1529 TraceAlloc("Live range %d already has a spill operand\n", current->id());
1530 LifetimePosition next_pos = position;
1531 if (IsGapAt(next_pos.InstructionIndex())) {
1532 next_pos = next_pos.NextInstruction();
1533 }
1534 UsePosition* pos = current->NextUsePositionRegisterIsBeneficial(next_pos);
1535 // If the range already has a spill operand and it doesn't need a
1536 // register immediately, split it and spill the first part of the range.
1537 if (pos == NULL) {
1538 Spill(current);
1539 continue;
1540 } else if (pos->pos().Value() >
1541 current->Start().NextInstruction().Value()) {
1542 // Do not spill live range eagerly if use position that can benefit from
1543 // the register is too close to the start of live range.
1544 SpillBetween(current, current->Start(), pos->pos());
1545 if (!AllocationOk()) return;
1546 ASSERT(UnhandledIsSorted());
1547 continue;
1548 }
1549 }
1550
1551 for (int i = 0; i < active_live_ranges_.length(); ++i) {
1552 LiveRange* cur_active = active_live_ranges_.at(i);
1553 if (cur_active->End().Value() <= position.Value()) {
1554 ActiveToHandled(cur_active);
1555 --i; // The live range was removed from the list of active live ranges.
1556 } else if (!cur_active->Covers(position)) {
1557 ActiveToInactive(cur_active);
1558 --i; // The live range was removed from the list of active live ranges.
1559 }
1560 }
1561
1562 for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1563 LiveRange* cur_inactive = inactive_live_ranges_.at(i);
1564 if (cur_inactive->End().Value() <= position.Value()) {
1565 InactiveToHandled(cur_inactive);
1566 --i; // Live range was removed from the list of inactive live ranges.
1567 } else if (cur_inactive->Covers(position)) {
1568 InactiveToActive(cur_inactive);
1569 --i; // Live range was removed from the list of inactive live ranges.
1570 }
1571 }
1572
1573 ASSERT(!current->HasRegisterAssigned() && !current->IsSpilled());
1574
1575 bool result = TryAllocateFreeReg(current);
1576 if (!AllocationOk()) return;
1577
1578 if (!result) AllocateBlockedReg(current);
1579 if (!AllocationOk()) return;
1580
1581 if (current->HasRegisterAssigned()) {
1582 AddToActive(current);
1583 }
1584 }
1585
1586 reusable_slots_.Rewind(0);
1587 active_live_ranges_.Rewind(0);
1588 inactive_live_ranges_.Rewind(0);
1589 }
1590
1591
RegisterName(int allocation_index)1592 const char* LAllocator::RegisterName(int allocation_index) {
1593 if (mode_ == GENERAL_REGISTERS) {
1594 return Register::AllocationIndexToString(allocation_index);
1595 } else {
1596 return DoubleRegister::AllocationIndexToString(allocation_index);
1597 }
1598 }
1599
1600
TraceAlloc(const char * msg,...)1601 void LAllocator::TraceAlloc(const char* msg, ...) {
1602 if (FLAG_trace_alloc) {
1603 va_list arguments;
1604 va_start(arguments, msg);
1605 OS::VPrint(msg, arguments);
1606 va_end(arguments);
1607 }
1608 }
1609
1610
HasTaggedValue(int virtual_register) const1611 bool LAllocator::HasTaggedValue(int virtual_register) const {
1612 HValue* value = graph_->LookupValue(virtual_register);
1613 if (value == NULL) return false;
1614 return value->representation().IsTagged();
1615 }
1616
1617
RequiredRegisterKind(int virtual_register) const1618 RegisterKind LAllocator::RequiredRegisterKind(int virtual_register) const {
1619 if (virtual_register < first_artificial_register_) {
1620 HValue* value = graph_->LookupValue(virtual_register);
1621 if (value != NULL && value->representation().IsDouble()) {
1622 return DOUBLE_REGISTERS;
1623 }
1624 } else if (double_artificial_registers_.Contains(
1625 virtual_register - first_artificial_register_)) {
1626 return DOUBLE_REGISTERS;
1627 }
1628
1629 return GENERAL_REGISTERS;
1630 }
1631
1632
AddToActive(LiveRange * range)1633 void LAllocator::AddToActive(LiveRange* range) {
1634 TraceAlloc("Add live range %d to active\n", range->id());
1635 active_live_ranges_.Add(range);
1636 }
1637
1638
AddToInactive(LiveRange * range)1639 void LAllocator::AddToInactive(LiveRange* range) {
1640 TraceAlloc("Add live range %d to inactive\n", range->id());
1641 inactive_live_ranges_.Add(range);
1642 }
1643
1644
AddToUnhandledSorted(LiveRange * range)1645 void LAllocator::AddToUnhandledSorted(LiveRange* range) {
1646 if (range == NULL || range->IsEmpty()) return;
1647 ASSERT(!range->HasRegisterAssigned() && !range->IsSpilled());
1648 for (int i = unhandled_live_ranges_.length() - 1; i >= 0; --i) {
1649 LiveRange* cur_range = unhandled_live_ranges_.at(i);
1650 if (range->ShouldBeAllocatedBefore(cur_range)) {
1651 TraceAlloc("Add live range %d to unhandled at %d\n", range->id(), i + 1);
1652 unhandled_live_ranges_.InsertAt(i + 1, range);
1653 ASSERT(UnhandledIsSorted());
1654 return;
1655 }
1656 }
1657 TraceAlloc("Add live range %d to unhandled at start\n", range->id());
1658 unhandled_live_ranges_.InsertAt(0, range);
1659 ASSERT(UnhandledIsSorted());
1660 }
1661
1662
AddToUnhandledUnsorted(LiveRange * range)1663 void LAllocator::AddToUnhandledUnsorted(LiveRange* range) {
1664 if (range == NULL || range->IsEmpty()) return;
1665 ASSERT(!range->HasRegisterAssigned() && !range->IsSpilled());
1666 TraceAlloc("Add live range %d to unhandled unsorted at end\n", range->id());
1667 unhandled_live_ranges_.Add(range);
1668 }
1669
1670
UnhandledSortHelper(LiveRange * const * a,LiveRange * const * b)1671 static int UnhandledSortHelper(LiveRange* const* a, LiveRange* const* b) {
1672 ASSERT(!(*a)->ShouldBeAllocatedBefore(*b) ||
1673 !(*b)->ShouldBeAllocatedBefore(*a));
1674 if ((*a)->ShouldBeAllocatedBefore(*b)) return 1;
1675 if ((*b)->ShouldBeAllocatedBefore(*a)) return -1;
1676 return (*a)->id() - (*b)->id();
1677 }
1678
1679
1680 // Sort the unhandled live ranges so that the ranges to be processed first are
1681 // at the end of the array list. This is convenient for the register allocation
1682 // algorithm because it is efficient to remove elements from the end.
SortUnhandled()1683 void LAllocator::SortUnhandled() {
1684 TraceAlloc("Sort unhandled\n");
1685 unhandled_live_ranges_.Sort(&UnhandledSortHelper);
1686 }
1687
1688
UnhandledIsSorted()1689 bool LAllocator::UnhandledIsSorted() {
1690 int len = unhandled_live_ranges_.length();
1691 for (int i = 1; i < len; i++) {
1692 LiveRange* a = unhandled_live_ranges_.at(i - 1);
1693 LiveRange* b = unhandled_live_ranges_.at(i);
1694 if (a->Start().Value() < b->Start().Value()) return false;
1695 }
1696 return true;
1697 }
1698
1699
FreeSpillSlot(LiveRange * range)1700 void LAllocator::FreeSpillSlot(LiveRange* range) {
1701 // Check that we are the last range.
1702 if (range->next() != NULL) return;
1703
1704 if (!range->TopLevel()->HasAllocatedSpillOperand()) return;
1705
1706 int index = range->TopLevel()->GetSpillOperand()->index();
1707 if (index >= 0) {
1708 reusable_slots_.Add(range);
1709 }
1710 }
1711
1712
TryReuseSpillSlot(LiveRange * range)1713 LOperand* LAllocator::TryReuseSpillSlot(LiveRange* range) {
1714 if (reusable_slots_.is_empty()) return NULL;
1715 if (reusable_slots_.first()->End().Value() >
1716 range->TopLevel()->Start().Value()) {
1717 return NULL;
1718 }
1719 LOperand* result = reusable_slots_.first()->TopLevel()->GetSpillOperand();
1720 reusable_slots_.Remove(0);
1721 return result;
1722 }
1723
1724
ActiveToHandled(LiveRange * range)1725 void LAllocator::ActiveToHandled(LiveRange* range) {
1726 ASSERT(active_live_ranges_.Contains(range));
1727 active_live_ranges_.RemoveElement(range);
1728 TraceAlloc("Moving live range %d from active to handled\n", range->id());
1729 FreeSpillSlot(range);
1730 }
1731
1732
ActiveToInactive(LiveRange * range)1733 void LAllocator::ActiveToInactive(LiveRange* range) {
1734 ASSERT(active_live_ranges_.Contains(range));
1735 active_live_ranges_.RemoveElement(range);
1736 inactive_live_ranges_.Add(range);
1737 TraceAlloc("Moving live range %d from active to inactive\n", range->id());
1738 }
1739
1740
InactiveToHandled(LiveRange * range)1741 void LAllocator::InactiveToHandled(LiveRange* range) {
1742 ASSERT(inactive_live_ranges_.Contains(range));
1743 inactive_live_ranges_.RemoveElement(range);
1744 TraceAlloc("Moving live range %d from inactive to handled\n", range->id());
1745 FreeSpillSlot(range);
1746 }
1747
1748
InactiveToActive(LiveRange * range)1749 void LAllocator::InactiveToActive(LiveRange* range) {
1750 ASSERT(inactive_live_ranges_.Contains(range));
1751 inactive_live_ranges_.RemoveElement(range);
1752 active_live_ranges_.Add(range);
1753 TraceAlloc("Moving live range %d from inactive to active\n", range->id());
1754 }
1755
1756
1757 // TryAllocateFreeReg and AllocateBlockedReg assume this
1758 // when allocating local arrays.
1759 STATIC_ASSERT(DoubleRegister::kNumAllocatableRegisters >=
1760 Register::kNumAllocatableRegisters);
1761
1762
TryAllocateFreeReg(LiveRange * current)1763 bool LAllocator::TryAllocateFreeReg(LiveRange* current) {
1764 LifetimePosition free_until_pos[DoubleRegister::kNumAllocatableRegisters];
1765
1766 for (int i = 0; i < DoubleRegister::kNumAllocatableRegisters; i++) {
1767 free_until_pos[i] = LifetimePosition::MaxPosition();
1768 }
1769
1770 for (int i = 0; i < active_live_ranges_.length(); ++i) {
1771 LiveRange* cur_active = active_live_ranges_.at(i);
1772 free_until_pos[cur_active->assigned_register()] =
1773 LifetimePosition::FromInstructionIndex(0);
1774 }
1775
1776 for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1777 LiveRange* cur_inactive = inactive_live_ranges_.at(i);
1778 ASSERT(cur_inactive->End().Value() > current->Start().Value());
1779 LifetimePosition next_intersection =
1780 cur_inactive->FirstIntersection(current);
1781 if (!next_intersection.IsValid()) continue;
1782 int cur_reg = cur_inactive->assigned_register();
1783 free_until_pos[cur_reg] = Min(free_until_pos[cur_reg], next_intersection);
1784 }
1785
1786 UsePosition* hinted_use = current->FirstPosWithHint();
1787 if (hinted_use != NULL) {
1788 LOperand* hint = hinted_use->hint();
1789 if (hint->IsRegister() || hint->IsDoubleRegister()) {
1790 int register_index = hint->index();
1791 TraceAlloc(
1792 "Found reg hint %s (free until [%d) for live range %d (end %d[).\n",
1793 RegisterName(register_index),
1794 free_until_pos[register_index].Value(),
1795 current->id(),
1796 current->End().Value());
1797
1798 // The desired register is free until the end of the current live range.
1799 if (free_until_pos[register_index].Value() >= current->End().Value()) {
1800 TraceAlloc("Assigning preferred reg %s to live range %d\n",
1801 RegisterName(register_index),
1802 current->id());
1803 current->set_assigned_register(register_index, mode_, zone_);
1804 return true;
1805 }
1806 }
1807 }
1808
1809 // Find the register which stays free for the longest time.
1810 int reg = 0;
1811 for (int i = 1; i < RegisterCount(); ++i) {
1812 if (free_until_pos[i].Value() > free_until_pos[reg].Value()) {
1813 reg = i;
1814 }
1815 }
1816
1817 LifetimePosition pos = free_until_pos[reg];
1818
1819 if (pos.Value() <= current->Start().Value()) {
1820 // All registers are blocked.
1821 return false;
1822 }
1823
1824 if (pos.Value() < current->End().Value()) {
1825 // Register reg is available at the range start but becomes blocked before
1826 // the range end. Split current at position where it becomes blocked.
1827 LiveRange* tail = SplitRangeAt(current, pos);
1828 if (!AllocationOk()) return false;
1829 AddToUnhandledSorted(tail);
1830 }
1831
1832
1833 // Register reg is available at the range start and is free until
1834 // the range end.
1835 ASSERT(pos.Value() >= current->End().Value());
1836 TraceAlloc("Assigning free reg %s to live range %d\n",
1837 RegisterName(reg),
1838 current->id());
1839 current->set_assigned_register(reg, mode_, zone_);
1840
1841 return true;
1842 }
1843
1844
AllocateBlockedReg(LiveRange * current)1845 void LAllocator::AllocateBlockedReg(LiveRange* current) {
1846 UsePosition* register_use = current->NextRegisterPosition(current->Start());
1847 if (register_use == NULL) {
1848 // There is no use in the current live range that requires a register.
1849 // We can just spill it.
1850 Spill(current);
1851 return;
1852 }
1853
1854
1855 LifetimePosition use_pos[DoubleRegister::kNumAllocatableRegisters];
1856 LifetimePosition block_pos[DoubleRegister::kNumAllocatableRegisters];
1857
1858 for (int i = 0; i < DoubleRegister::kNumAllocatableRegisters; i++) {
1859 use_pos[i] = block_pos[i] = LifetimePosition::MaxPosition();
1860 }
1861
1862 for (int i = 0; i < active_live_ranges_.length(); ++i) {
1863 LiveRange* range = active_live_ranges_[i];
1864 int cur_reg = range->assigned_register();
1865 if (range->IsFixed() || !range->CanBeSpilled(current->Start())) {
1866 block_pos[cur_reg] = use_pos[cur_reg] =
1867 LifetimePosition::FromInstructionIndex(0);
1868 } else {
1869 UsePosition* next_use = range->NextUsePositionRegisterIsBeneficial(
1870 current->Start());
1871 if (next_use == NULL) {
1872 use_pos[cur_reg] = range->End();
1873 } else {
1874 use_pos[cur_reg] = next_use->pos();
1875 }
1876 }
1877 }
1878
1879 for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1880 LiveRange* range = inactive_live_ranges_.at(i);
1881 ASSERT(range->End().Value() > current->Start().Value());
1882 LifetimePosition next_intersection = range->FirstIntersection(current);
1883 if (!next_intersection.IsValid()) continue;
1884 int cur_reg = range->assigned_register();
1885 if (range->IsFixed()) {
1886 block_pos[cur_reg] = Min(block_pos[cur_reg], next_intersection);
1887 use_pos[cur_reg] = Min(block_pos[cur_reg], use_pos[cur_reg]);
1888 } else {
1889 use_pos[cur_reg] = Min(use_pos[cur_reg], next_intersection);
1890 }
1891 }
1892
1893 int reg = 0;
1894 for (int i = 1; i < RegisterCount(); ++i) {
1895 if (use_pos[i].Value() > use_pos[reg].Value()) {
1896 reg = i;
1897 }
1898 }
1899
1900 LifetimePosition pos = use_pos[reg];
1901
1902 if (pos.Value() < register_use->pos().Value()) {
1903 // All registers are blocked before the first use that requires a register.
1904 // Spill starting part of live range up to that use.
1905 //
1906 // Corner case: the first use position is equal to the start of the range.
1907 // In this case we have nothing to spill and SpillBetween will just return
1908 // this range to the list of unhandled ones. This will lead to the infinite
1909 // loop.
1910 ASSERT(current->Start().Value() < register_use->pos().Value());
1911 SpillBetween(current, current->Start(), register_use->pos());
1912 return;
1913 }
1914
1915 if (block_pos[reg].Value() < current->End().Value()) {
1916 // Register becomes blocked before the current range end. Split before that
1917 // position.
1918 LiveRange* tail = SplitBetween(current,
1919 current->Start(),
1920 block_pos[reg].InstructionStart());
1921 AddToUnhandledSorted(tail);
1922 }
1923
1924 // Register reg is not blocked for the whole range.
1925 ASSERT(block_pos[reg].Value() >= current->End().Value());
1926 TraceAlloc("Assigning blocked reg %s to live range %d\n",
1927 RegisterName(reg),
1928 current->id());
1929 current->set_assigned_register(reg, mode_, zone_);
1930
1931 // This register was not free. Thus we need to find and spill
1932 // parts of active and inactive live regions that use the same register
1933 // at the same lifetime positions as current.
1934 SplitAndSpillIntersecting(current);
1935 }
1936
1937
SplitAndSpillIntersecting(LiveRange * current)1938 void LAllocator::SplitAndSpillIntersecting(LiveRange* current) {
1939 ASSERT(current->HasRegisterAssigned());
1940 int reg = current->assigned_register();
1941 LifetimePosition split_pos = current->Start();
1942 for (int i = 0; i < active_live_ranges_.length(); ++i) {
1943 LiveRange* range = active_live_ranges_[i];
1944 if (range->assigned_register() == reg) {
1945 UsePosition* next_pos = range->NextRegisterPosition(current->Start());
1946 if (next_pos == NULL) {
1947 SpillAfter(range, split_pos);
1948 } else {
1949 SpillBetween(range, split_pos, next_pos->pos());
1950 }
1951 ActiveToHandled(range);
1952 --i;
1953 }
1954 }
1955
1956 for (int i = 0; i < inactive_live_ranges_.length(); ++i) {
1957 LiveRange* range = inactive_live_ranges_[i];
1958 ASSERT(range->End().Value() > current->Start().Value());
1959 if (range->assigned_register() == reg && !range->IsFixed()) {
1960 LifetimePosition next_intersection = range->FirstIntersection(current);
1961 if (next_intersection.IsValid()) {
1962 UsePosition* next_pos = range->NextRegisterPosition(current->Start());
1963 if (next_pos == NULL) {
1964 SpillAfter(range, split_pos);
1965 } else {
1966 next_intersection = Min(next_intersection, next_pos->pos());
1967 SpillBetween(range, split_pos, next_intersection);
1968 }
1969 InactiveToHandled(range);
1970 --i;
1971 }
1972 }
1973 }
1974 }
1975
1976
IsBlockBoundary(LifetimePosition pos)1977 bool LAllocator::IsBlockBoundary(LifetimePosition pos) {
1978 return pos.IsInstructionStart() &&
1979 InstructionAt(pos.InstructionIndex())->IsLabel();
1980 }
1981
1982
SplitRangeAt(LiveRange * range,LifetimePosition pos)1983 LiveRange* LAllocator::SplitRangeAt(LiveRange* range, LifetimePosition pos) {
1984 ASSERT(!range->IsFixed());
1985 TraceAlloc("Splitting live range %d at %d\n", range->id(), pos.Value());
1986
1987 if (pos.Value() <= range->Start().Value()) return range;
1988
1989 // We can't properly connect liveranges if split occured at the end
1990 // of control instruction.
1991 ASSERT(pos.IsInstructionStart() ||
1992 !chunk_->instructions()->at(pos.InstructionIndex())->IsControl());
1993
1994 LiveRange* result = LiveRangeFor(GetVirtualRegister());
1995 if (!AllocationOk()) return NULL;
1996 range->SplitAt(pos, result, zone_);
1997 return result;
1998 }
1999
2000
SplitBetween(LiveRange * range,LifetimePosition start,LifetimePosition end)2001 LiveRange* LAllocator::SplitBetween(LiveRange* range,
2002 LifetimePosition start,
2003 LifetimePosition end) {
2004 ASSERT(!range->IsFixed());
2005 TraceAlloc("Splitting live range %d in position between [%d, %d]\n",
2006 range->id(),
2007 start.Value(),
2008 end.Value());
2009
2010 LifetimePosition split_pos = FindOptimalSplitPos(start, end);
2011 ASSERT(split_pos.Value() >= start.Value());
2012 return SplitRangeAt(range, split_pos);
2013 }
2014
2015
FindOptimalSplitPos(LifetimePosition start,LifetimePosition end)2016 LifetimePosition LAllocator::FindOptimalSplitPos(LifetimePosition start,
2017 LifetimePosition end) {
2018 int start_instr = start.InstructionIndex();
2019 int end_instr = end.InstructionIndex();
2020 ASSERT(start_instr <= end_instr);
2021
2022 // We have no choice
2023 if (start_instr == end_instr) return end;
2024
2025 HBasicBlock* start_block = GetBlock(start);
2026 HBasicBlock* end_block = GetBlock(end);
2027
2028 if (end_block == start_block) {
2029 // The interval is split in the same basic block. Split at the latest
2030 // possible position.
2031 return end;
2032 }
2033
2034 HBasicBlock* block = end_block;
2035 // Find header of outermost loop.
2036 while (block->parent_loop_header() != NULL &&
2037 block->parent_loop_header()->block_id() > start_block->block_id()) {
2038 block = block->parent_loop_header();
2039 }
2040
2041 // We did not find any suitable outer loop. Split at the latest possible
2042 // position unless end_block is a loop header itself.
2043 if (block == end_block && !end_block->IsLoopHeader()) return end;
2044
2045 return LifetimePosition::FromInstructionIndex(
2046 block->first_instruction_index());
2047 }
2048
2049
SpillAfter(LiveRange * range,LifetimePosition pos)2050 void LAllocator::SpillAfter(LiveRange* range, LifetimePosition pos) {
2051 LiveRange* second_part = SplitRangeAt(range, pos);
2052 if (!AllocationOk()) return;
2053 Spill(second_part);
2054 }
2055
2056
SpillBetween(LiveRange * range,LifetimePosition start,LifetimePosition end)2057 void LAllocator::SpillBetween(LiveRange* range,
2058 LifetimePosition start,
2059 LifetimePosition end) {
2060 ASSERT(start.Value() < end.Value());
2061 LiveRange* second_part = SplitRangeAt(range, start);
2062 if (!AllocationOk()) return;
2063
2064 if (second_part->Start().Value() < end.Value()) {
2065 // The split result intersects with [start, end[.
2066 // Split it at position between ]start+1, end[, spill the middle part
2067 // and put the rest to unhandled.
2068 LiveRange* third_part = SplitBetween(
2069 second_part,
2070 second_part->Start().InstructionEnd(),
2071 end.PrevInstruction().InstructionEnd());
2072
2073 ASSERT(third_part != second_part);
2074
2075 Spill(second_part);
2076 AddToUnhandledSorted(third_part);
2077 } else {
2078 // The split result does not intersect with [start, end[.
2079 // Nothing to spill. Just put it to unhandled as whole.
2080 AddToUnhandledSorted(second_part);
2081 }
2082 }
2083
2084
Spill(LiveRange * range)2085 void LAllocator::Spill(LiveRange* range) {
2086 ASSERT(!range->IsSpilled());
2087 TraceAlloc("Spilling live range %d\n", range->id());
2088 LiveRange* first = range->TopLevel();
2089
2090 if (!first->HasAllocatedSpillOperand()) {
2091 LOperand* op = TryReuseSpillSlot(range);
2092 if (op == NULL) op = chunk_->GetNextSpillSlot(mode_ == DOUBLE_REGISTERS);
2093 first->SetSpillOperand(op);
2094 }
2095 range->MakeSpilled(zone_);
2096 }
2097
2098
RegisterCount() const2099 int LAllocator::RegisterCount() const {
2100 return num_registers_;
2101 }
2102
2103
2104 #ifdef DEBUG
2105
2106
Verify() const2107 void LAllocator::Verify() const {
2108 for (int i = 0; i < live_ranges()->length(); ++i) {
2109 LiveRange* current = live_ranges()->at(i);
2110 if (current != NULL) current->Verify();
2111 }
2112 }
2113
2114
2115 #endif
2116
2117
2118 } } // namespace v8::internal
2119