src/v8/src/global-handles.cc

   1 // Copyright 2009 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/v8.h"
   6
   7 #include "src/api.h"
   8 #include "src/global-handles.h"
   9
  10 #include "src/vm-state-inl.h"
  11
  12 namespace v8 {
  13 namespace internal {
  14
  15
  16 ObjectGroup::~ObjectGroup() {
  17   if (info != NULL) info->Dispose();
  18   delete[] objects;
  19 }
  20
  21
  22 ImplicitRefGroup::~ImplicitRefGroup() {
  23   delete[] children;
  24 }
  25
  26
  27 class GlobalHandles::Node {
  28  public:
  29   // State transition diagram:
  30   // FREE -> NORMAL <-> WEAK -> PENDING -> NEAR_DEATH -> { NORMAL, WEAK, FREE }
  31   enum State {
  32     FREE = 0,
  33     NORMAL,     // Normal global handle.
  34     WEAK,       // Flagged as weak but not yet finalized.
  35     PENDING,    // Has been recognized as only reachable by weak handles.
  36     NEAR_DEATH  // Callback has informed the handle is near death.
  37   };
  38
  39   // Maps handle location (slot) to the containing node.
  40   static Node* FromLocation(Object** location) {
  41     DCHECK(OFFSET_OF(Node, object_) == 0);
  42     return reinterpret_cast<Node*>(location);
  43   }
  44
  45   Node() {
  46     DCHECK(OFFSET_OF(Node, class_id_) == Internals::kNodeClassIdOffset);
  47     DCHECK(OFFSET_OF(Node, flags_) == Internals::kNodeFlagsOffset);
  48     STATIC_ASSERT(static_cast<int>(NodeState::kMask) ==
  49                   Internals::kNodeStateMask);
  50     STATIC_ASSERT(WEAK == Internals::kNodeStateIsWeakValue);
  51     STATIC_ASSERT(PENDING == Internals::kNodeStateIsPendingValue);
  52     STATIC_ASSERT(NEAR_DEATH == Internals::kNodeStateIsNearDeathValue);
  53     STATIC_ASSERT(static_cast<int>(IsIndependent::kShift) ==
  54                   Internals::kNodeIsIndependentShift);
  55     STATIC_ASSERT(static_cast<int>(IsPartiallyDependent::kShift) ==
  56                   Internals::kNodeIsPartiallyDependentShift);
  57   }
  58
  59 #ifdef ENABLE_HANDLE_ZAPPING
  60   ~Node() {
  61     // TODO(1428): if it's a weak handle we should have invoked its callback.
  62     // Zap the values for eager trapping.
  63     object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
  64     class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
  65     index_ = 0;
  66     set_independent(false);
  67     set_partially_dependent(false);
  68     set_in_new_space_list(false);
  69     parameter_or_next_free_.next_free = NULL;
  70     weak_callback_ = NULL;
  71   }
  72 #endif
  73
  74   void Initialize(int index, Node** first_free) {
  75     index_ = static_cast<uint8_t>(index);
  76     DCHECK(static_cast<int>(index_) == index);
  77     set_state(FREE);
  78     set_in_new_space_list(false);
  79     parameter_or_next_free_.next_free = *first_free;
  80     *first_free = this;
  81   }
  82
  83   void Acquire(Object* object) {
  84     DCHECK(state() == FREE);
  85     object_ = object;
  86     class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
  87     set_independent(false);
  88     set_partially_dependent(false);
  89     set_state(NORMAL);
  90     parameter_or_next_free_.parameter = NULL;
  91     weak_callback_ = NULL;
  92     IncreaseBlockUses();
  93   }
  94
  95   void Release() {
  96     DCHECK(state() != FREE);
  97     set_state(FREE);
  98     // Zap the values for eager trapping.
  99     object_ = reinterpret_cast<Object*>(kGlobalHandleZapValue);
 100     class_id_ = v8::HeapProfiler::kPersistentHandleNoClassId;
 101     set_independent(false);
 102     set_partially_dependent(false);
 103     weak_callback_ = NULL;
 104     DecreaseBlockUses();
 105   }
 106
 107   // Object slot accessors.
 108   Object* object() const { return object_; }
 109   Object** location() { return &object_; }
 110   Handle<Object> handle() { return Handle<Object>(location()); }
 111
 112   // Wrapper class ID accessors.
 113   bool has_wrapper_class_id() const {
 114     return class_id_ != v8::HeapProfiler::kPersistentHandleNoClassId;
 115   }
 116
 117   uint16_t wrapper_class_id() const { return class_id_; }
 118
 119   // State and flag accessors.
 120
 121   State state() const {
 122     return NodeState::decode(flags_);
 123   }
 124   void set_state(State state) {
 125     flags_ = NodeState::update(flags_, state);
 126   }
 127
 128   bool is_independent() {
 129     return IsIndependent::decode(flags_);
 130   }
 131   void set_independent(bool v) {
 132     flags_ = IsIndependent::update(flags_, v);
 133   }
 134
 135   bool is_partially_dependent() {
 136     return IsPartiallyDependent::decode(flags_);
 137   }
 138   void set_partially_dependent(bool v) {
 139     flags_ = IsPartiallyDependent::update(flags_, v);
 140   }
 141
 142   bool is_in_new_space_list() {
 143     return IsInNewSpaceList::decode(flags_);
 144   }
 145   void set_in_new_space_list(bool v) {
 146     flags_ = IsInNewSpaceList::update(flags_, v);
 147   }
 148
 149   bool IsNearDeath() const {
 150     // Check for PENDING to ensure correct answer when processing callbacks.
 151     return state() == PENDING || state() == NEAR_DEATH;
 152   }
 153
 154   bool IsWeak() const { return state() == WEAK; }
 155
 156   bool IsRetainer() const { return state() != FREE; }
 157
 158   bool IsStrongRetainer() const { return state() == NORMAL; }
 159
 160   bool IsWeakRetainer() const {
 161     return state() == WEAK || state() == PENDING || state() == NEAR_DEATH;
 162   }
 163
 164   void MarkPending() {
 165     DCHECK(state() == WEAK);
 166     set_state(PENDING);
 167   }
 168
 169   // Independent flag accessors.
 170   void MarkIndependent() {
 171     DCHECK(state() != FREE);
 172     set_independent(true);
 173   }
 174
 175   void MarkPartiallyDependent() {
 176     DCHECK(state() != FREE);
 177     if (GetGlobalHandles()->isolate()->heap()->InNewSpace(object_)) {
 178       set_partially_dependent(true);
 179     }
 180   }
 181   void clear_partially_dependent() { set_partially_dependent(false); }
 182
 183   // Callback accessor.
 184   // TODO(svenpanne) Re-enable or nuke later.
 185   // WeakReferenceCallback callback() { return callback_; }
 186
 187   // Callback parameter accessors.
 188   void set_parameter(void* parameter) {
 189     DCHECK(state() != FREE);
 190     parameter_or_next_free_.parameter = parameter;
 191   }
 192   void* parameter() const {
 193     DCHECK(state() != FREE);
 194     return parameter_or_next_free_.parameter;
 195   }
 196
 197   // Accessors for next free node in the free list.
 198   Node* next_free() {
 199     DCHECK(state() == FREE);
 200     return parameter_or_next_free_.next_free;
 201   }
 202   void set_next_free(Node* value) {
 203     DCHECK(state() == FREE);
 204     parameter_or_next_free_.next_free = value;
 205   }
 206
 207   void MakeWeak(void* parameter, WeakCallback weak_callback) {
 208     DCHECK(weak_callback != NULL);
 209     DCHECK(state() != FREE);
 210     CHECK(object_ != NULL);
 211     set_state(WEAK);
 212     set_parameter(parameter);
 213     weak_callback_ = weak_callback;
 214   }
 215
 216   void* ClearWeakness() {
 217     DCHECK(state() != FREE);
 218     void* p = parameter();
 219     set_state(NORMAL);
 220     set_parameter(NULL);
 221     return p;
 222   }
 223
 224   bool PostGarbageCollectionProcessing(Isolate* isolate) {
 225     if (state() != Node::PENDING) return false;
 226     if (weak_callback_ == NULL) {
 227       Release();
 228       return false;
 229     }
 230     void* par = parameter();
 231     set_state(NEAR_DEATH);
 232     set_parameter(NULL);
 233
 234     Object** object = location();
 235     {
 236       // Check that we are not passing a finalized external string to
 237       // the callback.
 238       DCHECK(!object_->IsExternalAsciiString() ||
 239              ExternalAsciiString::cast(object_)->resource() != NULL);
 240       DCHECK(!object_->IsExternalTwoByteString() ||
 241              ExternalTwoByteString::cast(object_)->resource() != NULL);
 242       // Leaving V8.
 243       VMState<EXTERNAL> state(isolate);
 244       HandleScope handle_scope(isolate);
 245       Handle<Object> handle(*object, isolate);
 246       v8::WeakCallbackData<v8::Value, void> data(
 247           reinterpret_cast<v8::Isolate*>(isolate),
 248           v8::Utils::ToLocal(handle),
 249           par);
 250       weak_callback_(data);
 251     }
 252     // Absence of explicit cleanup or revival of weak handle
 253     // in most of the cases would lead to memory leak.
 254     CHECK(state() != NEAR_DEATH);
 255     return true;
 256   }
 257
 258   inline GlobalHandles* GetGlobalHandles();
 259
 260  private:
 261   inline NodeBlock* FindBlock();
 262   inline void IncreaseBlockUses();
 263   inline void DecreaseBlockUses();
 264
 265   // Storage for object pointer.
 266   // Placed first to avoid offset computation.
 267   Object* object_;
 268
 269   // Next word stores class_id, index, state, and independent.
 270   // Note: the most aligned fields should go first.
 271
 272   // Wrapper class ID.
 273   uint16_t class_id_;
 274
 275   // Index in the containing handle block.
 276   uint8_t index_;
 277
 278   // This stores three flags (independent, partially_dependent and
 279   // in_new_space_list) and a State.
 280   class NodeState:            public BitField<State, 0, 4> {};
 281   class IsIndependent:        public BitField<bool,  4, 1> {};
 282   class IsPartiallyDependent: public BitField<bool,  5, 1> {};
 283   class IsInNewSpaceList:     public BitField<bool,  6, 1> {};
 284
 285   uint8_t flags_;
 286
 287   // Handle specific callback - might be a weak reference in disguise.
 288   WeakCallback weak_callback_;
 289
 290   // Provided data for callback.  In FREE state, this is used for
 291   // the free list link.
 292   union {
 293     void* parameter;
 294     Node* next_free;
 295   } parameter_or_next_free_;
 296
 297   DISALLOW_COPY_AND_ASSIGN(Node);
 298 };
 299
 300
 301 class GlobalHandles::NodeBlock {
 302  public:
 303   static const int kSize = 256;
 304
 305   explicit NodeBlock(GlobalHandles* global_handles, NodeBlock* next)
 306       : next_(next),
 307         used_nodes_(0),
 308         next_used_(NULL),
 309         prev_used_(NULL),
 310         global_handles_(global_handles) {}
 311
 312   void PutNodesOnFreeList(Node** first_free) {
 313     for (int i = kSize - 1; i >= 0; --i) {
 314       nodes_[i].Initialize(i, first_free);
 315     }
 316   }
 317
 318   Node* node_at(int index) {
 319     DCHECK(0 <= index && index < kSize);
 320     return &nodes_[index];
 321   }
 322
 323   void IncreaseUses() {
 324     DCHECK(used_nodes_ < kSize);
 325     if (used_nodes_++ == 0) {
 326       NodeBlock* old_first = global_handles_->first_used_block_;
 327       global_handles_->first_used_block_ = this;
 328       next_used_ = old_first;
 329       prev_used_ = NULL;
 330       if (old_first == NULL) return;
 331       old_first->prev_used_ = this;
 332     }
 333   }
 334
 335   void DecreaseUses() {
 336     DCHECK(used_nodes_ > 0);
 337     if (--used_nodes_ == 0) {
 338       if (next_used_ != NULL) next_used_->prev_used_ = prev_used_;
 339       if (prev_used_ != NULL) prev_used_->next_used_ = next_used_;
 340       if (this == global_handles_->first_used_block_) {
 341         global_handles_->first_used_block_ = next_used_;
 342       }
 343     }
 344   }
 345
 346   GlobalHandles* global_handles() { return global_handles_; }
 347
 348   // Next block in the list of all blocks.
 349   NodeBlock* next() const { return next_; }
 350
 351   // Next/previous block in the list of blocks with used nodes.
 352   NodeBlock* next_used() const { return next_used_; }
 353   NodeBlock* prev_used() const { return prev_used_; }
 354
 355  private:
 356   Node nodes_[kSize];
 357   NodeBlock* const next_;
 358   int used_nodes_;
 359   NodeBlock* next_used_;
 360   NodeBlock* prev_used_;
 361   GlobalHandles* global_handles_;
 362 };
 363
 364
 365 GlobalHandles* GlobalHandles::Node::GetGlobalHandles() {
 366   return FindBlock()->global_handles();
 367 }
 368
 369
 370 GlobalHandles::NodeBlock* GlobalHandles::Node::FindBlock() {
 371   intptr_t ptr = reinterpret_cast<intptr_t>(this);
 372   ptr = ptr - index_ * sizeof(Node);
 373   NodeBlock* block = reinterpret_cast<NodeBlock*>(ptr);
 374   DCHECK(block->node_at(index_) == this);
 375   return block;
 376 }
 377
 378
 379 void GlobalHandles::Node::IncreaseBlockUses() {
 380   NodeBlock* node_block = FindBlock();
 381   node_block->IncreaseUses();
 382   GlobalHandles* global_handles = node_block->global_handles();
 383   global_handles->isolate()->counters()->global_handles()->Increment();
 384   global_handles->number_of_global_handles_++;
 385 }
 386
 387
 388 void GlobalHandles::Node::DecreaseBlockUses() {
 389   NodeBlock* node_block = FindBlock();
 390   GlobalHandles* global_handles = node_block->global_handles();
 391   parameter_or_next_free_.next_free = global_handles->first_free_;
 392   global_handles->first_free_ = this;
 393   node_block->DecreaseUses();
 394   global_handles->isolate()->counters()->global_handles()->Decrement();
 395   global_handles->number_of_global_handles_--;
 396 }
 397
 398
 399 class GlobalHandles::NodeIterator {
 400  public:
 401   explicit NodeIterator(GlobalHandles* global_handles)
 402       : block_(global_handles->first_used_block_),
 403         index_(0) {}
 404
 405   bool done() const { return block_ == NULL; }
 406
 407   Node* node() const {
 408     DCHECK(!done());
 409     return block_->node_at(index_);
 410   }
 411
 412   void Advance() {
 413     DCHECK(!done());
 414     if (++index_ < NodeBlock::kSize) return;
 415     index_ = 0;
 416     block_ = block_->next_used();
 417   }
 418
 419  private:
 420   NodeBlock* block_;
 421   int index_;
 422
 423   DISALLOW_COPY_AND_ASSIGN(NodeIterator);
 424 };
 425
 426
 427 GlobalHandles::GlobalHandles(Isolate* isolate)
 428     : isolate_(isolate),
 429       number_of_global_handles_(0),
 430       first_block_(NULL),
 431       first_used_block_(NULL),
 432       first_free_(NULL),
 433       post_gc_processing_count_(0),
 434       object_group_connections_(kObjectGroupConnectionsCapacity) {}
 435
 436
 437 GlobalHandles::~GlobalHandles() {
 438   NodeBlock* block = first_block_;
 439   while (block != NULL) {
 440     NodeBlock* tmp = block->next();
 441     delete block;
 442     block = tmp;
 443   }
 444   first_block_ = NULL;
 445 }
 446
 447
 448 Handle<Object> GlobalHandles::Create(Object* value) {
 449   if (first_free_ == NULL) {
 450     first_block_ = new NodeBlock(this, first_block_);
 451     first_block_->PutNodesOnFreeList(&first_free_);
 452   }
 453   DCHECK(first_free_ != NULL);
 454   // Take the first node in the free list.
 455   Node* result = first_free_;
 456   first_free_ = result->next_free();
 457   result->Acquire(value);
 458   if (isolate_->heap()->InNewSpace(value) &&
 459       !result->is_in_new_space_list()) {
 460     new_space_nodes_.Add(result);
 461     result->set_in_new_space_list(true);
 462   }
 463   return result->handle();
 464 }
 465
 466
 467 Handle<Object> GlobalHandles::CopyGlobal(Object** location) {
 468   DCHECK(location != NULL);
 469   return Node::FromLocation(location)->GetGlobalHandles()->Create(*location);
 470 }
 471
 472
 473 void GlobalHandles::Destroy(Object** location) {
 474   if (location != NULL) Node::FromLocation(location)->Release();
 475 }
 476
 477
 478 void GlobalHandles::MakeWeak(Object** location,
 479                              void* parameter,
 480                              WeakCallback weak_callback) {
 481   Node::FromLocation(location)->MakeWeak(parameter, weak_callback);
 482 }
 483
 484
 485 void* GlobalHandles::ClearWeakness(Object** location) {
 486   return Node::FromLocation(location)->ClearWeakness();
 487 }
 488
 489
 490 void GlobalHandles::MarkIndependent(Object** location) {
 491   Node::FromLocation(location)->MarkIndependent();
 492 }
 493
 494
 495 void GlobalHandles::MarkPartiallyDependent(Object** location) {
 496   Node::FromLocation(location)->MarkPartiallyDependent();
 497 }
 498
 499
 500 bool GlobalHandles::IsIndependent(Object** location) {
 501   return Node::FromLocation(location)->is_independent();
 502 }
 503
 504
 505 bool GlobalHandles::IsNearDeath(Object** location) {
 506   return Node::FromLocation(location)->IsNearDeath();
 507 }
 508
 509
 510 bool GlobalHandles::IsWeak(Object** location) {
 511   return Node::FromLocation(location)->IsWeak();
 512 }
 513
 514
 515 void GlobalHandles::IterateWeakRoots(ObjectVisitor* v) {
 516   for (NodeIterator it(this); !it.done(); it.Advance()) {
 517     if (it.node()->IsWeakRetainer()) v->VisitPointer(it.node()->location());
 518   }
 519 }
 520
 521
 522 void GlobalHandles::IdentifyWeakHandles(WeakSlotCallback f) {
 523   for (NodeIterator it(this); !it.done(); it.Advance()) {
 524     if (it.node()->IsWeak() && f(it.node()->location())) {
 525       it.node()->MarkPending();
 526     }
 527   }
 528 }
 529
 530
 531 void GlobalHandles::IterateNewSpaceStrongAndDependentRoots(ObjectVisitor* v) {
 532   for (int i = 0; i < new_space_nodes_.length(); ++i) {
 533     Node* node = new_space_nodes_[i];
 534     if (node->IsStrongRetainer() ||
 535         (node->IsWeakRetainer() && !node->is_independent() &&
 536          !node->is_partially_dependent())) {
 537         v->VisitPointer(node->location());
 538     }
 539   }
 540 }
 541
 542
 543 void GlobalHandles::IdentifyNewSpaceWeakIndependentHandles(
 544     WeakSlotCallbackWithHeap f) {
 545   for (int i = 0; i < new_space_nodes_.length(); ++i) {
 546     Node* node = new_space_nodes_[i];
 547     DCHECK(node->is_in_new_space_list());
 548     if ((node->is_independent() || node->is_partially_dependent()) &&
 549         node->IsWeak() && f(isolate_->heap(), node->location())) {
 550       node->MarkPending();
 551     }
 552   }
 553 }
 554
 555
 556 void GlobalHandles::IterateNewSpaceWeakIndependentRoots(ObjectVisitor* v) {
 557   for (int i = 0; i < new_space_nodes_.length(); ++i) {
 558     Node* node = new_space_nodes_[i];
 559     DCHECK(node->is_in_new_space_list());
 560     if ((node->is_independent() || node->is_partially_dependent()) &&
 561         node->IsWeakRetainer()) {
 562       v->VisitPointer(node->location());
 563     }
 564   }
 565 }
 566
 567
 568 bool GlobalHandles::IterateObjectGroups(ObjectVisitor* v,
 569                                         WeakSlotCallbackWithHeap can_skip) {
 570   ComputeObjectGroupsAndImplicitReferences();
 571   int last = 0;
 572   bool any_group_was_visited = false;
 573   for (int i = 0; i < object_groups_.length(); i++) {
 574     ObjectGroup* entry = object_groups_.at(i);
 575     DCHECK(entry != NULL);
 576
 577     Object*** objects = entry->objects;
 578     bool group_should_be_visited = false;
 579     for (size_t j = 0; j < entry->length; j++) {
 580       Object* object = *objects[j];
 581       if (object->IsHeapObject()) {
 582         if (!can_skip(isolate_->heap(), &object)) {
 583           group_should_be_visited = true;
 584           break;
 585         }
 586       }
 587     }
 588
 589     if (!group_should_be_visited) {
 590       object_groups_[last++] = entry;
 591       continue;
 592     }
 593
 594     // An object in the group requires visiting, so iterate over all
 595     // objects in the group.
 596     for (size_t j = 0; j < entry->length; ++j) {
 597       Object* object = *objects[j];
 598       if (object->IsHeapObject()) {
 599         v->VisitPointer(&object);
 600         any_group_was_visited = true;
 601       }
 602     }
 603
 604     // Once the entire group has been iterated over, set the object
 605     // group to NULL so it won't be processed again.
 606     delete entry;
 607     object_groups_.at(i) = NULL;
 608   }
 609   object_groups_.Rewind(last);
 610   return any_group_was_visited;
 611 }
 612
 613
 614 int GlobalHandles::PostGarbageCollectionProcessing(
 615     GarbageCollector collector) {
 616   // Process weak global handle callbacks. This must be done after the
 617   // GC is completely done, because the callbacks may invoke arbitrary
 618   // API functions.
 619   DCHECK(isolate_->heap()->gc_state() == Heap::NOT_IN_GC);
 620   const int initial_post_gc_processing_count = ++post_gc_processing_count_;
 621   int freed_nodes = 0;
 622   if (collector == SCAVENGER) {
 623     for (int i = 0; i < new_space_nodes_.length(); ++i) {
 624       Node* node = new_space_nodes_[i];
 625       DCHECK(node->is_in_new_space_list());
 626       if (!node->IsRetainer()) {
 627         // Free nodes do not have weak callbacks. Do not use them to compute
 628         // the freed_nodes.
 629         continue;
 630       }
 631       // Skip dependent handles. Their weak callbacks might expect to be
 632       // called between two global garbage collection callbacks which
 633       // are not called for minor collections.
 634       if (!node->is_independent() && !node->is_partially_dependent()) {
 635         continue;
 636       }
 637       node->clear_partially_dependent();
 638       if (node->PostGarbageCollectionProcessing(isolate_)) {
 639         if (initial_post_gc_processing_count != post_gc_processing_count_) {
 640           // Weak callback triggered another GC and another round of
 641           // PostGarbageCollection processing.  The current node might
 642           // have been deleted in that round, so we need to bail out (or
 643           // restart the processing).
 644           return freed_nodes;
 645         }
 646       }
 647       if (!node->IsRetainer()) {
 648         freed_nodes++;
 649       }
 650     }
 651   } else {
 652     for (NodeIterator it(this); !it.done(); it.Advance()) {
 653       if (!it.node()->IsRetainer()) {
 654         // Free nodes do not have weak callbacks. Do not use them to compute
 655         // the freed_nodes.
 656         continue;
 657       }
 658       it.node()->clear_partially_dependent();
 659       if (it.node()->PostGarbageCollectionProcessing(isolate_)) {
 660         if (initial_post_gc_processing_count != post_gc_processing_count_) {
 661           // See the comment above.
 662           return freed_nodes;
 663         }
 664       }
 665       if (!it.node()->IsRetainer()) {
 666         freed_nodes++;
 667       }
 668     }
 669   }
 670   // Update the list of new space nodes.
 671   int last = 0;
 672   for (int i = 0; i < new_space_nodes_.length(); ++i) {
 673     Node* node = new_space_nodes_[i];
 674     DCHECK(node->is_in_new_space_list());
 675     if (node->IsRetainer()) {
 676       if (isolate_->heap()->InNewSpace(node->object())) {
 677         new_space_nodes_[last++] = node;
 678         isolate_->heap()->IncrementNodesCopiedInNewSpace();
 679       } else {
 680         node->set_in_new_space_list(false);
 681         isolate_->heap()->IncrementNodesPromoted();
 682       }
 683     } else {
 684       node->set_in_new_space_list(false);
 685       isolate_->heap()->IncrementNodesDiedInNewSpace();
 686     }
 687   }
 688   new_space_nodes_.Rewind(last);
 689   return freed_nodes;
 690 }
 691
 692
 693 void GlobalHandles::IterateStrongRoots(ObjectVisitor* v) {
 694   for (NodeIterator it(this); !it.done(); it.Advance()) {
 695     if (it.node()->IsStrongRetainer()) {
 696       v->VisitPointer(it.node()->location());
 697     }
 698   }
 699 }
 700
 701
 702 void GlobalHandles::IterateAllRoots(ObjectVisitor* v) {
 703   for (NodeIterator it(this); !it.done(); it.Advance()) {
 704     if (it.node()->IsRetainer()) {
 705       v->VisitPointer(it.node()->location());
 706     }
 707   }
 708 }
 709
 710
 711 void GlobalHandles::IterateAllRootsWithClassIds(ObjectVisitor* v) {
 712   for (NodeIterator it(this); !it.done(); it.Advance()) {
 713     if (it.node()->IsRetainer() && it.node()->has_wrapper_class_id()) {
 714       v->VisitEmbedderReference(it.node()->location(),
 715                                 it.node()->wrapper_class_id());
 716     }
 717   }
 718 }
 719
 720
 721 void GlobalHandles::IterateAllRootsInNewSpaceWithClassIds(ObjectVisitor* v) {
 722   for (int i = 0; i < new_space_nodes_.length(); ++i) {
 723     Node* node = new_space_nodes_[i];
 724     if (node->IsRetainer() && node->has_wrapper_class_id()) {
 725       v->VisitEmbedderReference(node->location(),
 726                                 node->wrapper_class_id());
 727     }
 728   }
 729 }
 730
 731
 732 int GlobalHandles::NumberOfWeakHandles() {
 733   int count = 0;
 734   for (NodeIterator it(this); !it.done(); it.Advance()) {
 735     if (it.node()->IsWeakRetainer()) {
 736       count++;
 737     }
 738   }
 739   return count;
 740 }
 741
 742
 743 int GlobalHandles::NumberOfGlobalObjectWeakHandles() {
 744   int count = 0;
 745   for (NodeIterator it(this); !it.done(); it.Advance()) {
 746     if (it.node()->IsWeakRetainer() &&
 747         it.node()->object()->IsJSGlobalObject()) {
 748       count++;
 749     }
 750   }
 751   return count;
 752 }
 753
 754
 755 void GlobalHandles::RecordStats(HeapStats* stats) {
 756   *stats->global_handle_count = 0;
 757   *stats->weak_global_handle_count = 0;
 758   *stats->pending_global_handle_count = 0;
 759   *stats->near_death_global_handle_count = 0;
 760   *stats->free_global_handle_count = 0;
 761   for (NodeIterator it(this); !it.done(); it.Advance()) {
 762     *stats->global_handle_count += 1;
 763     if (it.node()->state() == Node::WEAK) {
 764       *stats->weak_global_handle_count += 1;
 765     } else if (it.node()->state() == Node::PENDING) {
 766       *stats->pending_global_handle_count += 1;
 767     } else if (it.node()->state() == Node::NEAR_DEATH) {
 768       *stats->near_death_global_handle_count += 1;
 769     } else if (it.node()->state() == Node::FREE) {
 770       *stats->free_global_handle_count += 1;
 771     }
 772   }
 773 }
 774
 775 #ifdef DEBUG
 776
 777 void GlobalHandles::PrintStats() {
 778   int total = 0;
 779   int weak = 0;
 780   int pending = 0;
 781   int near_death = 0;
 782   int destroyed = 0;
 783
 784   for (NodeIterator it(this); !it.done(); it.Advance()) {
 785     total++;
 786     if (it.node()->state() == Node::WEAK) weak++;
 787     if (it.node()->state() == Node::PENDING) pending++;
 788     if (it.node()->state() == Node::NEAR_DEATH) near_death++;
 789     if (it.node()->state() == Node::FREE) destroyed++;
 790   }
 791
 792   PrintF("Global Handle Statistics:\n");
 793   PrintF("  allocated memory = %" V8_PTR_PREFIX "dB\n", sizeof(Node) * total);
 794   PrintF("  # weak       = %d\n", weak);
 795   PrintF("  # pending    = %d\n", pending);
 796   PrintF("  # near_death = %d\n", near_death);
 797   PrintF("  # free       = %d\n", destroyed);
 798   PrintF("  # total      = %d\n", total);
 799 }
 800
 801
 802 void GlobalHandles::Print() {
 803   PrintF("Global handles:\n");
 804   for (NodeIterator it(this); !it.done(); it.Advance()) {
 805     PrintF("  handle %p to %p%s\n",
 806            reinterpret_cast<void*>(it.node()->location()),
 807            reinterpret_cast<void*>(it.node()->object()),
 808            it.node()->IsWeak() ? " (weak)" : "");
 809   }
 810 }
 811
 812 #endif
 813
 814
 815
 816 void GlobalHandles::AddObjectGroup(Object*** handles,
 817                                    size_t length,
 818                                    v8::RetainedObjectInfo* info) {
 819 #ifdef DEBUG
 820   for (size_t i = 0; i < length; ++i) {
 821     DCHECK(!Node::FromLocation(handles[i])->is_independent());
 822   }
 823 #endif
 824   if (length == 0) {
 825     if (info != NULL) info->Dispose();
 826     return;
 827   }
 828   ObjectGroup* group = new ObjectGroup(length);
 829   for (size_t i = 0; i < length; ++i)
 830     group->objects[i] = handles[i];
 831   group->info = info;
 832   object_groups_.Add(group);
 833 }
 834
 835
 836 void GlobalHandles::SetObjectGroupId(Object** handle,
 837                                      UniqueId id) {
 838   object_group_connections_.Add(ObjectGroupConnection(id, handle));
 839 }
 840
 841
 842 void GlobalHandles::SetRetainedObjectInfo(UniqueId id,
 843                                           RetainedObjectInfo* info) {
 844   retainer_infos_.Add(ObjectGroupRetainerInfo(id, info));
 845 }
 846
 847
 848 void GlobalHandles::AddImplicitReferences(HeapObject** parent,
 849                                           Object*** children,
 850                                           size_t length) {
 851 #ifdef DEBUG
 852   DCHECK(!Node::FromLocation(BitCast<Object**>(parent))->is_independent());
 853   for (size_t i = 0; i < length; ++i) {
 854     DCHECK(!Node::FromLocation(children[i])->is_independent());
 855   }
 856 #endif
 857   if (length == 0) return;
 858   ImplicitRefGroup* group = new ImplicitRefGroup(parent, length);
 859   for (size_t i = 0; i < length; ++i)
 860     group->children[i] = children[i];
 861   implicit_ref_groups_.Add(group);
 862 }
 863
 864
 865 void GlobalHandles::SetReferenceFromGroup(UniqueId id, Object** child) {
 866   DCHECK(!Node::FromLocation(child)->is_independent());
 867   implicit_ref_connections_.Add(ObjectGroupConnection(id, child));
 868 }
 869
 870
 871 void GlobalHandles::SetReference(HeapObject** parent, Object** child) {
 872   DCHECK(!Node::FromLocation(child)->is_independent());
 873   ImplicitRefGroup* group = new ImplicitRefGroup(parent, 1);
 874   group->children[0] = child;
 875   implicit_ref_groups_.Add(group);
 876 }
 877
 878
 879 void GlobalHandles::RemoveObjectGroups() {
 880   for (int i = 0; i < object_groups_.length(); i++)
 881     delete object_groups_.at(i);
 882   object_groups_.Clear();
 883   for (int i = 0; i < retainer_infos_.length(); ++i)
 884     retainer_infos_[i].info->Dispose();
 885   retainer_infos_.Clear();
 886   object_group_connections_.Clear();
 887   object_group_connections_.Initialize(kObjectGroupConnectionsCapacity);
 888 }
 889
 890
 891 void GlobalHandles::RemoveImplicitRefGroups() {
 892   for (int i = 0; i < implicit_ref_groups_.length(); i++) {
 893     delete implicit_ref_groups_.at(i);
 894   }
 895   implicit_ref_groups_.Clear();
 896   implicit_ref_connections_.Clear();
 897 }
 898
 899
 900 void GlobalHandles::TearDown() {
 901   // TODO(1428): invoke weak callbacks.
 902 }
 903
 904
 905 void GlobalHandles::ComputeObjectGroupsAndImplicitReferences() {
 906   if (object_group_connections_.length() == 0) {
 907     for (int i = 0; i < retainer_infos_.length(); ++i)
 908       retainer_infos_[i].info->Dispose();
 909     retainer_infos_.Clear();
 910     implicit_ref_connections_.Clear();
 911     return;
 912   }
 913
 914   object_group_connections_.Sort();
 915   retainer_infos_.Sort();
 916   implicit_ref_connections_.Sort();
 917
 918   int info_index = 0;  // For iterating retainer_infos_.
 919   UniqueId current_group_id(0);
 920   int current_group_start = 0;
 921
 922   int current_implicit_refs_start = 0;
 923   int current_implicit_refs_end = 0;
 924   for (int i = 0; i <= object_group_connections_.length(); ++i) {
 925     if (i == 0)
 926       current_group_id = object_group_connections_[i].id;
 927     if (i == object_group_connections_.length() ||
 928         current_group_id != object_group_connections_[i].id) {
 929       // Group detected: objects in indices [current_group_start, i[.
 930
 931       // Find out which implicit references are related to this group. (We want
 932       // to ignore object groups which only have 1 object, but that object is
 933       // needed as a representative object for the implicit refrerence group.)
 934       while (current_implicit_refs_start < implicit_ref_connections_.length() &&
 935              implicit_ref_connections_[current_implicit_refs_start].id <
 936                  current_group_id)
 937         ++current_implicit_refs_start;
 938       current_implicit_refs_end = current_implicit_refs_start;
 939       while (current_implicit_refs_end < implicit_ref_connections_.length() &&
 940              implicit_ref_connections_[current_implicit_refs_end].id ==
 941                  current_group_id)
 942         ++current_implicit_refs_end;
 943
 944       if (current_implicit_refs_end > current_implicit_refs_start) {
 945         // Find a representative object for the implicit references.
 946         HeapObject** representative = NULL;
 947         for (int j = current_group_start; j < i; ++j) {
 948           Object** object = object_group_connections_[j].object;
 949           if ((*object)->IsHeapObject()) {
 950             representative = reinterpret_cast<HeapObject**>(object);
 951             break;
 952           }
 953         }
 954         if (representative) {
 955           ImplicitRefGroup* group = new ImplicitRefGroup(
 956               representative,
 957               current_implicit_refs_end - current_implicit_refs_start);
 958           for (int j = current_implicit_refs_start;
 959                j < current_implicit_refs_end;
 960                ++j) {
 961             group->children[j - current_implicit_refs_start] =
 962                 implicit_ref_connections_[j].object;
 963           }
 964           implicit_ref_groups_.Add(group);
 965         }
 966         current_implicit_refs_start = current_implicit_refs_end;
 967       }
 968
 969       // Find a RetainedObjectInfo for the group.
 970       RetainedObjectInfo* info = NULL;
 971       while (info_index < retainer_infos_.length() &&
 972              retainer_infos_[info_index].id < current_group_id) {
 973         retainer_infos_[info_index].info->Dispose();
 974         ++info_index;
 975       }
 976       if (info_index < retainer_infos_.length() &&
 977           retainer_infos_[info_index].id == current_group_id) {
 978         // This object group has an associated ObjectGroupRetainerInfo.
 979         info = retainer_infos_[info_index].info;
 980         ++info_index;
 981       }
 982
 983       // Ignore groups which only contain one object.
 984       if (i > current_group_start + 1) {
 985         ObjectGroup* group = new ObjectGroup(i - current_group_start);
 986         for (int j = current_group_start; j < i; ++j) {
 987           group->objects[j - current_group_start] =
 988               object_group_connections_[j].object;
 989         }
 990         group->info = info;
 991         object_groups_.Add(group);
 992       } else if (info) {
 993         info->Dispose();
 994       }
 995
 996       if (i < object_group_connections_.length()) {
 997         current_group_id = object_group_connections_[i].id;
 998         current_group_start = i;
 999       }
1000     }
1001   }
1002   object_group_connections_.Clear();
1003   object_group_connections_.Initialize(kObjectGroupConnectionsCapacity);
1004   retainer_infos_.Clear();
1005   implicit_ref_connections_.Clear();
1006 }
1007
1008
1009 EternalHandles::EternalHandles() : size_(0) {
1010   for (unsigned i = 0; i < ARRAY_SIZE(singleton_handles_); i++) {
1011     singleton_handles_[i] = kInvalidIndex;
1012   }
1013 }
1014
1015
1016 EternalHandles::~EternalHandles() {
1017   for (int i = 0; i < blocks_.length(); i++) delete[] blocks_[i];
1018 }
1019
1020
1021 void EternalHandles::IterateAllRoots(ObjectVisitor* visitor) {
1022   int limit = size_;
1023   for (int i = 0; i < blocks_.length(); i++) {
1024     DCHECK(limit > 0);
1025     Object** block = blocks_[i];
1026     visitor->VisitPointers(block, block + Min(limit, kSize));
1027     limit -= kSize;
1028   }
1029 }
1030
1031
1032 void EternalHandles::IterateNewSpaceRoots(ObjectVisitor* visitor) {
1033   for (int i = 0; i < new_space_indices_.length(); i++) {
1034     visitor->VisitPointer(GetLocation(new_space_indices_[i]));
1035   }
1036 }
1037
1038
1039 void EternalHandles::PostGarbageCollectionProcessing(Heap* heap) {
1040   int last = 0;
1041   for (int i = 0; i < new_space_indices_.length(); i++) {
1042     int index = new_space_indices_[i];
1043     if (heap->InNewSpace(*GetLocation(index))) {
1044       new_space_indices_[last++] = index;
1045     }
1046   }
1047   new_space_indices_.Rewind(last);
1048 }
1049
1050
1051 void EternalHandles::Create(Isolate* isolate, Object* object, int* index) {
1052   DCHECK_EQ(kInvalidIndex, *index);
1053   if (object == NULL) return;
1054   DCHECK_NE(isolate->heap()->the_hole_value(), object);
1055   int block = size_ >> kShift;
1056   int offset = size_ & kMask;
1057   // need to resize
1058   if (offset == 0) {
1059     Object** next_block = new Object*[kSize];
1060     Object* the_hole = isolate->heap()->the_hole_value();
1061     MemsetPointer(next_block, the_hole, kSize);
1062     blocks_.Add(next_block);
1063   }
1064   DCHECK_EQ(isolate->heap()->the_hole_value(), blocks_[block][offset]);
1065   blocks_[block][offset] = object;
1066   if (isolate->heap()->InNewSpace(object)) {
1067     new_space_indices_.Add(size_);
1068   }
1069   *index = size_++;
1070 }
1071
1072
1073 } }  // namespace v8::internal