deps/v8/src/heap.cc

   1 // Copyright 2012 the V8 project authors. All rights reserved.
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   5 //
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   7 //       notice, this list of conditions and the following disclaimer.
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  27
  28 #include "v8.h"
  29
  30 #include "accessors.h"
  31 #include "api.h"
  32 #include "bootstrapper.h"
  33 #include "codegen.h"
  34 #include "compilation-cache.h"
  35 #include "debug.h"
  36 #include "deoptimizer.h"
  37 #include "global-handles.h"
  38 #include "heap-profiler.h"
  39 #include "incremental-marking.h"
  40 #include "liveobjectlist-inl.h"
  41 #include "mark-compact.h"
  42 #include "natives.h"
  43 #include "objects-visiting.h"
  44 #include "objects-visiting-inl.h"
  45 #include "once.h"
  46 #include "runtime-profiler.h"
  47 #include "scopeinfo.h"
  48 #include "snapshot.h"
  49 #include "store-buffer.h"
  50 #include "v8threads.h"
  51 #include "v8utils.h"
  52 #include "vm-state-inl.h"
  53 #if V8_TARGET_ARCH_ARM && !V8_INTERPRETED_REGEXP
  54 #include "regexp-macro-assembler.h"
  55 #include "arm/regexp-macro-assembler-arm.h"
  56 #endif
  57 #if V8_TARGET_ARCH_MIPS && !V8_INTERPRETED_REGEXP
  58 #include "regexp-macro-assembler.h"
  59 #include "mips/regexp-macro-assembler-mips.h"
  60 #endif
  61
  62 namespace v8 {
  63 namespace internal {
  64
  65
  66 Heap::Heap()
  67     : isolate_(NULL),
  68 // semispace_size_ should be a power of 2 and old_generation_size_ should be
  69 // a multiple of Page::kPageSize.
  70 #if defined(V8_TARGET_ARCH_X64)
  71 #define LUMP_OF_MEMORY (2 * MB)
  72       code_range_size_(512*MB),
  73 #else
  74 #define LUMP_OF_MEMORY MB
  75       code_range_size_(0),
  76 #endif
  77 #if defined(ANDROID)
  78       reserved_semispace_size_(4 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
  79       max_semispace_size_(4 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
  80       initial_semispace_size_(Page::kPageSize),
  81       max_old_generation_size_(192*MB),
  82       max_executable_size_(max_old_generation_size_),
  83 #else
  84       reserved_semispace_size_(8 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
  85       max_semispace_size_(8 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
  86       initial_semispace_size_(Page::kPageSize),
  87       max_old_generation_size_(700ul * LUMP_OF_MEMORY),
  88       max_executable_size_(256l * LUMP_OF_MEMORY),
  89 #endif
  90
  91 // Variables set based on semispace_size_ and old_generation_size_ in
  92 // ConfigureHeap (survived_since_last_expansion_, external_allocation_limit_)
  93 // Will be 4 * reserved_semispace_size_ to ensure that young
  94 // generation can be aligned to its size.
  95       survived_since_last_expansion_(0),
  96       sweep_generation_(0),
  97       always_allocate_scope_depth_(0),
  98       linear_allocation_scope_depth_(0),
  99       contexts_disposed_(0),
 100       global_ic_age_(0),
 101       flush_monomorphic_ics_(false),
 102       scan_on_scavenge_pages_(0),
 103       new_space_(this),
 104       old_pointer_space_(NULL),
 105       old_data_space_(NULL),
 106       code_space_(NULL),
 107       map_space_(NULL),
 108       cell_space_(NULL),
 109       lo_space_(NULL),
 110       gc_state_(NOT_IN_GC),
 111       gc_post_processing_depth_(0),
 112       ms_count_(0),
 113       gc_count_(0),
 114       remembered_unmapped_pages_index_(0),
 115       unflattened_strings_length_(0),
 116 #ifdef DEBUG
 117       allocation_allowed_(true),
 118       allocation_timeout_(0),
 119       disallow_allocation_failure_(false),
 120       debug_utils_(NULL),
 121 #endif  // DEBUG
 122       new_space_high_promotion_mode_active_(false),
 123       old_gen_promotion_limit_(kMinimumPromotionLimit),
 124       old_gen_allocation_limit_(kMinimumAllocationLimit),
 125       old_gen_limit_factor_(1),
 126       size_of_old_gen_at_last_old_space_gc_(0),
 127       external_allocation_limit_(0),
 128       amount_of_external_allocated_memory_(0),
 129       amount_of_external_allocated_memory_at_last_global_gc_(0),
 130       old_gen_exhausted_(false),
 131       store_buffer_rebuilder_(store_buffer()),
 132       hidden_symbol_(NULL),
 133       global_gc_prologue_callback_(NULL),
 134       global_gc_epilogue_callback_(NULL),
 135       gc_safe_size_of_old_object_(NULL),
 136       total_regexp_code_generated_(0),
 137       tracer_(NULL),
 138       young_survivors_after_last_gc_(0),
 139       high_survival_rate_period_length_(0),
 140       survival_rate_(0),
 141       previous_survival_rate_trend_(Heap::STABLE),
 142       survival_rate_trend_(Heap::STABLE),
 143       max_gc_pause_(0),
 144       total_gc_time_ms_(0),
 145       max_alive_after_gc_(0),
 146       min_in_mutator_(kMaxInt),
 147       alive_after_last_gc_(0),
 148       last_gc_end_timestamp_(0.0),
 149       store_buffer_(this),
 150       marking_(this),
 151       incremental_marking_(this),
 152       number_idle_notifications_(0),
 153       last_idle_notification_gc_count_(0),
 154       last_idle_notification_gc_count_init_(false),
 155       mark_sweeps_since_idle_round_started_(0),
 156       ms_count_at_last_idle_notification_(0),
 157       gc_count_at_last_idle_gc_(0),
 158       scavenges_since_last_idle_round_(kIdleScavengeThreshold),
 159       promotion_queue_(this),
 160       configured_(false),
 161       chunks_queued_for_free_(NULL),
 162       relocation_mutex_(NULL) {
 163   // Allow build-time customization of the max semispace size. Building
 164   // V8 with snapshots and a non-default max semispace size is much
 165   // easier if you can define it as part of the build environment.
 166 #if defined(V8_MAX_SEMISPACE_SIZE)
 167   max_semispace_size_ = reserved_semispace_size_ = V8_MAX_SEMISPACE_SIZE;
 168 #endif
 169
 170   intptr_t max_virtual = OS::MaxVirtualMemory();
 171
 172   if (max_virtual > 0) {
 173     if (code_range_size_ > 0) {
 174       // Reserve no more than 1/8 of the memory for the code range.
 175       code_range_size_ = Min(code_range_size_, max_virtual >> 3);
 176     }
 177   }
 178
 179   memset(roots_, 0, sizeof(roots_[0]) * kRootListLength);
 180   native_contexts_list_ = NULL;
 181   mark_compact_collector_.heap_ = this;
 182   external_string_table_.heap_ = this;
 183   // Put a dummy entry in the remembered pages so we can find the list the
 184   // minidump even if there are no real unmapped pages.
 185   RememberUnmappedPage(NULL, false);
 186
 187   ClearObjectStats(true);
 188 }
 189
 190
 191 intptr_t Heap::Capacity() {
 192   if (!HasBeenSetUp()) return 0;
 193
 194   return new_space_.Capacity() +
 195       old_pointer_space_->Capacity() +
 196       old_data_space_->Capacity() +
 197       code_space_->Capacity() +
 198       map_space_->Capacity() +
 199       cell_space_->Capacity();
 200 }
 201
 202
 203 intptr_t Heap::CommittedMemory() {
 204   if (!HasBeenSetUp()) return 0;
 205
 206   return new_space_.CommittedMemory() +
 207       old_pointer_space_->CommittedMemory() +
 208       old_data_space_->CommittedMemory() +
 209       code_space_->CommittedMemory() +
 210       map_space_->CommittedMemory() +
 211       cell_space_->CommittedMemory() +
 212       lo_space_->Size();
 213 }
 214
 215 intptr_t Heap::CommittedMemoryExecutable() {
 216   if (!HasBeenSetUp()) return 0;
 217
 218   return isolate()->memory_allocator()->SizeExecutable();
 219 }
 220
 221
 222 intptr_t Heap::Available() {
 223   if (!HasBeenSetUp()) return 0;
 224
 225   return new_space_.Available() +
 226       old_pointer_space_->Available() +
 227       old_data_space_->Available() +
 228       code_space_->Available() +
 229       map_space_->Available() +
 230       cell_space_->Available();
 231 }
 232
 233
 234 bool Heap::HasBeenSetUp() {
 235   return old_pointer_space_ != NULL &&
 236          old_data_space_ != NULL &&
 237          code_space_ != NULL &&
 238          map_space_ != NULL &&
 239          cell_space_ != NULL &&
 240          lo_space_ != NULL;
 241 }
 242
 243
 244 int Heap::GcSafeSizeOfOldObject(HeapObject* object) {
 245   if (IntrusiveMarking::IsMarked(object)) {
 246     return IntrusiveMarking::SizeOfMarkedObject(object);
 247   }
 248   return object->SizeFromMap(object->map());
 249 }
 250
 251
 252 GarbageCollector Heap::SelectGarbageCollector(AllocationSpace space,
 253                                               const char** reason) {
 254   // Is global GC requested?
 255   if (space != NEW_SPACE) {
 256     isolate_->counters()->gc_compactor_caused_by_request()->Increment();
 257     *reason = "GC in old space requested";
 258     return MARK_COMPACTOR;
 259   }
 260
 261   if (FLAG_gc_global || (FLAG_stress_compaction && (gc_count_ & 1) != 0)) {
 262     *reason = "GC in old space forced by flags";
 263     return MARK_COMPACTOR;
 264   }
 265
 266   // Is enough data promoted to justify a global GC?
 267   if (OldGenerationPromotionLimitReached()) {
 268     isolate_->counters()->gc_compactor_caused_by_promoted_data()->Increment();
 269     *reason = "promotion limit reached";
 270     return MARK_COMPACTOR;
 271   }
 272
 273   // Have allocation in OLD and LO failed?
 274   if (old_gen_exhausted_) {
 275     isolate_->counters()->
 276         gc_compactor_caused_by_oldspace_exhaustion()->Increment();
 277     *reason = "old generations exhausted";
 278     return MARK_COMPACTOR;
 279   }
 280
 281   // Is there enough space left in OLD to guarantee that a scavenge can
 282   // succeed?
 283   //
 284   // Note that MemoryAllocator->MaxAvailable() undercounts the memory available
 285   // for object promotion. It counts only the bytes that the memory
 286   // allocator has not yet allocated from the OS and assigned to any space,
 287   // and does not count available bytes already in the old space or code
 288   // space.  Undercounting is safe---we may get an unrequested full GC when
 289   // a scavenge would have succeeded.
 290   if (isolate_->memory_allocator()->MaxAvailable() <= new_space_.Size()) {
 291     isolate_->counters()->
 292         gc_compactor_caused_by_oldspace_exhaustion()->Increment();
 293     *reason = "scavenge might not succeed";
 294     return MARK_COMPACTOR;
 295   }
 296
 297   // Default
 298   *reason = NULL;
 299   return SCAVENGER;
 300 }
 301
 302
 303 // TODO(1238405): Combine the infrastructure for --heap-stats and
 304 // --log-gc to avoid the complicated preprocessor and flag testing.
 305 void Heap::ReportStatisticsBeforeGC() {
 306   // Heap::ReportHeapStatistics will also log NewSpace statistics when
 307   // compiled --log-gc is set.  The following logic is used to avoid
 308   // double logging.
 309 #ifdef DEBUG
 310   if (FLAG_heap_stats || FLAG_log_gc) new_space_.CollectStatistics();
 311   if (FLAG_heap_stats) {
 312     ReportHeapStatistics("Before GC");
 313   } else if (FLAG_log_gc) {
 314     new_space_.ReportStatistics();
 315   }
 316   if (FLAG_heap_stats || FLAG_log_gc) new_space_.ClearHistograms();
 317 #else
 318   if (FLAG_log_gc) {
 319     new_space_.CollectStatistics();
 320     new_space_.ReportStatistics();
 321     new_space_.ClearHistograms();
 322   }
 323 #endif  // DEBUG
 324 }
 325
 326
 327 void Heap::PrintShortHeapStatistics() {
 328   if (!FLAG_trace_gc_verbose) return;
 329   PrintPID("Memory allocator,   used: %6" V8_PTR_PREFIX "d KB"
 330                ", available: %6" V8_PTR_PREFIX "d KB\n",
 331            isolate_->memory_allocator()->Size() / KB,
 332            isolate_->memory_allocator()->Available() / KB);
 333   PrintPID("New space,          used: %6" V8_PTR_PREFIX "d KB"
 334                ", available: %6" V8_PTR_PREFIX "d KB"
 335                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 336            new_space_.Size() / KB,
 337            new_space_.Available() / KB,
 338            new_space_.CommittedMemory() / KB);
 339   PrintPID("Old pointers,       used: %6" V8_PTR_PREFIX "d KB"
 340                ", available: %6" V8_PTR_PREFIX "d KB"
 341                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 342            old_pointer_space_->SizeOfObjects() / KB,
 343            old_pointer_space_->Available() / KB,
 344            old_pointer_space_->CommittedMemory() / KB);
 345   PrintPID("Old data space,     used: %6" V8_PTR_PREFIX "d KB"
 346                ", available: %6" V8_PTR_PREFIX "d KB"
 347                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 348            old_data_space_->SizeOfObjects() / KB,
 349            old_data_space_->Available() / KB,
 350            old_data_space_->CommittedMemory() / KB);
 351   PrintPID("Code space,         used: %6" V8_PTR_PREFIX "d KB"
 352                ", available: %6" V8_PTR_PREFIX "d KB"
 353                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 354            code_space_->SizeOfObjects() / KB,
 355            code_space_->Available() / KB,
 356            code_space_->CommittedMemory() / KB);
 357   PrintPID("Map space,          used: %6" V8_PTR_PREFIX "d KB"
 358                ", available: %6" V8_PTR_PREFIX "d KB"
 359                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 360            map_space_->SizeOfObjects() / KB,
 361            map_space_->Available() / KB,
 362            map_space_->CommittedMemory() / KB);
 363   PrintPID("Cell space,         used: %6" V8_PTR_PREFIX "d KB"
 364                ", available: %6" V8_PTR_PREFIX "d KB"
 365                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 366            cell_space_->SizeOfObjects() / KB,
 367            cell_space_->Available() / KB,
 368            cell_space_->CommittedMemory() / KB);
 369   PrintPID("Large object space, used: %6" V8_PTR_PREFIX "d KB"
 370                ", available: %6" V8_PTR_PREFIX "d KB"
 371                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 372            lo_space_->SizeOfObjects() / KB,
 373            lo_space_->Available() / KB,
 374            lo_space_->CommittedMemory() / KB);
 375   PrintPID("All spaces,         used: %6" V8_PTR_PREFIX "d KB"
 376                ", available: %6" V8_PTR_PREFIX "d KB"
 377                ", committed: %6" V8_PTR_PREFIX "d KB\n",
 378            this->SizeOfObjects() / KB,
 379            this->Available() / KB,
 380            this->CommittedMemory() / KB);
 381   PrintPID("Total time spent in GC  : %d ms\n", total_gc_time_ms_);
 382 }
 383
 384
 385 // TODO(1238405): Combine the infrastructure for --heap-stats and
 386 // --log-gc to avoid the complicated preprocessor and flag testing.
 387 void Heap::ReportStatisticsAfterGC() {
 388   // Similar to the before GC, we use some complicated logic to ensure that
 389   // NewSpace statistics are logged exactly once when --log-gc is turned on.
 390 #if defined(DEBUG)
 391   if (FLAG_heap_stats) {
 392     new_space_.CollectStatistics();
 393     ReportHeapStatistics("After GC");
 394   } else if (FLAG_log_gc) {
 395     new_space_.ReportStatistics();
 396   }
 397 #else
 398   if (FLAG_log_gc) new_space_.ReportStatistics();
 399 #endif  // DEBUG
 400 }
 401
 402
 403 void Heap::GarbageCollectionPrologue() {
 404   isolate_->transcendental_cache()->Clear();
 405   ClearJSFunctionResultCaches();
 406   gc_count_++;
 407   unflattened_strings_length_ = 0;
 408
 409 #ifdef VERIFY_HEAP
 410   if (FLAG_verify_heap) {
 411     Verify();
 412   }
 413 #endif
 414
 415 #ifdef DEBUG
 416   ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);
 417   allow_allocation(false);
 418
 419   if (FLAG_gc_verbose) Print();
 420
 421   ReportStatisticsBeforeGC();
 422 #endif  // DEBUG
 423
 424   LiveObjectList::GCPrologue();
 425   store_buffer()->GCPrologue();
 426 }
 427
 428
 429 intptr_t Heap::SizeOfObjects() {
 430   intptr_t total = 0;
 431   AllSpaces spaces;
 432   for (Space* space = spaces.next(); space != NULL; space = spaces.next()) {
 433     total += space->SizeOfObjects();
 434   }
 435   return total;
 436 }
 437
 438
 439 void Heap::RepairFreeListsAfterBoot() {
 440   PagedSpaces spaces;
 441   for (PagedSpace* space = spaces.next();
 442        space != NULL;
 443        space = spaces.next()) {
 444     space->RepairFreeListsAfterBoot();
 445   }
 446 }
 447
 448
 449 void Heap::GarbageCollectionEpilogue() {
 450   store_buffer()->GCEpilogue();
 451   LiveObjectList::GCEpilogue();
 452
 453   // In release mode, we only zap the from space under heap verification.
 454   if (Heap::ShouldZapGarbage()) {
 455     ZapFromSpace();
 456   }
 457
 458 #ifdef VERIFY_HEAP
 459   if (FLAG_verify_heap) {
 460     Verify();
 461   }
 462 #endif
 463
 464 #ifdef DEBUG
 465   allow_allocation(true);
 466   if (FLAG_print_global_handles) isolate_->global_handles()->Print();
 467   if (FLAG_print_handles) PrintHandles();
 468   if (FLAG_gc_verbose) Print();
 469   if (FLAG_code_stats) ReportCodeStatistics("After GC");
 470 #endif
 471
 472   isolate_->counters()->alive_after_last_gc()->Set(
 473       static_cast<int>(SizeOfObjects()));
 474
 475   isolate_->counters()->symbol_table_capacity()->Set(
 476       symbol_table()->Capacity());
 477   isolate_->counters()->number_of_symbols()->Set(
 478       symbol_table()->NumberOfElements());
 479
 480   if (CommittedMemory() > 0) {
 481     isolate_->counters()->external_fragmentation_total()->AddSample(
 482         static_cast<int>(100 - (SizeOfObjects() * 100.0) / CommittedMemory()));
 483
 484     isolate_->counters()->heap_fraction_map_space()->AddSample(
 485         static_cast<int>(
 486             (map_space()->CommittedMemory() * 100.0) / CommittedMemory()));
 487     isolate_->counters()->heap_fraction_cell_space()->AddSample(
 488         static_cast<int>(
 489             (cell_space()->CommittedMemory() * 100.0) / CommittedMemory()));
 490
 491     isolate_->counters()->heap_sample_total_committed()->AddSample(
 492         static_cast<int>(CommittedMemory() / KB));
 493     isolate_->counters()->heap_sample_total_used()->AddSample(
 494         static_cast<int>(SizeOfObjects() / KB));
 495     isolate_->counters()->heap_sample_map_space_committed()->AddSample(
 496         static_cast<int>(map_space()->CommittedMemory() / KB));
 497     isolate_->counters()->heap_sample_cell_space_committed()->AddSample(
 498         static_cast<int>(cell_space()->CommittedMemory() / KB));
 499   }
 500
 501 #define UPDATE_COUNTERS_FOR_SPACE(space)                                       \
 502   isolate_->counters()->space##_bytes_available()->Set(                        \
 503       static_cast<int>(space()->Available()));                                 \
 504   isolate_->counters()->space##_bytes_committed()->Set(                        \
 505       static_cast<int>(space()->CommittedMemory()));                           \
 506   isolate_->counters()->space##_bytes_used()->Set(                             \
 507       static_cast<int>(space()->SizeOfObjects()));
 508 #define UPDATE_FRAGMENTATION_FOR_SPACE(space)                                  \
 509   if (space()->CommittedMemory() > 0) {                                        \
 510     isolate_->counters()->external_fragmentation_##space()->AddSample(         \
 511         static_cast<int>(100 -                                                 \
 512             (space()->SizeOfObjects() * 100.0) / space()->CommittedMemory())); \
 513   }
 514 #define UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(space)                     \
 515   UPDATE_COUNTERS_FOR_SPACE(space)                                             \
 516   UPDATE_FRAGMENTATION_FOR_SPACE(space)
 517
 518   UPDATE_COUNTERS_FOR_SPACE(new_space)
 519   UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(old_pointer_space)
 520   UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(old_data_space)
 521   UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(code_space)
 522   UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(map_space)
 523   UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(cell_space)
 524   UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE(lo_space)
 525 #undef UPDATE_COUNTERS_FOR_SPACE
 526 #undef UPDATE_FRAGMENTATION_FOR_SPACE
 527 #undef UPDATE_COUNTERS_AND_FRAGMENTATION_FOR_SPACE
 528
 529 #if defined(DEBUG)
 530   ReportStatisticsAfterGC();
 531 #endif  // DEBUG
 532 #ifdef ENABLE_DEBUGGER_SUPPORT
 533   isolate_->debug()->AfterGarbageCollection();
 534 #endif  // ENABLE_DEBUGGER_SUPPORT
 535 }
 536
 537
 538 void Heap::CollectAllGarbage(int flags, const char* gc_reason) {
 539   // Since we are ignoring the return value, the exact choice of space does
 540   // not matter, so long as we do not specify NEW_SPACE, which would not
 541   // cause a full GC.
 542   mark_compact_collector_.SetFlags(flags);
 543   CollectGarbage(OLD_POINTER_SPACE, gc_reason);
 544   mark_compact_collector_.SetFlags(kNoGCFlags);
 545 }
 546
 547
 548 void Heap::CollectAllAvailableGarbage(const char* gc_reason) {
 549   // Since we are ignoring the return value, the exact choice of space does
 550   // not matter, so long as we do not specify NEW_SPACE, which would not
 551   // cause a full GC.
 552   // Major GC would invoke weak handle callbacks on weakly reachable
 553   // handles, but won't collect weakly reachable objects until next
 554   // major GC.  Therefore if we collect aggressively and weak handle callback
 555   // has been invoked, we rerun major GC to release objects which become
 556   // garbage.
 557   // Note: as weak callbacks can execute arbitrary code, we cannot
 558   // hope that eventually there will be no weak callbacks invocations.
 559   // Therefore stop recollecting after several attempts.
 560   mark_compact_collector()->SetFlags(kMakeHeapIterableMask |
 561                                      kReduceMemoryFootprintMask);
 562   isolate_->compilation_cache()->Clear();
 563   const int kMaxNumberOfAttempts = 7;
 564   for (int attempt = 0; attempt < kMaxNumberOfAttempts; attempt++) {
 565     if (!CollectGarbage(OLD_POINTER_SPACE, MARK_COMPACTOR, gc_reason, NULL)) {
 566       break;
 567     }
 568   }
 569   mark_compact_collector()->SetFlags(kNoGCFlags);
 570   new_space_.Shrink();
 571   UncommitFromSpace();
 572   Shrink();
 573   incremental_marking()->UncommitMarkingDeque();
 574 }
 575
 576
 577 bool Heap::CollectGarbage(AllocationSpace space,
 578                           GarbageCollector collector,
 579                           const char* gc_reason,
 580                           const char* collector_reason) {
 581   // The VM is in the GC state until exiting this function.
 582   VMState state(isolate_, GC);
 583
 584 #ifdef DEBUG
 585   // Reset the allocation timeout to the GC interval, but make sure to
 586   // allow at least a few allocations after a collection. The reason
 587   // for this is that we have a lot of allocation sequences and we
 588   // assume that a garbage collection will allow the subsequent
 589   // allocation attempts to go through.
 590   allocation_timeout_ = Max(6, FLAG_gc_interval);
 591 #endif
 592
 593   if (collector == SCAVENGER && !incremental_marking()->IsStopped()) {
 594     if (FLAG_trace_incremental_marking) {
 595       PrintF("[IncrementalMarking] Scavenge during marking.\n");
 596     }
 597   }
 598
 599   if (collector == MARK_COMPACTOR &&
 600       !mark_compact_collector()->abort_incremental_marking_ &&
 601       !incremental_marking()->IsStopped() &&
 602       !incremental_marking()->should_hurry() &&
 603       FLAG_incremental_marking_steps) {
 604     // Make progress in incremental marking.
 605     const intptr_t kStepSizeWhenDelayedByScavenge = 1 * MB;
 606     incremental_marking()->Step(kStepSizeWhenDelayedByScavenge,
 607                                 IncrementalMarking::NO_GC_VIA_STACK_GUARD);
 608     if (!incremental_marking()->IsComplete()) {
 609       if (FLAG_trace_incremental_marking) {
 610         PrintF("[IncrementalMarking] Delaying MarkSweep.\n");
 611       }
 612       collector = SCAVENGER;
 613       collector_reason = "incremental marking delaying mark-sweep";
 614     }
 615   }
 616
 617   bool next_gc_likely_to_collect_more = false;
 618
 619   { GCTracer tracer(this, gc_reason, collector_reason);
 620     GarbageCollectionPrologue();
 621     // The GC count was incremented in the prologue.  Tell the tracer about
 622     // it.
 623     tracer.set_gc_count(gc_count_);
 624
 625     // Tell the tracer which collector we've selected.
 626     tracer.set_collector(collector);
 627
 628     HistogramTimer* rate = (collector == SCAVENGER)
 629         ? isolate_->counters()->gc_scavenger()
 630         : isolate_->counters()->gc_compactor();
 631     rate->Start();
 632     next_gc_likely_to_collect_more =
 633         PerformGarbageCollection(collector, &tracer);
 634     rate->Stop();
 635
 636     ASSERT(collector == SCAVENGER || incremental_marking()->IsStopped());
 637
 638     // This can do debug callbacks and restart incremental marking.
 639     GarbageCollectionEpilogue();
 640   }
 641
 642   if (incremental_marking()->IsStopped()) {
 643     if (incremental_marking()->WorthActivating() && NextGCIsLikelyToBeFull()) {
 644       incremental_marking()->Start();
 645     }
 646   }
 647
 648   return next_gc_likely_to_collect_more;
 649 }
 650
 651
 652 void Heap::PerformScavenge() {
 653   GCTracer tracer(this, NULL, NULL);
 654   if (incremental_marking()->IsStopped()) {
 655     PerformGarbageCollection(SCAVENGER, &tracer);
 656   } else {
 657     PerformGarbageCollection(MARK_COMPACTOR, &tracer);
 658   }
 659 }
 660
 661
 662 #ifdef VERIFY_HEAP
 663 // Helper class for verifying the symbol table.
 664 class SymbolTableVerifier : public ObjectVisitor {
 665  public:
 666   void VisitPointers(Object** start, Object** end) {
 667     // Visit all HeapObject pointers in [start, end).
 668     for (Object** p = start; p < end; p++) {
 669       if ((*p)->IsHeapObject()) {
 670         // Check that the symbol is actually a symbol.
 671         CHECK((*p)->IsTheHole() || (*p)->IsUndefined() || (*p)->IsSymbol());
 672       }
 673     }
 674   }
 675 };
 676
 677
 678 static void VerifySymbolTable() {
 679   SymbolTableVerifier verifier;
 680   HEAP->symbol_table()->IterateElements(&verifier);
 681 }
 682 #endif  // VERIFY_HEAP
 683
 684
 685 static bool AbortIncrementalMarkingAndCollectGarbage(
 686     Heap* heap,
 687     AllocationSpace space,
 688     const char* gc_reason = NULL) {
 689   heap->mark_compact_collector()->SetFlags(Heap::kAbortIncrementalMarkingMask);
 690   bool result = heap->CollectGarbage(space, gc_reason);
 691   heap->mark_compact_collector()->SetFlags(Heap::kNoGCFlags);
 692   return result;
 693 }
 694
 695
 696 void Heap::ReserveSpace(
 697     int *sizes,
 698     Address *locations_out) {
 699   bool gc_performed = true;
 700   int counter = 0;
 701   static const int kThreshold = 20;
 702   while (gc_performed && counter++ < kThreshold) {
 703     gc_performed = false;
 704     ASSERT(NEW_SPACE == FIRST_PAGED_SPACE - 1);
 705     for (int space = NEW_SPACE; space <= LAST_PAGED_SPACE; space++) {
 706       if (sizes[space] != 0) {
 707         MaybeObject* allocation;
 708         if (space == NEW_SPACE) {
 709           allocation = new_space()->AllocateRaw(sizes[space]);
 710         } else {
 711           allocation = paged_space(space)->AllocateRaw(sizes[space]);
 712         }
 713         FreeListNode* node;
 714         if (!allocation->To<FreeListNode>(&node)) {
 715           if (space == NEW_SPACE) {
 716             Heap::CollectGarbage(NEW_SPACE,
 717                                  "failed to reserve space in the new space");
 718           } else {
 719             AbortIncrementalMarkingAndCollectGarbage(
 720                 this,
 721                 static_cast<AllocationSpace>(space),
 722                 "failed to reserve space in paged space");
 723           }
 724           gc_performed = true;
 725           break;
 726         } else {
 727           // Mark with a free list node, in case we have a GC before
 728           // deserializing.
 729           node->set_size(this, sizes[space]);
 730           locations_out[space] = node->address();
 731         }
 732       }
 733     }
 734   }
 735
 736   if (gc_performed) {
 737     // Failed to reserve the space after several attempts.
 738     V8::FatalProcessOutOfMemory("Heap::ReserveSpace");
 739   }
 740 }
 741
 742
 743 void Heap::EnsureFromSpaceIsCommitted() {
 744   if (new_space_.CommitFromSpaceIfNeeded()) return;
 745
 746   // Committing memory to from space failed.
 747   // Try shrinking and try again.
 748   Shrink();
 749   if (new_space_.CommitFromSpaceIfNeeded()) return;
 750
 751   // Committing memory to from space failed again.
 752   // Memory is exhausted and we will die.
 753   V8::FatalProcessOutOfMemory("Committing semi space failed.");
 754 }
 755
 756
 757 void Heap::ClearJSFunctionResultCaches() {
 758   if (isolate_->bootstrapper()->IsActive()) return;
 759
 760   Object* context = native_contexts_list_;
 761   while (!context->IsUndefined()) {
 762     // Get the caches for this context. GC can happen when the context
 763     // is not fully initialized, so the caches can be undefined.
 764     Object* caches_or_undefined =
 765         Context::cast(context)->get(Context::JSFUNCTION_RESULT_CACHES_INDEX);
 766     if (!caches_or_undefined->IsUndefined()) {
 767       FixedArray* caches = FixedArray::cast(caches_or_undefined);
 768       // Clear the caches:
 769       int length = caches->length();
 770       for (int i = 0; i < length; i++) {
 771         JSFunctionResultCache::cast(caches->get(i))->Clear();
 772       }
 773     }
 774     // Get the next context:
 775     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
 776   }
 777 }
 778
 779
 780
 781 void Heap::ClearNormalizedMapCaches() {
 782   if (isolate_->bootstrapper()->IsActive() &&
 783       !incremental_marking()->IsMarking()) {
 784     return;
 785   }
 786
 787   Object* context = native_contexts_list_;
 788   while (!context->IsUndefined()) {
 789     // GC can happen when the context is not fully initialized,
 790     // so the cache can be undefined.
 791     Object* cache =
 792         Context::cast(context)->get(Context::NORMALIZED_MAP_CACHE_INDEX);
 793     if (!cache->IsUndefined()) {
 794       NormalizedMapCache::cast(cache)->Clear();
 795     }
 796     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
 797   }
 798 }
 799
 800
 801 void Heap::UpdateSurvivalRateTrend(int start_new_space_size) {
 802   double survival_rate =
 803       (static_cast<double>(young_survivors_after_last_gc_) * 100) /
 804       start_new_space_size;
 805
 806   if (survival_rate > kYoungSurvivalRateHighThreshold) {
 807     high_survival_rate_period_length_++;
 808   } else {
 809     high_survival_rate_period_length_ = 0;
 810   }
 811
 812   if (survival_rate < kYoungSurvivalRateLowThreshold) {
 813     low_survival_rate_period_length_++;
 814   } else {
 815     low_survival_rate_period_length_ = 0;
 816   }
 817
 818   double survival_rate_diff = survival_rate_ - survival_rate;
 819
 820   if (survival_rate_diff > kYoungSurvivalRateAllowedDeviation) {
 821     set_survival_rate_trend(DECREASING);
 822   } else if (survival_rate_diff < -kYoungSurvivalRateAllowedDeviation) {
 823     set_survival_rate_trend(INCREASING);
 824   } else {
 825     set_survival_rate_trend(STABLE);
 826   }
 827
 828   survival_rate_ = survival_rate;
 829 }
 830
 831 bool Heap::PerformGarbageCollection(GarbageCollector collector,
 832                                     GCTracer* tracer) {
 833   bool next_gc_likely_to_collect_more = false;
 834
 835   if (collector != SCAVENGER) {
 836     PROFILE(isolate_, CodeMovingGCEvent());
 837   }
 838
 839 #ifdef VERIFY_HEAP
 840   if (FLAG_verify_heap) {
 841     VerifySymbolTable();
 842   }
 843 #endif
 844
 845   if (collector == MARK_COMPACTOR && global_gc_prologue_callback_) {
 846     ASSERT(!allocation_allowed_);
 847     GCTracer::Scope scope(tracer, GCTracer::Scope::EXTERNAL);
 848     global_gc_prologue_callback_();
 849   }
 850
 851   GCType gc_type =
 852       collector == MARK_COMPACTOR ? kGCTypeMarkSweepCompact : kGCTypeScavenge;
 853
 854   for (int i = 0; i < gc_prologue_callbacks_.length(); ++i) {
 855     if (gc_type & gc_prologue_callbacks_[i].gc_type) {
 856       gc_prologue_callbacks_[i].callback(gc_type, kNoGCCallbackFlags);
 857     }
 858   }
 859
 860   EnsureFromSpaceIsCommitted();
 861
 862   int start_new_space_size = Heap::new_space()->SizeAsInt();
 863
 864   if (IsHighSurvivalRate()) {
 865     // We speed up the incremental marker if it is running so that it
 866     // does not fall behind the rate of promotion, which would cause a
 867     // constantly growing old space.
 868     incremental_marking()->NotifyOfHighPromotionRate();
 869   }
 870
 871   if (collector == MARK_COMPACTOR) {
 872     // Perform mark-sweep with optional compaction.
 873     MarkCompact(tracer);
 874     sweep_generation_++;
 875     bool high_survival_rate_during_scavenges = IsHighSurvivalRate() &&
 876         IsStableOrIncreasingSurvivalTrend();
 877
 878     UpdateSurvivalRateTrend(start_new_space_size);
 879
 880     size_of_old_gen_at_last_old_space_gc_ = PromotedSpaceSizeOfObjects();
 881
 882     if (high_survival_rate_during_scavenges &&
 883         IsStableOrIncreasingSurvivalTrend()) {
 884       // Stable high survival rates of young objects both during partial and
 885       // full collection indicate that mutator is either building or modifying
 886       // a structure with a long lifetime.
 887       // In this case we aggressively raise old generation memory limits to
 888       // postpone subsequent mark-sweep collection and thus trade memory
 889       // space for the mutation speed.
 890       old_gen_limit_factor_ = 2;
 891     } else {
 892       old_gen_limit_factor_ = 1;
 893     }
 894
 895     old_gen_promotion_limit_ =
 896         OldGenPromotionLimit(size_of_old_gen_at_last_old_space_gc_);
 897     old_gen_allocation_limit_ =
 898         OldGenAllocationLimit(size_of_old_gen_at_last_old_space_gc_);
 899
 900     old_gen_exhausted_ = false;
 901   } else {
 902     tracer_ = tracer;
 903     Scavenge();
 904     tracer_ = NULL;
 905
 906     UpdateSurvivalRateTrend(start_new_space_size);
 907   }
 908
 909   if (!new_space_high_promotion_mode_active_ &&
 910       new_space_.Capacity() == new_space_.MaximumCapacity() &&
 911       IsStableOrIncreasingSurvivalTrend() &&
 912       IsHighSurvivalRate()) {
 913     // Stable high survival rates even though young generation is at
 914     // maximum capacity indicates that most objects will be promoted.
 915     // To decrease scavenger pauses and final mark-sweep pauses, we
 916     // have to limit maximal capacity of the young generation.
 917     new_space_high_promotion_mode_active_ = true;
 918     if (FLAG_trace_gc) {
 919       PrintPID("Limited new space size due to high promotion rate: %d MB\n",
 920                new_space_.InitialCapacity() / MB);
 921     }
 922   } else if (new_space_high_promotion_mode_active_ &&
 923       IsStableOrDecreasingSurvivalTrend() &&
 924       IsLowSurvivalRate()) {
 925     // Decreasing low survival rates might indicate that the above high
 926     // promotion mode is over and we should allow the young generation
 927     // to grow again.
 928     new_space_high_promotion_mode_active_ = false;
 929     if (FLAG_trace_gc) {
 930       PrintPID("Unlimited new space size due to low promotion rate: %d MB\n",
 931                new_space_.MaximumCapacity() / MB);
 932     }
 933   }
 934
 935   if (new_space_high_promotion_mode_active_ &&
 936       new_space_.Capacity() > new_space_.InitialCapacity()) {
 937     new_space_.Shrink();
 938   }
 939
 940   isolate_->counters()->objs_since_last_young()->Set(0);
 941
 942   gc_post_processing_depth_++;
 943   { DisableAssertNoAllocation allow_allocation;
 944     GCTracer::Scope scope(tracer, GCTracer::Scope::EXTERNAL);
 945     next_gc_likely_to_collect_more =
 946         isolate_->global_handles()->PostGarbageCollectionProcessing(collector);
 947   }
 948   gc_post_processing_depth_--;
 949
 950   // Update relocatables.
 951   Relocatable::PostGarbageCollectionProcessing();
 952
 953   if (collector == MARK_COMPACTOR) {
 954     // Register the amount of external allocated memory.
 955     amount_of_external_allocated_memory_at_last_global_gc_ =
 956         amount_of_external_allocated_memory_;
 957   }
 958
 959   GCCallbackFlags callback_flags = kNoGCCallbackFlags;
 960   for (int i = 0; i < gc_epilogue_callbacks_.length(); ++i) {
 961     if (gc_type & gc_epilogue_callbacks_[i].gc_type) {
 962       gc_epilogue_callbacks_[i].callback(gc_type, callback_flags);
 963     }
 964   }
 965
 966   if (collector == MARK_COMPACTOR && global_gc_epilogue_callback_) {
 967     ASSERT(!allocation_allowed_);
 968     GCTracer::Scope scope(tracer, GCTracer::Scope::EXTERNAL);
 969     global_gc_epilogue_callback_();
 970   }
 971
 972 #ifdef VERIFY_HEAP
 973   if (FLAG_verify_heap) {
 974     VerifySymbolTable();
 975   }
 976 #endif
 977
 978   return next_gc_likely_to_collect_more;
 979 }
 980
 981
 982 void Heap::MarkCompact(GCTracer* tracer) {
 983   gc_state_ = MARK_COMPACT;
 984   LOG(isolate_, ResourceEvent("markcompact", "begin"));
 985
 986   mark_compact_collector_.Prepare(tracer);
 987
 988   ms_count_++;
 989   tracer->set_full_gc_count(ms_count_);
 990
 991   MarkCompactPrologue();
 992
 993   mark_compact_collector_.CollectGarbage();
 994
 995   LOG(isolate_, ResourceEvent("markcompact", "end"));
 996
 997   gc_state_ = NOT_IN_GC;
 998
 999   isolate_->counters()->objs_since_last_full()->Set(0);
1000
1001   contexts_disposed_ = 0;
1002
1003   flush_monomorphic_ics_ = false;
1004 }
1005
1006
1007 void Heap::MarkCompactPrologue() {
1008   // At any old GC clear the keyed lookup cache to enable collection of unused
1009   // maps.
1010   isolate_->keyed_lookup_cache()->Clear();
1011   isolate_->context_slot_cache()->Clear();
1012   isolate_->descriptor_lookup_cache()->Clear();
1013   RegExpResultsCache::Clear(string_split_cache());
1014   RegExpResultsCache::Clear(regexp_multiple_cache());
1015
1016   isolate_->compilation_cache()->MarkCompactPrologue();
1017
1018   CompletelyClearInstanceofCache();
1019
1020   FlushNumberStringCache();
1021   if (FLAG_cleanup_code_caches_at_gc) {
1022     polymorphic_code_cache()->set_cache(undefined_value());
1023   }
1024
1025   ClearNormalizedMapCaches();
1026 }
1027
1028
1029 Object* Heap::FindCodeObject(Address a) {
1030   return isolate()->inner_pointer_to_code_cache()->
1031       GcSafeFindCodeForInnerPointer(a);
1032 }
1033
1034
1035 // Helper class for copying HeapObjects
1036 class ScavengeVisitor: public ObjectVisitor {
1037  public:
1038   explicit ScavengeVisitor(Heap* heap) : heap_(heap) {}
1039
1040   void VisitPointer(Object** p) { ScavengePointer(p); }
1041
1042   void VisitPointers(Object** start, Object** end) {
1043     // Copy all HeapObject pointers in [start, end)
1044     for (Object** p = start; p < end; p++) ScavengePointer(p);
1045   }
1046
1047  private:
1048   void ScavengePointer(Object** p) {
1049     Object* object = *p;
1050     if (!heap_->InNewSpace(object)) return;
1051     Heap::ScavengeObject(reinterpret_cast<HeapObject**>(p),
1052                          reinterpret_cast<HeapObject*>(object));
1053   }
1054
1055   Heap* heap_;
1056 };
1057
1058
1059 #ifdef VERIFY_HEAP
1060 // Visitor class to verify pointers in code or data space do not point into
1061 // new space.
1062 class VerifyNonPointerSpacePointersVisitor: public ObjectVisitor {
1063  public:
1064   void VisitPointers(Object** start, Object**end) {
1065     for (Object** current = start; current < end; current++) {
1066       if ((*current)->IsHeapObject()) {
1067         CHECK(!HEAP->InNewSpace(HeapObject::cast(*current)));
1068       }
1069     }
1070   }
1071 };
1072
1073
1074 static void VerifyNonPointerSpacePointers() {
1075   // Verify that there are no pointers to new space in spaces where we
1076   // do not expect them.
1077   VerifyNonPointerSpacePointersVisitor v;
1078   HeapObjectIterator code_it(HEAP->code_space());
1079   for (HeapObject* object = code_it.Next();
1080        object != NULL; object = code_it.Next())
1081     object->Iterate(&v);
1082
1083   // The old data space was normally swept conservatively so that the iterator
1084   // doesn't work, so we normally skip the next bit.
1085   if (!HEAP->old_data_space()->was_swept_conservatively()) {
1086     HeapObjectIterator data_it(HEAP->old_data_space());
1087     for (HeapObject* object = data_it.Next();
1088          object != NULL; object = data_it.Next())
1089       object->Iterate(&v);
1090   }
1091 }
1092 #endif  // VERIFY_HEAP
1093
1094
1095 void Heap::CheckNewSpaceExpansionCriteria() {
1096   if (new_space_.Capacity() < new_space_.MaximumCapacity() &&
1097       survived_since_last_expansion_ > new_space_.Capacity() &&
1098       !new_space_high_promotion_mode_active_) {
1099     // Grow the size of new space if there is room to grow, enough data
1100     // has survived scavenge since the last expansion and we are not in
1101     // high promotion mode.
1102     new_space_.Grow();
1103     survived_since_last_expansion_ = 0;
1104   }
1105 }
1106
1107
1108 static bool IsUnscavengedHeapObject(Heap* heap, Object** p) {
1109   return heap->InNewSpace(*p) &&
1110       !HeapObject::cast(*p)->map_word().IsForwardingAddress();
1111 }
1112
1113
1114 void Heap::ScavengeStoreBufferCallback(
1115     Heap* heap,
1116     MemoryChunk* page,
1117     StoreBufferEvent event) {
1118   heap->store_buffer_rebuilder_.Callback(page, event);
1119 }
1120
1121
1122 void StoreBufferRebuilder::Callback(MemoryChunk* page, StoreBufferEvent event) {
1123   if (event == kStoreBufferStartScanningPagesEvent) {
1124     start_of_current_page_ = NULL;
1125     current_page_ = NULL;
1126   } else if (event == kStoreBufferScanningPageEvent) {
1127     if (current_page_ != NULL) {
1128       // If this page already overflowed the store buffer during this iteration.
1129       if (current_page_->scan_on_scavenge()) {
1130         // Then we should wipe out the entries that have been added for it.
1131         store_buffer_->SetTop(start_of_current_page_);
1132       } else if (store_buffer_->Top() - start_of_current_page_ >=
1133                  (store_buffer_->Limit() - store_buffer_->Top()) >> 2) {
1134         // Did we find too many pointers in the previous page?  The heuristic is
1135         // that no page can take more then 1/5 the remaining slots in the store
1136         // buffer.
1137         current_page_->set_scan_on_scavenge(true);
1138         store_buffer_->SetTop(start_of_current_page_);
1139       } else {
1140         // In this case the page we scanned took a reasonable number of slots in
1141         // the store buffer.  It has now been rehabilitated and is no longer
1142         // marked scan_on_scavenge.
1143         ASSERT(!current_page_->scan_on_scavenge());
1144       }
1145     }
1146     start_of_current_page_ = store_buffer_->Top();
1147     current_page_ = page;
1148   } else if (event == kStoreBufferFullEvent) {
1149     // The current page overflowed the store buffer again.  Wipe out its entries
1150     // in the store buffer and mark it scan-on-scavenge again.  This may happen
1151     // several times while scanning.
1152     if (current_page_ == NULL) {
1153       // Store Buffer overflowed while scanning promoted objects.  These are not
1154       // in any particular page, though they are likely to be clustered by the
1155       // allocation routines.
1156       store_buffer_->EnsureSpace(StoreBuffer::kStoreBufferSize);
1157     } else {
1158       // Store Buffer overflowed while scanning a particular old space page for
1159       // pointers to new space.
1160       ASSERT(current_page_ == page);
1161       ASSERT(page != NULL);
1162       current_page_->set_scan_on_scavenge(true);
1163       ASSERT(start_of_current_page_ != store_buffer_->Top());
1164       store_buffer_->SetTop(start_of_current_page_);
1165     }
1166   } else {
1167     UNREACHABLE();
1168   }
1169 }
1170
1171
1172 void PromotionQueue::Initialize() {
1173   // Assumes that a NewSpacePage exactly fits a number of promotion queue
1174   // entries (where each is a pair of intptr_t). This allows us to simplify
1175   // the test fpr when to switch pages.
1176   ASSERT((Page::kPageSize - MemoryChunk::kBodyOffset) % (2 * kPointerSize)
1177          == 0);
1178   limit_ = reinterpret_cast<intptr_t*>(heap_->new_space()->ToSpaceStart());
1179   front_ = rear_ =
1180       reinterpret_cast<intptr_t*>(heap_->new_space()->ToSpaceEnd());
1181   emergency_stack_ = NULL;
1182   guard_ = false;
1183 }
1184
1185
1186 void PromotionQueue::RelocateQueueHead() {
1187   ASSERT(emergency_stack_ == NULL);
1188
1189   Page* p = Page::FromAllocationTop(reinterpret_cast<Address>(rear_));
1190   intptr_t* head_start = rear_;
1191   intptr_t* head_end =
1192       Min(front_, reinterpret_cast<intptr_t*>(p->area_end()));
1193
1194   int entries_count =
1195       static_cast<int>(head_end - head_start) / kEntrySizeInWords;
1196
1197   emergency_stack_ = new List<Entry>(2 * entries_count);
1198
1199   while (head_start != head_end) {
1200     int size = static_cast<int>(*(head_start++));
1201     HeapObject* obj = reinterpret_cast<HeapObject*>(*(head_start++));
1202     emergency_stack_->Add(Entry(obj, size));
1203   }
1204   rear_ = head_end;
1205 }
1206
1207
1208 class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
1209  public:
1210   explicit ScavengeWeakObjectRetainer(Heap* heap) : heap_(heap) { }
1211
1212   virtual Object* RetainAs(Object* object) {
1213     if (!heap_->InFromSpace(object)) {
1214       return object;
1215     }
1216
1217     MapWord map_word = HeapObject::cast(object)->map_word();
1218     if (map_word.IsForwardingAddress()) {
1219       return map_word.ToForwardingAddress();
1220     }
1221     return NULL;
1222   }
1223
1224  private:
1225   Heap* heap_;
1226 };
1227
1228
1229 void Heap::Scavenge() {
1230   RelocationLock relocation_lock(this);
1231
1232 #ifdef VERIFY_HEAP
1233   if (FLAG_verify_heap) VerifyNonPointerSpacePointers();
1234 #endif
1235
1236   gc_state_ = SCAVENGE;
1237
1238   // Implements Cheney's copying algorithm
1239   LOG(isolate_, ResourceEvent("scavenge", "begin"));
1240
1241   // Clear descriptor cache.
1242   isolate_->descriptor_lookup_cache()->Clear();
1243
1244   // Used for updating survived_since_last_expansion_ at function end.
1245   intptr_t survived_watermark = PromotedSpaceSizeOfObjects();
1246
1247   CheckNewSpaceExpansionCriteria();
1248
1249   SelectScavengingVisitorsTable();
1250
1251   incremental_marking()->PrepareForScavenge();
1252
1253   AdvanceSweepers(static_cast<int>(new_space_.Size()));
1254
1255   // Flip the semispaces.  After flipping, to space is empty, from space has
1256   // live objects.
1257   new_space_.Flip();
1258   new_space_.ResetAllocationInfo();
1259
1260   // We need to sweep newly copied objects which can be either in the
1261   // to space or promoted to the old generation.  For to-space
1262   // objects, we treat the bottom of the to space as a queue.  Newly
1263   // copied and unswept objects lie between a 'front' mark and the
1264   // allocation pointer.
1265   //
1266   // Promoted objects can go into various old-generation spaces, and
1267   // can be allocated internally in the spaces (from the free list).
1268   // We treat the top of the to space as a queue of addresses of
1269   // promoted objects.  The addresses of newly promoted and unswept
1270   // objects lie between a 'front' mark and a 'rear' mark that is
1271   // updated as a side effect of promoting an object.
1272   //
1273   // There is guaranteed to be enough room at the top of the to space
1274   // for the addresses of promoted objects: every object promoted
1275   // frees up its size in bytes from the top of the new space, and
1276   // objects are at least one pointer in size.
1277   Address new_space_front = new_space_.ToSpaceStart();
1278   promotion_queue_.Initialize();
1279
1280 #ifdef DEBUG
1281   store_buffer()->Clean();
1282 #endif
1283
1284   ScavengeVisitor scavenge_visitor(this);
1285   // Copy roots.
1286   IterateRoots(&scavenge_visitor, VISIT_ALL_IN_SCAVENGE);
1287
1288   // Copy objects reachable from the old generation.
1289   {
1290     StoreBufferRebuildScope scope(this,
1291                                   store_buffer(),
1292                                   &ScavengeStoreBufferCallback);
1293     store_buffer()->IteratePointersToNewSpace(&ScavengeObject);
1294   }
1295
1296   // Copy objects reachable from cells by scavenging cell values directly.
1297   HeapObjectIterator cell_iterator(cell_space_);
1298   for (HeapObject* heap_object = cell_iterator.Next();
1299        heap_object != NULL;
1300        heap_object = cell_iterator.Next()) {
1301     if (heap_object->IsJSGlobalPropertyCell()) {
1302       JSGlobalPropertyCell* cell = JSGlobalPropertyCell::cast(heap_object);
1303       Address value_address = cell->ValueAddress();
1304       scavenge_visitor.VisitPointer(reinterpret_cast<Object**>(value_address));
1305     }
1306   }
1307
1308   // Scavenge object reachable from the native contexts list directly.
1309   scavenge_visitor.VisitPointer(BitCast<Object**>(&native_contexts_list_));
1310
1311   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
1312   isolate_->global_handles()->IdentifyNewSpaceWeakIndependentHandles(
1313       &IsUnscavengedHeapObject);
1314   isolate_->global_handles()->IterateNewSpaceWeakIndependentRoots(
1315       &scavenge_visitor);
1316   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
1317
1318   UpdateNewSpaceReferencesInExternalStringTable(
1319       &UpdateNewSpaceReferenceInExternalStringTableEntry);
1320
1321   promotion_queue_.Destroy();
1322
1323   LiveObjectList::UpdateReferencesForScavengeGC();
1324   if (!FLAG_watch_ic_patching) {
1325     isolate()->runtime_profiler()->UpdateSamplesAfterScavenge();
1326   }
1327   incremental_marking()->UpdateMarkingDequeAfterScavenge();
1328
1329   ScavengeWeakObjectRetainer weak_object_retainer(this);
1330   ProcessWeakReferences(&weak_object_retainer);
1331
1332   ASSERT(new_space_front == new_space_.top());
1333
1334   // Set age mark.
1335   new_space_.set_age_mark(new_space_.top());
1336
1337   new_space_.LowerInlineAllocationLimit(
1338       new_space_.inline_allocation_limit_step());
1339
1340   // Update how much has survived scavenge.
1341   IncrementYoungSurvivorsCounter(static_cast<int>(
1342       (PromotedSpaceSizeOfObjects() - survived_watermark) + new_space_.Size()));
1343
1344   LOG(isolate_, ResourceEvent("scavenge", "end"));
1345
1346   gc_state_ = NOT_IN_GC;
1347
1348   scavenges_since_last_idle_round_++;
1349 }
1350
1351
1352 String* Heap::UpdateNewSpaceReferenceInExternalStringTableEntry(Heap* heap,
1353                                                                 Object** p) {
1354   MapWord first_word = HeapObject::cast(*p)->map_word();
1355
1356   if (!first_word.IsForwardingAddress()) {
1357     // Unreachable external string can be finalized.
1358     heap->FinalizeExternalString(String::cast(*p));
1359     return NULL;
1360   }
1361
1362   // String is still reachable.
1363   return String::cast(first_word.ToForwardingAddress());
1364 }
1365
1366
1367 void Heap::UpdateNewSpaceReferencesInExternalStringTable(
1368     ExternalStringTableUpdaterCallback updater_func) {
1369 #ifdef VERIFY_HEAP
1370   if (FLAG_verify_heap) {
1371     external_string_table_.Verify();
1372   }
1373 #endif
1374
1375   if (external_string_table_.new_space_strings_.is_empty()) return;
1376
1377   Object** start = &external_string_table_.new_space_strings_[0];
1378   Object** end = start + external_string_table_.new_space_strings_.length();
1379   Object** last = start;
1380
1381   for (Object** p = start; p < end; ++p) {
1382     ASSERT(InFromSpace(*p));
1383     String* target = updater_func(this, p);
1384
1385     if (target == NULL) continue;
1386
1387     ASSERT(target->IsExternalString());
1388
1389     if (InNewSpace(target)) {
1390       // String is still in new space.  Update the table entry.
1391       *last = target;
1392       ++last;
1393     } else {
1394       // String got promoted.  Move it to the old string list.
1395       external_string_table_.AddOldString(target);
1396     }
1397   }
1398
1399   ASSERT(last <= end);
1400   external_string_table_.ShrinkNewStrings(static_cast<int>(last - start));
1401 }
1402
1403
1404 void Heap::UpdateReferencesInExternalStringTable(
1405     ExternalStringTableUpdaterCallback updater_func) {
1406
1407   // Update old space string references.
1408   if (external_string_table_.old_space_strings_.length() > 0) {
1409     Object** start = &external_string_table_.old_space_strings_[0];
1410     Object** end = start + external_string_table_.old_space_strings_.length();
1411     for (Object** p = start; p < end; ++p) *p = updater_func(this, p);
1412   }
1413
1414   UpdateNewSpaceReferencesInExternalStringTable(updater_func);
1415 }
1416
1417
1418 static Object* ProcessFunctionWeakReferences(Heap* heap,
1419                                              Object* function,
1420                                              WeakObjectRetainer* retainer,
1421                                              bool record_slots) {
1422   Object* undefined = heap->undefined_value();
1423   Object* head = undefined;
1424   JSFunction* tail = NULL;
1425   Object* candidate = function;
1426   while (candidate != undefined) {
1427     // Check whether to keep the candidate in the list.
1428     JSFunction* candidate_function = reinterpret_cast<JSFunction*>(candidate);
1429     Object* retain = retainer->RetainAs(candidate);
1430     if (retain != NULL) {
1431       if (head == undefined) {
1432         // First element in the list.
1433         head = retain;
1434       } else {
1435         // Subsequent elements in the list.
1436         ASSERT(tail != NULL);
1437         tail->set_next_function_link(retain);
1438         if (record_slots) {
1439           Object** next_function =
1440               HeapObject::RawField(tail, JSFunction::kNextFunctionLinkOffset);
1441           heap->mark_compact_collector()->RecordSlot(
1442               next_function, next_function, retain);
1443         }
1444       }
1445       // Retained function is new tail.
1446       candidate_function = reinterpret_cast<JSFunction*>(retain);
1447       tail = candidate_function;
1448
1449       ASSERT(retain->IsUndefined() || retain->IsJSFunction());
1450
1451       if (retain == undefined) break;
1452     }
1453
1454     // Move to next element in the list.
1455     candidate = candidate_function->next_function_link();
1456   }
1457
1458   // Terminate the list if there is one or more elements.
1459   if (tail != NULL) {
1460     tail->set_next_function_link(undefined);
1461   }
1462
1463   return head;
1464 }
1465
1466
1467 void Heap::ProcessWeakReferences(WeakObjectRetainer* retainer) {
1468   Object* undefined = undefined_value();
1469   Object* head = undefined;
1470   Context* tail = NULL;
1471   Object* candidate = native_contexts_list_;
1472
1473   // We don't record weak slots during marking or scavenges.
1474   // Instead we do it once when we complete mark-compact cycle.
1475   // Note that write barrier has no effect if we are already in the middle of
1476   // compacting mark-sweep cycle and we have to record slots manually.
1477   bool record_slots =
1478       gc_state() == MARK_COMPACT &&
1479       mark_compact_collector()->is_compacting();
1480
1481   while (candidate != undefined) {
1482     // Check whether to keep the candidate in the list.
1483     Context* candidate_context = reinterpret_cast<Context*>(candidate);
1484     Object* retain = retainer->RetainAs(candidate);
1485     if (retain != NULL) {
1486       if (head == undefined) {
1487         // First element in the list.
1488         head = retain;
1489       } else {
1490         // Subsequent elements in the list.
1491         ASSERT(tail != NULL);
1492         tail->set_unchecked(this,
1493                             Context::NEXT_CONTEXT_LINK,
1494                             retain,
1495                             UPDATE_WRITE_BARRIER);
1496
1497         if (record_slots) {
1498           Object** next_context =
1499               HeapObject::RawField(
1500                   tail, FixedArray::SizeFor(Context::NEXT_CONTEXT_LINK));
1501           mark_compact_collector()->RecordSlot(
1502               next_context, next_context, retain);
1503         }
1504       }
1505       // Retained context is new tail.
1506       candidate_context = reinterpret_cast<Context*>(retain);
1507       tail = candidate_context;
1508
1509       if (retain == undefined) break;
1510
1511       // Process the weak list of optimized functions for the context.
1512       Object* function_list_head =
1513           ProcessFunctionWeakReferences(
1514               this,
1515               candidate_context->get(Context::OPTIMIZED_FUNCTIONS_LIST),
1516               retainer,
1517               record_slots);
1518       candidate_context->set_unchecked(this,
1519                                        Context::OPTIMIZED_FUNCTIONS_LIST,
1520                                        function_list_head,
1521                                        UPDATE_WRITE_BARRIER);
1522       if (record_slots) {
1523         Object** optimized_functions =
1524             HeapObject::RawField(
1525                 tail, FixedArray::SizeFor(Context::OPTIMIZED_FUNCTIONS_LIST));
1526         mark_compact_collector()->RecordSlot(
1527             optimized_functions, optimized_functions, function_list_head);
1528       }
1529     }
1530
1531     // Move to next element in the list.
1532     candidate = candidate_context->get(Context::NEXT_CONTEXT_LINK);
1533   }
1534
1535   // Terminate the list if there is one or more elements.
1536   if (tail != NULL) {
1537     tail->set_unchecked(this,
1538                         Context::NEXT_CONTEXT_LINK,
1539                         Heap::undefined_value(),
1540                         UPDATE_WRITE_BARRIER);
1541   }
1542
1543   // Update the head of the list of contexts.
1544   native_contexts_list_ = head;
1545 }
1546
1547
1548 void Heap::VisitExternalResources(v8::ExternalResourceVisitor* visitor) {
1549   AssertNoAllocation no_allocation;
1550
1551   class VisitorAdapter : public ObjectVisitor {
1552    public:
1553     explicit VisitorAdapter(v8::ExternalResourceVisitor* visitor)
1554         : visitor_(visitor) {}
1555     virtual void VisitPointers(Object** start, Object** end) {
1556       for (Object** p = start; p < end; p++) {
1557         if ((*p)->IsExternalString()) {
1558           visitor_->VisitExternalString(Utils::ToLocal(
1559               Handle<String>(String::cast(*p))));
1560         }
1561       }
1562     }
1563    private:
1564     v8::ExternalResourceVisitor* visitor_;
1565   } visitor_adapter(visitor);
1566   external_string_table_.Iterate(&visitor_adapter);
1567 }
1568
1569
1570 class NewSpaceScavenger : public StaticNewSpaceVisitor<NewSpaceScavenger> {
1571  public:
1572   static inline void VisitPointer(Heap* heap, Object** p) {
1573     Object* object = *p;
1574     if (!heap->InNewSpace(object)) return;
1575     Heap::ScavengeObject(reinterpret_cast<HeapObject**>(p),
1576                          reinterpret_cast<HeapObject*>(object));
1577   }
1578 };
1579
1580
1581 Address Heap::DoScavenge(ObjectVisitor* scavenge_visitor,
1582                          Address new_space_front) {
1583   do {
1584     SemiSpace::AssertValidRange(new_space_front, new_space_.top());
1585     // The addresses new_space_front and new_space_.top() define a
1586     // queue of unprocessed copied objects.  Process them until the
1587     // queue is empty.
1588     while (new_space_front != new_space_.top()) {
1589       if (!NewSpacePage::IsAtEnd(new_space_front)) {
1590         HeapObject* object = HeapObject::FromAddress(new_space_front);
1591         new_space_front +=
1592           NewSpaceScavenger::IterateBody(object->map(), object);
1593       } else {
1594         new_space_front =
1595             NewSpacePage::FromLimit(new_space_front)->next_page()->area_start();
1596       }
1597     }
1598
1599     // Promote and process all the to-be-promoted objects.
1600     {
1601       StoreBufferRebuildScope scope(this,
1602                                     store_buffer(),
1603                                     &ScavengeStoreBufferCallback);
1604       while (!promotion_queue()->is_empty()) {
1605         HeapObject* target;
1606         int size;
1607         promotion_queue()->remove(&target, &size);
1608
1609         // Promoted object might be already partially visited
1610         // during old space pointer iteration. Thus we search specificly
1611         // for pointers to from semispace instead of looking for pointers
1612         // to new space.
1613         ASSERT(!target->IsMap());
1614         IterateAndMarkPointersToFromSpace(target->address(),
1615                                           target->address() + size,
1616                                           &ScavengeObject);
1617       }
1618     }
1619
1620     // Take another spin if there are now unswept objects in new space
1621     // (there are currently no more unswept promoted objects).
1622   } while (new_space_front != new_space_.top());
1623
1624   return new_space_front;
1625 }
1626
1627
1628 STATIC_ASSERT((FixedDoubleArray::kHeaderSize & kDoubleAlignmentMask) == 0);
1629
1630
1631 INLINE(static HeapObject* EnsureDoubleAligned(Heap* heap,
1632                                               HeapObject* object,
1633                                               int size));
1634
1635 static HeapObject* EnsureDoubleAligned(Heap* heap,
1636                                        HeapObject* object,
1637                                        int size) {
1638   if ((OffsetFrom(object->address()) & kDoubleAlignmentMask) != 0) {
1639     heap->CreateFillerObjectAt(object->address(), kPointerSize);
1640     return HeapObject::FromAddress(object->address() + kPointerSize);
1641   } else {
1642     heap->CreateFillerObjectAt(object->address() + size - kPointerSize,
1643                                kPointerSize);
1644     return object;
1645   }
1646 }
1647
1648
1649 enum LoggingAndProfiling {
1650   LOGGING_AND_PROFILING_ENABLED,
1651   LOGGING_AND_PROFILING_DISABLED
1652 };
1653
1654
1655 enum MarksHandling { TRANSFER_MARKS, IGNORE_MARKS };
1656
1657
1658 template<MarksHandling marks_handling,
1659          LoggingAndProfiling logging_and_profiling_mode>
1660 class ScavengingVisitor : public StaticVisitorBase {
1661  public:
1662   static void Initialize() {
1663     table_.Register(kVisitSeqAsciiString, &EvacuateSeqAsciiString);
1664     table_.Register(kVisitSeqTwoByteString, &EvacuateSeqTwoByteString);
1665     table_.Register(kVisitShortcutCandidate, &EvacuateShortcutCandidate);
1666     table_.Register(kVisitByteArray, &EvacuateByteArray);
1667     table_.Register(kVisitFixedArray, &EvacuateFixedArray);
1668     table_.Register(kVisitFixedDoubleArray, &EvacuateFixedDoubleArray);
1669
1670     table_.Register(kVisitNativeContext,
1671                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
1672                         template VisitSpecialized<Context::kSize>);
1673
1674     table_.Register(kVisitConsString,
1675                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
1676                         template VisitSpecialized<ConsString::kSize>);
1677
1678     table_.Register(kVisitSlicedString,
1679                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
1680                         template VisitSpecialized<SlicedString::kSize>);
1681
1682     table_.Register(kVisitSharedFunctionInfo,
1683                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
1684                         template VisitSpecialized<SharedFunctionInfo::kSize>);
1685
1686     table_.Register(kVisitJSWeakMap,
1687                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
1688                     Visit);
1689
1690     table_.Register(kVisitJSRegExp,
1691                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
1692                     Visit);
1693
1694     if (marks_handling == IGNORE_MARKS) {
1695       table_.Register(kVisitJSFunction,
1696                       &ObjectEvacuationStrategy<POINTER_OBJECT>::
1697                           template VisitSpecialized<JSFunction::kSize>);
1698     } else {
1699       table_.Register(kVisitJSFunction, &EvacuateJSFunction);
1700     }
1701
1702     table_.RegisterSpecializations<ObjectEvacuationStrategy<DATA_OBJECT>,
1703                                    kVisitDataObject,
1704                                    kVisitDataObjectGeneric>();
1705
1706     table_.RegisterSpecializations<ObjectEvacuationStrategy<POINTER_OBJECT>,
1707                                    kVisitJSObject,
1708                                    kVisitJSObjectGeneric>();
1709
1710     table_.RegisterSpecializations<ObjectEvacuationStrategy<POINTER_OBJECT>,
1711                                    kVisitStruct,
1712                                    kVisitStructGeneric>();
1713   }
1714
1715   static VisitorDispatchTable<ScavengingCallback>* GetTable() {
1716     return &table_;
1717   }
1718
1719  private:
1720   enum ObjectContents  { DATA_OBJECT, POINTER_OBJECT };
1721   enum SizeRestriction { SMALL, UNKNOWN_SIZE };
1722
1723   static void RecordCopiedObject(Heap* heap, HeapObject* obj) {
1724     bool should_record = false;
1725 #ifdef DEBUG
1726     should_record = FLAG_heap_stats;
1727 #endif
1728     should_record = should_record || FLAG_log_gc;
1729     if (should_record) {
1730       if (heap->new_space()->Contains(obj)) {
1731         heap->new_space()->RecordAllocation(obj);
1732       } else {
1733         heap->new_space()->RecordPromotion(obj);
1734       }
1735     }
1736   }
1737
1738   // Helper function used by CopyObject to copy a source object to an
1739   // allocated target object and update the forwarding pointer in the source
1740   // object.  Returns the target object.
1741   INLINE(static void MigrateObject(Heap* heap,
1742                                    HeapObject* source,
1743                                    HeapObject* target,
1744                                    int size)) {
1745     // Copy the content of source to target.
1746     heap->CopyBlock(target->address(), source->address(), size);
1747
1748     // Set the forwarding address.
1749     source->set_map_word(MapWord::FromForwardingAddress(target));
1750
1751     if (logging_and_profiling_mode == LOGGING_AND_PROFILING_ENABLED) {
1752       // Update NewSpace stats if necessary.
1753       RecordCopiedObject(heap, target);
1754       HEAP_PROFILE(heap, ObjectMoveEvent(source->address(), target->address()));
1755       Isolate* isolate = heap->isolate();
1756       if (isolate->logger()->is_logging_code_events() ||
1757           CpuProfiler::is_profiling(isolate)) {
1758         if (target->IsSharedFunctionInfo()) {
1759           PROFILE(isolate, SharedFunctionInfoMoveEvent(
1760               source->address(), target->address()));
1761         }
1762       }
1763     }
1764
1765     if (marks_handling == TRANSFER_MARKS) {
1766       if (Marking::TransferColor(source, target)) {
1767         MemoryChunk::IncrementLiveBytesFromGC(target->address(), size);
1768       }
1769     }
1770   }
1771
1772
1773   template<ObjectContents object_contents,
1774            SizeRestriction size_restriction,
1775            int alignment>
1776   static inline void EvacuateObject(Map* map,
1777                                     HeapObject** slot,
1778                                     HeapObject* object,
1779                                     int object_size) {
1780     SLOW_ASSERT((size_restriction != SMALL) ||
1781                 (object_size <= Page::kMaxNonCodeHeapObjectSize));
1782     SLOW_ASSERT(object->Size() == object_size);
1783
1784     int allocation_size = object_size;
1785     if (alignment != kObjectAlignment) {
1786       ASSERT(alignment == kDoubleAlignment);
1787       allocation_size += kPointerSize;
1788     }
1789
1790     Heap* heap = map->GetHeap();
1791     if (heap->ShouldBePromoted(object->address(), object_size)) {
1792       MaybeObject* maybe_result;
1793
1794       if ((size_restriction != SMALL) &&
1795           (allocation_size > Page::kMaxNonCodeHeapObjectSize)) {
1796         maybe_result = heap->lo_space()->AllocateRaw(allocation_size,
1797                                                      NOT_EXECUTABLE);
1798       } else {
1799         if (object_contents == DATA_OBJECT) {
1800           maybe_result = heap->old_data_space()->AllocateRaw(allocation_size);
1801         } else {
1802           maybe_result =
1803               heap->old_pointer_space()->AllocateRaw(allocation_size);
1804         }
1805       }
1806
1807       Object* result = NULL;  // Initialization to please compiler.
1808       if (maybe_result->ToObject(&result)) {
1809         HeapObject* target = HeapObject::cast(result);
1810
1811         if (alignment != kObjectAlignment) {
1812           target = EnsureDoubleAligned(heap, target, allocation_size);
1813         }
1814
1815         // Order is important: slot might be inside of the target if target
1816         // was allocated over a dead object and slot comes from the store
1817         // buffer.
1818         *slot = target;
1819         MigrateObject(heap, object, target, object_size);
1820
1821         if (object_contents == POINTER_OBJECT) {
1822           if (map->instance_type() == JS_FUNCTION_TYPE) {
1823             heap->promotion_queue()->insert(
1824                 target, JSFunction::kNonWeakFieldsEndOffset);
1825           } else {
1826             heap->promotion_queue()->insert(target, object_size);
1827           }
1828         }
1829
1830         heap->tracer()->increment_promoted_objects_size(object_size);
1831         return;
1832       }
1833     }
1834     MaybeObject* allocation = heap->new_space()->AllocateRaw(allocation_size);
1835     heap->promotion_queue()->SetNewLimit(heap->new_space()->top());
1836     Object* result = allocation->ToObjectUnchecked();
1837     HeapObject* target = HeapObject::cast(result);
1838
1839     if (alignment != kObjectAlignment) {
1840       target = EnsureDoubleAligned(heap, target, allocation_size);
1841     }
1842
1843     // Order is important: slot might be inside of the target if target
1844     // was allocated over a dead object and slot comes from the store
1845     // buffer.
1846     *slot = target;
1847     MigrateObject(heap, object, target, object_size);
1848     return;
1849   }
1850
1851
1852   static inline void EvacuateJSFunction(Map* map,
1853                                         HeapObject** slot,
1854                                         HeapObject* object) {
1855     ObjectEvacuationStrategy<POINTER_OBJECT>::
1856         template VisitSpecialized<JSFunction::kSize>(map, slot, object);
1857
1858     HeapObject* target = *slot;
1859     MarkBit mark_bit = Marking::MarkBitFrom(target);
1860     if (Marking::IsBlack(mark_bit)) {
1861       // This object is black and it might not be rescanned by marker.
1862       // We should explicitly record code entry slot for compaction because
1863       // promotion queue processing (IterateAndMarkPointersToFromSpace) will
1864       // miss it as it is not HeapObject-tagged.
1865       Address code_entry_slot =
1866           target->address() + JSFunction::kCodeEntryOffset;
1867       Code* code = Code::cast(Code::GetObjectFromEntryAddress(code_entry_slot));
1868       map->GetHeap()->mark_compact_collector()->
1869           RecordCodeEntrySlot(code_entry_slot, code);
1870     }
1871   }
1872
1873
1874   static inline void EvacuateFixedArray(Map* map,
1875                                         HeapObject** slot,
1876                                         HeapObject* object) {
1877     int object_size = FixedArray::BodyDescriptor::SizeOf(map, object);
1878     EvacuateObject<POINTER_OBJECT, UNKNOWN_SIZE, kObjectAlignment>(map,
1879                                                  slot,
1880                                                  object,
1881                                                  object_size);
1882   }
1883
1884
1885   static inline void EvacuateFixedDoubleArray(Map* map,
1886                                               HeapObject** slot,
1887                                               HeapObject* object) {
1888     int length = reinterpret_cast<FixedDoubleArray*>(object)->length();
1889     int object_size = FixedDoubleArray::SizeFor(length);
1890     EvacuateObject<DATA_OBJECT, UNKNOWN_SIZE, kDoubleAlignment>(
1891         map,
1892         slot,
1893         object,
1894         object_size);
1895   }
1896
1897
1898   static inline void EvacuateByteArray(Map* map,
1899                                        HeapObject** slot,
1900                                        HeapObject* object) {
1901     int object_size = reinterpret_cast<ByteArray*>(object)->ByteArraySize();
1902     EvacuateObject<DATA_OBJECT, UNKNOWN_SIZE, kObjectAlignment>(
1903         map, slot, object, object_size);
1904   }
1905
1906
1907   static inline void EvacuateSeqAsciiString(Map* map,
1908                                             HeapObject** slot,
1909                                             HeapObject* object) {
1910     int object_size = SeqAsciiString::cast(object)->
1911         SeqAsciiStringSize(map->instance_type());
1912     EvacuateObject<DATA_OBJECT, UNKNOWN_SIZE, kObjectAlignment>(
1913         map, slot, object, object_size);
1914   }
1915
1916
1917   static inline void EvacuateSeqTwoByteString(Map* map,
1918                                               HeapObject** slot,
1919                                               HeapObject* object) {
1920     int object_size = SeqTwoByteString::cast(object)->
1921         SeqTwoByteStringSize(map->instance_type());
1922     EvacuateObject<DATA_OBJECT, UNKNOWN_SIZE, kObjectAlignment>(
1923         map, slot, object, object_size);
1924   }
1925
1926
1927   static inline bool IsShortcutCandidate(int type) {
1928     return ((type & kShortcutTypeMask) == kShortcutTypeTag);
1929   }
1930
1931   static inline void EvacuateShortcutCandidate(Map* map,
1932                                                HeapObject** slot,
1933                                                HeapObject* object) {
1934     ASSERT(IsShortcutCandidate(map->instance_type()));
1935
1936     Heap* heap = map->GetHeap();
1937
1938     if (marks_handling == IGNORE_MARKS &&
1939         ConsString::cast(object)->unchecked_second() ==
1940         heap->empty_string()) {
1941       HeapObject* first =
1942           HeapObject::cast(ConsString::cast(object)->unchecked_first());
1943
1944       *slot = first;
1945
1946       if (!heap->InNewSpace(first)) {
1947         object->set_map_word(MapWord::FromForwardingAddress(first));
1948         return;
1949       }
1950
1951       MapWord first_word = first->map_word();
1952       if (first_word.IsForwardingAddress()) {
1953         HeapObject* target = first_word.ToForwardingAddress();
1954
1955         *slot = target;
1956         object->set_map_word(MapWord::FromForwardingAddress(target));
1957         return;
1958       }
1959
1960       heap->DoScavengeObject(first->map(), slot, first);
1961       object->set_map_word(MapWord::FromForwardingAddress(*slot));
1962       return;
1963     }
1964
1965     int object_size = ConsString::kSize;
1966     EvacuateObject<POINTER_OBJECT, SMALL, kObjectAlignment>(
1967         map, slot, object, object_size);
1968   }
1969
1970   template<ObjectContents object_contents>
1971   class ObjectEvacuationStrategy {
1972    public:
1973     template<int object_size>
1974     static inline void VisitSpecialized(Map* map,
1975                                         HeapObject** slot,
1976                                         HeapObject* object) {
1977       EvacuateObject<object_contents, SMALL, kObjectAlignment>(
1978           map, slot, object, object_size);
1979     }
1980
1981     static inline void Visit(Map* map,
1982                              HeapObject** slot,
1983                              HeapObject* object) {
1984       int object_size = map->instance_size();
1985       EvacuateObject<object_contents, SMALL, kObjectAlignment>(
1986           map, slot, object, object_size);
1987     }
1988   };
1989
1990   static VisitorDispatchTable<ScavengingCallback> table_;
1991 };
1992
1993
1994 template<MarksHandling marks_handling,
1995          LoggingAndProfiling logging_and_profiling_mode>
1996 VisitorDispatchTable<ScavengingCallback>
1997     ScavengingVisitor<marks_handling, logging_and_profiling_mode>::table_;
1998
1999
2000 static void InitializeScavengingVisitorsTables() {
2001   ScavengingVisitor<TRANSFER_MARKS,
2002                     LOGGING_AND_PROFILING_DISABLED>::Initialize();
2003   ScavengingVisitor<IGNORE_MARKS, LOGGING_AND_PROFILING_DISABLED>::Initialize();
2004   ScavengingVisitor<TRANSFER_MARKS,
2005                     LOGGING_AND_PROFILING_ENABLED>::Initialize();
2006   ScavengingVisitor<IGNORE_MARKS, LOGGING_AND_PROFILING_ENABLED>::Initialize();
2007 }
2008
2009
2010 void Heap::SelectScavengingVisitorsTable() {
2011   bool logging_and_profiling =
2012       isolate()->logger()->is_logging() ||
2013       CpuProfiler::is_profiling(isolate()) ||
2014       (isolate()->heap_profiler() != NULL &&
2015        isolate()->heap_profiler()->is_profiling());
2016
2017   if (!incremental_marking()->IsMarking()) {
2018     if (!logging_and_profiling) {
2019       scavenging_visitors_table_.CopyFrom(
2020           ScavengingVisitor<IGNORE_MARKS,
2021                             LOGGING_AND_PROFILING_DISABLED>::GetTable());
2022     } else {
2023       scavenging_visitors_table_.CopyFrom(
2024           ScavengingVisitor<IGNORE_MARKS,
2025                             LOGGING_AND_PROFILING_ENABLED>::GetTable());
2026     }
2027   } else {
2028     if (!logging_and_profiling) {
2029       scavenging_visitors_table_.CopyFrom(
2030           ScavengingVisitor<TRANSFER_MARKS,
2031                             LOGGING_AND_PROFILING_DISABLED>::GetTable());
2032     } else {
2033       scavenging_visitors_table_.CopyFrom(
2034           ScavengingVisitor<TRANSFER_MARKS,
2035                             LOGGING_AND_PROFILING_ENABLED>::GetTable());
2036     }
2037
2038     if (incremental_marking()->IsCompacting()) {
2039       // When compacting forbid short-circuiting of cons-strings.
2040       // Scavenging code relies on the fact that new space object
2041       // can't be evacuated into evacuation candidate but
2042       // short-circuiting violates this assumption.
2043       scavenging_visitors_table_.Register(
2044           StaticVisitorBase::kVisitShortcutCandidate,
2045           scavenging_visitors_table_.GetVisitorById(
2046               StaticVisitorBase::kVisitConsString));
2047     }
2048   }
2049 }
2050
2051
2052 void Heap::ScavengeObjectSlow(HeapObject** p, HeapObject* object) {
2053   SLOW_ASSERT(HEAP->InFromSpace(object));
2054   MapWord first_word = object->map_word();
2055   SLOW_ASSERT(!first_word.IsForwardingAddress());
2056   Map* map = first_word.ToMap();
2057   map->GetHeap()->DoScavengeObject(map, p, object);
2058 }
2059
2060
2061 MaybeObject* Heap::AllocatePartialMap(InstanceType instance_type,
2062                                       int instance_size) {
2063   Object* result;
2064   MaybeObject* maybe_result = AllocateRawMap();
2065   if (!maybe_result->ToObject(&result)) return maybe_result;
2066
2067   // Map::cast cannot be used due to uninitialized map field.
2068   reinterpret_cast<Map*>(result)->set_map(raw_unchecked_meta_map());
2069   reinterpret_cast<Map*>(result)->set_instance_type(instance_type);
2070   reinterpret_cast<Map*>(result)->set_instance_size(instance_size);
2071   reinterpret_cast<Map*>(result)->set_visitor_id(
2072         StaticVisitorBase::GetVisitorId(instance_type, instance_size));
2073   reinterpret_cast<Map*>(result)->set_inobject_properties(0);
2074   reinterpret_cast<Map*>(result)->set_pre_allocated_property_fields(0);
2075   reinterpret_cast<Map*>(result)->set_unused_property_fields(0);
2076   reinterpret_cast<Map*>(result)->set_bit_field(0);
2077   reinterpret_cast<Map*>(result)->set_bit_field2(0);
2078   int bit_field3 = Map::EnumLengthBits::encode(Map::kInvalidEnumCache) |
2079                    Map::OwnsDescriptors::encode(true);
2080   reinterpret_cast<Map*>(result)->set_bit_field3(bit_field3);
2081   return result;
2082 }
2083
2084
2085 MaybeObject* Heap::AllocateMap(InstanceType instance_type,
2086                                int instance_size,
2087                                ElementsKind elements_kind) {
2088   Object* result;
2089   MaybeObject* maybe_result = AllocateRawMap();
2090   if (!maybe_result->To(&result)) return maybe_result;
2091
2092   Map* map = reinterpret_cast<Map*>(result);
2093   map->set_map_no_write_barrier(meta_map());
2094   map->set_instance_type(instance_type);
2095   map->set_visitor_id(
2096       StaticVisitorBase::GetVisitorId(instance_type, instance_size));
2097   map->set_prototype(null_value(), SKIP_WRITE_BARRIER);
2098   map->set_constructor(null_value(), SKIP_WRITE_BARRIER);
2099   map->set_instance_size(instance_size);
2100   map->set_inobject_properties(0);
2101   map->set_pre_allocated_property_fields(0);
2102   map->set_code_cache(empty_fixed_array(), SKIP_WRITE_BARRIER);
2103   map->init_back_pointer(undefined_value());
2104   map->set_unused_property_fields(0);
2105   map->set_instance_descriptors(empty_descriptor_array());
2106   map->set_bit_field(0);
2107   map->set_bit_field2(1 << Map::kIsExtensible);
2108   int bit_field3 = Map::EnumLengthBits::encode(Map::kInvalidEnumCache) |
2109                    Map::OwnsDescriptors::encode(true);
2110   map->set_bit_field3(bit_field3);
2111   map->set_elements_kind(elements_kind);
2112
2113   return map;
2114 }
2115
2116
2117 MaybeObject* Heap::AllocateCodeCache() {
2118   CodeCache* code_cache;
2119   { MaybeObject* maybe_code_cache = AllocateStruct(CODE_CACHE_TYPE);
2120     if (!maybe_code_cache->To(&code_cache)) return maybe_code_cache;
2121   }
2122   code_cache->set_default_cache(empty_fixed_array(), SKIP_WRITE_BARRIER);
2123   code_cache->set_normal_type_cache(undefined_value(), SKIP_WRITE_BARRIER);
2124   return code_cache;
2125 }
2126
2127
2128 MaybeObject* Heap::AllocatePolymorphicCodeCache() {
2129   return AllocateStruct(POLYMORPHIC_CODE_CACHE_TYPE);
2130 }
2131
2132
2133 MaybeObject* Heap::AllocateAccessorPair() {
2134   AccessorPair* accessors;
2135   { MaybeObject* maybe_accessors = AllocateStruct(ACCESSOR_PAIR_TYPE);
2136     if (!maybe_accessors->To(&accessors)) return maybe_accessors;
2137   }
2138   accessors->set_getter(the_hole_value(), SKIP_WRITE_BARRIER);
2139   accessors->set_setter(the_hole_value(), SKIP_WRITE_BARRIER);
2140   return accessors;
2141 }
2142
2143
2144 MaybeObject* Heap::AllocateTypeFeedbackInfo() {
2145   TypeFeedbackInfo* info;
2146   { MaybeObject* maybe_info = AllocateStruct(TYPE_FEEDBACK_INFO_TYPE);
2147     if (!maybe_info->To(&info)) return maybe_info;
2148   }
2149   info->initialize_storage();
2150   info->set_type_feedback_cells(TypeFeedbackCells::cast(empty_fixed_array()),
2151                                 SKIP_WRITE_BARRIER);
2152   return info;
2153 }
2154
2155
2156 MaybeObject* Heap::AllocateAliasedArgumentsEntry(int aliased_context_slot) {
2157   AliasedArgumentsEntry* entry;
2158   { MaybeObject* maybe_entry = AllocateStruct(ALIASED_ARGUMENTS_ENTRY_TYPE);
2159     if (!maybe_entry->To(&entry)) return maybe_entry;
2160   }
2161   entry->set_aliased_context_slot(aliased_context_slot);
2162   return entry;
2163 }
2164
2165
2166 const Heap::StringTypeTable Heap::string_type_table[] = {
2167 #define STRING_TYPE_ELEMENT(type, size, name, camel_name)                      \
2168   {type, size, k##camel_name##MapRootIndex},
2169   STRING_TYPE_LIST(STRING_TYPE_ELEMENT)
2170 #undef STRING_TYPE_ELEMENT
2171 };
2172
2173
2174 const Heap::ConstantSymbolTable Heap::constant_symbol_table[] = {
2175 #define CONSTANT_SYMBOL_ELEMENT(name, contents)                                \
2176   {contents, k##name##RootIndex},
2177   SYMBOL_LIST(CONSTANT_SYMBOL_ELEMENT)
2178 #undef CONSTANT_SYMBOL_ELEMENT
2179 };
2180
2181
2182 const Heap::StructTable Heap::struct_table[] = {
2183 #define STRUCT_TABLE_ELEMENT(NAME, Name, name)                                 \
2184   { NAME##_TYPE, Name::kSize, k##Name##MapRootIndex },
2185   STRUCT_LIST(STRUCT_TABLE_ELEMENT)
2186 #undef STRUCT_TABLE_ELEMENT
2187 };
2188
2189
2190 bool Heap::CreateInitialMaps() {
2191   Object* obj;
2192   { MaybeObject* maybe_obj = AllocatePartialMap(MAP_TYPE, Map::kSize);
2193     if (!maybe_obj->ToObject(&obj)) return false;
2194   }
2195   // Map::cast cannot be used due to uninitialized map field.
2196   Map* new_meta_map = reinterpret_cast<Map*>(obj);
2197   set_meta_map(new_meta_map);
2198   new_meta_map->set_map(new_meta_map);
2199
2200   { MaybeObject* maybe_obj =
2201         AllocatePartialMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2202     if (!maybe_obj->ToObject(&obj)) return false;
2203   }
2204   set_fixed_array_map(Map::cast(obj));
2205
2206   { MaybeObject* maybe_obj = AllocatePartialMap(ODDBALL_TYPE, Oddball::kSize);
2207     if (!maybe_obj->ToObject(&obj)) return false;
2208   }
2209   set_oddball_map(Map::cast(obj));
2210
2211   // Allocate the empty array.
2212   { MaybeObject* maybe_obj = AllocateEmptyFixedArray();
2213     if (!maybe_obj->ToObject(&obj)) return false;
2214   }
2215   set_empty_fixed_array(FixedArray::cast(obj));
2216
2217   { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_POINTER_SPACE);
2218     if (!maybe_obj->ToObject(&obj)) return false;
2219   }
2220   set_null_value(Oddball::cast(obj));
2221   Oddball::cast(obj)->set_kind(Oddball::kNull);
2222
2223   { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_POINTER_SPACE);
2224     if (!maybe_obj->ToObject(&obj)) return false;
2225   }
2226   set_undefined_value(Oddball::cast(obj));
2227   Oddball::cast(obj)->set_kind(Oddball::kUndefined);
2228   ASSERT(!InNewSpace(undefined_value()));
2229
2230   // Allocate the empty descriptor array.
2231   { MaybeObject* maybe_obj = AllocateEmptyFixedArray();
2232     if (!maybe_obj->ToObject(&obj)) return false;
2233   }
2234   set_empty_descriptor_array(DescriptorArray::cast(obj));
2235
2236   // Fix the instance_descriptors for the existing maps.
2237   meta_map()->set_code_cache(empty_fixed_array());
2238   meta_map()->init_back_pointer(undefined_value());
2239   meta_map()->set_instance_descriptors(empty_descriptor_array());
2240
2241   fixed_array_map()->set_code_cache(empty_fixed_array());
2242   fixed_array_map()->init_back_pointer(undefined_value());
2243   fixed_array_map()->set_instance_descriptors(empty_descriptor_array());
2244
2245   oddball_map()->set_code_cache(empty_fixed_array());
2246   oddball_map()->init_back_pointer(undefined_value());
2247   oddball_map()->set_instance_descriptors(empty_descriptor_array());
2248
2249   // Fix prototype object for existing maps.
2250   meta_map()->set_prototype(null_value());
2251   meta_map()->set_constructor(null_value());
2252
2253   fixed_array_map()->set_prototype(null_value());
2254   fixed_array_map()->set_constructor(null_value());
2255
2256   oddball_map()->set_prototype(null_value());
2257   oddball_map()->set_constructor(null_value());
2258
2259   { MaybeObject* maybe_obj =
2260         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2261     if (!maybe_obj->ToObject(&obj)) return false;
2262   }
2263   set_fixed_cow_array_map(Map::cast(obj));
2264   ASSERT(fixed_array_map() != fixed_cow_array_map());
2265
2266   { MaybeObject* maybe_obj =
2267         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2268     if (!maybe_obj->ToObject(&obj)) return false;
2269   }
2270   set_scope_info_map(Map::cast(obj));
2271
2272   { MaybeObject* maybe_obj = AllocateMap(HEAP_NUMBER_TYPE, HeapNumber::kSize);
2273     if (!maybe_obj->ToObject(&obj)) return false;
2274   }
2275   set_heap_number_map(Map::cast(obj));
2276
2277   { MaybeObject* maybe_obj = AllocateMap(FOREIGN_TYPE, Foreign::kSize);
2278     if (!maybe_obj->ToObject(&obj)) return false;
2279   }
2280   set_foreign_map(Map::cast(obj));
2281
2282   for (unsigned i = 0; i < ARRAY_SIZE(string_type_table); i++) {
2283     const StringTypeTable& entry = string_type_table[i];
2284     { MaybeObject* maybe_obj = AllocateMap(entry.type, entry.size);
2285       if (!maybe_obj->ToObject(&obj)) return false;
2286     }
2287     roots_[entry.index] = Map::cast(obj);
2288   }
2289
2290   { MaybeObject* maybe_obj = AllocateMap(STRING_TYPE, kVariableSizeSentinel);
2291     if (!maybe_obj->ToObject(&obj)) return false;
2292   }
2293   set_undetectable_string_map(Map::cast(obj));
2294   Map::cast(obj)->set_is_undetectable();
2295
2296   { MaybeObject* maybe_obj =
2297         AllocateMap(ASCII_STRING_TYPE, kVariableSizeSentinel);
2298     if (!maybe_obj->ToObject(&obj)) return false;
2299   }
2300   set_undetectable_ascii_string_map(Map::cast(obj));
2301   Map::cast(obj)->set_is_undetectable();
2302
2303   { MaybeObject* maybe_obj =
2304         AllocateMap(FIXED_DOUBLE_ARRAY_TYPE, kVariableSizeSentinel);
2305     if (!maybe_obj->ToObject(&obj)) return false;
2306   }
2307   set_fixed_double_array_map(Map::cast(obj));
2308
2309   { MaybeObject* maybe_obj =
2310         AllocateMap(BYTE_ARRAY_TYPE, kVariableSizeSentinel);
2311     if (!maybe_obj->ToObject(&obj)) return false;
2312   }
2313   set_byte_array_map(Map::cast(obj));
2314
2315   { MaybeObject* maybe_obj =
2316         AllocateMap(FREE_SPACE_TYPE, kVariableSizeSentinel);
2317     if (!maybe_obj->ToObject(&obj)) return false;
2318   }
2319   set_free_space_map(Map::cast(obj));
2320
2321   { MaybeObject* maybe_obj = AllocateByteArray(0, TENURED);
2322     if (!maybe_obj->ToObject(&obj)) return false;
2323   }
2324   set_empty_byte_array(ByteArray::cast(obj));
2325
2326   { MaybeObject* maybe_obj =
2327         AllocateMap(EXTERNAL_PIXEL_ARRAY_TYPE, ExternalArray::kAlignedSize);
2328     if (!maybe_obj->ToObject(&obj)) return false;
2329   }
2330   set_external_pixel_array_map(Map::cast(obj));
2331
2332   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_BYTE_ARRAY_TYPE,
2333                                          ExternalArray::kAlignedSize);
2334     if (!maybe_obj->ToObject(&obj)) return false;
2335   }
2336   set_external_byte_array_map(Map::cast(obj));
2337
2338   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_UNSIGNED_BYTE_ARRAY_TYPE,
2339                                          ExternalArray::kAlignedSize);
2340     if (!maybe_obj->ToObject(&obj)) return false;
2341   }
2342   set_external_unsigned_byte_array_map(Map::cast(obj));
2343
2344   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_SHORT_ARRAY_TYPE,
2345                                          ExternalArray::kAlignedSize);
2346     if (!maybe_obj->ToObject(&obj)) return false;
2347   }
2348   set_external_short_array_map(Map::cast(obj));
2349
2350   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_UNSIGNED_SHORT_ARRAY_TYPE,
2351                                          ExternalArray::kAlignedSize);
2352     if (!maybe_obj->ToObject(&obj)) return false;
2353   }
2354   set_external_unsigned_short_array_map(Map::cast(obj));
2355
2356   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_INT_ARRAY_TYPE,
2357                                          ExternalArray::kAlignedSize);
2358     if (!maybe_obj->ToObject(&obj)) return false;
2359   }
2360   set_external_int_array_map(Map::cast(obj));
2361
2362   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_UNSIGNED_INT_ARRAY_TYPE,
2363                                          ExternalArray::kAlignedSize);
2364     if (!maybe_obj->ToObject(&obj)) return false;
2365   }
2366   set_external_unsigned_int_array_map(Map::cast(obj));
2367
2368   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_FLOAT_ARRAY_TYPE,
2369                                          ExternalArray::kAlignedSize);
2370     if (!maybe_obj->ToObject(&obj)) return false;
2371   }
2372   set_external_float_array_map(Map::cast(obj));
2373
2374   { MaybeObject* maybe_obj =
2375         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2376     if (!maybe_obj->ToObject(&obj)) return false;
2377   }
2378   set_non_strict_arguments_elements_map(Map::cast(obj));
2379
2380   { MaybeObject* maybe_obj = AllocateMap(EXTERNAL_DOUBLE_ARRAY_TYPE,
2381                                          ExternalArray::kAlignedSize);
2382     if (!maybe_obj->ToObject(&obj)) return false;
2383   }
2384   set_external_double_array_map(Map::cast(obj));
2385
2386   { MaybeObject* maybe_obj = AllocateMap(CODE_TYPE, kVariableSizeSentinel);
2387     if (!maybe_obj->ToObject(&obj)) return false;
2388   }
2389   set_code_map(Map::cast(obj));
2390
2391   { MaybeObject* maybe_obj = AllocateMap(JS_GLOBAL_PROPERTY_CELL_TYPE,
2392                                          JSGlobalPropertyCell::kSize);
2393     if (!maybe_obj->ToObject(&obj)) return false;
2394   }
2395   set_global_property_cell_map(Map::cast(obj));
2396
2397   { MaybeObject* maybe_obj = AllocateMap(FILLER_TYPE, kPointerSize);
2398     if (!maybe_obj->ToObject(&obj)) return false;
2399   }
2400   set_one_pointer_filler_map(Map::cast(obj));
2401
2402   { MaybeObject* maybe_obj = AllocateMap(FILLER_TYPE, 2 * kPointerSize);
2403     if (!maybe_obj->ToObject(&obj)) return false;
2404   }
2405   set_two_pointer_filler_map(Map::cast(obj));
2406
2407   for (unsigned i = 0; i < ARRAY_SIZE(struct_table); i++) {
2408     const StructTable& entry = struct_table[i];
2409     { MaybeObject* maybe_obj = AllocateMap(entry.type, entry.size);
2410       if (!maybe_obj->ToObject(&obj)) return false;
2411     }
2412     roots_[entry.index] = Map::cast(obj);
2413   }
2414
2415   { MaybeObject* maybe_obj =
2416         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2417     if (!maybe_obj->ToObject(&obj)) return false;
2418   }
2419   set_hash_table_map(Map::cast(obj));
2420
2421   { MaybeObject* maybe_obj =
2422         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2423     if (!maybe_obj->ToObject(&obj)) return false;
2424   }
2425   set_function_context_map(Map::cast(obj));
2426
2427   { MaybeObject* maybe_obj =
2428         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2429     if (!maybe_obj->ToObject(&obj)) return false;
2430   }
2431   set_catch_context_map(Map::cast(obj));
2432
2433   { MaybeObject* maybe_obj =
2434         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2435     if (!maybe_obj->ToObject(&obj)) return false;
2436   }
2437   set_with_context_map(Map::cast(obj));
2438
2439   { MaybeObject* maybe_obj =
2440         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2441     if (!maybe_obj->ToObject(&obj)) return false;
2442   }
2443   set_block_context_map(Map::cast(obj));
2444
2445   { MaybeObject* maybe_obj =
2446         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2447     if (!maybe_obj->ToObject(&obj)) return false;
2448   }
2449   set_module_context_map(Map::cast(obj));
2450
2451   { MaybeObject* maybe_obj =
2452         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2453     if (!maybe_obj->ToObject(&obj)) return false;
2454   }
2455   set_global_context_map(Map::cast(obj));
2456
2457   { MaybeObject* maybe_obj =
2458         AllocateMap(FIXED_ARRAY_TYPE, kVariableSizeSentinel);
2459     if (!maybe_obj->ToObject(&obj)) return false;
2460   }
2461   Map* native_context_map = Map::cast(obj);
2462   native_context_map->set_dictionary_map(true);
2463   native_context_map->set_visitor_id(StaticVisitorBase::kVisitNativeContext);
2464   set_native_context_map(native_context_map);
2465
2466   { MaybeObject* maybe_obj = AllocateMap(SHARED_FUNCTION_INFO_TYPE,
2467                                          SharedFunctionInfo::kAlignedSize);
2468     if (!maybe_obj->ToObject(&obj)) return false;
2469   }
2470   set_shared_function_info_map(Map::cast(obj));
2471
2472   { MaybeObject* maybe_obj = AllocateMap(JS_MESSAGE_OBJECT_TYPE,
2473                                          JSMessageObject::kSize);
2474     if (!maybe_obj->ToObject(&obj)) return false;
2475   }
2476   set_message_object_map(Map::cast(obj));
2477
2478   ASSERT(!InNewSpace(empty_fixed_array()));
2479   return true;
2480 }
2481
2482
2483 MaybeObject* Heap::AllocateHeapNumber(double value, PretenureFlag pretenure) {
2484   // Statically ensure that it is safe to allocate heap numbers in paged
2485   // spaces.
2486   STATIC_ASSERT(HeapNumber::kSize <= Page::kNonCodeObjectAreaSize);
2487   AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
2488
2489   Object* result;
2490   { MaybeObject* maybe_result =
2491         AllocateRaw(HeapNumber::kSize, space, OLD_DATA_SPACE);
2492     if (!maybe_result->ToObject(&result)) return maybe_result;
2493   }
2494
2495   HeapObject::cast(result)->set_map_no_write_barrier(heap_number_map());
2496   HeapNumber::cast(result)->set_value(value);
2497   return result;
2498 }
2499
2500
2501 MaybeObject* Heap::AllocateHeapNumber(double value) {
2502   // Use general version, if we're forced to always allocate.
2503   if (always_allocate()) return AllocateHeapNumber(value, TENURED);
2504
2505   // This version of AllocateHeapNumber is optimized for
2506   // allocation in new space.
2507   STATIC_ASSERT(HeapNumber::kSize <= Page::kMaxNonCodeHeapObjectSize);
2508   ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);
2509   Object* result;
2510   { MaybeObject* maybe_result = new_space_.AllocateRaw(HeapNumber::kSize);
2511     if (!maybe_result->ToObject(&result)) return maybe_result;
2512   }
2513   HeapObject::cast(result)->set_map_no_write_barrier(heap_number_map());
2514   HeapNumber::cast(result)->set_value(value);
2515   return result;
2516 }
2517
2518
2519 MaybeObject* Heap::AllocateJSGlobalPropertyCell(Object* value) {
2520   Object* result;
2521   { MaybeObject* maybe_result = AllocateRawCell();
2522     if (!maybe_result->ToObject(&result)) return maybe_result;
2523   }
2524   HeapObject::cast(result)->set_map_no_write_barrier(
2525       global_property_cell_map());
2526   JSGlobalPropertyCell::cast(result)->set_value(value);
2527   return result;
2528 }
2529
2530
2531 MaybeObject* Heap::CreateOddball(const char* to_string,
2532                                  Object* to_number,
2533                                  byte kind) {
2534   Object* result;
2535   { MaybeObject* maybe_result = Allocate(oddball_map(), OLD_POINTER_SPACE);
2536     if (!maybe_result->ToObject(&result)) return maybe_result;
2537   }
2538   return Oddball::cast(result)->Initialize(to_string, to_number, kind);
2539 }
2540
2541
2542 bool Heap::CreateApiObjects() {
2543   Object* obj;
2544
2545   { MaybeObject* maybe_obj = AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
2546     if (!maybe_obj->ToObject(&obj)) return false;
2547   }
2548   // Don't use Smi-only elements optimizations for objects with the neander
2549   // map. There are too many cases where element values are set directly with a
2550   // bottleneck to trap the Smi-only -> fast elements transition, and there
2551   // appears to be no benefit for optimize this case.
2552   Map* new_neander_map = Map::cast(obj);
2553   new_neander_map->set_elements_kind(TERMINAL_FAST_ELEMENTS_KIND);
2554   set_neander_map(new_neander_map);
2555
2556   { MaybeObject* maybe_obj = AllocateJSObjectFromMap(neander_map());
2557     if (!maybe_obj->ToObject(&obj)) return false;
2558   }
2559   Object* elements;
2560   { MaybeObject* maybe_elements = AllocateFixedArray(2);
2561     if (!maybe_elements->ToObject(&elements)) return false;
2562   }
2563   FixedArray::cast(elements)->set(0, Smi::FromInt(0));
2564   JSObject::cast(obj)->set_elements(FixedArray::cast(elements));
2565   set_message_listeners(JSObject::cast(obj));
2566
2567   return true;
2568 }
2569
2570
2571 void Heap::CreateJSEntryStub() {
2572   JSEntryStub stub;
2573   set_js_entry_code(*stub.GetCode());
2574 }
2575
2576
2577 void Heap::CreateJSConstructEntryStub() {
2578   JSConstructEntryStub stub;
2579   set_js_construct_entry_code(*stub.GetCode());
2580 }
2581
2582
2583 void Heap::CreateFixedStubs() {
2584   // Here we create roots for fixed stubs. They are needed at GC
2585   // for cooking and uncooking (check out frames.cc).
2586   // The eliminates the need for doing dictionary lookup in the
2587   // stub cache for these stubs.
2588   HandleScope scope;
2589   // gcc-4.4 has problem generating correct code of following snippet:
2590   // {  JSEntryStub stub;
2591   //    js_entry_code_ = *stub.GetCode();
2592   // }
2593   // {  JSConstructEntryStub stub;
2594   //    js_construct_entry_code_ = *stub.GetCode();
2595   // }
2596   // To workaround the problem, make separate functions without inlining.
2597   Heap::CreateJSEntryStub();
2598   Heap::CreateJSConstructEntryStub();
2599
2600   // Create stubs that should be there, so we don't unexpectedly have to
2601   // create them if we need them during the creation of another stub.
2602   // Stub creation mixes raw pointers and handles in an unsafe manner so
2603   // we cannot create stubs while we are creating stubs.
2604   CodeStub::GenerateStubsAheadOfTime();
2605 }
2606
2607
2608 bool Heap::CreateInitialObjects() {
2609   Object* obj;
2610
2611   // The -0 value must be set before NumberFromDouble works.
2612   { MaybeObject* maybe_obj = AllocateHeapNumber(-0.0, TENURED);
2613     if (!maybe_obj->ToObject(&obj)) return false;
2614   }
2615   set_minus_zero_value(HeapNumber::cast(obj));
2616   ASSERT(signbit(minus_zero_value()->Number()) != 0);
2617
2618   { MaybeObject* maybe_obj = AllocateHeapNumber(OS::nan_value(), TENURED);
2619     if (!maybe_obj->ToObject(&obj)) return false;
2620   }
2621   set_nan_value(HeapNumber::cast(obj));
2622
2623   { MaybeObject* maybe_obj = AllocateHeapNumber(V8_INFINITY, TENURED);
2624     if (!maybe_obj->ToObject(&obj)) return false;
2625   }
2626   set_infinity_value(HeapNumber::cast(obj));
2627
2628   // The hole has not been created yet, but we want to put something
2629   // predictable in the gaps in the symbol table, so lets make that Smi zero.
2630   set_the_hole_value(reinterpret_cast<Oddball*>(Smi::FromInt(0)));
2631
2632   // Allocate initial symbol table.
2633   { MaybeObject* maybe_obj = SymbolTable::Allocate(kInitialSymbolTableSize);
2634     if (!maybe_obj->ToObject(&obj)) return false;
2635   }
2636   // Don't use set_symbol_table() due to asserts.
2637   roots_[kSymbolTableRootIndex] = obj;
2638
2639   // Finish initializing oddballs after creating symboltable.
2640   { MaybeObject* maybe_obj =
2641         undefined_value()->Initialize("undefined",
2642                                       nan_value(),
2643                                       Oddball::kUndefined);
2644     if (!maybe_obj->ToObject(&obj)) return false;
2645   }
2646
2647   // Initialize the null_value.
2648   { MaybeObject* maybe_obj =
2649         null_value()->Initialize("null", Smi::FromInt(0), Oddball::kNull);
2650     if (!maybe_obj->ToObject(&obj)) return false;
2651   }
2652
2653   { MaybeObject* maybe_obj = CreateOddball("true",
2654                                            Smi::FromInt(1),
2655                                            Oddball::kTrue);
2656     if (!maybe_obj->ToObject(&obj)) return false;
2657   }
2658   set_true_value(Oddball::cast(obj));
2659
2660   { MaybeObject* maybe_obj = CreateOddball("false",
2661                                            Smi::FromInt(0),
2662                                            Oddball::kFalse);
2663     if (!maybe_obj->ToObject(&obj)) return false;
2664   }
2665   set_false_value(Oddball::cast(obj));
2666
2667   { MaybeObject* maybe_obj = CreateOddball("hole",
2668                                            Smi::FromInt(-1),
2669                                            Oddball::kTheHole);
2670     if (!maybe_obj->ToObject(&obj)) return false;
2671   }
2672   set_the_hole_value(Oddball::cast(obj));
2673
2674   { MaybeObject* maybe_obj = CreateOddball("arguments_marker",
2675                                            Smi::FromInt(-4),
2676                                            Oddball::kArgumentMarker);
2677     if (!maybe_obj->ToObject(&obj)) return false;
2678   }
2679   set_arguments_marker(Oddball::cast(obj));
2680
2681   { MaybeObject* maybe_obj = CreateOddball("no_interceptor_result_sentinel",
2682                                            Smi::FromInt(-2),
2683                                            Oddball::kOther);
2684     if (!maybe_obj->ToObject(&obj)) return false;
2685   }
2686   set_no_interceptor_result_sentinel(obj);
2687
2688   { MaybeObject* maybe_obj = CreateOddball("termination_exception",
2689                                            Smi::FromInt(-3),
2690                                            Oddball::kOther);
2691     if (!maybe_obj->ToObject(&obj)) return false;
2692   }
2693   set_termination_exception(obj);
2694
2695   // Allocate the empty string.
2696   { MaybeObject* maybe_obj = AllocateRawAsciiString(0, TENURED);
2697     if (!maybe_obj->ToObject(&obj)) return false;
2698   }
2699   set_empty_string(String::cast(obj));
2700
2701   for (unsigned i = 0; i < ARRAY_SIZE(constant_symbol_table); i++) {
2702     { MaybeObject* maybe_obj =
2703           LookupAsciiSymbol(constant_symbol_table[i].contents);
2704       if (!maybe_obj->ToObject(&obj)) return false;
2705     }
2706     roots_[constant_symbol_table[i].index] = String::cast(obj);
2707   }
2708
2709   // Allocate the hidden symbol which is used to identify the hidden properties
2710   // in JSObjects. The hash code has a special value so that it will not match
2711   // the empty string when searching for the property. It cannot be part of the
2712   // loop above because it needs to be allocated manually with the special
2713   // hash code in place. The hash code for the hidden_symbol is zero to ensure
2714   // that it will always be at the first entry in property descriptors.
2715   { MaybeObject* maybe_obj =
2716         AllocateSymbol(CStrVector(""), 0, String::kEmptyStringHash);
2717     if (!maybe_obj->ToObject(&obj)) return false;
2718   }
2719   hidden_symbol_ = String::cast(obj);
2720
2721   // Allocate the foreign for __proto__.
2722   { MaybeObject* maybe_obj =
2723         AllocateForeign((Address) &Accessors::ObjectPrototype);
2724     if (!maybe_obj->ToObject(&obj)) return false;
2725   }
2726   set_prototype_accessors(Foreign::cast(obj));
2727
2728   // Allocate the code_stubs dictionary. The initial size is set to avoid
2729   // expanding the dictionary during bootstrapping.
2730   { MaybeObject* maybe_obj = UnseededNumberDictionary::Allocate(128);
2731     if (!maybe_obj->ToObject(&obj)) return false;
2732   }
2733   set_code_stubs(UnseededNumberDictionary::cast(obj));
2734
2735
2736   // Allocate the non_monomorphic_cache used in stub-cache.cc. The initial size
2737   // is set to avoid expanding the dictionary during bootstrapping.
2738   { MaybeObject* maybe_obj = UnseededNumberDictionary::Allocate(64);
2739     if (!maybe_obj->ToObject(&obj)) return false;
2740   }
2741   set_non_monomorphic_cache(UnseededNumberDictionary::cast(obj));
2742
2743   { MaybeObject* maybe_obj = AllocatePolymorphicCodeCache();
2744     if (!maybe_obj->ToObject(&obj)) return false;
2745   }
2746   set_polymorphic_code_cache(PolymorphicCodeCache::cast(obj));
2747
2748   set_instanceof_cache_function(Smi::FromInt(0));
2749   set_instanceof_cache_map(Smi::FromInt(0));
2750   set_instanceof_cache_answer(Smi::FromInt(0));
2751
2752   CreateFixedStubs();
2753
2754   // Allocate the dictionary of intrinsic function names.
2755   { MaybeObject* maybe_obj = StringDictionary::Allocate(Runtime::kNumFunctions);
2756     if (!maybe_obj->ToObject(&obj)) return false;
2757   }
2758   { MaybeObject* maybe_obj = Runtime::InitializeIntrinsicFunctionNames(this,
2759                                                                        obj);
2760     if (!maybe_obj->ToObject(&obj)) return false;
2761   }
2762   set_intrinsic_function_names(StringDictionary::cast(obj));
2763
2764   { MaybeObject* maybe_obj = AllocateInitialNumberStringCache();
2765     if (!maybe_obj->ToObject(&obj)) return false;
2766   }
2767   set_number_string_cache(FixedArray::cast(obj));
2768
2769   // Allocate cache for single character ASCII strings.
2770   { MaybeObject* maybe_obj =
2771         AllocateFixedArray(String::kMaxAsciiCharCode + 1, TENURED);
2772     if (!maybe_obj->ToObject(&obj)) return false;
2773   }
2774   set_single_character_string_cache(FixedArray::cast(obj));
2775
2776   // Allocate cache for string split.
2777   { MaybeObject* maybe_obj = AllocateFixedArray(
2778       RegExpResultsCache::kRegExpResultsCacheSize, TENURED);
2779     if (!maybe_obj->ToObject(&obj)) return false;
2780   }
2781   set_string_split_cache(FixedArray::cast(obj));
2782
2783   { MaybeObject* maybe_obj = AllocateFixedArray(
2784       RegExpResultsCache::kRegExpResultsCacheSize, TENURED);
2785     if (!maybe_obj->ToObject(&obj)) return false;
2786   }
2787   set_regexp_multiple_cache(FixedArray::cast(obj));
2788
2789   // Allocate cache for external strings pointing to native source code.
2790   { MaybeObject* maybe_obj = AllocateFixedArray(Natives::GetBuiltinsCount());
2791     if (!maybe_obj->ToObject(&obj)) return false;
2792   }
2793   set_natives_source_cache(FixedArray::cast(obj));
2794
2795   // Handling of script id generation is in FACTORY->NewScript.
2796   set_last_script_id(undefined_value());
2797
2798   // Initialize keyed lookup cache.
2799   isolate_->keyed_lookup_cache()->Clear();
2800
2801   // Initialize context slot cache.
2802   isolate_->context_slot_cache()->Clear();
2803
2804   // Initialize descriptor cache.
2805   isolate_->descriptor_lookup_cache()->Clear();
2806
2807   // Initialize compilation cache.
2808   isolate_->compilation_cache()->Clear();
2809
2810   return true;
2811 }
2812
2813
2814 Object* RegExpResultsCache::Lookup(Heap* heap,
2815                                    String* key_string,
2816                                    Object* key_pattern,
2817                                    ResultsCacheType type) {
2818   FixedArray* cache;
2819   if (!key_string->IsSymbol()) return Smi::FromInt(0);
2820   if (type == STRING_SPLIT_SUBSTRINGS) {
2821     ASSERT(key_pattern->IsString());
2822     if (!key_pattern->IsSymbol()) return Smi::FromInt(0);
2823     cache = heap->string_split_cache();
2824   } else {
2825     ASSERT(type == REGEXP_MULTIPLE_INDICES);
2826     ASSERT(key_pattern->IsFixedArray());
2827     cache = heap->regexp_multiple_cache();
2828   }
2829
2830   uint32_t hash = key_string->Hash();
2831   uint32_t index = ((hash & (kRegExpResultsCacheSize - 1)) &
2832       ~(kArrayEntriesPerCacheEntry - 1));
2833   if (cache->get(index + kStringOffset) == key_string &&
2834       cache->get(index + kPatternOffset) == key_pattern) {
2835     return cache->get(index + kArrayOffset);
2836   }
2837   index =
2838       ((index + kArrayEntriesPerCacheEntry) & (kRegExpResultsCacheSize - 1));
2839   if (cache->get(index + kStringOffset) == key_string &&
2840       cache->get(index + kPatternOffset) == key_pattern) {
2841     return cache->get(index + kArrayOffset);
2842   }
2843   return Smi::FromInt(0);
2844 }
2845
2846
2847 void RegExpResultsCache::Enter(Heap* heap,
2848                                String* key_string,
2849                                Object* key_pattern,
2850                                FixedArray* value_array,
2851                                ResultsCacheType type) {
2852   FixedArray* cache;
2853   if (!key_string->IsSymbol()) return;
2854   if (type == STRING_SPLIT_SUBSTRINGS) {
2855     ASSERT(key_pattern->IsString());
2856     if (!key_pattern->IsSymbol()) return;
2857     cache = heap->string_split_cache();
2858   } else {
2859     ASSERT(type == REGEXP_MULTIPLE_INDICES);
2860     ASSERT(key_pattern->IsFixedArray());
2861     cache = heap->regexp_multiple_cache();
2862   }
2863
2864   uint32_t hash = key_string->Hash();
2865   uint32_t index = ((hash & (kRegExpResultsCacheSize - 1)) &
2866       ~(kArrayEntriesPerCacheEntry - 1));
2867   if (cache->get(index + kStringOffset) == Smi::FromInt(0)) {
2868     cache->set(index + kStringOffset, key_string);
2869     cache->set(index + kPatternOffset, key_pattern);
2870     cache->set(index + kArrayOffset, value_array);
2871   } else {
2872     uint32_t index2 =
2873         ((index + kArrayEntriesPerCacheEntry) & (kRegExpResultsCacheSize - 1));
2874     if (cache->get(index2 + kStringOffset) == Smi::FromInt(0)) {
2875       cache->set(index2 + kStringOffset, key_string);
2876       cache->set(index2 + kPatternOffset, key_pattern);
2877       cache->set(index2 + kArrayOffset, value_array);
2878     } else {
2879       cache->set(index2 + kStringOffset, Smi::FromInt(0));
2880       cache->set(index2 + kPatternOffset, Smi::FromInt(0));
2881       cache->set(index2 + kArrayOffset, Smi::FromInt(0));
2882       cache->set(index + kStringOffset, key_string);
2883       cache->set(index + kPatternOffset, key_pattern);
2884       cache->set(index + kArrayOffset, value_array);
2885     }
2886   }
2887   // If the array is a reasonably short list of substrings, convert it into a
2888   // list of symbols.
2889   if (type == STRING_SPLIT_SUBSTRINGS && value_array->length() < 100) {
2890     for (int i = 0; i < value_array->length(); i++) {
2891       String* str = String::cast(value_array->get(i));
2892       Object* symbol;
2893       MaybeObject* maybe_symbol = heap->LookupSymbol(str);
2894       if (maybe_symbol->ToObject(&symbol)) {
2895         value_array->set(i, symbol);
2896       }
2897     }
2898   }
2899   // Convert backing store to a copy-on-write array.
2900   value_array->set_map_no_write_barrier(heap->fixed_cow_array_map());
2901 }
2902
2903
2904 void RegExpResultsCache::Clear(FixedArray* cache) {
2905   for (int i = 0; i < kRegExpResultsCacheSize; i++) {
2906     cache->set(i, Smi::FromInt(0));
2907   }
2908 }
2909
2910
2911 MaybeObject* Heap::AllocateInitialNumberStringCache() {
2912   MaybeObject* maybe_obj =
2913       AllocateFixedArray(kInitialNumberStringCacheSize * 2, TENURED);
2914   return maybe_obj;
2915 }
2916
2917
2918 int Heap::FullSizeNumberStringCacheLength() {
2919   // Compute the size of the number string cache based on the max newspace size.
2920   // The number string cache has a minimum size based on twice the initial cache
2921   // size to ensure that it is bigger after being made 'full size'.
2922   int number_string_cache_size = max_semispace_size_ / 512;
2923   number_string_cache_size = Max(kInitialNumberStringCacheSize * 2,
2924                                  Min(0x4000, number_string_cache_size));
2925   // There is a string and a number per entry so the length is twice the number
2926   // of entries.
2927   return number_string_cache_size * 2;
2928 }
2929
2930
2931 void Heap::AllocateFullSizeNumberStringCache() {
2932   // The idea is to have a small number string cache in the snapshot to keep
2933   // boot-time memory usage down.  If we expand the number string cache already
2934   // while creating the snapshot then that didn't work out.
2935   ASSERT(!Serializer::enabled() || FLAG_extra_code != NULL);
2936   MaybeObject* maybe_obj =
2937       AllocateFixedArray(FullSizeNumberStringCacheLength(), TENURED);
2938   Object* new_cache;
2939   if (maybe_obj->ToObject(&new_cache)) {
2940     // We don't bother to repopulate the cache with entries from the old cache.
2941     // It will be repopulated soon enough with new strings.
2942     set_number_string_cache(FixedArray::cast(new_cache));
2943   }
2944   // If allocation fails then we just return without doing anything.  It is only
2945   // a cache, so best effort is OK here.
2946 }
2947
2948
2949 void Heap::FlushNumberStringCache() {
2950   // Flush the number to string cache.
2951   int len = number_string_cache()->length();
2952   for (int i = 0; i < len; i++) {
2953     number_string_cache()->set_undefined(this, i);
2954   }
2955 }
2956
2957
2958 static inline int double_get_hash(double d) {
2959   DoubleRepresentation rep(d);
2960   return static_cast<int>(rep.bits) ^ static_cast<int>(rep.bits >> 32);
2961 }
2962
2963
2964 static inline int smi_get_hash(Smi* smi) {
2965   return smi->value();
2966 }
2967
2968
2969 Object* Heap::GetNumberStringCache(Object* number) {
2970   int hash;
2971   int mask = (number_string_cache()->length() >> 1) - 1;
2972   if (number->IsSmi()) {
2973     hash = smi_get_hash(Smi::cast(number)) & mask;
2974   } else {
2975     hash = double_get_hash(number->Number()) & mask;
2976   }
2977   Object* key = number_string_cache()->get(hash * 2);
2978   if (key == number) {
2979     return String::cast(number_string_cache()->get(hash * 2 + 1));
2980   } else if (key->IsHeapNumber() &&
2981              number->IsHeapNumber() &&
2982              key->Number() == number->Number()) {
2983     return String::cast(number_string_cache()->get(hash * 2 + 1));
2984   }
2985   return undefined_value();
2986 }
2987
2988
2989 void Heap::SetNumberStringCache(Object* number, String* string) {
2990   int hash;
2991   int mask = (number_string_cache()->length() >> 1) - 1;
2992   if (number->IsSmi()) {
2993     hash = smi_get_hash(Smi::cast(number)) & mask;
2994   } else {
2995     hash = double_get_hash(number->Number()) & mask;
2996   }
2997   if (number_string_cache()->get(hash * 2) != undefined_value() &&
2998       number_string_cache()->length() != FullSizeNumberStringCacheLength()) {
2999     // The first time we have a hash collision, we move to the full sized
3000     // number string cache.
3001     AllocateFullSizeNumberStringCache();
3002     return;
3003   }
3004   number_string_cache()->set(hash * 2, number);
3005   number_string_cache()->set(hash * 2 + 1, string);
3006 }
3007
3008
3009 MaybeObject* Heap::NumberToString(Object* number,
3010                                   bool check_number_string_cache) {
3011   isolate_->counters()->number_to_string_runtime()->Increment();
3012   if (check_number_string_cache) {
3013     Object* cached = GetNumberStringCache(number);
3014     if (cached != undefined_value()) {
3015       return cached;
3016     }
3017   }
3018
3019   char arr[100];
3020   Vector<char> buffer(arr, ARRAY_SIZE(arr));
3021   const char* str;
3022   if (number->IsSmi()) {
3023     int num = Smi::cast(number)->value();
3024     str = IntToCString(num, buffer);
3025   } else {
3026     double num = HeapNumber::cast(number)->value();
3027     str = DoubleToCString(num, buffer);
3028   }
3029
3030   Object* js_string;
3031   MaybeObject* maybe_js_string = AllocateStringFromAscii(CStrVector(str));
3032   if (maybe_js_string->ToObject(&js_string)) {
3033     SetNumberStringCache(number, String::cast(js_string));
3034   }
3035   return maybe_js_string;
3036 }
3037
3038
3039 MaybeObject* Heap::Uint32ToString(uint32_t value,
3040                                   bool check_number_string_cache) {
3041   Object* number;
3042   MaybeObject* maybe = NumberFromUint32(value);
3043   if (!maybe->To<Object>(&number)) return maybe;
3044   return NumberToString(number, check_number_string_cache);
3045 }
3046
3047
3048 Map* Heap::MapForExternalArrayType(ExternalArrayType array_type) {
3049   return Map::cast(roots_[RootIndexForExternalArrayType(array_type)]);
3050 }
3051
3052
3053 Heap::RootListIndex Heap::RootIndexForExternalArrayType(
3054     ExternalArrayType array_type) {
3055   switch (array_type) {
3056     case kExternalByteArray:
3057       return kExternalByteArrayMapRootIndex;
3058     case kExternalUnsignedByteArray:
3059       return kExternalUnsignedByteArrayMapRootIndex;
3060     case kExternalShortArray:
3061       return kExternalShortArrayMapRootIndex;
3062     case kExternalUnsignedShortArray:
3063       return kExternalUnsignedShortArrayMapRootIndex;
3064     case kExternalIntArray:
3065       return kExternalIntArrayMapRootIndex;
3066     case kExternalUnsignedIntArray:
3067       return kExternalUnsignedIntArrayMapRootIndex;
3068     case kExternalFloatArray:
3069       return kExternalFloatArrayMapRootIndex;
3070     case kExternalDoubleArray:
3071       return kExternalDoubleArrayMapRootIndex;
3072     case kExternalPixelArray:
3073       return kExternalPixelArrayMapRootIndex;
3074     default:
3075       UNREACHABLE();
3076       return kUndefinedValueRootIndex;
3077   }
3078 }
3079
3080
3081 MaybeObject* Heap::NumberFromDouble(double value, PretenureFlag pretenure) {
3082   // We need to distinguish the minus zero value and this cannot be
3083   // done after conversion to int. Doing this by comparing bit
3084   // patterns is faster than using fpclassify() et al.
3085   static const DoubleRepresentation minus_zero(-0.0);
3086
3087   DoubleRepresentation rep(value);
3088   if (rep.bits == minus_zero.bits) {
3089     return AllocateHeapNumber(-0.0, pretenure);
3090   }
3091
3092   int int_value = FastD2I(value);
3093   if (value == int_value && Smi::IsValid(int_value)) {
3094     return Smi::FromInt(int_value);
3095   }
3096
3097   // Materialize the value in the heap.
3098   return AllocateHeapNumber(value, pretenure);
3099 }
3100
3101
3102 MaybeObject* Heap::AllocateForeign(Address address, PretenureFlag pretenure) {
3103   // Statically ensure that it is safe to allocate foreigns in paged spaces.
3104   STATIC_ASSERT(Foreign::kSize <= Page::kMaxNonCodeHeapObjectSize);
3105   AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
3106   Foreign* result;
3107   MaybeObject* maybe_result = Allocate(foreign_map(), space);
3108   if (!maybe_result->To(&result)) return maybe_result;
3109   result->set_foreign_address(address);
3110   return result;
3111 }
3112
3113
3114 MaybeObject* Heap::AllocateSharedFunctionInfo(Object* name) {
3115   SharedFunctionInfo* share;
3116   MaybeObject* maybe = Allocate(shared_function_info_map(), OLD_POINTER_SPACE);
3117   if (!maybe->To<SharedFunctionInfo>(&share)) return maybe;
3118
3119   // Set pointer fields.
3120   share->set_name(name);
3121   Code* illegal = isolate_->builtins()->builtin(Builtins::kIllegal);
3122   share->set_code(illegal);
3123   share->ClearOptimizedCodeMap();
3124   share->set_scope_info(ScopeInfo::Empty());
3125   Code* construct_stub =
3126       isolate_->builtins()->builtin(Builtins::kJSConstructStubGeneric);
3127   share->set_construct_stub(construct_stub);
3128   share->set_instance_class_name(Object_symbol());
3129   share->set_function_data(undefined_value(), SKIP_WRITE_BARRIER);
3130   share->set_script(undefined_value(), SKIP_WRITE_BARRIER);
3131   share->set_debug_info(undefined_value(), SKIP_WRITE_BARRIER);
3132   share->set_inferred_name(empty_string(), SKIP_WRITE_BARRIER);
3133   share->set_initial_map(undefined_value(), SKIP_WRITE_BARRIER);
3134   share->set_this_property_assignments(undefined_value(), SKIP_WRITE_BARRIER);
3135   share->set_ast_node_count(0);
3136   share->set_stress_deopt_counter(FLAG_deopt_every_n_times);
3137   share->set_counters(0);
3138
3139   // Set integer fields (smi or int, depending on the architecture).
3140   share->set_length(0);
3141   share->set_formal_parameter_count(0);
3142   share->set_expected_nof_properties(0);
3143   share->set_num_literals(0);
3144   share->set_start_position_and_type(0);
3145   share->set_end_position(0);
3146   share->set_function_token_position(0);
3147   // All compiler hints default to false or 0.
3148   share->set_compiler_hints(0);
3149   share->set_this_property_assignments_count(0);
3150   share->set_opt_count(0);
3151
3152   return share;
3153 }
3154
3155
3156 MaybeObject* Heap::AllocateJSMessageObject(String* type,
3157                                            JSArray* arguments,
3158                                            int start_position,
3159                                            int end_position,
3160                                            Object* script,
3161                                            Object* stack_trace,
3162                                            Object* stack_frames) {
3163   Object* result;
3164   { MaybeObject* maybe_result = Allocate(message_object_map(), NEW_SPACE);
3165     if (!maybe_result->ToObject(&result)) return maybe_result;
3166   }
3167   JSMessageObject* message = JSMessageObject::cast(result);
3168   message->set_properties(Heap::empty_fixed_array(), SKIP_WRITE_BARRIER);
3169   message->initialize_elements();
3170   message->set_elements(Heap::empty_fixed_array(), SKIP_WRITE_BARRIER);
3171   message->set_type(type);
3172   message->set_arguments(arguments);
3173   message->set_start_position(start_position);
3174   message->set_end_position(end_position);
3175   message->set_script(script);
3176   message->set_stack_trace(stack_trace);
3177   message->set_stack_frames(stack_frames);
3178   return result;
3179 }
3180
3181
3182
3183 // Returns true for a character in a range.  Both limits are inclusive.
3184 static inline bool Between(uint32_t character, uint32_t from, uint32_t to) {
3185   // This makes uses of the the unsigned wraparound.
3186   return character - from <= to - from;
3187 }
3188
3189
3190 MUST_USE_RESULT static inline MaybeObject* MakeOrFindTwoCharacterString(
3191     Heap* heap,
3192     uint32_t c1,
3193     uint32_t c2) {
3194   String* symbol;
3195   // Numeric strings have a different hash algorithm not known by
3196   // LookupTwoCharsSymbolIfExists, so we skip this step for such strings.
3197   if ((!Between(c1, '0', '9') || !Between(c2, '0', '9')) &&
3198       heap->symbol_table()->LookupTwoCharsSymbolIfExists(c1, c2, &symbol)) {
3199     return symbol;
3200   // Now we know the length is 2, we might as well make use of that fact
3201   // when building the new string.
3202   } else if ((c1 | c2) <= String::kMaxAsciiCharCodeU) {  // We can do this
3203     ASSERT(IsPowerOf2(String::kMaxAsciiCharCodeU + 1));  // because of this.
3204     Object* result;
3205     { MaybeObject* maybe_result = heap->AllocateRawAsciiString(2);
3206       if (!maybe_result->ToObject(&result)) return maybe_result;
3207     }
3208     char* dest = SeqAsciiString::cast(result)->GetChars();
3209     dest[0] = c1;
3210     dest[1] = c2;
3211     return result;
3212   } else {
3213     Object* result;
3214     { MaybeObject* maybe_result = heap->AllocateRawTwoByteString(2);
3215       if (!maybe_result->ToObject(&result)) return maybe_result;
3216     }
3217     uc16* dest = SeqTwoByteString::cast(result)->GetChars();
3218     dest[0] = c1;
3219     dest[1] = c2;
3220     return result;
3221   }
3222 }
3223
3224
3225 MaybeObject* Heap::AllocateConsString(String* first, String* second) {
3226   int first_length = first->length();
3227   if (first_length == 0) {
3228     return second;
3229   }
3230
3231   int second_length = second->length();
3232   if (second_length == 0) {
3233     return first;
3234   }
3235
3236   int length = first_length + second_length;
3237
3238   // Optimization for 2-byte strings often used as keys in a decompression
3239   // dictionary.  Check whether we already have the string in the symbol
3240   // table to prevent creation of many unneccesary strings.
3241   if (length == 2) {
3242     unsigned c1 = first->Get(0);
3243     unsigned c2 = second->Get(0);
3244     return MakeOrFindTwoCharacterString(this, c1, c2);
3245   }
3246
3247   bool first_is_ascii = first->IsAsciiRepresentation();
3248   bool second_is_ascii = second->IsAsciiRepresentation();
3249   bool is_ascii = first_is_ascii && second_is_ascii;
3250
3251   // Make sure that an out of memory exception is thrown if the length
3252   // of the new cons string is too large.
3253   if (length > String::kMaxLength || length < 0) {
3254     isolate()->context()->mark_out_of_memory();
3255     return Failure::OutOfMemoryException();
3256   }
3257
3258   bool is_ascii_data_in_two_byte_string = false;
3259   if (!is_ascii) {
3260     // At least one of the strings uses two-byte representation so we
3261     // can't use the fast case code for short ASCII strings below, but
3262     // we can try to save memory if all chars actually fit in ASCII.
3263     is_ascii_data_in_two_byte_string =
3264         first->HasOnlyAsciiChars() && second->HasOnlyAsciiChars();
3265     if (is_ascii_data_in_two_byte_string) {
3266       isolate_->counters()->string_add_runtime_ext_to_ascii()->Increment();
3267     }
3268   }
3269
3270   // If the resulting string is small make a flat string.
3271   if (length < ConsString::kMinLength) {
3272     // Note that neither of the two inputs can be a slice because:
3273     STATIC_ASSERT(ConsString::kMinLength <= SlicedString::kMinLength);
3274     ASSERT(first->IsFlat());
3275     ASSERT(second->IsFlat());
3276     if (is_ascii) {
3277       Object* result;
3278       { MaybeObject* maybe_result = AllocateRawAsciiString(length);
3279         if (!maybe_result->ToObject(&result)) return maybe_result;
3280       }
3281       // Copy the characters into the new object.
3282       char* dest = SeqAsciiString::cast(result)->GetChars();
3283       // Copy first part.
3284       const char* src;
3285       if (first->IsExternalString()) {
3286         src = ExternalAsciiString::cast(first)->GetChars();
3287       } else {
3288         src = SeqAsciiString::cast(first)->GetChars();
3289       }
3290       for (int i = 0; i < first_length; i++) *dest++ = src[i];
3291       // Copy second part.
3292       if (second->IsExternalString()) {
3293         src = ExternalAsciiString::cast(second)->GetChars();
3294       } else {
3295         src = SeqAsciiString::cast(second)->GetChars();
3296       }
3297       for (int i = 0; i < second_length; i++) *dest++ = src[i];
3298       return result;
3299     } else {
3300       if (is_ascii_data_in_two_byte_string) {
3301         Object* result;
3302         { MaybeObject* maybe_result = AllocateRawAsciiString(length);
3303           if (!maybe_result->ToObject(&result)) return maybe_result;
3304         }
3305         // Copy the characters into the new object.
3306         char* dest = SeqAsciiString::cast(result)->GetChars();
3307         String::WriteToFlat(first, dest, 0, first_length);
3308         String::WriteToFlat(second, dest + first_length, 0, second_length);
3309         isolate_->counters()->string_add_runtime_ext_to_ascii()->Increment();
3310         return result;
3311       }
3312
3313       Object* result;
3314       { MaybeObject* maybe_result = AllocateRawTwoByteString(length);
3315         if (!maybe_result->ToObject(&result)) return maybe_result;
3316       }
3317       // Copy the characters into the new object.
3318       uc16* dest = SeqTwoByteString::cast(result)->GetChars();
3319       String::WriteToFlat(first, dest, 0, first_length);
3320       String::WriteToFlat(second, dest + first_length, 0, second_length);
3321       return result;
3322     }
3323   }
3324
3325   Map* map = (is_ascii || is_ascii_data_in_two_byte_string) ?
3326       cons_ascii_string_map() : cons_string_map();
3327
3328   Object* result;
3329   { MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
3330     if (!maybe_result->ToObject(&result)) return maybe_result;
3331   }
3332
3333   AssertNoAllocation no_gc;
3334   ConsString* cons_string = ConsString::cast(result);
3335   WriteBarrierMode mode = cons_string->GetWriteBarrierMode(no_gc);
3336   cons_string->set_length(length);
3337   cons_string->set_hash_field(String::kEmptyHashField);
3338   cons_string->set_first(first, mode);
3339   cons_string->set_second(second, mode);
3340   return result;
3341 }
3342
3343
3344 MaybeObject* Heap::AllocateSubString(String* buffer,
3345                                      int start,
3346                                      int end,
3347                                      PretenureFlag pretenure) {
3348   int length = end - start;
3349   if (length <= 0) {
3350     return empty_string();
3351   } else if (length == 1) {
3352     return LookupSingleCharacterStringFromCode(buffer->Get(start));
3353   } else if (length == 2) {
3354     // Optimization for 2-byte strings often used as keys in a decompression
3355     // dictionary.  Check whether we already have the string in the symbol
3356     // table to prevent creation of many unneccesary strings.
3357     unsigned c1 = buffer->Get(start);
3358     unsigned c2 = buffer->Get(start + 1);
3359     return MakeOrFindTwoCharacterString(this, c1, c2);
3360   }
3361
3362   // Make an attempt to flatten the buffer to reduce access time.
3363   buffer = buffer->TryFlattenGetString();
3364
3365   if (!FLAG_string_slices ||
3366       !buffer->IsFlat() ||
3367       length < SlicedString::kMinLength ||
3368       pretenure == TENURED) {
3369     Object* result;
3370     // WriteToFlat takes care of the case when an indirect string has a
3371     // different encoding from its underlying string.  These encodings may
3372     // differ because of externalization.
3373     bool is_ascii = buffer->IsAsciiRepresentation();
3374     { MaybeObject* maybe_result = is_ascii
3375                                   ? AllocateRawAsciiString(length, pretenure)
3376                                   : AllocateRawTwoByteString(length, pretenure);
3377       if (!maybe_result->ToObject(&result)) return maybe_result;
3378     }
3379     String* string_result = String::cast(result);
3380     // Copy the characters into the new object.
3381     if (is_ascii) {
3382       ASSERT(string_result->IsAsciiRepresentation());
3383       char* dest = SeqAsciiString::cast(string_result)->GetChars();
3384       String::WriteToFlat(buffer, dest, start, end);
3385     } else {
3386       ASSERT(string_result->IsTwoByteRepresentation());
3387       uc16* dest = SeqTwoByteString::cast(string_result)->GetChars();
3388       String::WriteToFlat(buffer, dest, start, end);
3389     }
3390     return result;
3391   }
3392
3393   ASSERT(buffer->IsFlat());
3394 #if VERIFY_HEAP
3395   if (FLAG_verify_heap) {
3396     buffer->StringVerify();
3397   }
3398 #endif
3399
3400   Object* result;
3401   // When slicing an indirect string we use its encoding for a newly created
3402   // slice and don't check the encoding of the underlying string.  This is safe
3403   // even if the encodings are different because of externalization.  If an
3404   // indirect ASCII string is pointing to a two-byte string, the two-byte char
3405   // codes of the underlying string must still fit into ASCII (because
3406   // externalization must not change char codes).
3407   { Map* map = buffer->IsAsciiRepresentation()
3408                  ? sliced_ascii_string_map()
3409                  : sliced_string_map();
3410     MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
3411     if (!maybe_result->ToObject(&result)) return maybe_result;
3412   }
3413
3414   AssertNoAllocation no_gc;
3415   SlicedString* sliced_string = SlicedString::cast(result);
3416   sliced_string->set_length(length);
3417   sliced_string->set_hash_field(String::kEmptyHashField);
3418   if (buffer->IsConsString()) {
3419     ConsString* cons = ConsString::cast(buffer);
3420     ASSERT(cons->second()->length() == 0);
3421     sliced_string->set_parent(cons->first());
3422     sliced_string->set_offset(start);
3423   } else if (buffer->IsSlicedString()) {
3424     // Prevent nesting sliced strings.
3425     SlicedString* parent_slice = SlicedString::cast(buffer);
3426     sliced_string->set_parent(parent_slice->parent());
3427     sliced_string->set_offset(start + parent_slice->offset());
3428   } else {
3429     sliced_string->set_parent(buffer);
3430     sliced_string->set_offset(start);
3431   }
3432   ASSERT(sliced_string->parent()->IsSeqString() ||
3433          sliced_string->parent()->IsExternalString());
3434   return result;
3435 }
3436
3437
3438 MaybeObject* Heap::AllocateExternalStringFromAscii(
3439     const ExternalAsciiString::Resource* resource) {
3440   size_t length = resource->length();
3441   if (length > static_cast<size_t>(String::kMaxLength)) {
3442     isolate()->context()->mark_out_of_memory();
3443     return Failure::OutOfMemoryException();
3444   }
3445
3446   ASSERT(String::IsAscii(resource->data(), static_cast<int>(length)));
3447
3448   Map* map = external_ascii_string_map();
3449   Object* result;
3450   { MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
3451     if (!maybe_result->ToObject(&result)) return maybe_result;
3452   }
3453
3454   ExternalAsciiString* external_string = ExternalAsciiString::cast(result);
3455   external_string->set_length(static_cast<int>(length));
3456   external_string->set_hash_field(String::kEmptyHashField);
3457   external_string->set_resource(resource);
3458
3459   return result;
3460 }
3461
3462
3463 MaybeObject* Heap::AllocateExternalStringFromTwoByte(
3464     const ExternalTwoByteString::Resource* resource) {
3465   size_t length = resource->length();
3466   if (length > static_cast<size_t>(String::kMaxLength)) {
3467     isolate()->context()->mark_out_of_memory();
3468     return Failure::OutOfMemoryException();
3469   }
3470
3471   // For small strings we check whether the resource contains only
3472   // ASCII characters.  If yes, we use a different string map.
3473   static const size_t kAsciiCheckLengthLimit = 32;
3474   bool is_ascii = length <= kAsciiCheckLengthLimit &&
3475       String::IsAscii(resource->data(), static_cast<int>(length));
3476   Map* map = is_ascii ?
3477       external_string_with_ascii_data_map() : external_string_map();
3478   Object* result;
3479   { MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
3480     if (!maybe_result->ToObject(&result)) return maybe_result;
3481   }
3482
3483   ExternalTwoByteString* external_string = ExternalTwoByteString::cast(result);
3484   external_string->set_length(static_cast<int>(length));
3485   external_string->set_hash_field(String::kEmptyHashField);
3486   external_string->set_resource(resource);
3487
3488   return result;
3489 }
3490
3491
3492 MaybeObject* Heap::LookupSingleCharacterStringFromCode(uint16_t code) {
3493   if (code <= String::kMaxAsciiCharCode) {
3494     Object* value = single_character_string_cache()->get(code);
3495     if (value != undefined_value()) return value;
3496
3497     char buffer[1];
3498     buffer[0] = static_cast<char>(code);
3499     Object* result;
3500     MaybeObject* maybe_result = LookupSymbol(Vector<const char>(buffer, 1));
3501
3502     if (!maybe_result->ToObject(&result)) return maybe_result;
3503     single_character_string_cache()->set(code, result);
3504     return result;
3505   }
3506
3507   Object* result;
3508   { MaybeObject* maybe_result = AllocateRawTwoByteString(1);
3509     if (!maybe_result->ToObject(&result)) return maybe_result;
3510   }
3511   String* answer = String::cast(result);
3512   answer->Set(0, code);
3513   return answer;
3514 }
3515
3516
3517 MaybeObject* Heap::AllocateByteArray(int length, PretenureFlag pretenure) {
3518   if (length < 0 || length > ByteArray::kMaxLength) {
3519     return Failure::OutOfMemoryException();
3520   }
3521   if (pretenure == NOT_TENURED) {
3522     return AllocateByteArray(length);
3523   }
3524   int size = ByteArray::SizeFor(length);
3525   Object* result;
3526   { MaybeObject* maybe_result = (size <= Page::kMaxNonCodeHeapObjectSize)
3527                    ? old_data_space_->AllocateRaw(size)
3528                    : lo_space_->AllocateRaw(size, NOT_EXECUTABLE);
3529     if (!maybe_result->ToObject(&result)) return maybe_result;
3530   }
3531
3532   reinterpret_cast<ByteArray*>(result)->set_map_no_write_barrier(
3533       byte_array_map());
3534   reinterpret_cast<ByteArray*>(result)->set_length(length);
3535   return result;
3536 }
3537
3538
3539 MaybeObject* Heap::AllocateByteArray(int length) {
3540   if (length < 0 || length > ByteArray::kMaxLength) {
3541     return Failure::OutOfMemoryException();
3542   }
3543   int size = ByteArray::SizeFor(length);
3544   AllocationSpace space =
3545       (size > Page::kMaxNonCodeHeapObjectSize) ? LO_SPACE : NEW_SPACE;
3546   Object* result;
3547   { MaybeObject* maybe_result = AllocateRaw(size, space, OLD_DATA_SPACE);
3548     if (!maybe_result->ToObject(&result)) return maybe_result;
3549   }
3550
3551   reinterpret_cast<ByteArray*>(result)->set_map_no_write_barrier(
3552       byte_array_map());
3553   reinterpret_cast<ByteArray*>(result)->set_length(length);
3554   return result;
3555 }
3556
3557
3558 void Heap::CreateFillerObjectAt(Address addr, int size) {
3559   if (size == 0) return;
3560   HeapObject* filler = HeapObject::FromAddress(addr);
3561   if (size == kPointerSize) {
3562     filler->set_map_no_write_barrier(one_pointer_filler_map());
3563   } else if (size == 2 * kPointerSize) {
3564     filler->set_map_no_write_barrier(two_pointer_filler_map());
3565   } else {
3566     filler->set_map_no_write_barrier(free_space_map());
3567     FreeSpace::cast(filler)->set_size(size);
3568   }
3569 }
3570
3571
3572 MaybeObject* Heap::AllocateExternalArray(int length,
3573                                          ExternalArrayType array_type,
3574                                          void* external_pointer,
3575                                          PretenureFlag pretenure) {
3576   AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
3577   Object* result;
3578   { MaybeObject* maybe_result = AllocateRaw(ExternalArray::kAlignedSize,
3579                                             space,
3580                                             OLD_DATA_SPACE);
3581     if (!maybe_result->ToObject(&result)) return maybe_result;
3582   }
3583
3584   reinterpret_cast<ExternalArray*>(result)->set_map_no_write_barrier(
3585       MapForExternalArrayType(array_type));
3586   reinterpret_cast<ExternalArray*>(result)->set_length(length);
3587   reinterpret_cast<ExternalArray*>(result)->set_external_pointer(
3588       external_pointer);
3589
3590   return result;
3591 }
3592
3593
3594 MaybeObject* Heap::CreateCode(const CodeDesc& desc,
3595                               Code::Flags flags,
3596                               Handle<Object> self_reference,
3597                               bool immovable) {
3598   // Allocate ByteArray before the Code object, so that we do not risk
3599   // leaving uninitialized Code object (and breaking the heap).
3600   ByteArray* reloc_info;
3601   MaybeObject* maybe_reloc_info = AllocateByteArray(desc.reloc_size, TENURED);
3602   if (!maybe_reloc_info->To(&reloc_info)) return maybe_reloc_info;
3603
3604   // Compute size.
3605   int body_size = RoundUp(desc.instr_size, kObjectAlignment);
3606   int obj_size = Code::SizeFor(body_size);
3607   ASSERT(IsAligned(static_cast<intptr_t>(obj_size), kCodeAlignment));
3608   MaybeObject* maybe_result;
3609   // Large code objects and code objects which should stay at a fixed address
3610   // are allocated in large object space.
3611   HeapObject* result;
3612   bool force_lo_space = obj_size > code_space()->AreaSize();
3613   if (force_lo_space) {
3614     maybe_result = lo_space_->AllocateRaw(obj_size, EXECUTABLE);
3615   } else {
3616     maybe_result = code_space_->AllocateRaw(obj_size);
3617   }
3618   if (!maybe_result->To<HeapObject>(&result)) return maybe_result;
3619
3620   if (immovable && !force_lo_space &&
3621       // Objects on the first page of each space are never moved.
3622       !code_space_->FirstPage()->Contains(result->address())) {
3623     // Discard the first code allocation, which was on a page where it could be
3624     // moved.
3625     CreateFillerObjectAt(result->address(), obj_size);
3626     maybe_result = lo_space_->AllocateRaw(obj_size, EXECUTABLE);
3627     if (!maybe_result->To<HeapObject>(&result)) return maybe_result;
3628   }
3629
3630   // Initialize the object
3631   result->set_map_no_write_barrier(code_map());
3632   Code* code = Code::cast(result);
3633   ASSERT(!isolate_->code_range()->exists() ||
3634       isolate_->code_range()->contains(code->address()));
3635   code->set_instruction_size(desc.instr_size);
3636   code->set_relocation_info(reloc_info);
3637   code->set_flags(flags);
3638   if (code->is_call_stub() || code->is_keyed_call_stub()) {
3639     code->set_check_type(RECEIVER_MAP_CHECK);
3640   }
3641   code->set_deoptimization_data(empty_fixed_array(), SKIP_WRITE_BARRIER);
3642   code->set_type_feedback_info(undefined_value(), SKIP_WRITE_BARRIER);
3643   code->set_handler_table(empty_fixed_array(), SKIP_WRITE_BARRIER);
3644   code->set_gc_metadata(Smi::FromInt(0));
3645   code->set_ic_age(global_ic_age_);
3646   // Allow self references to created code object by patching the handle to
3647   // point to the newly allocated Code object.
3648   if (!self_reference.is_null()) {
3649     *(self_reference.location()) = code;
3650   }
3651   // Migrate generated code.
3652   // The generated code can contain Object** values (typically from handles)
3653   // that are dereferenced during the copy to point directly to the actual heap
3654   // objects. These pointers can include references to the code object itself,
3655   // through the self_reference parameter.
3656   code->CopyFrom(desc);
3657
3658 #ifdef VERIFY_HEAP
3659   if (FLAG_verify_heap) {
3660     code->Verify();
3661   }
3662 #endif
3663   return code;
3664 }
3665
3666
3667 MaybeObject* Heap::CopyCode(Code* code) {
3668   // Allocate an object the same size as the code object.
3669   int obj_size = code->Size();
3670   MaybeObject* maybe_result;
3671   if (obj_size > code_space()->AreaSize()) {
3672     maybe_result = lo_space_->AllocateRaw(obj_size, EXECUTABLE);
3673   } else {
3674     maybe_result = code_space_->AllocateRaw(obj_size);
3675   }
3676
3677   Object* result;
3678   if (!maybe_result->ToObject(&result)) return maybe_result;
3679
3680   // Copy code object.
3681   Address old_addr = code->address();
3682   Address new_addr = reinterpret_cast<HeapObject*>(result)->address();
3683   CopyBlock(new_addr, old_addr, obj_size);
3684   // Relocate the copy.
3685   Code* new_code = Code::cast(result);
3686   ASSERT(!isolate_->code_range()->exists() ||
3687       isolate_->code_range()->contains(code->address()));
3688   new_code->Relocate(new_addr - old_addr);
3689   return new_code;
3690 }
3691
3692
3693 MaybeObject* Heap::CopyCode(Code* code, Vector<byte> reloc_info) {
3694   // Allocate ByteArray before the Code object, so that we do not risk
3695   // leaving uninitialized Code object (and breaking the heap).
3696   Object* reloc_info_array;
3697   { MaybeObject* maybe_reloc_info_array =
3698         AllocateByteArray(reloc_info.length(), TENURED);
3699     if (!maybe_reloc_info_array->ToObject(&reloc_info_array)) {
3700       return maybe_reloc_info_array;
3701     }
3702   }
3703
3704   int new_body_size = RoundUp(code->instruction_size(), kObjectAlignment);
3705
3706   int new_obj_size = Code::SizeFor(new_body_size);
3707
3708   Address old_addr = code->address();
3709
3710   size_t relocation_offset =
3711       static_cast<size_t>(code->instruction_end() - old_addr);
3712
3713   MaybeObject* maybe_result;
3714   if (new_obj_size > code_space()->AreaSize()) {
3715     maybe_result = lo_space_->AllocateRaw(new_obj_size, EXECUTABLE);
3716   } else {
3717     maybe_result = code_space_->AllocateRaw(new_obj_size);
3718   }
3719
3720   Object* result;
3721   if (!maybe_result->ToObject(&result)) return maybe_result;
3722
3723   // Copy code object.
3724   Address new_addr = reinterpret_cast<HeapObject*>(result)->address();
3725
3726   // Copy header and instructions.
3727   memcpy(new_addr, old_addr, relocation_offset);
3728
3729   Code* new_code = Code::cast(result);
3730   new_code->set_relocation_info(ByteArray::cast(reloc_info_array));
3731
3732   // Copy patched rinfo.
3733   memcpy(new_code->relocation_start(), reloc_info.start(), reloc_info.length());
3734
3735   // Relocate the copy.
3736   ASSERT(!isolate_->code_range()->exists() ||
3737       isolate_->code_range()->contains(code->address()));
3738   new_code->Relocate(new_addr - old_addr);
3739
3740 #ifdef VERIFY_HEAP
3741   if (FLAG_verify_heap) {
3742     code->Verify();
3743   }
3744 #endif
3745   return new_code;
3746 }
3747
3748
3749 MaybeObject* Heap::Allocate(Map* map, AllocationSpace space) {
3750   ASSERT(gc_state_ == NOT_IN_GC);
3751   ASSERT(map->instance_type() != MAP_TYPE);
3752   // If allocation failures are disallowed, we may allocate in a different
3753   // space when new space is full and the object is not a large object.
3754   AllocationSpace retry_space =
3755       (space != NEW_SPACE) ? space : TargetSpaceId(map->instance_type());
3756   Object* result;
3757   { MaybeObject* maybe_result =
3758         AllocateRaw(map->instance_size(), space, retry_space);
3759     if (!maybe_result->ToObject(&result)) return maybe_result;
3760   }
3761   // No need for write barrier since object is white and map is in old space.
3762   HeapObject::cast(result)->set_map_no_write_barrier(map);
3763   return result;
3764 }
3765
3766
3767 void Heap::InitializeFunction(JSFunction* function,
3768                               SharedFunctionInfo* shared,
3769                               Object* prototype) {
3770   ASSERT(!prototype->IsMap());
3771   function->initialize_properties();
3772   function->initialize_elements();
3773   function->set_shared(shared);
3774   function->set_code(shared->code());
3775   function->set_prototype_or_initial_map(prototype);
3776   function->set_context(undefined_value());
3777   function->set_literals_or_bindings(empty_fixed_array());
3778   function->set_next_function_link(undefined_value());
3779 }
3780
3781
3782 MaybeObject* Heap::AllocateFunctionPrototype(JSFunction* function) {
3783   // Allocate the prototype.  Make sure to use the object function
3784   // from the function's context, since the function can be from a
3785   // different context.
3786   JSFunction* object_function =
3787       function->context()->native_context()->object_function();
3788
3789   // Each function prototype gets a copy of the object function map.
3790   // This avoid unwanted sharing of maps between prototypes of different
3791   // constructors.
3792   Map* new_map;
3793   ASSERT(object_function->has_initial_map());
3794   MaybeObject* maybe_map = object_function->initial_map()->Copy();
3795   if (!maybe_map->To(&new_map)) return maybe_map;
3796
3797   Object* prototype;
3798   MaybeObject* maybe_prototype = AllocateJSObjectFromMap(new_map);
3799   if (!maybe_prototype->ToObject(&prototype)) return maybe_prototype;
3800
3801   // When creating the prototype for the function we must set its
3802   // constructor to the function.
3803   MaybeObject* maybe_failure =
3804       JSObject::cast(prototype)->SetLocalPropertyIgnoreAttributes(
3805           constructor_symbol(), function, DONT_ENUM);
3806   if (maybe_failure->IsFailure()) return maybe_failure;
3807
3808   return prototype;
3809 }
3810
3811
3812 MaybeObject* Heap::AllocateFunction(Map* function_map,
3813                                     SharedFunctionInfo* shared,
3814                                     Object* prototype,
3815                                     PretenureFlag pretenure) {
3816   AllocationSpace space =
3817       (pretenure == TENURED) ? OLD_POINTER_SPACE : NEW_SPACE;
3818   Object* result;
3819   { MaybeObject* maybe_result = Allocate(function_map, space);
3820     if (!maybe_result->ToObject(&result)) return maybe_result;
3821   }
3822   InitializeFunction(JSFunction::cast(result), shared, prototype);
3823   return result;
3824 }
3825
3826
3827 MaybeObject* Heap::AllocateArgumentsObject(Object* callee, int length) {
3828   // To get fast allocation and map sharing for arguments objects we
3829   // allocate them based on an arguments boilerplate.
3830
3831   JSObject* boilerplate;
3832   int arguments_object_size;
3833   bool strict_mode_callee = callee->IsJSFunction() &&
3834       !JSFunction::cast(callee)->shared()->is_classic_mode();
3835   if (strict_mode_callee) {
3836     boilerplate =
3837         isolate()->context()->native_context()->
3838             strict_mode_arguments_boilerplate();
3839     arguments_object_size = kArgumentsObjectSizeStrict;
3840   } else {
3841     boilerplate =
3842         isolate()->context()->native_context()->arguments_boilerplate();
3843     arguments_object_size = kArgumentsObjectSize;
3844   }
3845
3846   // This calls Copy directly rather than using Heap::AllocateRaw so we
3847   // duplicate the check here.
3848   ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);
3849
3850   // Check that the size of the boilerplate matches our
3851   // expectations. The ArgumentsAccessStub::GenerateNewObject relies
3852   // on the size being a known constant.
3853   ASSERT(arguments_object_size == boilerplate->map()->instance_size());
3854
3855   // Do the allocation.
3856   Object* result;
3857   { MaybeObject* maybe_result =
3858         AllocateRaw(arguments_object_size, NEW_SPACE, OLD_POINTER_SPACE);
3859     if (!maybe_result->ToObject(&result)) return maybe_result;
3860   }
3861
3862   // Copy the content. The arguments boilerplate doesn't have any
3863   // fields that point to new space so it's safe to skip the write
3864   // barrier here.
3865   CopyBlock(HeapObject::cast(result)->address(),
3866             boilerplate->address(),
3867             JSObject::kHeaderSize);
3868
3869   // Set the length property.
3870   JSObject::cast(result)->InObjectPropertyAtPut(kArgumentsLengthIndex,
3871                                                 Smi::FromInt(length),
3872                                                 SKIP_WRITE_BARRIER);
3873   // Set the callee property for non-strict mode arguments object only.
3874   if (!strict_mode_callee) {
3875     JSObject::cast(result)->InObjectPropertyAtPut(kArgumentsCalleeIndex,
3876                                                   callee);
3877   }
3878
3879   // Check the state of the object
3880   ASSERT(JSObject::cast(result)->HasFastProperties());
3881   ASSERT(JSObject::cast(result)->HasFastObjectElements());
3882
3883   return result;
3884 }
3885
3886
3887 static bool HasDuplicates(DescriptorArray* descriptors) {
3888   int count = descriptors->number_of_descriptors();
3889   if (count > 1) {
3890     String* prev_key = descriptors->GetKey(0);
3891     for (int i = 1; i != count; i++) {
3892       String* current_key = descriptors->GetKey(i);
3893       if (prev_key == current_key) return true;
3894       prev_key = current_key;
3895     }
3896   }
3897   return false;
3898 }
3899
3900
3901 MaybeObject* Heap::AllocateInitialMap(JSFunction* fun) {
3902   ASSERT(!fun->has_initial_map());
3903
3904   // First create a new map with the size and number of in-object properties
3905   // suggested by the function.
3906   int instance_size = fun->shared()->CalculateInstanceSize();
3907   int in_object_properties = fun->shared()->CalculateInObjectProperties();
3908   Map* map;
3909   MaybeObject* maybe_map = AllocateMap(JS_OBJECT_TYPE, instance_size);
3910   if (!maybe_map->To(&map)) return maybe_map;
3911
3912   // Fetch or allocate prototype.
3913   Object* prototype;
3914   if (fun->has_instance_prototype()) {
3915     prototype = fun->instance_prototype();
3916   } else {
3917     MaybeObject* maybe_prototype = AllocateFunctionPrototype(fun);
3918     if (!maybe_prototype->To(&prototype)) return maybe_prototype;
3919   }
3920   map->set_inobject_properties(in_object_properties);
3921   map->set_unused_property_fields(in_object_properties);
3922   map->set_prototype(prototype);
3923   ASSERT(map->has_fast_object_elements());
3924
3925   // If the function has only simple this property assignments add
3926   // field descriptors for these to the initial map as the object
3927   // cannot be constructed without having these properties.  Guard by
3928   // the inline_new flag so we only change the map if we generate a
3929   // specialized construct stub.
3930   ASSERT(in_object_properties <= Map::kMaxPreAllocatedPropertyFields);
3931   if (fun->shared()->CanGenerateInlineConstructor(prototype)) {
3932     int count = fun->shared()->this_property_assignments_count();
3933     if (count > in_object_properties) {
3934       // Inline constructor can only handle inobject properties.
3935       fun->shared()->ForbidInlineConstructor();
3936     } else {
3937       DescriptorArray* descriptors;
3938       MaybeObject* maybe_descriptors = DescriptorArray::Allocate(count);
3939       if (!maybe_descriptors->To(&descriptors)) return maybe_descriptors;
3940
3941       DescriptorArray::WhitenessWitness witness(descriptors);
3942       for (int i = 0; i < count; i++) {
3943         String* name = fun->shared()->GetThisPropertyAssignmentName(i);
3944         ASSERT(name->IsSymbol());
3945         FieldDescriptor field(name, i, NONE, i + 1);
3946         descriptors->Set(i, &field, witness);
3947       }
3948       descriptors->Sort();
3949
3950       // The descriptors may contain duplicates because the compiler does not
3951       // guarantee the uniqueness of property names (it would have required
3952       // quadratic time). Once the descriptors are sorted we can check for
3953       // duplicates in linear time.
3954       if (HasDuplicates(descriptors)) {
3955         fun->shared()->ForbidInlineConstructor();
3956       } else {
3957         map->InitializeDescriptors(descriptors);
3958         map->set_pre_allocated_property_fields(count);
3959         map->set_unused_property_fields(in_object_properties - count);
3960       }
3961     }
3962   }
3963
3964   fun->shared()->StartInobjectSlackTracking(map);
3965
3966   return map;
3967 }
3968
3969
3970 void Heap::InitializeJSObjectFromMap(JSObject* obj,
3971                                      FixedArray* properties,
3972                                      Map* map) {
3973   obj->set_properties(properties);
3974   obj->initialize_elements();
3975   // TODO(1240798): Initialize the object's body using valid initial values
3976   // according to the object's initial map.  For example, if the map's
3977   // instance type is JS_ARRAY_TYPE, the length field should be initialized
3978   // to a number (e.g. Smi::FromInt(0)) and the elements initialized to a
3979   // fixed array (e.g. Heap::empty_fixed_array()).  Currently, the object
3980   // verification code has to cope with (temporarily) invalid objects.  See
3981   // for example, JSArray::JSArrayVerify).
3982   Object* filler;
3983   // We cannot always fill with one_pointer_filler_map because objects
3984   // created from API functions expect their internal fields to be initialized
3985   // with undefined_value.
3986   // Pre-allocated fields need to be initialized with undefined_value as well
3987   // so that object accesses before the constructor completes (e.g. in the
3988   // debugger) will not cause a crash.
3989   if (map->constructor()->IsJSFunction() &&
3990       JSFunction::cast(map->constructor())->shared()->
3991           IsInobjectSlackTrackingInProgress()) {
3992     // We might want to shrink the object later.
3993     ASSERT(obj->GetInternalFieldCount() == 0);
3994     filler = Heap::one_pointer_filler_map();
3995   } else {
3996     filler = Heap::undefined_value();
3997   }
3998   obj->InitializeBody(map, Heap::undefined_value(), filler);
3999 }
4000
4001
4002 MaybeObject* Heap::AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure) {
4003   // JSFunctions should be allocated using AllocateFunction to be
4004   // properly initialized.
4005   ASSERT(map->instance_type() != JS_FUNCTION_TYPE);
4006
4007   // Both types of global objects should be allocated using
4008   // AllocateGlobalObject to be properly initialized.
4009   ASSERT(map->instance_type() != JS_GLOBAL_OBJECT_TYPE);
4010   ASSERT(map->instance_type() != JS_BUILTINS_OBJECT_TYPE);
4011
4012   // Allocate the backing storage for the properties.
4013   int prop_size =
4014       map->pre_allocated_property_fields() +
4015       map->unused_property_fields() -
4016       map->inobject_properties();
4017   ASSERT(prop_size >= 0);
4018   Object* properties;
4019   { MaybeObject* maybe_properties = AllocateFixedArray(prop_size, pretenure);
4020     if (!maybe_properties->ToObject(&properties)) return maybe_properties;
4021   }
4022
4023   // Allocate the JSObject.
4024   AllocationSpace space =
4025       (pretenure == TENURED) ? OLD_POINTER_SPACE : NEW_SPACE;
4026   if (map->instance_size() > Page::kMaxNonCodeHeapObjectSize) space = LO_SPACE;
4027   Object* obj;
4028   { MaybeObject* maybe_obj = Allocate(map, space);
4029     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
4030   }
4031
4032   // Initialize the JSObject.
4033   InitializeJSObjectFromMap(JSObject::cast(obj),
4034                             FixedArray::cast(properties),
4035                             map);
4036   ASSERT(JSObject::cast(obj)->HasFastSmiOrObjectElements());
4037   return obj;
4038 }
4039
4040
4041 MaybeObject* Heap::AllocateJSObject(JSFunction* constructor,
4042                                     PretenureFlag pretenure) {
4043   // Allocate the initial map if absent.
4044   if (!constructor->has_initial_map()) {
4045     Object* initial_map;
4046     { MaybeObject* maybe_initial_map = AllocateInitialMap(constructor);
4047       if (!maybe_initial_map->ToObject(&initial_map)) return maybe_initial_map;
4048     }
4049     constructor->set_initial_map(Map::cast(initial_map));
4050     Map::cast(initial_map)->set_constructor(constructor);
4051   }
4052   // Allocate the object based on the constructors initial map.
4053   MaybeObject* result = AllocateJSObjectFromMap(
4054       constructor->initial_map(), pretenure);
4055 #ifdef DEBUG
4056   // Make sure result is NOT a global object if valid.
4057   Object* non_failure;
4058   ASSERT(!result->ToObject(&non_failure) || !non_failure->IsGlobalObject());
4059 #endif
4060   return result;
4061 }
4062
4063
4064 MaybeObject* Heap::AllocateJSModule(Context* context, ScopeInfo* scope_info) {
4065   // Allocate a fresh map. Modules do not have a prototype.
4066   Map* map;
4067   MaybeObject* maybe_map = AllocateMap(JS_MODULE_TYPE, JSModule::kSize);
4068   if (!maybe_map->To(&map)) return maybe_map;
4069   // Allocate the object based on the map.
4070   JSModule* module;
4071   MaybeObject* maybe_module = AllocateJSObjectFromMap(map, TENURED);
4072   if (!maybe_module->To(&module)) return maybe_module;
4073   module->set_context(context);
4074   module->set_scope_info(scope_info);
4075   return module;
4076 }
4077
4078
4079 MaybeObject* Heap::AllocateJSArrayAndStorage(
4080     ElementsKind elements_kind,
4081     int length,
4082     int capacity,
4083     ArrayStorageAllocationMode mode,
4084     PretenureFlag pretenure) {
4085   ASSERT(capacity >= length);
4086   if (length != 0 && mode == INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE) {
4087     elements_kind = GetHoleyElementsKind(elements_kind);
4088   }
4089   MaybeObject* maybe_array = AllocateJSArray(elements_kind, pretenure);
4090   JSArray* array;
4091   if (!maybe_array->To(&array)) return maybe_array;
4092
4093   if (capacity == 0) {
4094     array->set_length(Smi::FromInt(0));
4095     array->set_elements(empty_fixed_array());
4096     return array;
4097   }
4098
4099   FixedArrayBase* elms;
4100   MaybeObject* maybe_elms = NULL;
4101   if (elements_kind == FAST_DOUBLE_ELEMENTS) {
4102     if (mode == DONT_INITIALIZE_ARRAY_ELEMENTS) {
4103       maybe_elms = AllocateUninitializedFixedDoubleArray(capacity);
4104     } else {
4105       ASSERT(mode == INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
4106       maybe_elms = AllocateFixedDoubleArrayWithHoles(capacity);
4107     }
4108   } else {
4109     ASSERT(IsFastSmiOrObjectElementsKind(elements_kind));
4110     if (mode == DONT_INITIALIZE_ARRAY_ELEMENTS) {
4111       maybe_elms = AllocateUninitializedFixedArray(capacity);
4112     } else {
4113       ASSERT(mode == INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE);
4114       maybe_elms = AllocateFixedArrayWithHoles(capacity);
4115     }
4116   }
4117   if (!maybe_elms->To(&elms)) return maybe_elms;
4118
4119   array->set_elements(elms);
4120   array->set_length(Smi::FromInt(length));
4121   return array;
4122 }
4123
4124
4125 MaybeObject* Heap::AllocateJSArrayWithElements(
4126     FixedArrayBase* elements,
4127     ElementsKind elements_kind,
4128     PretenureFlag pretenure) {
4129   MaybeObject* maybe_array = AllocateJSArray(elements_kind, pretenure);
4130   JSArray* array;
4131   if (!maybe_array->To(&array)) return maybe_array;
4132
4133   array->set_elements(elements);
4134   array->set_length(Smi::FromInt(elements->length()));
4135   array->ValidateElements();
4136   return array;
4137 }
4138
4139
4140 MaybeObject* Heap::AllocateJSProxy(Object* handler, Object* prototype) {
4141   // Allocate map.
4142   // TODO(rossberg): Once we optimize proxies, think about a scheme to share
4143   // maps. Will probably depend on the identity of the handler object, too.
4144   Map* map;
4145   MaybeObject* maybe_map_obj = AllocateMap(JS_PROXY_TYPE, JSProxy::kSize);
4146   if (!maybe_map_obj->To<Map>(&map)) return maybe_map_obj;
4147   map->set_prototype(prototype);
4148
4149   // Allocate the proxy object.
4150   JSProxy* result;
4151   MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
4152   if (!maybe_result->To<JSProxy>(&result)) return maybe_result;
4153   result->InitializeBody(map->instance_size(), Smi::FromInt(0));
4154   result->set_handler(handler);
4155   result->set_hash(undefined_value(), SKIP_WRITE_BARRIER);
4156   return result;
4157 }
4158
4159
4160 MaybeObject* Heap::AllocateJSFunctionProxy(Object* handler,
4161                                            Object* call_trap,
4162                                            Object* construct_trap,
4163                                            Object* prototype) {
4164   // Allocate map.
4165   // TODO(rossberg): Once we optimize proxies, think about a scheme to share
4166   // maps. Will probably depend on the identity of the handler object, too.
4167   Map* map;
4168   MaybeObject* maybe_map_obj =
4169       AllocateMap(JS_FUNCTION_PROXY_TYPE, JSFunctionProxy::kSize);
4170   if (!maybe_map_obj->To<Map>(&map)) return maybe_map_obj;
4171   map->set_prototype(prototype);
4172
4173   // Allocate the proxy object.
4174   JSFunctionProxy* result;
4175   MaybeObject* maybe_result = Allocate(map, NEW_SPACE);
4176   if (!maybe_result->To<JSFunctionProxy>(&result)) return maybe_result;
4177   result->InitializeBody(map->instance_size(), Smi::FromInt(0));
4178   result->set_handler(handler);
4179   result->set_hash(undefined_value(), SKIP_WRITE_BARRIER);
4180   result->set_call_trap(call_trap);
4181   result->set_construct_trap(construct_trap);
4182   return result;
4183 }
4184
4185
4186 MaybeObject* Heap::AllocateGlobalObject(JSFunction* constructor) {
4187   ASSERT(constructor->has_initial_map());
4188   Map* map = constructor->initial_map();
4189   ASSERT(map->is_dictionary_map());
4190
4191   // Make sure no field properties are described in the initial map.
4192   // This guarantees us that normalizing the properties does not
4193   // require us to change property values to JSGlobalPropertyCells.
4194   ASSERT(map->NextFreePropertyIndex() == 0);
4195
4196   // Make sure we don't have a ton of pre-allocated slots in the
4197   // global objects. They will be unused once we normalize the object.
4198   ASSERT(map->unused_property_fields() == 0);
4199   ASSERT(map->inobject_properties() == 0);
4200
4201   // Initial size of the backing store to avoid resize of the storage during
4202   // bootstrapping. The size differs between the JS global object ad the
4203   // builtins object.
4204   int initial_size = map->instance_type() == JS_GLOBAL_OBJECT_TYPE ? 64 : 512;
4205
4206   // Allocate a dictionary object for backing storage.
4207   StringDictionary* dictionary;
4208   MaybeObject* maybe_dictionary =
4209       StringDictionary::Allocate(
4210           map->NumberOfOwnDescriptors() * 2 + initial_size);
4211   if (!maybe_dictionary->To(&dictionary)) return maybe_dictionary;
4212
4213   // The global object might be created from an object template with accessors.
4214   // Fill these accessors into the dictionary.
4215   DescriptorArray* descs = map->instance_descriptors();
4216   for (int i = 0; i < descs->number_of_descriptors(); i++) {
4217     PropertyDetails details = descs->GetDetails(i);
4218     ASSERT(details.type() == CALLBACKS);  // Only accessors are expected.
4219     PropertyDetails d = PropertyDetails(details.attributes(),
4220                                         CALLBACKS,
4221                                         details.descriptor_index());
4222     Object* value = descs->GetCallbacksObject(i);
4223     MaybeObject* maybe_value = AllocateJSGlobalPropertyCell(value);
4224     if (!maybe_value->ToObject(&value)) return maybe_value;
4225
4226     MaybeObject* maybe_added = dictionary->Add(descs->GetKey(i), value, d);
4227     if (!maybe_added->To(&dictionary)) return maybe_added;
4228   }
4229
4230   // Allocate the global object and initialize it with the backing store.
4231   JSObject* global;
4232   MaybeObject* maybe_global = Allocate(map, OLD_POINTER_SPACE);
4233   if (!maybe_global->To(&global)) return maybe_global;
4234
4235   InitializeJSObjectFromMap(global, dictionary, map);
4236
4237   // Create a new map for the global object.
4238   Map* new_map;
4239   MaybeObject* maybe_map = map->CopyDropDescriptors();
4240   if (!maybe_map->To(&new_map)) return maybe_map;
4241   new_map->set_dictionary_map(true);
4242
4243   // Set up the global object as a normalized object.
4244   global->set_map(new_map);
4245   global->set_properties(dictionary);
4246
4247   // Make sure result is a global object with properties in dictionary.
4248   ASSERT(global->IsGlobalObject());
4249   ASSERT(!global->HasFastProperties());
4250   return global;
4251 }
4252
4253
4254 MaybeObject* Heap::CopyJSObject(JSObject* source) {
4255   // Never used to copy functions.  If functions need to be copied we
4256   // have to be careful to clear the literals array.
4257   SLOW_ASSERT(!source->IsJSFunction());
4258
4259   // Make the clone.
4260   Map* map = source->map();
4261   int object_size = map->instance_size();
4262   Object* clone;
4263
4264   WriteBarrierMode wb_mode = UPDATE_WRITE_BARRIER;
4265
4266   // If we're forced to always allocate, we use the general allocation
4267   // functions which may leave us with an object in old space.
4268   if (always_allocate()) {
4269     { MaybeObject* maybe_clone =
4270           AllocateRaw(object_size, NEW_SPACE, OLD_POINTER_SPACE);
4271       if (!maybe_clone->ToObject(&clone)) return maybe_clone;
4272     }
4273     Address clone_address = HeapObject::cast(clone)->address();
4274     CopyBlock(clone_address,
4275               source->address(),
4276               object_size);
4277     // Update write barrier for all fields that lie beyond the header.
4278     RecordWrites(clone_address,
4279                  JSObject::kHeaderSize,
4280                  (object_size - JSObject::kHeaderSize) / kPointerSize);
4281   } else {
4282     wb_mode = SKIP_WRITE_BARRIER;
4283     { MaybeObject* maybe_clone = new_space_.AllocateRaw(object_size);
4284       if (!maybe_clone->ToObject(&clone)) return maybe_clone;
4285     }
4286     SLOW_ASSERT(InNewSpace(clone));
4287     // Since we know the clone is allocated in new space, we can copy
4288     // the contents without worrying about updating the write barrier.
4289     CopyBlock(HeapObject::cast(clone)->address(),
4290               source->address(),
4291               object_size);
4292   }
4293
4294   SLOW_ASSERT(
4295       JSObject::cast(clone)->GetElementsKind() == source->GetElementsKind());
4296   FixedArrayBase* elements = FixedArrayBase::cast(source->elements());
4297   FixedArray* properties = FixedArray::cast(source->properties());
4298   // Update elements if necessary.
4299   if (elements->length() > 0) {
4300     Object* elem;
4301     { MaybeObject* maybe_elem;
4302       if (elements->map() == fixed_cow_array_map()) {
4303         maybe_elem = FixedArray::cast(elements);
4304       } else if (source->HasFastDoubleElements()) {
4305         maybe_elem = CopyFixedDoubleArray(FixedDoubleArray::cast(elements));
4306       } else {
4307         maybe_elem = CopyFixedArray(FixedArray::cast(elements));
4308       }
4309       if (!maybe_elem->ToObject(&elem)) return maybe_elem;
4310     }
4311     JSObject::cast(clone)->set_elements(FixedArrayBase::cast(elem), wb_mode);
4312   }
4313   // Update properties if necessary.
4314   if (properties->length() > 0) {
4315     Object* prop;
4316     { MaybeObject* maybe_prop = CopyFixedArray(properties);
4317       if (!maybe_prop->ToObject(&prop)) return maybe_prop;
4318     }
4319     JSObject::cast(clone)->set_properties(FixedArray::cast(prop), wb_mode);
4320   }
4321   // Return the new clone.
4322   return clone;
4323 }
4324
4325
4326 MaybeObject* Heap::ReinitializeJSReceiver(
4327     JSReceiver* object, InstanceType type, int size) {
4328   ASSERT(type >= FIRST_JS_OBJECT_TYPE);
4329
4330   // Allocate fresh map.
4331   // TODO(rossberg): Once we optimize proxies, cache these maps.
4332   Map* map;
4333   MaybeObject* maybe = AllocateMap(type, size);
4334   if (!maybe->To<Map>(&map)) return maybe;
4335
4336   // Check that the receiver has at least the size of the fresh object.
4337   int size_difference = object->map()->instance_size() - map->instance_size();
4338   ASSERT(size_difference >= 0);
4339
4340   map->set_prototype(object->map()->prototype());
4341
4342   // Allocate the backing storage for the properties.
4343   int prop_size = map->unused_property_fields() - map->inobject_properties();
4344   Object* properties;
4345   maybe = AllocateFixedArray(prop_size, TENURED);
4346   if (!maybe->ToObject(&properties)) return maybe;
4347
4348   // Functions require some allocation, which might fail here.
4349   SharedFunctionInfo* shared = NULL;
4350   if (type == JS_FUNCTION_TYPE) {
4351     String* name;
4352     maybe = LookupAsciiSymbol("<freezing call trap>");
4353     if (!maybe->To<String>(&name)) return maybe;
4354     maybe = AllocateSharedFunctionInfo(name);
4355     if (!maybe->To<SharedFunctionInfo>(&shared)) return maybe;
4356   }
4357
4358   // Because of possible retries of this function after failure,
4359   // we must NOT fail after this point, where we have changed the type!
4360
4361   // Reset the map for the object.
4362   object->set_map(map);
4363   JSObject* jsobj = JSObject::cast(object);
4364
4365   // Reinitialize the object from the constructor map.
4366   InitializeJSObjectFromMap(jsobj, FixedArray::cast(properties), map);
4367
4368   // Functions require some minimal initialization.
4369   if (type == JS_FUNCTION_TYPE) {
4370     map->set_function_with_prototype(true);
4371     InitializeFunction(JSFunction::cast(object), shared, the_hole_value());
4372     JSFunction::cast(object)->set_context(
4373         isolate()->context()->native_context());
4374   }
4375
4376   // Put in filler if the new object is smaller than the old.
4377   if (size_difference > 0) {
4378     CreateFillerObjectAt(
4379         object->address() + map->instance_size(), size_difference);
4380   }
4381
4382   return object;
4383 }
4384
4385
4386 MaybeObject* Heap::ReinitializeJSGlobalProxy(JSFunction* constructor,
4387                                              JSGlobalProxy* object) {
4388   ASSERT(constructor->has_initial_map());
4389   Map* map = constructor->initial_map();
4390
4391   // Check that the already allocated object has the same size and type as
4392   // objects allocated using the constructor.
4393   ASSERT(map->instance_size() == object->map()->instance_size());
4394   ASSERT(map->instance_type() == object->map()->instance_type());
4395
4396   // Allocate the backing storage for the properties.
4397   int prop_size = map->unused_property_fields() - map->inobject_properties();
4398   Object* properties;
4399   { MaybeObject* maybe_properties = AllocateFixedArray(prop_size, TENURED);
4400     if (!maybe_properties->ToObject(&properties)) return maybe_properties;
4401   }
4402
4403   // Reset the map for the object.
4404   object->set_map(constructor->initial_map());
4405
4406   // Reinitialize the object from the constructor map.
4407   InitializeJSObjectFromMap(object, FixedArray::cast(properties), map);
4408   return object;
4409 }
4410
4411
4412 MaybeObject* Heap::AllocateStringFromAscii(Vector<const char> string,
4413                                            PretenureFlag pretenure) {
4414   int length = string.length();
4415   if (length == 1) {
4416     return Heap::LookupSingleCharacterStringFromCode(string[0]);
4417   }
4418   Object* result;
4419   { MaybeObject* maybe_result =
4420         AllocateRawAsciiString(string.length(), pretenure);
4421     if (!maybe_result->ToObject(&result)) return maybe_result;
4422   }
4423
4424   // Copy the characters into the new object.
4425   CopyChars(SeqAsciiString::cast(result)->GetChars(), string.start(), length);
4426   return result;
4427 }
4428
4429
4430 MaybeObject* Heap::AllocateStringFromUtf8Slow(Vector<const char> string,
4431                                               int non_ascii_start,
4432                                               PretenureFlag pretenure) {
4433   // Continue counting the number of characters in the UTF-8 string, starting
4434   // from the first non-ascii character or word.
4435   int chars = non_ascii_start;
4436   Access<UnicodeCache::Utf8Decoder>
4437       decoder(isolate_->unicode_cache()->utf8_decoder());
4438   decoder->Reset(string.start() + non_ascii_start, string.length() - chars);
4439   while (decoder->has_more()) {
4440     uint32_t r = decoder->GetNext();
4441     if (r <= unibrow::Utf16::kMaxNonSurrogateCharCode) {
4442       chars++;
4443     } else {
4444       chars += 2;
4445     }
4446   }
4447
4448   Object* result;
4449   { MaybeObject* maybe_result = AllocateRawTwoByteString(chars, pretenure);
4450     if (!maybe_result->ToObject(&result)) return maybe_result;
4451   }
4452
4453   // Convert and copy the characters into the new object.
4454   SeqTwoByteString* twobyte = SeqTwoByteString::cast(result);
4455   decoder->Reset(string.start(), string.length());
4456   int i = 0;
4457   while (i < chars) {
4458     uint32_t r = decoder->GetNext();
4459     if (r > unibrow::Utf16::kMaxNonSurrogateCharCode) {
4460       twobyte->SeqTwoByteStringSet(i++, unibrow::Utf16::LeadSurrogate(r));
4461       twobyte->SeqTwoByteStringSet(i++, unibrow::Utf16::TrailSurrogate(r));
4462     } else {
4463       twobyte->SeqTwoByteStringSet(i++, r);
4464     }
4465   }
4466   return result;
4467 }
4468
4469
4470 MaybeObject* Heap::AllocateStringFromTwoByte(Vector<const uc16> string,
4471                                              PretenureFlag pretenure) {
4472   // Check if the string is an ASCII string.
4473   Object* result;
4474   int length = string.length();
4475   const uc16* start = string.start();
4476
4477   if (String::IsAscii(start, length)) {
4478     MaybeObject* maybe_result = AllocateRawAsciiString(length, pretenure);
4479     if (!maybe_result->ToObject(&result)) return maybe_result;
4480     CopyChars(SeqAsciiString::cast(result)->GetChars(), start, length);
4481   } else {  // It's not an ASCII string.
4482     MaybeObject* maybe_result = AllocateRawTwoByteString(length, pretenure);
4483     if (!maybe_result->ToObject(&result)) return maybe_result;
4484     CopyChars(SeqTwoByteString::cast(result)->GetChars(), start, length);
4485   }
4486   return result;
4487 }
4488
4489
4490 Map* Heap::SymbolMapForString(String* string) {
4491   // If the string is in new space it cannot be used as a symbol.
4492   if (InNewSpace(string)) return NULL;
4493
4494   // Find the corresponding symbol map for strings.
4495   switch (string->map()->instance_type()) {
4496     case STRING_TYPE: return symbol_map();
4497     case ASCII_STRING_TYPE: return ascii_symbol_map();
4498     case CONS_STRING_TYPE: return cons_symbol_map();
4499     case CONS_ASCII_STRING_TYPE: return cons_ascii_symbol_map();
4500     case EXTERNAL_STRING_TYPE: return external_symbol_map();
4501     case EXTERNAL_ASCII_STRING_TYPE: return external_ascii_symbol_map();
4502     case EXTERNAL_STRING_WITH_ASCII_DATA_TYPE:
4503       return external_symbol_with_ascii_data_map();
4504     case SHORT_EXTERNAL_STRING_TYPE: return short_external_symbol_map();
4505     case SHORT_EXTERNAL_ASCII_STRING_TYPE:
4506       return short_external_ascii_symbol_map();
4507     case SHORT_EXTERNAL_STRING_WITH_ASCII_DATA_TYPE:
4508       return short_external_symbol_with_ascii_data_map();
4509     default: return NULL;  // No match found.
4510   }
4511 }
4512
4513
4514 MaybeObject* Heap::AllocateInternalSymbol(unibrow::CharacterStream* buffer,
4515                                           int chars,
4516                                           uint32_t hash_field) {
4517   ASSERT(chars >= 0);
4518   // Ensure the chars matches the number of characters in the buffer.
4519   ASSERT(static_cast<unsigned>(chars) == buffer->Utf16Length());
4520   // Determine whether the string is ASCII.
4521   bool is_ascii = true;
4522   while (buffer->has_more()) {
4523     if (buffer->GetNext() > unibrow::Utf8::kMaxOneByteChar) {
4524       is_ascii = false;
4525       break;
4526     }
4527   }
4528   buffer->Rewind();
4529
4530   // Compute map and object size.
4531   int size;
4532   Map* map;
4533
4534   if (is_ascii) {
4535     if (chars > SeqAsciiString::kMaxLength) {
4536       return Failure::OutOfMemoryException();
4537     }
4538     map = ascii_symbol_map();
4539     size = SeqAsciiString::SizeFor(chars);
4540   } else {
4541     if (chars > SeqTwoByteString::kMaxLength) {
4542       return Failure::OutOfMemoryException();
4543     }
4544     map = symbol_map();
4545     size = SeqTwoByteString::SizeFor(chars);
4546   }
4547
4548   // Allocate string.
4549   Object* result;
4550   { MaybeObject* maybe_result = (size > Page::kMaxNonCodeHeapObjectSize)
4551                    ? lo_space_->AllocateRaw(size, NOT_EXECUTABLE)
4552                    : old_data_space_->AllocateRaw(size);
4553     if (!maybe_result->ToObject(&result)) return maybe_result;
4554   }
4555
4556   reinterpret_cast<HeapObject*>(result)->set_map_no_write_barrier(map);
4557   // Set length and hash fields of the allocated string.
4558   String* answer = String::cast(result);
4559   answer->set_length(chars);
4560   answer->set_hash_field(hash_field);
4561
4562   ASSERT_EQ(size, answer->Size());
4563
4564   // Fill in the characters.
4565   int i = 0;
4566   while (i < chars) {
4567     uint32_t character = buffer->GetNext();
4568     if (character > unibrow::Utf16::kMaxNonSurrogateCharCode) {
4569       answer->Set(i++, unibrow::Utf16::LeadSurrogate(character));
4570       answer->Set(i++, unibrow::Utf16::TrailSurrogate(character));
4571     } else {
4572       answer->Set(i++, character);
4573     }
4574   }
4575   return answer;
4576 }
4577
4578
4579 MaybeObject* Heap::AllocateRawAsciiString(int length, PretenureFlag pretenure) {
4580   if (length < 0 || length > SeqAsciiString::kMaxLength) {
4581     return Failure::OutOfMemoryException();
4582   }
4583
4584   int size = SeqAsciiString::SizeFor(length);
4585   ASSERT(size <= SeqAsciiString::kMaxSize);
4586
4587   AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
4588   AllocationSpace retry_space = OLD_DATA_SPACE;
4589
4590   if (space == NEW_SPACE) {
4591     if (size > kMaxObjectSizeInNewSpace) {
4592       // Allocate in large object space, retry space will be ignored.
4593       space = LO_SPACE;
4594     } else if (size > Page::kMaxNonCodeHeapObjectSize) {
4595       // Allocate in new space, retry in large object space.
4596       retry_space = LO_SPACE;
4597     }
4598   } else if (space == OLD_DATA_SPACE &&
4599              size > Page::kMaxNonCodeHeapObjectSize) {
4600     space = LO_SPACE;
4601   }
4602   Object* result;
4603   { MaybeObject* maybe_result = AllocateRaw(size, space, retry_space);
4604     if (!maybe_result->ToObject(&result)) return maybe_result;
4605   }
4606
4607   // Partially initialize the object.
4608   HeapObject::cast(result)->set_map_no_write_barrier(ascii_string_map());
4609   String::cast(result)->set_length(length);
4610   String::cast(result)->set_hash_field(String::kEmptyHashField);
4611   ASSERT_EQ(size, HeapObject::cast(result)->Size());
4612
4613 #ifdef VERIFY_HEAP
4614   if (FLAG_verify_heap) {
4615     // Initialize string's content to ensure ASCII-ness (character range 0-127)
4616     // as required when verifying the heap.
4617     char* dest = SeqAsciiString::cast(result)->GetChars();
4618     memset(dest, 0x0F, length * kCharSize);
4619   }
4620 #endif
4621
4622   return result;
4623 }
4624
4625
4626 MaybeObject* Heap::AllocateRawTwoByteString(int length,
4627                                             PretenureFlag pretenure) {
4628   if (length < 0 || length > SeqTwoByteString::kMaxLength) {
4629     return Failure::OutOfMemoryException();
4630   }
4631   int size = SeqTwoByteString::SizeFor(length);
4632   ASSERT(size <= SeqTwoByteString::kMaxSize);
4633   AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
4634   AllocationSpace retry_space = OLD_DATA_SPACE;
4635
4636   if (space == NEW_SPACE) {
4637     if (size > kMaxObjectSizeInNewSpace) {
4638       // Allocate in large object space, retry space will be ignored.
4639       space = LO_SPACE;
4640     } else if (size > Page::kMaxNonCodeHeapObjectSize) {
4641       // Allocate in new space, retry in large object space.
4642       retry_space = LO_SPACE;
4643     }
4644   } else if (space == OLD_DATA_SPACE &&
4645              size > Page::kMaxNonCodeHeapObjectSize) {
4646     space = LO_SPACE;
4647   }
4648   Object* result;
4649   { MaybeObject* maybe_result = AllocateRaw(size, space, retry_space);
4650     if (!maybe_result->ToObject(&result)) return maybe_result;
4651   }
4652
4653   // Partially initialize the object.
4654   HeapObject::cast(result)->set_map_no_write_barrier(string_map());
4655   String::cast(result)->set_length(length);
4656   String::cast(result)->set_hash_field(String::kEmptyHashField);
4657   ASSERT_EQ(size, HeapObject::cast(result)->Size());
4658   return result;
4659 }
4660
4661
4662 MaybeObject* Heap::AllocateJSArray(
4663     ElementsKind elements_kind,
4664     PretenureFlag pretenure) {
4665   Context* native_context = isolate()->context()->native_context();
4666   JSFunction* array_function = native_context->array_function();
4667   Map* map = array_function->initial_map();
4668   Object* maybe_map_array = native_context->js_array_maps();
4669   if (!maybe_map_array->IsUndefined()) {
4670     Object* maybe_transitioned_map =
4671         FixedArray::cast(maybe_map_array)->get(elements_kind);
4672     if (!maybe_transitioned_map->IsUndefined()) {
4673       map = Map::cast(maybe_transitioned_map);
4674     }
4675   }
4676
4677   return AllocateJSObjectFromMap(map, pretenure);
4678 }
4679
4680
4681 MaybeObject* Heap::AllocateEmptyFixedArray() {
4682   int size = FixedArray::SizeFor(0);
4683   Object* result;
4684   { MaybeObject* maybe_result =
4685         AllocateRaw(size, OLD_DATA_SPACE, OLD_DATA_SPACE);
4686     if (!maybe_result->ToObject(&result)) return maybe_result;
4687   }
4688   // Initialize the object.
4689   reinterpret_cast<FixedArray*>(result)->set_map_no_write_barrier(
4690       fixed_array_map());
4691   reinterpret_cast<FixedArray*>(result)->set_length(0);
4692   return result;
4693 }
4694
4695
4696 MaybeObject* Heap::AllocateRawFixedArray(int length) {
4697   if (length < 0 || length > FixedArray::kMaxLength) {
4698     return Failure::OutOfMemoryException();
4699   }
4700   ASSERT(length > 0);
4701   // Use the general function if we're forced to always allocate.
4702   if (always_allocate()) return AllocateFixedArray(length, TENURED);
4703   // Allocate the raw data for a fixed array.
4704   int size = FixedArray::SizeFor(length);
4705   return size <= kMaxObjectSizeInNewSpace
4706       ? new_space_.AllocateRaw(size)
4707       : lo_space_->AllocateRaw(size, NOT_EXECUTABLE);
4708 }
4709
4710
4711 MaybeObject* Heap::CopyFixedArrayWithMap(FixedArray* src, Map* map) {
4712   int len = src->length();
4713   Object* obj;
4714   { MaybeObject* maybe_obj = AllocateRawFixedArray(len);
4715     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
4716   }
4717   if (InNewSpace(obj)) {
4718     HeapObject* dst = HeapObject::cast(obj);
4719     dst->set_map_no_write_barrier(map);
4720     CopyBlock(dst->address() + kPointerSize,
4721               src->address() + kPointerSize,
4722               FixedArray::SizeFor(len) - kPointerSize);
4723     return obj;
4724   }
4725   HeapObject::cast(obj)->set_map_no_write_barrier(map);
4726   FixedArray* result = FixedArray::cast(obj);
4727   result->set_length(len);
4728
4729   // Copy the content
4730   AssertNoAllocation no_gc;
4731   WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
4732   for (int i = 0; i < len; i++) result->set(i, src->get(i), mode);
4733   return result;
4734 }
4735
4736
4737 MaybeObject* Heap::CopyFixedDoubleArrayWithMap(FixedDoubleArray* src,
4738                                                Map* map) {
4739   int len = src->length();
4740   Object* obj;
4741   { MaybeObject* maybe_obj = AllocateRawFixedDoubleArray(len, NOT_TENURED);
4742     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
4743   }
4744   HeapObject* dst = HeapObject::cast(obj);
4745   dst->set_map_no_write_barrier(map);
4746   CopyBlock(
4747       dst->address() + FixedDoubleArray::kLengthOffset,
4748       src->address() + FixedDoubleArray::kLengthOffset,
4749       FixedDoubleArray::SizeFor(len) - FixedDoubleArray::kLengthOffset);
4750   return obj;
4751 }
4752
4753
4754 MaybeObject* Heap::AllocateFixedArray(int length) {
4755   ASSERT(length >= 0);
4756   if (length == 0) return empty_fixed_array();
4757   Object* result;
4758   { MaybeObject* maybe_result = AllocateRawFixedArray(length);
4759     if (!maybe_result->ToObject(&result)) return maybe_result;
4760   }
4761   // Initialize header.
4762   FixedArray* array = reinterpret_cast<FixedArray*>(result);
4763   array->set_map_no_write_barrier(fixed_array_map());
4764   array->set_length(length);
4765   // Initialize body.
4766   ASSERT(!InNewSpace(undefined_value()));
4767   MemsetPointer(array->data_start(), undefined_value(), length);
4768   return result;
4769 }
4770
4771
4772 MaybeObject* Heap::AllocateRawFixedArray(int length, PretenureFlag pretenure) {
4773   if (length < 0 || length > FixedArray::kMaxLength) {
4774     return Failure::OutOfMemoryException();
4775   }
4776
4777   AllocationSpace space =
4778       (pretenure == TENURED) ? OLD_POINTER_SPACE : NEW_SPACE;
4779   int size = FixedArray::SizeFor(length);
4780   if (space == NEW_SPACE && size > kMaxObjectSizeInNewSpace) {
4781     // Too big for new space.
4782     space = LO_SPACE;
4783   } else if (space == OLD_POINTER_SPACE &&
4784              size > Page::kMaxNonCodeHeapObjectSize) {
4785     // Too big for old pointer space.
4786     space = LO_SPACE;
4787   }
4788
4789   AllocationSpace retry_space =
4790       (size <= Page::kMaxNonCodeHeapObjectSize) ? OLD_POINTER_SPACE : LO_SPACE;
4791
4792   return AllocateRaw(size, space, retry_space);
4793 }
4794
4795
4796 MUST_USE_RESULT static MaybeObject* AllocateFixedArrayWithFiller(
4797     Heap* heap,
4798     int length,
4799     PretenureFlag pretenure,
4800     Object* filler) {
4801   ASSERT(length >= 0);
4802   ASSERT(heap->empty_fixed_array()->IsFixedArray());
4803   if (length == 0) return heap->empty_fixed_array();
4804
4805   ASSERT(!heap->InNewSpace(filler));
4806   Object* result;
4807   { MaybeObject* maybe_result = heap->AllocateRawFixedArray(length, pretenure);
4808     if (!maybe_result->ToObject(&result)) return maybe_result;
4809   }
4810
4811   HeapObject::cast(result)->set_map_no_write_barrier(heap->fixed_array_map());
4812   FixedArray* array = FixedArray::cast(result);
4813   array->set_length(length);
4814   MemsetPointer(array->data_start(), filler, length);
4815   return array;
4816 }
4817
4818
4819 MaybeObject* Heap::AllocateFixedArray(int length, PretenureFlag pretenure) {
4820   return AllocateFixedArrayWithFiller(this,
4821                                       length,
4822                                       pretenure,
4823                                       undefined_value());
4824 }
4825
4826
4827 MaybeObject* Heap::AllocateFixedArrayWithHoles(int length,
4828                                                PretenureFlag pretenure) {
4829   return AllocateFixedArrayWithFiller(this,
4830                                       length,
4831                                       pretenure,
4832                                       the_hole_value());
4833 }
4834
4835
4836 MaybeObject* Heap::AllocateUninitializedFixedArray(int length) {
4837   if (length == 0) return empty_fixed_array();
4838
4839   Object* obj;
4840   { MaybeObject* maybe_obj = AllocateRawFixedArray(length);
4841     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
4842   }
4843
4844   reinterpret_cast<FixedArray*>(obj)->set_map_no_write_barrier(
4845       fixed_array_map());
4846   FixedArray::cast(obj)->set_length(length);
4847   return obj;
4848 }
4849
4850
4851 MaybeObject* Heap::AllocateEmptyFixedDoubleArray() {
4852   int size = FixedDoubleArray::SizeFor(0);
4853   Object* result;
4854   { MaybeObject* maybe_result =
4855         AllocateRaw(size, OLD_DATA_SPACE, OLD_DATA_SPACE);
4856     if (!maybe_result->ToObject(&result)) return maybe_result;
4857   }
4858   // Initialize the object.
4859   reinterpret_cast<FixedDoubleArray*>(result)->set_map_no_write_barrier(
4860       fixed_double_array_map());
4861   reinterpret_cast<FixedDoubleArray*>(result)->set_length(0);
4862   return result;
4863 }
4864
4865
4866 MaybeObject* Heap::AllocateUninitializedFixedDoubleArray(
4867     int length,
4868     PretenureFlag pretenure) {
4869   if (length == 0) return empty_fixed_array();
4870
4871   Object* elements_object;
4872   MaybeObject* maybe_obj = AllocateRawFixedDoubleArray(length, pretenure);
4873   if (!maybe_obj->ToObject(&elements_object)) return maybe_obj;
4874   FixedDoubleArray* elements =
4875       reinterpret_cast<FixedDoubleArray*>(elements_object);
4876
4877   elements->set_map_no_write_barrier(fixed_double_array_map());
4878   elements->set_length(length);
4879   return elements;
4880 }
4881
4882
4883 MaybeObject* Heap::AllocateFixedDoubleArrayWithHoles(
4884     int length,
4885     PretenureFlag pretenure) {
4886   if (length == 0) return empty_fixed_array();
4887
4888   Object* elements_object;
4889   MaybeObject* maybe_obj = AllocateRawFixedDoubleArray(length, pretenure);
4890   if (!maybe_obj->ToObject(&elements_object)) return maybe_obj;
4891   FixedDoubleArray* elements =
4892       reinterpret_cast<FixedDoubleArray*>(elements_object);
4893
4894   for (int i = 0; i < length; ++i) {
4895     elements->set_the_hole(i);
4896   }
4897
4898   elements->set_map_no_write_barrier(fixed_double_array_map());
4899   elements->set_length(length);
4900   return elements;
4901 }
4902
4903
4904 MaybeObject* Heap::AllocateRawFixedDoubleArray(int length,
4905                                                PretenureFlag pretenure) {
4906   if (length < 0 || length > FixedDoubleArray::kMaxLength) {
4907     return Failure::OutOfMemoryException();
4908   }
4909
4910   AllocationSpace space =
4911       (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
4912   int size = FixedDoubleArray::SizeFor(length);
4913
4914 #ifndef V8_HOST_ARCH_64_BIT
4915   size += kPointerSize;
4916 #endif
4917
4918   if (space == NEW_SPACE && size > kMaxObjectSizeInNewSpace) {
4919     // Too big for new space.
4920     space = LO_SPACE;
4921   } else if (space == OLD_DATA_SPACE &&
4922              size > Page::kMaxNonCodeHeapObjectSize) {
4923     // Too big for old data space.
4924     space = LO_SPACE;
4925   }
4926
4927   AllocationSpace retry_space =
4928       (size <= Page::kMaxNonCodeHeapObjectSize) ? OLD_DATA_SPACE : LO_SPACE;
4929
4930   HeapObject* object;
4931   { MaybeObject* maybe_object = AllocateRaw(size, space, retry_space);
4932     if (!maybe_object->To<HeapObject>(&object)) return maybe_object;
4933   }
4934
4935   return EnsureDoubleAligned(this, object, size);
4936 }
4937
4938
4939 MaybeObject* Heap::AllocateHashTable(int length, PretenureFlag pretenure) {
4940   Object* result;
4941   { MaybeObject* maybe_result = AllocateFixedArray(length, pretenure);
4942     if (!maybe_result->ToObject(&result)) return maybe_result;
4943   }
4944   reinterpret_cast<HeapObject*>(result)->set_map_no_write_barrier(
4945       hash_table_map());
4946   ASSERT(result->IsHashTable());
4947   return result;
4948 }
4949
4950
4951 MaybeObject* Heap::AllocateNativeContext() {
4952   Object* result;
4953   { MaybeObject* maybe_result =
4954         AllocateFixedArray(Context::NATIVE_CONTEXT_SLOTS);
4955     if (!maybe_result->ToObject(&result)) return maybe_result;
4956   }
4957   Context* context = reinterpret_cast<Context*>(result);
4958   context->set_map_no_write_barrier(native_context_map());
4959   context->set_js_array_maps(undefined_value());
4960   ASSERT(context->IsNativeContext());
4961   ASSERT(result->IsContext());
4962   return result;
4963 }
4964
4965
4966 MaybeObject* Heap::AllocateGlobalContext(JSFunction* function,
4967                                          ScopeInfo* scope_info) {
4968   Object* result;
4969   { MaybeObject* maybe_result =
4970         AllocateFixedArray(scope_info->ContextLength(), TENURED);
4971     if (!maybe_result->ToObject(&result)) return maybe_result;
4972   }
4973   Context* context = reinterpret_cast<Context*>(result);
4974   context->set_map_no_write_barrier(global_context_map());
4975   context->set_closure(function);
4976   context->set_previous(function->context());
4977   context->set_extension(scope_info);
4978   context->set_global_object(function->context()->global_object());
4979   ASSERT(context->IsGlobalContext());
4980   ASSERT(result->IsContext());
4981   return context;
4982 }
4983
4984
4985 MaybeObject* Heap::AllocateModuleContext(ScopeInfo* scope_info) {
4986   Object* result;
4987   { MaybeObject* maybe_result =
4988         AllocateFixedArray(scope_info->ContextLength(), TENURED);
4989     if (!maybe_result->ToObject(&result)) return maybe_result;
4990   }
4991   Context* context = reinterpret_cast<Context*>(result);
4992   context->set_map_no_write_barrier(module_context_map());
4993   // Context links will be set later.
4994   context->set_extension(Smi::FromInt(0));
4995   return context;
4996 }
4997
4998
4999 MaybeObject* Heap::AllocateFunctionContext(int length, JSFunction* function) {
5000   ASSERT(length >= Context::MIN_CONTEXT_SLOTS);
5001   Object* result;
5002   { MaybeObject* maybe_result = AllocateFixedArray(length);
5003     if (!maybe_result->ToObject(&result)) return maybe_result;
5004   }
5005   Context* context = reinterpret_cast<Context*>(result);
5006   context->set_map_no_write_barrier(function_context_map());
5007   context->set_closure(function);
5008   context->set_previous(function->context());
5009   context->set_extension(Smi::FromInt(0));
5010   context->set_global_object(function->context()->global_object());
5011   return context;
5012 }
5013
5014
5015 MaybeObject* Heap::AllocateCatchContext(JSFunction* function,
5016                                         Context* previous,
5017                                         String* name,
5018                                         Object* thrown_object) {
5019   STATIC_ASSERT(Context::MIN_CONTEXT_SLOTS == Context::THROWN_OBJECT_INDEX);
5020   Object* result;
5021   { MaybeObject* maybe_result =
5022         AllocateFixedArray(Context::MIN_CONTEXT_SLOTS + 1);
5023     if (!maybe_result->ToObject(&result)) return maybe_result;
5024   }
5025   Context* context = reinterpret_cast<Context*>(result);
5026   context->set_map_no_write_barrier(catch_context_map());
5027   context->set_closure(function);
5028   context->set_previous(previous);
5029   context->set_extension(name);
5030   context->set_global_object(previous->global_object());
5031   context->set(Context::THROWN_OBJECT_INDEX, thrown_object);
5032   return context;
5033 }
5034
5035
5036 MaybeObject* Heap::AllocateWithContext(JSFunction* function,
5037                                        Context* previous,
5038                                        JSObject* extension) {
5039   Object* result;
5040   { MaybeObject* maybe_result = AllocateFixedArray(Context::MIN_CONTEXT_SLOTS);
5041     if (!maybe_result->ToObject(&result)) return maybe_result;
5042   }
5043   Context* context = reinterpret_cast<Context*>(result);
5044   context->set_map_no_write_barrier(with_context_map());
5045   context->set_closure(function);
5046   context->set_previous(previous);
5047   context->set_extension(extension);
5048   context->set_global_object(previous->global_object());
5049   return context;
5050 }
5051
5052
5053 MaybeObject* Heap::AllocateBlockContext(JSFunction* function,
5054                                         Context* previous,
5055                                         ScopeInfo* scope_info) {
5056   Object* result;
5057   { MaybeObject* maybe_result =
5058         AllocateFixedArrayWithHoles(scope_info->ContextLength());
5059     if (!maybe_result->ToObject(&result)) return maybe_result;
5060   }
5061   Context* context = reinterpret_cast<Context*>(result);
5062   context->set_map_no_write_barrier(block_context_map());
5063   context->set_closure(function);
5064   context->set_previous(previous);
5065   context->set_extension(scope_info);
5066   context->set_global_object(previous->global_object());
5067   return context;
5068 }
5069
5070
5071 MaybeObject* Heap::AllocateScopeInfo(int length) {
5072   FixedArray* scope_info;
5073   MaybeObject* maybe_scope_info = AllocateFixedArray(length, TENURED);
5074   if (!maybe_scope_info->To(&scope_info)) return maybe_scope_info;
5075   scope_info->set_map_no_write_barrier(scope_info_map());
5076   return scope_info;
5077 }
5078
5079
5080 MaybeObject* Heap::AllocateStruct(InstanceType type) {
5081   Map* map;
5082   switch (type) {
5083 #define MAKE_CASE(NAME, Name, name) \
5084     case NAME##_TYPE: map = name##_map(); break;
5085 STRUCT_LIST(MAKE_CASE)
5086 #undef MAKE_CASE
5087     default:
5088       UNREACHABLE();
5089       return Failure::InternalError();
5090   }
5091   int size = map->instance_size();
5092   AllocationSpace space =
5093       (size > Page::kMaxNonCodeHeapObjectSize) ? LO_SPACE : OLD_POINTER_SPACE;
5094   Object* result;
5095   { MaybeObject* maybe_result = Allocate(map, space);
5096     if (!maybe_result->ToObject(&result)) return maybe_result;
5097   }
5098   Struct::cast(result)->InitializeBody(size);
5099   return result;
5100 }
5101
5102
5103 bool Heap::IsHeapIterable() {
5104   return (!old_pointer_space()->was_swept_conservatively() &&
5105           !old_data_space()->was_swept_conservatively());
5106 }
5107
5108
5109 void Heap::EnsureHeapIsIterable() {
5110   ASSERT(IsAllocationAllowed());
5111   if (!IsHeapIterable()) {
5112     CollectAllGarbage(kMakeHeapIterableMask, "Heap::EnsureHeapIsIterable");
5113   }
5114   ASSERT(IsHeapIterable());
5115 }
5116
5117
5118 void Heap::AdvanceIdleIncrementalMarking(intptr_t step_size) {
5119   incremental_marking()->Step(step_size,
5120                               IncrementalMarking::NO_GC_VIA_STACK_GUARD);
5121
5122   if (incremental_marking()->IsComplete()) {
5123     bool uncommit = false;
5124     if (gc_count_at_last_idle_gc_ == gc_count_) {
5125       // No GC since the last full GC, the mutator is probably not active.
5126       isolate_->compilation_cache()->Clear();
5127       uncommit = true;
5128     }
5129     CollectAllGarbage(kNoGCFlags, "idle notification: finalize incremental");
5130     gc_count_at_last_idle_gc_ = gc_count_;
5131     if (uncommit) {
5132       new_space_.Shrink();
5133       UncommitFromSpace();
5134     }
5135   }
5136 }
5137
5138
5139 bool Heap::IdleNotification(int hint) {
5140   // Hints greater than this value indicate that
5141   // the embedder is requesting a lot of GC work.
5142   const int kMaxHint = 1000;
5143   // Minimal hint that allows to do full GC.
5144   const int kMinHintForFullGC = 100;
5145   intptr_t size_factor = Min(Max(hint, 20), kMaxHint) / 4;
5146   // The size factor is in range [5..250]. The numbers here are chosen from
5147   // experiments. If you changes them, make sure to test with
5148   // chrome/performance_ui_tests --gtest_filter="GeneralMixMemoryTest.*
5149   intptr_t step_size =
5150       size_factor * IncrementalMarking::kAllocatedThreshold;
5151
5152   if (contexts_disposed_ > 0) {
5153     if (hint >= kMaxHint) {
5154       // The embedder is requesting a lot of GC work after context disposal,
5155       // we age inline caches so that they don't keep objects from
5156       // the old context alive.
5157       AgeInlineCaches();
5158     }
5159     int mark_sweep_time = Min(TimeMarkSweepWouldTakeInMs(), 1000);
5160     if (hint >= mark_sweep_time && !FLAG_expose_gc &&
5161         incremental_marking()->IsStopped()) {
5162       HistogramTimerScope scope(isolate_->counters()->gc_context());
5163       CollectAllGarbage(kReduceMemoryFootprintMask,
5164                         "idle notification: contexts disposed");
5165     } else {
5166       AdvanceIdleIncrementalMarking(step_size);
5167       contexts_disposed_ = 0;
5168     }
5169     // Make sure that we have no pending context disposals.
5170     // Take into account that we might have decided to delay full collection
5171     // because incremental marking is in progress.
5172     ASSERT((contexts_disposed_ == 0) || !incremental_marking()->IsStopped());
5173     // After context disposal there is likely a lot of garbage remaining, reset
5174     // the idle notification counters in order to trigger more incremental GCs
5175     // on subsequent idle notifications.
5176     StartIdleRound();
5177     return false;
5178   }
5179
5180   if (!FLAG_incremental_marking || FLAG_expose_gc || Serializer::enabled()) {
5181     return IdleGlobalGC();
5182   }
5183
5184   // By doing small chunks of GC work in each IdleNotification,
5185   // perform a round of incremental GCs and after that wait until
5186   // the mutator creates enough garbage to justify a new round.
5187   // An incremental GC progresses as follows:
5188   // 1. many incremental marking steps,
5189   // 2. one old space mark-sweep-compact,
5190   // 3. many lazy sweep steps.
5191   // Use mark-sweep-compact events to count incremental GCs in a round.
5192
5193
5194   if (incremental_marking()->IsStopped()) {
5195     if (!IsSweepingComplete() &&
5196         !AdvanceSweepers(static_cast<int>(step_size))) {
5197       return false;
5198     }
5199   }
5200
5201   if (mark_sweeps_since_idle_round_started_ >= kMaxMarkSweepsInIdleRound) {
5202     if (EnoughGarbageSinceLastIdleRound()) {
5203       StartIdleRound();
5204     } else {
5205       return true;
5206     }
5207   }
5208
5209   int new_mark_sweeps = ms_count_ - ms_count_at_last_idle_notification_;
5210   mark_sweeps_since_idle_round_started_ += new_mark_sweeps;
5211   ms_count_at_last_idle_notification_ = ms_count_;
5212
5213   int remaining_mark_sweeps = kMaxMarkSweepsInIdleRound -
5214                               mark_sweeps_since_idle_round_started_;
5215
5216   if (remaining_mark_sweeps <= 0) {
5217     FinishIdleRound();
5218     return true;
5219   }
5220
5221   if (incremental_marking()->IsStopped()) {
5222     // If there are no more than two GCs left in this idle round and we are
5223     // allowed to do a full GC, then make those GCs full in order to compact
5224     // the code space.
5225     // TODO(ulan): Once we enable code compaction for incremental marking,
5226     // we can get rid of this special case and always start incremental marking.
5227     if (remaining_mark_sweeps <= 2 && hint >= kMinHintForFullGC) {
5228       CollectAllGarbage(kReduceMemoryFootprintMask,
5229                         "idle notification: finalize idle round");
5230     } else {
5231       incremental_marking()->Start();
5232     }
5233   }
5234   if (!incremental_marking()->IsStopped()) {
5235     AdvanceIdleIncrementalMarking(step_size);
5236   }
5237   return false;
5238 }
5239
5240
5241 bool Heap::IdleGlobalGC() {
5242   static const int kIdlesBeforeScavenge = 4;
5243   static const int kIdlesBeforeMarkSweep = 7;
5244   static const int kIdlesBeforeMarkCompact = 8;
5245   static const int kMaxIdleCount = kIdlesBeforeMarkCompact + 1;
5246   static const unsigned int kGCsBetweenCleanup = 4;
5247
5248   if (!last_idle_notification_gc_count_init_) {
5249     last_idle_notification_gc_count_ = gc_count_;
5250     last_idle_notification_gc_count_init_ = true;
5251   }
5252
5253   bool uncommit = true;
5254   bool finished = false;
5255
5256   // Reset the number of idle notifications received when a number of
5257   // GCs have taken place. This allows another round of cleanup based
5258   // on idle notifications if enough work has been carried out to
5259   // provoke a number of garbage collections.
5260   if (gc_count_ - last_idle_notification_gc_count_ < kGCsBetweenCleanup) {
5261     number_idle_notifications_ =
5262         Min(number_idle_notifications_ + 1, kMaxIdleCount);
5263   } else {
5264     number_idle_notifications_ = 0;
5265     last_idle_notification_gc_count_ = gc_count_;
5266   }
5267
5268   if (number_idle_notifications_ == kIdlesBeforeScavenge) {
5269     CollectGarbage(NEW_SPACE, "idle notification");
5270     new_space_.Shrink();
5271     last_idle_notification_gc_count_ = gc_count_;
5272   } else if (number_idle_notifications_ == kIdlesBeforeMarkSweep) {
5273     // Before doing the mark-sweep collections we clear the
5274     // compilation cache to avoid hanging on to source code and
5275     // generated code for cached functions.
5276     isolate_->compilation_cache()->Clear();
5277
5278     CollectAllGarbage(kReduceMemoryFootprintMask, "idle notification");
5279     new_space_.Shrink();
5280     last_idle_notification_gc_count_ = gc_count_;
5281
5282   } else if (number_idle_notifications_ == kIdlesBeforeMarkCompact) {
5283     CollectAllGarbage(kReduceMemoryFootprintMask, "idle notification");
5284     new_space_.Shrink();
5285     last_idle_notification_gc_count_ = gc_count_;
5286     number_idle_notifications_ = 0;
5287     finished = true;
5288   } else if (number_idle_notifications_ > kIdlesBeforeMarkCompact) {
5289     // If we have received more than kIdlesBeforeMarkCompact idle
5290     // notifications we do not perform any cleanup because we don't
5291     // expect to gain much by doing so.
5292     finished = true;
5293   }
5294
5295   if (uncommit) UncommitFromSpace();
5296
5297   return finished;
5298 }
5299
5300
5301 #ifdef DEBUG
5302
5303 void Heap::Print() {
5304   if (!HasBeenSetUp()) return;
5305   isolate()->PrintStack();
5306   AllSpaces spaces;
5307   for (Space* space = spaces.next(); space != NULL; space = spaces.next())
5308     space->Print();
5309 }
5310
5311
5312 void Heap::ReportCodeStatistics(const char* title) {
5313   PrintF(">>>>>> Code Stats (%s) >>>>>>\n", title);
5314   PagedSpace::ResetCodeStatistics();
5315   // We do not look for code in new space, map space, or old space.  If code
5316   // somehow ends up in those spaces, we would miss it here.
5317   code_space_->CollectCodeStatistics();
5318   lo_space_->CollectCodeStatistics();
5319   PagedSpace::ReportCodeStatistics();
5320 }
5321
5322
5323 // This function expects that NewSpace's allocated objects histogram is
5324 // populated (via a call to CollectStatistics or else as a side effect of a
5325 // just-completed scavenge collection).
5326 void Heap::ReportHeapStatistics(const char* title) {
5327   USE(title);
5328   PrintF(">>>>>> =============== %s (%d) =============== >>>>>>\n",
5329          title, gc_count_);
5330   PrintF("old_gen_promotion_limit_ %" V8_PTR_PREFIX "d\n",
5331          old_gen_promotion_limit_);
5332   PrintF("old_gen_allocation_limit_ %" V8_PTR_PREFIX "d\n",
5333          old_gen_allocation_limit_);
5334   PrintF("old_gen_limit_factor_ %d\n", old_gen_limit_factor_);
5335
5336   PrintF("\n");
5337   PrintF("Number of handles : %d\n", HandleScope::NumberOfHandles());
5338   isolate_->global_handles()->PrintStats();
5339   PrintF("\n");
5340
5341   PrintF("Heap statistics : ");
5342   isolate_->memory_allocator()->ReportStatistics();
5343   PrintF("To space : ");
5344   new_space_.ReportStatistics();
5345   PrintF("Old pointer space : ");
5346   old_pointer_space_->ReportStatistics();
5347   PrintF("Old data space : ");
5348   old_data_space_->ReportStatistics();
5349   PrintF("Code space : ");
5350   code_space_->ReportStatistics();
5351   PrintF("Map space : ");
5352   map_space_->ReportStatistics();
5353   PrintF("Cell space : ");
5354   cell_space_->ReportStatistics();
5355   PrintF("Large object space : ");
5356   lo_space_->ReportStatistics();
5357   PrintF(">>>>>> ========================================= >>>>>>\n");
5358 }
5359
5360 #endif  // DEBUG
5361
5362 bool Heap::Contains(HeapObject* value) {
5363   return Contains(value->address());
5364 }
5365
5366
5367 bool Heap::Contains(Address addr) {
5368   if (OS::IsOutsideAllocatedSpace(addr)) return false;
5369   return HasBeenSetUp() &&
5370     (new_space_.ToSpaceContains(addr) ||
5371      old_pointer_space_->Contains(addr) ||
5372      old_data_space_->Contains(addr) ||
5373      code_space_->Contains(addr) ||
5374      map_space_->Contains(addr) ||
5375      cell_space_->Contains(addr) ||
5376      lo_space_->SlowContains(addr));
5377 }
5378
5379
5380 bool Heap::InSpace(HeapObject* value, AllocationSpace space) {
5381   return InSpace(value->address(), space);
5382 }
5383
5384
5385 bool Heap::InSpace(Address addr, AllocationSpace space) {
5386   if (OS::IsOutsideAllocatedSpace(addr)) return false;
5387   if (!HasBeenSetUp()) return false;
5388
5389   switch (space) {
5390     case NEW_SPACE:
5391       return new_space_.ToSpaceContains(addr);
5392     case OLD_POINTER_SPACE:
5393       return old_pointer_space_->Contains(addr);
5394     case OLD_DATA_SPACE:
5395       return old_data_space_->Contains(addr);
5396     case CODE_SPACE:
5397       return code_space_->Contains(addr);
5398     case MAP_SPACE:
5399       return map_space_->Contains(addr);
5400     case CELL_SPACE:
5401       return cell_space_->Contains(addr);
5402     case LO_SPACE:
5403       return lo_space_->SlowContains(addr);
5404   }
5405
5406   return false;
5407 }
5408
5409
5410 #ifdef VERIFY_HEAP
5411 void Heap::Verify() {
5412   CHECK(HasBeenSetUp());
5413
5414   store_buffer()->Verify();
5415
5416   VerifyPointersVisitor visitor;
5417   IterateRoots(&visitor, VISIT_ONLY_STRONG);
5418
5419   new_space_.Verify();
5420
5421   old_pointer_space_->Verify(&visitor);
5422   map_space_->Verify(&visitor);
5423
5424   VerifyPointersVisitor no_dirty_regions_visitor;
5425   old_data_space_->Verify(&no_dirty_regions_visitor);
5426   code_space_->Verify(&no_dirty_regions_visitor);
5427   cell_space_->Verify(&no_dirty_regions_visitor);
5428
5429   lo_space_->Verify();
5430 }
5431 #endif
5432
5433
5434 MaybeObject* Heap::LookupSymbol(Vector<const char> string) {
5435   Object* symbol = NULL;
5436   Object* new_table;
5437   { MaybeObject* maybe_new_table =
5438         symbol_table()->LookupSymbol(string, &symbol);
5439     if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
5440   }
5441   // Can't use set_symbol_table because SymbolTable::cast knows that
5442   // SymbolTable is a singleton and checks for identity.
5443   roots_[kSymbolTableRootIndex] = new_table;
5444   ASSERT(symbol != NULL);
5445   return symbol;
5446 }
5447
5448
5449 MaybeObject* Heap::LookupAsciiSymbol(Vector<const char> string) {
5450   Object* symbol = NULL;
5451   Object* new_table;
5452   { MaybeObject* maybe_new_table =
5453         symbol_table()->LookupAsciiSymbol(string, &symbol);
5454     if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
5455   }
5456   // Can't use set_symbol_table because SymbolTable::cast knows that
5457   // SymbolTable is a singleton and checks for identity.
5458   roots_[kSymbolTableRootIndex] = new_table;
5459   ASSERT(symbol != NULL);
5460   return symbol;
5461 }
5462
5463
5464 MaybeObject* Heap::LookupAsciiSymbol(Handle<SeqAsciiString> string,
5465                                      int from,
5466                                      int length) {
5467   Object* symbol = NULL;
5468   Object* new_table;
5469   { MaybeObject* maybe_new_table =
5470         symbol_table()->LookupSubStringAsciiSymbol(string,
5471                                                    from,
5472                                                    length,
5473                                                    &symbol);
5474     if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
5475   }
5476   // Can't use set_symbol_table because SymbolTable::cast knows that
5477   // SymbolTable is a singleton and checks for identity.
5478   roots_[kSymbolTableRootIndex] = new_table;
5479   ASSERT(symbol != NULL);
5480   return symbol;
5481 }
5482
5483
5484 MaybeObject* Heap::LookupTwoByteSymbol(Vector<const uc16> string) {
5485   Object* symbol = NULL;
5486   Object* new_table;
5487   { MaybeObject* maybe_new_table =
5488         symbol_table()->LookupTwoByteSymbol(string, &symbol);
5489     if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
5490   }
5491   // Can't use set_symbol_table because SymbolTable::cast knows that
5492   // SymbolTable is a singleton and checks for identity.
5493   roots_[kSymbolTableRootIndex] = new_table;
5494   ASSERT(symbol != NULL);
5495   return symbol;
5496 }
5497
5498
5499 MaybeObject* Heap::LookupSymbol(String* string) {
5500   if (string->IsSymbol()) return string;
5501   Object* symbol = NULL;
5502   Object* new_table;
5503   { MaybeObject* maybe_new_table =
5504         symbol_table()->LookupString(string, &symbol);
5505     if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
5506   }
5507   // Can't use set_symbol_table because SymbolTable::cast knows that
5508   // SymbolTable is a singleton and checks for identity.
5509   roots_[kSymbolTableRootIndex] = new_table;
5510   ASSERT(symbol != NULL);
5511   return symbol;
5512 }
5513
5514
5515 bool Heap::LookupSymbolIfExists(String* string, String** symbol) {
5516   if (string->IsSymbol()) {
5517     *symbol = string;
5518     return true;
5519   }
5520   return symbol_table()->LookupSymbolIfExists(string, symbol);
5521 }
5522
5523 void Heap::ZapFromSpace() {
5524   NewSpacePageIterator it(new_space_.FromSpaceStart(),
5525                           new_space_.FromSpaceEnd());
5526   while (it.has_next()) {
5527     NewSpacePage* page = it.next();
5528     for (Address cursor = page->area_start(), limit = page->area_end();
5529          cursor < limit;
5530          cursor += kPointerSize) {
5531       Memory::Address_at(cursor) = kFromSpaceZapValue;
5532     }
5533   }
5534 }
5535
5536
5537 void Heap::IterateAndMarkPointersToFromSpace(Address start,
5538                                              Address end,
5539                                              ObjectSlotCallback callback) {
5540   Address slot_address = start;
5541
5542   // We are not collecting slots on new space objects during mutation
5543   // thus we have to scan for pointers to evacuation candidates when we
5544   // promote objects. But we should not record any slots in non-black
5545   // objects. Grey object's slots would be rescanned.
5546   // White object might not survive until the end of collection
5547   // it would be a violation of the invariant to record it's slots.
5548   bool record_slots = false;
5549   if (incremental_marking()->IsCompacting()) {
5550     MarkBit mark_bit = Marking::MarkBitFrom(HeapObject::FromAddress(start));
5551     record_slots = Marking::IsBlack(mark_bit);
5552   }
5553
5554   while (slot_address < end) {
5555     Object** slot = reinterpret_cast<Object**>(slot_address);
5556     Object* object = *slot;
5557     // If the store buffer becomes overfull we mark pages as being exempt from
5558     // the store buffer.  These pages are scanned to find pointers that point
5559     // to the new space.  In that case we may hit newly promoted objects and
5560     // fix the pointers before the promotion queue gets to them.  Thus the 'if'.
5561     if (object->IsHeapObject()) {
5562       if (Heap::InFromSpace(object)) {
5563         callback(reinterpret_cast<HeapObject**>(slot),
5564                  HeapObject::cast(object));
5565         Object* new_object = *slot;
5566         if (InNewSpace(new_object)) {
5567           SLOW_ASSERT(Heap::InToSpace(new_object));
5568           SLOW_ASSERT(new_object->IsHeapObject());
5569           store_buffer_.EnterDirectlyIntoStoreBuffer(
5570               reinterpret_cast<Address>(slot));
5571         }
5572         SLOW_ASSERT(!MarkCompactCollector::IsOnEvacuationCandidate(new_object));
5573       } else if (record_slots &&
5574                  MarkCompactCollector::IsOnEvacuationCandidate(object)) {
5575         mark_compact_collector()->RecordSlot(slot, slot, object);
5576       }
5577     }
5578     slot_address += kPointerSize;
5579   }
5580 }
5581
5582
5583 #ifdef DEBUG
5584 typedef bool (*CheckStoreBufferFilter)(Object** addr);
5585
5586
5587 bool IsAMapPointerAddress(Object** addr) {
5588   uintptr_t a = reinterpret_cast<uintptr_t>(addr);
5589   int mod = a % Map::kSize;
5590   return mod >= Map::kPointerFieldsBeginOffset &&
5591          mod < Map::kPointerFieldsEndOffset;
5592 }
5593
5594
5595 bool EverythingsAPointer(Object** addr) {
5596   return true;
5597 }
5598
5599
5600 static void CheckStoreBuffer(Heap* heap,
5601                              Object** current,
5602                              Object** limit,
5603                              Object**** store_buffer_position,
5604                              Object*** store_buffer_top,
5605                              CheckStoreBufferFilter filter,
5606                              Address special_garbage_start,
5607                              Address special_garbage_end) {
5608   Map* free_space_map = heap->free_space_map();
5609   for ( ; current < limit; current++) {
5610     Object* o = *current;
5611     Address current_address = reinterpret_cast<Address>(current);
5612     // Skip free space.
5613     if (o == free_space_map) {
5614       Address current_address = reinterpret_cast<Address>(current);
5615       FreeSpace* free_space =
5616           FreeSpace::cast(HeapObject::FromAddress(current_address));
5617       int skip = free_space->Size();
5618       ASSERT(current_address + skip <= reinterpret_cast<Address>(limit));
5619       ASSERT(skip > 0);
5620       current_address += skip - kPointerSize;
5621       current = reinterpret_cast<Object**>(current_address);
5622       continue;
5623     }
5624     // Skip the current linear allocation space between top and limit which is
5625     // unmarked with the free space map, but can contain junk.
5626     if (current_address == special_garbage_start &&
5627         special_garbage_end != special_garbage_start) {
5628       current_address = special_garbage_end - kPointerSize;
5629       current = reinterpret_cast<Object**>(current_address);
5630       continue;
5631     }
5632     if (!(*filter)(current)) continue;
5633     ASSERT(current_address < special_garbage_start ||
5634            current_address >= special_garbage_end);
5635     ASSERT(reinterpret_cast<uintptr_t>(o) != kFreeListZapValue);
5636     // We have to check that the pointer does not point into new space
5637     // without trying to cast it to a heap object since the hash field of
5638     // a string can contain values like 1 and 3 which are tagged null
5639     // pointers.
5640     if (!heap->InNewSpace(o)) continue;
5641     while (**store_buffer_position < current &&
5642            *store_buffer_position < store_buffer_top) {
5643       (*store_buffer_position)++;
5644     }
5645     if (**store_buffer_position != current ||
5646         *store_buffer_position == store_buffer_top) {
5647       Object** obj_start = current;
5648       while (!(*obj_start)->IsMap()) obj_start--;
5649       UNREACHABLE();
5650     }
5651   }
5652 }
5653
5654
5655 // Check that the store buffer contains all intergenerational pointers by
5656 // scanning a page and ensuring that all pointers to young space are in the
5657 // store buffer.
5658 void Heap::OldPointerSpaceCheckStoreBuffer() {
5659   OldSpace* space = old_pointer_space();
5660   PageIterator pages(space);
5661
5662   store_buffer()->SortUniq();
5663
5664   while (pages.has_next()) {
5665     Page* page = pages.next();
5666     Object** current = reinterpret_cast<Object**>(page->area_start());
5667
5668     Address end = page->area_end();
5669
5670     Object*** store_buffer_position = store_buffer()->Start();
5671     Object*** store_buffer_top = store_buffer()->Top();
5672
5673     Object** limit = reinterpret_cast<Object**>(end);
5674     CheckStoreBuffer(this,
5675                      current,
5676                      limit,
5677                      &store_buffer_position,
5678                      store_buffer_top,
5679                      &EverythingsAPointer,
5680                      space->top(),
5681                      space->limit());
5682   }
5683 }
5684
5685
5686 void Heap::MapSpaceCheckStoreBuffer() {
5687   MapSpace* space = map_space();
5688   PageIterator pages(space);
5689
5690   store_buffer()->SortUniq();
5691
5692   while (pages.has_next()) {
5693     Page* page = pages.next();
5694     Object** current = reinterpret_cast<Object**>(page->area_start());
5695
5696     Address end = page->area_end();
5697
5698     Object*** store_buffer_position = store_buffer()->Start();
5699     Object*** store_buffer_top = store_buffer()->Top();
5700
5701     Object** limit = reinterpret_cast<Object**>(end);
5702     CheckStoreBuffer(this,
5703                      current,
5704                      limit,
5705                      &store_buffer_position,
5706                      store_buffer_top,
5707                      &IsAMapPointerAddress,
5708                      space->top(),
5709                      space->limit());
5710   }
5711 }
5712
5713
5714 void Heap::LargeObjectSpaceCheckStoreBuffer() {
5715   LargeObjectIterator it(lo_space());
5716   for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
5717     // We only have code, sequential strings, or fixed arrays in large
5718     // object space, and only fixed arrays can possibly contain pointers to
5719     // the young generation.
5720     if (object->IsFixedArray()) {
5721       Object*** store_buffer_position = store_buffer()->Start();
5722       Object*** store_buffer_top = store_buffer()->Top();
5723       Object** current = reinterpret_cast<Object**>(object->address());
5724       Object** limit =
5725           reinterpret_cast<Object**>(object->address() + object->Size());
5726       CheckStoreBuffer(this,
5727                        current,
5728                        limit,
5729                        &store_buffer_position,
5730                        store_buffer_top,
5731                        &EverythingsAPointer,
5732                        NULL,
5733                        NULL);
5734     }
5735   }
5736 }
5737 #endif
5738
5739
5740 void Heap::IterateRoots(ObjectVisitor* v, VisitMode mode) {
5741   IterateStrongRoots(v, mode);
5742   IterateWeakRoots(v, mode);
5743 }
5744
5745
5746 void Heap::IterateWeakRoots(ObjectVisitor* v, VisitMode mode) {
5747   v->VisitPointer(reinterpret_cast<Object**>(&roots_[kSymbolTableRootIndex]));
5748   v->Synchronize(VisitorSynchronization::kSymbolTable);
5749   if (mode != VISIT_ALL_IN_SCAVENGE &&
5750       mode != VISIT_ALL_IN_SWEEP_NEWSPACE) {
5751     // Scavenge collections have special processing for this.
5752     external_string_table_.Iterate(v);
5753   }
5754   v->Synchronize(VisitorSynchronization::kExternalStringsTable);
5755 }
5756
5757
5758 void Heap::IterateStrongRoots(ObjectVisitor* v, VisitMode mode) {
5759   v->VisitPointers(&roots_[0], &roots_[kStrongRootListLength]);
5760   v->Synchronize(VisitorSynchronization::kStrongRootList);
5761
5762   v->VisitPointer(BitCast<Object**>(&hidden_symbol_));
5763   v->Synchronize(VisitorSynchronization::kSymbol);
5764
5765   isolate_->bootstrapper()->Iterate(v);
5766   v->Synchronize(VisitorSynchronization::kBootstrapper);
5767   isolate_->Iterate(v);
5768   v->Synchronize(VisitorSynchronization::kTop);
5769   Relocatable::Iterate(v);
5770   v->Synchronize(VisitorSynchronization::kRelocatable);
5771
5772 #ifdef ENABLE_DEBUGGER_SUPPORT
5773   isolate_->debug()->Iterate(v);
5774   if (isolate_->deoptimizer_data() != NULL) {
5775     isolate_->deoptimizer_data()->Iterate(v);
5776   }
5777 #endif
5778   v->Synchronize(VisitorSynchronization::kDebug);
5779   isolate_->compilation_cache()->Iterate(v);
5780   v->Synchronize(VisitorSynchronization::kCompilationCache);
5781
5782   // Iterate over local handles in handle scopes.
5783   isolate_->handle_scope_implementer()->Iterate(v);
5784   isolate_->IterateDeferredHandles(v);
5785   v->Synchronize(VisitorSynchronization::kHandleScope);
5786
5787   // Iterate over the builtin code objects and code stubs in the
5788   // heap. Note that it is not necessary to iterate over code objects
5789   // on scavenge collections.
5790   if (mode != VISIT_ALL_IN_SCAVENGE) {
5791     isolate_->builtins()->IterateBuiltins(v);
5792   }
5793   v->Synchronize(VisitorSynchronization::kBuiltins);
5794
5795   // Iterate over global handles.
5796   switch (mode) {
5797     case VISIT_ONLY_STRONG:
5798       isolate_->global_handles()->IterateStrongRoots(v);
5799       break;
5800     case VISIT_ALL_IN_SCAVENGE:
5801       isolate_->global_handles()->IterateNewSpaceStrongAndDependentRoots(v);
5802       break;
5803     case VISIT_ALL_IN_SWEEP_NEWSPACE:
5804     case VISIT_ALL:
5805       isolate_->global_handles()->IterateAllRoots(v);
5806       break;
5807   }
5808   v->Synchronize(VisitorSynchronization::kGlobalHandles);
5809
5810   // Iterate over pointers being held by inactive threads.
5811   isolate_->thread_manager()->Iterate(v);
5812   v->Synchronize(VisitorSynchronization::kThreadManager);
5813
5814   // Iterate over the pointers the Serialization/Deserialization code is
5815   // holding.
5816   // During garbage collection this keeps the partial snapshot cache alive.
5817   // During deserialization of the startup snapshot this creates the partial
5818   // snapshot cache and deserializes the objects it refers to.  During
5819   // serialization this does nothing, since the partial snapshot cache is
5820   // empty.  However the next thing we do is create the partial snapshot,
5821   // filling up the partial snapshot cache with objects it needs as we go.
5822   SerializerDeserializer::Iterate(v);
5823   // We don't do a v->Synchronize call here, because in debug mode that will
5824   // output a flag to the snapshot.  However at this point the serializer and
5825   // deserializer are deliberately a little unsynchronized (see above) so the
5826   // checking of the sync flag in the snapshot would fail.
5827 }
5828
5829
5830 // TODO(1236194): Since the heap size is configurable on the command line
5831 // and through the API, we should gracefully handle the case that the heap
5832 // size is not big enough to fit all the initial objects.
5833 bool Heap::ConfigureHeap(int max_semispace_size,
5834                          intptr_t max_old_gen_size,
5835                          intptr_t max_executable_size) {
5836   if (HasBeenSetUp()) return false;
5837
5838   if (FLAG_stress_compaction) {
5839     // This will cause more frequent GCs when stressing.
5840     max_semispace_size_ = Page::kPageSize;
5841   }
5842
5843   if (max_semispace_size > 0) {
5844     if (max_semispace_size < Page::kPageSize) {
5845       max_semispace_size = Page::kPageSize;
5846       if (FLAG_trace_gc) {
5847         PrintPID("Max semispace size cannot be less than %dkbytes\n",
5848                  Page::kPageSize >> 10);
5849       }
5850     }
5851     max_semispace_size_ = max_semispace_size;
5852   }
5853
5854   if (Snapshot::IsEnabled()) {
5855     // If we are using a snapshot we always reserve the default amount
5856     // of memory for each semispace because code in the snapshot has
5857     // write-barrier code that relies on the size and alignment of new
5858     // space.  We therefore cannot use a larger max semispace size
5859     // than the default reserved semispace size.
5860     if (max_semispace_size_ > reserved_semispace_size_) {
5861       max_semispace_size_ = reserved_semispace_size_;
5862       if (FLAG_trace_gc) {
5863         PrintPID("Max semispace size cannot be more than %dkbytes\n",
5864                  reserved_semispace_size_ >> 10);
5865       }
5866     }
5867   } else {
5868     // If we are not using snapshots we reserve space for the actual
5869     // max semispace size.
5870     reserved_semispace_size_ = max_semispace_size_;
5871   }
5872
5873   if (max_old_gen_size > 0) max_old_generation_size_ = max_old_gen_size;
5874   if (max_executable_size > 0) {
5875     max_executable_size_ = RoundUp(max_executable_size, Page::kPageSize);
5876   }
5877
5878   // The max executable size must be less than or equal to the max old
5879   // generation size.
5880   if (max_executable_size_ > max_old_generation_size_) {
5881     max_executable_size_ = max_old_generation_size_;
5882   }
5883
5884   // The new space size must be a power of two to support single-bit testing
5885   // for containment.
5886   max_semispace_size_ = RoundUpToPowerOf2(max_semispace_size_);
5887   reserved_semispace_size_ = RoundUpToPowerOf2(reserved_semispace_size_);
5888   initial_semispace_size_ = Min(initial_semispace_size_, max_semispace_size_);
5889   external_allocation_limit_ = 16 * max_semispace_size_;
5890
5891   // The old generation is paged and needs at least one page for each space.
5892   int paged_space_count = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1;
5893   max_old_generation_size_ = Max(static_cast<intptr_t>(paged_space_count *
5894                                                        Page::kPageSize),
5895                                  RoundUp(max_old_generation_size_,
5896                                          Page::kPageSize));
5897
5898   configured_ = true;
5899   return true;
5900 }
5901
5902
5903 bool Heap::ConfigureHeapDefault() {
5904   return ConfigureHeap(static_cast<intptr_t>(FLAG_max_new_space_size / 2) * KB,
5905                        static_cast<intptr_t>(FLAG_max_old_space_size) * MB,
5906                        static_cast<intptr_t>(FLAG_max_executable_size) * MB);
5907 }
5908
5909
5910 void Heap::RecordStats(HeapStats* stats, bool take_snapshot) {
5911   *stats->start_marker = HeapStats::kStartMarker;
5912   *stats->end_marker = HeapStats::kEndMarker;
5913   *stats->new_space_size = new_space_.SizeAsInt();
5914   *stats->new_space_capacity = static_cast<int>(new_space_.Capacity());
5915   *stats->old_pointer_space_size = old_pointer_space_->SizeOfObjects();
5916   *stats->old_pointer_space_capacity = old_pointer_space_->Capacity();
5917   *stats->old_data_space_size = old_data_space_->SizeOfObjects();
5918   *stats->old_data_space_capacity = old_data_space_->Capacity();
5919   *stats->code_space_size = code_space_->SizeOfObjects();
5920   *stats->code_space_capacity = code_space_->Capacity();
5921   *stats->map_space_size = map_space_->SizeOfObjects();
5922   *stats->map_space_capacity = map_space_->Capacity();
5923   *stats->cell_space_size = cell_space_->SizeOfObjects();
5924   *stats->cell_space_capacity = cell_space_->Capacity();
5925   *stats->lo_space_size = lo_space_->Size();
5926   isolate_->global_handles()->RecordStats(stats);
5927   *stats->memory_allocator_size = isolate()->memory_allocator()->Size();
5928   *stats->memory_allocator_capacity =
5929       isolate()->memory_allocator()->Size() +
5930       isolate()->memory_allocator()->Available();
5931   *stats->os_error = OS::GetLastError();
5932       isolate()->memory_allocator()->Available();
5933   if (take_snapshot) {
5934     HeapIterator iterator;
5935     for (HeapObject* obj = iterator.next();
5936          obj != NULL;
5937          obj = iterator.next()) {
5938       InstanceType type = obj->map()->instance_type();
5939       ASSERT(0 <= type && type <= LAST_TYPE);
5940       stats->objects_per_type[type]++;
5941       stats->size_per_type[type] += obj->Size();
5942     }
5943   }
5944 }
5945
5946
5947 intptr_t Heap::PromotedSpaceSizeOfObjects() {
5948   return old_pointer_space_->SizeOfObjects()
5949       + old_data_space_->SizeOfObjects()
5950       + code_space_->SizeOfObjects()
5951       + map_space_->SizeOfObjects()
5952       + cell_space_->SizeOfObjects()
5953       + lo_space_->SizeOfObjects();
5954 }
5955
5956
5957 intptr_t Heap::PromotedExternalMemorySize() {
5958   if (amount_of_external_allocated_memory_
5959       <= amount_of_external_allocated_memory_at_last_global_gc_) return 0;
5960   return amount_of_external_allocated_memory_
5961       - amount_of_external_allocated_memory_at_last_global_gc_;
5962 }
5963
5964 #ifdef DEBUG
5965
5966 // Tags 0, 1, and 3 are used. Use 2 for marking visited HeapObject.
5967 static const int kMarkTag = 2;
5968
5969
5970 class HeapDebugUtils {
5971  public:
5972   explicit HeapDebugUtils(Heap* heap)
5973     : search_for_any_global_(false),
5974       search_target_(NULL),
5975       found_target_(false),
5976       object_stack_(20),
5977       heap_(heap) {
5978   }
5979
5980   class MarkObjectVisitor : public ObjectVisitor {
5981    public:
5982     explicit MarkObjectVisitor(HeapDebugUtils* utils) : utils_(utils) { }
5983
5984     void VisitPointers(Object** start, Object** end) {
5985       // Copy all HeapObject pointers in [start, end)
5986       for (Object** p = start; p < end; p++) {
5987         if ((*p)->IsHeapObject())
5988           utils_->MarkObjectRecursively(p);
5989       }
5990     }
5991
5992     HeapDebugUtils* utils_;
5993   };
5994
5995   void MarkObjectRecursively(Object** p) {
5996     if (!(*p)->IsHeapObject()) return;
5997
5998     HeapObject* obj = HeapObject::cast(*p);
5999
6000     Object* map = obj->map();
6001
6002     if (!map->IsHeapObject()) return;  // visited before
6003
6004     if (found_target_) return;  // stop if target found
6005     object_stack_.Add(obj);
6006     if ((search_for_any_global_ && obj->IsJSGlobalObject()) ||
6007         (!search_for_any_global_ && (obj == search_target_))) {
6008       found_target_ = true;
6009       return;
6010     }
6011
6012     // not visited yet
6013     Map* map_p = reinterpret_cast<Map*>(HeapObject::cast(map));
6014
6015     Address map_addr = map_p->address();
6016
6017     obj->set_map_no_write_barrier(reinterpret_cast<Map*>(map_addr + kMarkTag));
6018
6019     MarkObjectRecursively(&map);
6020
6021     MarkObjectVisitor mark_visitor(this);
6022
6023     obj->IterateBody(map_p->instance_type(), obj->SizeFromMap(map_p),
6024                      &mark_visitor);
6025
6026     if (!found_target_)  // don't pop if found the target
6027       object_stack_.RemoveLast();
6028   }
6029
6030
6031   class UnmarkObjectVisitor : public ObjectVisitor {
6032    public:
6033     explicit UnmarkObjectVisitor(HeapDebugUtils* utils) : utils_(utils) { }
6034
6035     void VisitPointers(Object** start, Object** end) {
6036       // Copy all HeapObject pointers in [start, end)
6037       for (Object** p = start; p < end; p++) {
6038         if ((*p)->IsHeapObject())
6039           utils_->UnmarkObjectRecursively(p);
6040       }
6041     }
6042
6043     HeapDebugUtils* utils_;
6044   };
6045
6046
6047   void UnmarkObjectRecursively(Object** p) {
6048     if (!(*p)->IsHeapObject()) return;
6049
6050     HeapObject* obj = HeapObject::cast(*p);
6051
6052     Object* map = obj->map();
6053
6054     if (map->IsHeapObject()) return;  // unmarked already
6055
6056     Address map_addr = reinterpret_cast<Address>(map);
6057
6058     map_addr -= kMarkTag;
6059
6060     ASSERT_TAG_ALIGNED(map_addr);
6061
6062     HeapObject* map_p = HeapObject::FromAddress(map_addr);
6063
6064     obj->set_map_no_write_barrier(reinterpret_cast<Map*>(map_p));
6065
6066     UnmarkObjectRecursively(reinterpret_cast<Object**>(&map_p));
6067
6068     UnmarkObjectVisitor unmark_visitor(this);
6069
6070     obj->IterateBody(Map::cast(map_p)->instance_type(),
6071                      obj->SizeFromMap(Map::cast(map_p)),
6072                      &unmark_visitor);
6073   }
6074
6075
6076   void MarkRootObjectRecursively(Object** root) {
6077     if (search_for_any_global_) {
6078       ASSERT(search_target_ == NULL);
6079     } else {
6080       ASSERT(search_target_->IsHeapObject());
6081     }
6082     found_target_ = false;
6083     object_stack_.Clear();
6084
6085     MarkObjectRecursively(root);
6086     UnmarkObjectRecursively(root);
6087
6088     if (found_target_) {
6089       PrintF("=====================================\n");
6090       PrintF("====        Path to object       ====\n");
6091       PrintF("=====================================\n\n");
6092
6093       ASSERT(!object_stack_.is_empty());
6094       for (int i = 0; i < object_stack_.length(); i++) {
6095         if (i > 0) PrintF("\n     |\n     |\n     V\n\n");
6096         Object* obj = object_stack_[i];
6097         obj->Print();
6098       }
6099       PrintF("=====================================\n");
6100     }
6101   }
6102
6103   // Helper class for visiting HeapObjects recursively.
6104   class MarkRootVisitor: public ObjectVisitor {
6105    public:
6106     explicit MarkRootVisitor(HeapDebugUtils* utils) : utils_(utils) { }
6107
6108     void VisitPointers(Object** start, Object** end) {
6109       // Visit all HeapObject pointers in [start, end)
6110       for (Object** p = start; p < end; p++) {
6111         if ((*p)->IsHeapObject())
6112           utils_->MarkRootObjectRecursively(p);
6113       }
6114     }
6115
6116     HeapDebugUtils* utils_;
6117   };
6118
6119   bool search_for_any_global_;
6120   Object* search_target_;
6121   bool found_target_;
6122   List<Object*> object_stack_;
6123   Heap* heap_;
6124
6125   friend class Heap;
6126 };
6127
6128 #endif
6129
6130
6131 V8_DECLARE_ONCE(initialize_gc_once);
6132
6133 static void InitializeGCOnce() {
6134   InitializeScavengingVisitorsTables();
6135   NewSpaceScavenger::Initialize();
6136   MarkCompactCollector::Initialize();
6137 }
6138
6139 bool Heap::SetUp(bool create_heap_objects) {
6140 #ifdef DEBUG
6141   allocation_timeout_ = FLAG_gc_interval;
6142   debug_utils_ = new HeapDebugUtils(this);
6143 #endif
6144
6145   // Initialize heap spaces and initial maps and objects. Whenever something
6146   // goes wrong, just return false. The caller should check the results and
6147   // call Heap::TearDown() to release allocated memory.
6148   //
6149   // If the heap is not yet configured (e.g. through the API), configure it.
6150   // Configuration is based on the flags new-space-size (really the semispace
6151   // size) and old-space-size if set or the initial values of semispace_size_
6152   // and old_generation_size_ otherwise.
6153   if (!configured_) {
6154     if (!ConfigureHeapDefault()) return false;
6155   }
6156
6157   CallOnce(&initialize_gc_once, &InitializeGCOnce);
6158
6159   MarkMapPointersAsEncoded(false);
6160
6161   // Set up memory allocator.
6162   if (!isolate_->memory_allocator()->SetUp(MaxReserved(), MaxExecutableSize()))
6163       return false;
6164
6165   // Set up new space.
6166   if (!new_space_.SetUp(reserved_semispace_size_, max_semispace_size_)) {
6167     return false;
6168   }
6169
6170   // Initialize old pointer space.
6171   old_pointer_space_ =
6172       new OldSpace(this,
6173                    max_old_generation_size_,
6174                    OLD_POINTER_SPACE,
6175                    NOT_EXECUTABLE);
6176   if (old_pointer_space_ == NULL) return false;
6177   if (!old_pointer_space_->SetUp()) return false;
6178
6179   // Initialize old data space.
6180   old_data_space_ =
6181       new OldSpace(this,
6182                    max_old_generation_size_,
6183                    OLD_DATA_SPACE,
6184                    NOT_EXECUTABLE);
6185   if (old_data_space_ == NULL) return false;
6186   if (!old_data_space_->SetUp()) return false;
6187
6188   // Initialize the code space, set its maximum capacity to the old
6189   // generation size. It needs executable memory.
6190   // On 64-bit platform(s), we put all code objects in a 2 GB range of
6191   // virtual address space, so that they can call each other with near calls.
6192   if (code_range_size_ > 0) {
6193     if (!isolate_->code_range()->SetUp(code_range_size_)) {
6194       return false;
6195     }
6196   }
6197
6198   code_space_ =
6199       new OldSpace(this, max_old_generation_size_, CODE_SPACE, EXECUTABLE);
6200   if (code_space_ == NULL) return false;
6201   if (!code_space_->SetUp()) return false;
6202
6203   // Initialize map space.
6204   map_space_ = new MapSpace(this, max_old_generation_size_, MAP_SPACE);
6205   if (map_space_ == NULL) return false;
6206   if (!map_space_->SetUp()) return false;
6207
6208   // Initialize global property cell space.
6209   cell_space_ = new CellSpace(this, max_old_generation_size_, CELL_SPACE);
6210   if (cell_space_ == NULL) return false;
6211   if (!cell_space_->SetUp()) return false;
6212
6213   // The large object code space may contain code or data.  We set the memory
6214   // to be non-executable here for safety, but this means we need to enable it
6215   // explicitly when allocating large code objects.
6216   lo_space_ = new LargeObjectSpace(this, max_old_generation_size_, LO_SPACE);
6217   if (lo_space_ == NULL) return false;
6218   if (!lo_space_->SetUp()) return false;
6219
6220   // Set up the seed that is used to randomize the string hash function.
6221   ASSERT(hash_seed() == 0);
6222   if (FLAG_randomize_hashes) {
6223     if (FLAG_hash_seed == 0) {
6224       set_hash_seed(
6225           Smi::FromInt(V8::RandomPrivate(isolate()) & 0x3fffffff));
6226     } else {
6227       set_hash_seed(Smi::FromInt(FLAG_hash_seed));
6228     }
6229   }
6230
6231   if (create_heap_objects) {
6232     // Create initial maps.
6233     if (!CreateInitialMaps()) return false;
6234     if (!CreateApiObjects()) return false;
6235
6236     // Create initial objects
6237     if (!CreateInitialObjects()) return false;
6238
6239     native_contexts_list_ = undefined_value();
6240   }
6241
6242   LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
6243   LOG(isolate_, IntPtrTEvent("heap-available", Available()));
6244
6245   store_buffer()->SetUp();
6246
6247   if (FLAG_parallel_recompilation) relocation_mutex_ = OS::CreateMutex();
6248
6249   return true;
6250 }
6251
6252
6253 void Heap::SetStackLimits() {
6254   ASSERT(isolate_ != NULL);
6255   ASSERT(isolate_ == isolate());
6256   // On 64 bit machines, pointers are generally out of range of Smis.  We write
6257   // something that looks like an out of range Smi to the GC.
6258
6259   // Set up the special root array entries containing the stack limits.
6260   // These are actually addresses, but the tag makes the GC ignore it.
6261   roots_[kStackLimitRootIndex] =
6262       reinterpret_cast<Object*>(
6263           (isolate_->stack_guard()->jslimit() & ~kSmiTagMask) | kSmiTag);
6264   roots_[kRealStackLimitRootIndex] =
6265       reinterpret_cast<Object*>(
6266           (isolate_->stack_guard()->real_jslimit() & ~kSmiTagMask) | kSmiTag);
6267 }
6268
6269
6270 void Heap::TearDown() {
6271 #ifdef VERIFY_HEAP
6272   if (FLAG_verify_heap) {
6273     Verify();
6274   }
6275 #endif
6276
6277   if (FLAG_print_cumulative_gc_stat) {
6278     PrintF("\n\n");
6279     PrintF("gc_count=%d ", gc_count_);
6280     PrintF("mark_sweep_count=%d ", ms_count_);
6281     PrintF("max_gc_pause=%d ", get_max_gc_pause());
6282     PrintF("total_gc_time=%d ", total_gc_time_ms_);
6283     PrintF("min_in_mutator=%d ", get_min_in_mutator());
6284     PrintF("max_alive_after_gc=%" V8_PTR_PREFIX "d ",
6285            get_max_alive_after_gc());
6286     PrintF("\n\n");
6287   }
6288
6289   isolate_->global_handles()->TearDown();
6290
6291   external_string_table_.TearDown();
6292
6293   new_space_.TearDown();
6294
6295   if (old_pointer_space_ != NULL) {
6296     old_pointer_space_->TearDown();
6297     delete old_pointer_space_;
6298     old_pointer_space_ = NULL;
6299   }
6300
6301   if (old_data_space_ != NULL) {
6302     old_data_space_->TearDown();
6303     delete old_data_space_;
6304     old_data_space_ = NULL;
6305   }
6306
6307   if (code_space_ != NULL) {
6308     code_space_->TearDown();
6309     delete code_space_;
6310     code_space_ = NULL;
6311   }
6312
6313   if (map_space_ != NULL) {
6314     map_space_->TearDown();
6315     delete map_space_;
6316     map_space_ = NULL;
6317   }
6318
6319   if (cell_space_ != NULL) {
6320     cell_space_->TearDown();
6321     delete cell_space_;
6322     cell_space_ = NULL;
6323   }
6324
6325   if (lo_space_ != NULL) {
6326     lo_space_->TearDown();
6327     delete lo_space_;
6328     lo_space_ = NULL;
6329   }
6330
6331   store_buffer()->TearDown();
6332   incremental_marking()->TearDown();
6333
6334   isolate_->memory_allocator()->TearDown();
6335
6336   delete relocation_mutex_;
6337
6338 #ifdef DEBUG
6339   delete debug_utils_;
6340   debug_utils_ = NULL;
6341 #endif
6342 }
6343
6344
6345 void Heap::Shrink() {
6346   // Try to shrink all paged spaces.
6347   PagedSpaces spaces;
6348   for (PagedSpace* space = spaces.next();
6349        space != NULL;
6350        space = spaces.next()) {
6351     space->ReleaseAllUnusedPages();
6352   }
6353 }
6354
6355
6356 void Heap::AddGCPrologueCallback(GCPrologueCallback callback, GCType gc_type) {
6357   ASSERT(callback != NULL);
6358   GCPrologueCallbackPair pair(callback, gc_type);
6359   ASSERT(!gc_prologue_callbacks_.Contains(pair));
6360   return gc_prologue_callbacks_.Add(pair);
6361 }
6362
6363
6364 void Heap::RemoveGCPrologueCallback(GCPrologueCallback callback) {
6365   ASSERT(callback != NULL);
6366   for (int i = 0; i < gc_prologue_callbacks_.length(); ++i) {
6367     if (gc_prologue_callbacks_[i].callback == callback) {
6368       gc_prologue_callbacks_.Remove(i);
6369       return;
6370     }
6371   }
6372   UNREACHABLE();
6373 }
6374
6375
6376 void Heap::AddGCEpilogueCallback(GCEpilogueCallback callback, GCType gc_type) {
6377   ASSERT(callback != NULL);
6378   GCEpilogueCallbackPair pair(callback, gc_type);
6379   ASSERT(!gc_epilogue_callbacks_.Contains(pair));
6380   return gc_epilogue_callbacks_.Add(pair);
6381 }
6382
6383
6384 void Heap::RemoveGCEpilogueCallback(GCEpilogueCallback callback) {
6385   ASSERT(callback != NULL);
6386   for (int i = 0; i < gc_epilogue_callbacks_.length(); ++i) {
6387     if (gc_epilogue_callbacks_[i].callback == callback) {
6388       gc_epilogue_callbacks_.Remove(i);
6389       return;
6390     }
6391   }
6392   UNREACHABLE();
6393 }
6394
6395
6396 #ifdef DEBUG
6397
6398 class PrintHandleVisitor: public ObjectVisitor {
6399  public:
6400   void VisitPointers(Object** start, Object** end) {
6401     for (Object** p = start; p < end; p++)
6402       PrintF("  handle %p to %p\n",
6403              reinterpret_cast<void*>(p),
6404              reinterpret_cast<void*>(*p));
6405   }
6406 };
6407
6408 void Heap::PrintHandles() {
6409   PrintF("Handles:\n");
6410   PrintHandleVisitor v;
6411   isolate_->handle_scope_implementer()->Iterate(&v);
6412 }
6413
6414 #endif
6415
6416
6417 Space* AllSpaces::next() {
6418   switch (counter_++) {
6419     case NEW_SPACE:
6420       return HEAP->new_space();
6421     case OLD_POINTER_SPACE:
6422       return HEAP->old_pointer_space();
6423     case OLD_DATA_SPACE:
6424       return HEAP->old_data_space();
6425     case CODE_SPACE:
6426       return HEAP->code_space();
6427     case MAP_SPACE:
6428       return HEAP->map_space();
6429     case CELL_SPACE:
6430       return HEAP->cell_space();
6431     case LO_SPACE:
6432       return HEAP->lo_space();
6433     default:
6434       return NULL;
6435   }
6436 }
6437
6438
6439 PagedSpace* PagedSpaces::next() {
6440   switch (counter_++) {
6441     case OLD_POINTER_SPACE:
6442       return HEAP->old_pointer_space();
6443     case OLD_DATA_SPACE:
6444       return HEAP->old_data_space();
6445     case CODE_SPACE:
6446       return HEAP->code_space();
6447     case MAP_SPACE:
6448       return HEAP->map_space();
6449     case CELL_SPACE:
6450       return HEAP->cell_space();
6451     default:
6452       return NULL;
6453   }
6454 }
6455
6456
6457
6458 OldSpace* OldSpaces::next() {
6459   switch (counter_++) {
6460     case OLD_POINTER_SPACE:
6461       return HEAP->old_pointer_space();
6462     case OLD_DATA_SPACE:
6463       return HEAP->old_data_space();
6464     case CODE_SPACE:
6465       return HEAP->code_space();
6466     default:
6467       return NULL;
6468   }
6469 }
6470
6471
6472 SpaceIterator::SpaceIterator()
6473     : current_space_(FIRST_SPACE),
6474       iterator_(NULL),
6475       size_func_(NULL) {
6476 }
6477
6478
6479 SpaceIterator::SpaceIterator(HeapObjectCallback size_func)
6480     : current_space_(FIRST_SPACE),
6481       iterator_(NULL),
6482       size_func_(size_func) {
6483 }
6484
6485
6486 SpaceIterator::~SpaceIterator() {
6487   // Delete active iterator if any.
6488   delete iterator_;
6489 }
6490
6491
6492 bool SpaceIterator::has_next() {
6493   // Iterate until no more spaces.
6494   return current_space_ != LAST_SPACE;
6495 }
6496
6497
6498 ObjectIterator* SpaceIterator::next() {
6499   if (iterator_ != NULL) {
6500     delete iterator_;
6501     iterator_ = NULL;
6502     // Move to the next space
6503     current_space_++;
6504     if (current_space_ > LAST_SPACE) {
6505       return NULL;
6506     }
6507   }
6508
6509   // Return iterator for the new current space.
6510   return CreateIterator();
6511 }
6512
6513
6514 // Create an iterator for the space to iterate.
6515 ObjectIterator* SpaceIterator::CreateIterator() {
6516   ASSERT(iterator_ == NULL);
6517
6518   switch (current_space_) {
6519     case NEW_SPACE:
6520       iterator_ = new SemiSpaceIterator(HEAP->new_space(), size_func_);
6521       break;
6522     case OLD_POINTER_SPACE:
6523       iterator_ = new HeapObjectIterator(HEAP->old_pointer_space(), size_func_);
6524       break;
6525     case OLD_DATA_SPACE:
6526       iterator_ = new HeapObjectIterator(HEAP->old_data_space(), size_func_);
6527       break;
6528     case CODE_SPACE:
6529       iterator_ = new HeapObjectIterator(HEAP->code_space(), size_func_);
6530       break;
6531     case MAP_SPACE:
6532       iterator_ = new HeapObjectIterator(HEAP->map_space(), size_func_);
6533       break;
6534     case CELL_SPACE:
6535       iterator_ = new HeapObjectIterator(HEAP->cell_space(), size_func_);
6536       break;
6537     case LO_SPACE:
6538       iterator_ = new LargeObjectIterator(HEAP->lo_space(), size_func_);
6539       break;
6540   }
6541
6542   // Return the newly allocated iterator;
6543   ASSERT(iterator_ != NULL);
6544   return iterator_;
6545 }
6546
6547
6548 class HeapObjectsFilter {
6549  public:
6550   virtual ~HeapObjectsFilter() {}
6551   virtual bool SkipObject(HeapObject* object) = 0;
6552 };
6553
6554
6555 class UnreachableObjectsFilter : public HeapObjectsFilter {
6556  public:
6557   UnreachableObjectsFilter() {
6558     MarkReachableObjects();
6559   }
6560
6561   ~UnreachableObjectsFilter() {
6562     Isolate::Current()->heap()->mark_compact_collector()->ClearMarkbits();
6563   }
6564
6565   bool SkipObject(HeapObject* object) {
6566     MarkBit mark_bit = Marking::MarkBitFrom(object);
6567     return !mark_bit.Get();
6568   }
6569
6570  private:
6571   class MarkingVisitor : public ObjectVisitor {
6572    public:
6573     MarkingVisitor() : marking_stack_(10) {}
6574
6575     void VisitPointers(Object** start, Object** end) {
6576       for (Object** p = start; p < end; p++) {
6577         if (!(*p)->IsHeapObject()) continue;
6578         HeapObject* obj = HeapObject::cast(*p);
6579         MarkBit mark_bit = Marking::MarkBitFrom(obj);
6580         if (!mark_bit.Get()) {
6581           mark_bit.Set();
6582           marking_stack_.Add(obj);
6583         }
6584       }
6585     }
6586
6587     void TransitiveClosure() {
6588       while (!marking_stack_.is_empty()) {
6589         HeapObject* obj = marking_stack_.RemoveLast();
6590         obj->Iterate(this);
6591       }
6592     }
6593
6594    private:
6595     List<HeapObject*> marking_stack_;
6596   };
6597
6598   void MarkReachableObjects() {
6599     Heap* heap = Isolate::Current()->heap();
6600     MarkingVisitor visitor;
6601     heap->IterateRoots(&visitor, VISIT_ALL);
6602     visitor.TransitiveClosure();
6603   }
6604
6605   AssertNoAllocation no_alloc;
6606 };
6607
6608
6609 HeapIterator::HeapIterator()
6610     : filtering_(HeapIterator::kNoFiltering),
6611       filter_(NULL) {
6612   Init();
6613 }
6614
6615
6616 HeapIterator::HeapIterator(HeapIterator::HeapObjectsFiltering filtering)
6617     : filtering_(filtering),
6618       filter_(NULL) {
6619   Init();
6620 }
6621
6622
6623 HeapIterator::~HeapIterator() {
6624   Shutdown();
6625 }
6626
6627
6628 void HeapIterator::Init() {
6629   // Start the iteration.
6630   space_iterator_ = new SpaceIterator;
6631   switch (filtering_) {
6632     case kFilterUnreachable:
6633       filter_ = new UnreachableObjectsFilter;
6634       break;
6635     default:
6636       break;
6637   }
6638   object_iterator_ = space_iterator_->next();
6639 }
6640
6641
6642 void HeapIterator::Shutdown() {
6643 #ifdef DEBUG
6644   // Assert that in filtering mode we have iterated through all
6645   // objects. Otherwise, heap will be left in an inconsistent state.
6646   if (filtering_ != kNoFiltering) {
6647     ASSERT(object_iterator_ == NULL);
6648   }
6649 #endif
6650   // Make sure the last iterator is deallocated.
6651   delete space_iterator_;
6652   space_iterator_ = NULL;
6653   object_iterator_ = NULL;
6654   delete filter_;
6655   filter_ = NULL;
6656 }
6657
6658
6659 HeapObject* HeapIterator::next() {
6660   if (filter_ == NULL) return NextObject();
6661
6662   HeapObject* obj = NextObject();
6663   while (obj != NULL && filter_->SkipObject(obj)) obj = NextObject();
6664   return obj;
6665 }
6666
6667
6668 HeapObject* HeapIterator::NextObject() {
6669   // No iterator means we are done.
6670   if (object_iterator_ == NULL) return NULL;
6671
6672   if (HeapObject* obj = object_iterator_->next_object()) {
6673     // If the current iterator has more objects we are fine.
6674     return obj;
6675   } else {
6676     // Go though the spaces looking for one that has objects.
6677     while (space_iterator_->has_next()) {
6678       object_iterator_ = space_iterator_->next();
6679       if (HeapObject* obj = object_iterator_->next_object()) {
6680         return obj;
6681       }
6682     }
6683   }
6684   // Done with the last space.
6685   object_iterator_ = NULL;
6686   return NULL;
6687 }
6688
6689
6690 void HeapIterator::reset() {
6691   // Restart the iterator.
6692   Shutdown();
6693   Init();
6694 }
6695
6696
6697 #if defined(DEBUG) || defined(LIVE_OBJECT_LIST)
6698
6699 Object* const PathTracer::kAnyGlobalObject = reinterpret_cast<Object*>(NULL);
6700
6701 class PathTracer::MarkVisitor: public ObjectVisitor {
6702  public:
6703   explicit MarkVisitor(PathTracer* tracer) : tracer_(tracer) {}
6704   void VisitPointers(Object** start, Object** end) {
6705     // Scan all HeapObject pointers in [start, end)
6706     for (Object** p = start; !tracer_->found() && (p < end); p++) {
6707       if ((*p)->IsHeapObject())
6708         tracer_->MarkRecursively(p, this);
6709     }
6710   }
6711
6712  private:
6713   PathTracer* tracer_;
6714 };
6715
6716
6717 class PathTracer::UnmarkVisitor: public ObjectVisitor {
6718  public:
6719   explicit UnmarkVisitor(PathTracer* tracer) : tracer_(tracer) {}
6720   void VisitPointers(Object** start, Object** end) {
6721     // Scan all HeapObject pointers in [start, end)
6722     for (Object** p = start; p < end; p++) {
6723       if ((*p)->IsHeapObject())
6724         tracer_->UnmarkRecursively(p, this);
6725     }
6726   }
6727
6728  private:
6729   PathTracer* tracer_;
6730 };
6731
6732
6733 void PathTracer::VisitPointers(Object** start, Object** end) {
6734   bool done = ((what_to_find_ == FIND_FIRST) && found_target_);
6735   // Visit all HeapObject pointers in [start, end)
6736   for (Object** p = start; !done && (p < end); p++) {
6737     if ((*p)->IsHeapObject()) {
6738       TracePathFrom(p);
6739       done = ((what_to_find_ == FIND_FIRST) && found_target_);
6740     }
6741   }
6742 }
6743
6744
6745 void PathTracer::Reset() {
6746   found_target_ = false;
6747   object_stack_.Clear();
6748 }
6749
6750
6751 void PathTracer::TracePathFrom(Object** root) {
6752   ASSERT((search_target_ == kAnyGlobalObject) ||
6753          search_target_->IsHeapObject());
6754   found_target_in_trace_ = false;
6755   Reset();
6756
6757   MarkVisitor mark_visitor(this);
6758   MarkRecursively(root, &mark_visitor);
6759
6760   UnmarkVisitor unmark_visitor(this);
6761   UnmarkRecursively(root, &unmark_visitor);
6762
6763   ProcessResults();
6764 }
6765
6766
6767 static bool SafeIsNativeContext(HeapObject* obj) {
6768   return obj->map() == obj->GetHeap()->raw_unchecked_native_context_map();
6769 }
6770
6771
6772 void PathTracer::MarkRecursively(Object** p, MarkVisitor* mark_visitor) {
6773   if (!(*p)->IsHeapObject()) return;
6774
6775   HeapObject* obj = HeapObject::cast(*p);
6776
6777   Object* map = obj->map();
6778
6779   if (!map->IsHeapObject()) return;  // visited before
6780
6781   if (found_target_in_trace_) return;  // stop if target found
6782   object_stack_.Add(obj);
6783   if (((search_target_ == kAnyGlobalObject) && obj->IsJSGlobalObject()) ||
6784       (obj == search_target_)) {
6785     found_target_in_trace_ = true;
6786     found_target_ = true;
6787     return;
6788   }
6789
6790   bool is_native_context = SafeIsNativeContext(obj);
6791
6792   // not visited yet
6793   Map* map_p = reinterpret_cast<Map*>(HeapObject::cast(map));
6794
6795   Address map_addr = map_p->address();
6796
6797   obj->set_map_no_write_barrier(reinterpret_cast<Map*>(map_addr + kMarkTag));
6798
6799   // Scan the object body.
6800   if (is_native_context && (visit_mode_ == VISIT_ONLY_STRONG)) {
6801     // This is specialized to scan Context's properly.
6802     Object** start = reinterpret_cast<Object**>(obj->address() +
6803                                                 Context::kHeaderSize);
6804     Object** end = reinterpret_cast<Object**>(obj->address() +
6805         Context::kHeaderSize + Context::FIRST_WEAK_SLOT * kPointerSize);
6806     mark_visitor->VisitPointers(start, end);
6807   } else {
6808     obj->IterateBody(map_p->instance_type(),
6809                      obj->SizeFromMap(map_p),
6810                      mark_visitor);
6811   }
6812
6813   // Scan the map after the body because the body is a lot more interesting
6814   // when doing leak detection.
6815   MarkRecursively(&map, mark_visitor);
6816
6817   if (!found_target_in_trace_)  // don't pop if found the target
6818     object_stack_.RemoveLast();
6819 }
6820
6821
6822 void PathTracer::UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor) {
6823   if (!(*p)->IsHeapObject()) return;
6824
6825   HeapObject* obj = HeapObject::cast(*p);
6826
6827   Object* map = obj->map();
6828
6829   if (map->IsHeapObject()) return;  // unmarked already
6830
6831   Address map_addr = reinterpret_cast<Address>(map);
6832
6833   map_addr -= kMarkTag;
6834
6835   ASSERT_TAG_ALIGNED(map_addr);
6836
6837   HeapObject* map_p = HeapObject::FromAddress(map_addr);
6838
6839   obj->set_map_no_write_barrier(reinterpret_cast<Map*>(map_p));
6840
6841   UnmarkRecursively(reinterpret_cast<Object**>(&map_p), unmark_visitor);
6842
6843   obj->IterateBody(Map::cast(map_p)->instance_type(),
6844                    obj->SizeFromMap(Map::cast(map_p)),
6845                    unmark_visitor);
6846 }
6847
6848
6849 void PathTracer::ProcessResults() {
6850   if (found_target_) {
6851     PrintF("=====================================\n");
6852     PrintF("====        Path to object       ====\n");
6853     PrintF("=====================================\n\n");
6854
6855     ASSERT(!object_stack_.is_empty());
6856     for (int i = 0; i < object_stack_.length(); i++) {
6857       if (i > 0) PrintF("\n     |\n     |\n     V\n\n");
6858       Object* obj = object_stack_[i];
6859       obj->Print();
6860     }
6861     PrintF("=====================================\n");
6862   }
6863 }
6864 #endif  // DEBUG || LIVE_OBJECT_LIST
6865
6866
6867 #ifdef DEBUG
6868 // Triggers a depth-first traversal of reachable objects from one
6869 // given root object and finds a path to a specific heap object and
6870 // prints it.
6871 void Heap::TracePathToObjectFrom(Object* target, Object* root) {
6872   PathTracer tracer(target, PathTracer::FIND_ALL, VISIT_ALL);
6873   tracer.VisitPointer(&root);
6874 }
6875
6876
6877 // Triggers a depth-first traversal of reachable objects from roots
6878 // and finds a path to a specific heap object and prints it.
6879 void Heap::TracePathToObject(Object* target) {
6880   PathTracer tracer(target, PathTracer::FIND_ALL, VISIT_ALL);
6881   IterateRoots(&tracer, VISIT_ONLY_STRONG);
6882 }
6883
6884
6885 // Triggers a depth-first traversal of reachable objects from roots
6886 // and finds a path to any global object and prints it. Useful for
6887 // determining the source for leaks of global objects.
6888 void Heap::TracePathToGlobal() {
6889   PathTracer tracer(PathTracer::kAnyGlobalObject,
6890                     PathTracer::FIND_ALL,
6891                     VISIT_ALL);
6892   IterateRoots(&tracer, VISIT_ONLY_STRONG);
6893 }
6894 #endif
6895
6896
6897 static intptr_t CountTotalHolesSize() {
6898   intptr_t holes_size = 0;
6899   OldSpaces spaces;
6900   for (OldSpace* space = spaces.next();
6901        space != NULL;
6902        space = spaces.next()) {
6903     holes_size += space->Waste() + space->Available();
6904   }
6905   return holes_size;
6906 }
6907
6908
6909 GCTracer::GCTracer(Heap* heap,
6910                    const char* gc_reason,
6911                    const char* collector_reason)
6912     : start_time_(0.0),
6913       start_object_size_(0),
6914       start_memory_size_(0),
6915       gc_count_(0),
6916       full_gc_count_(0),
6917       allocated_since_last_gc_(0),
6918       spent_in_mutator_(0),
6919       promoted_objects_size_(0),
6920       heap_(heap),
6921       gc_reason_(gc_reason),
6922       collector_reason_(collector_reason) {
6923   if (!FLAG_trace_gc && !FLAG_print_cumulative_gc_stat) return;
6924   start_time_ = OS::TimeCurrentMillis();
6925   start_object_size_ = heap_->SizeOfObjects();
6926   start_memory_size_ = heap_->isolate()->memory_allocator()->Size();
6927
6928   for (int i = 0; i < Scope::kNumberOfScopes; i++) {
6929     scopes_[i] = 0;
6930   }
6931
6932   in_free_list_or_wasted_before_gc_ = CountTotalHolesSize();
6933
6934   allocated_since_last_gc_ =
6935       heap_->SizeOfObjects() - heap_->alive_after_last_gc_;
6936
6937   if (heap_->last_gc_end_timestamp_ > 0) {
6938     spent_in_mutator_ = Max(start_time_ - heap_->last_gc_end_timestamp_, 0.0);
6939   }
6940
6941   steps_count_ = heap_->incremental_marking()->steps_count();
6942   steps_took_ = heap_->incremental_marking()->steps_took();
6943   longest_step_ = heap_->incremental_marking()->longest_step();
6944   steps_count_since_last_gc_ =
6945       heap_->incremental_marking()->steps_count_since_last_gc();
6946   steps_took_since_last_gc_ =
6947       heap_->incremental_marking()->steps_took_since_last_gc();
6948 }
6949
6950
6951 GCTracer::~GCTracer() {
6952   // Printf ONE line iff flag is set.
6953   if (!FLAG_trace_gc && !FLAG_print_cumulative_gc_stat) return;
6954
6955   bool first_gc = (heap_->last_gc_end_timestamp_ == 0);
6956
6957   heap_->alive_after_last_gc_ = heap_->SizeOfObjects();
6958   heap_->last_gc_end_timestamp_ = OS::TimeCurrentMillis();
6959
6960   int time = static_cast<int>(heap_->last_gc_end_timestamp_ - start_time_);
6961
6962   // Update cumulative GC statistics if required.
6963   if (FLAG_print_cumulative_gc_stat) {
6964     heap_->total_gc_time_ms_ += time;
6965     heap_->max_gc_pause_ = Max(heap_->max_gc_pause_, time);
6966     heap_->max_alive_after_gc_ = Max(heap_->max_alive_after_gc_,
6967                                      heap_->alive_after_last_gc_);
6968     if (!first_gc) {
6969       heap_->min_in_mutator_ = Min(heap_->min_in_mutator_,
6970                                    static_cast<int>(spent_in_mutator_));
6971     }
6972   } else if (FLAG_trace_gc_verbose) {
6973     heap_->total_gc_time_ms_ += time;
6974   }
6975
6976   if (collector_ == SCAVENGER && FLAG_trace_gc_ignore_scavenger) return;
6977
6978   PrintPID("%8.0f ms: ", heap_->isolate()->time_millis_since_init());
6979
6980   if (!FLAG_trace_gc_nvp) {
6981     int external_time = static_cast<int>(scopes_[Scope::EXTERNAL]);
6982
6983     double end_memory_size_mb =
6984         static_cast<double>(heap_->isolate()->memory_allocator()->Size()) / MB;
6985
6986     PrintF("%s %.1f (%.1f) -> %.1f (%.1f) MB, ",
6987            CollectorString(),
6988            static_cast<double>(start_object_size_) / MB,
6989            static_cast<double>(start_memory_size_) / MB,
6990            SizeOfHeapObjects(),
6991            end_memory_size_mb);
6992
6993     if (external_time > 0) PrintF("%d / ", external_time);
6994     PrintF("%d ms", time);
6995     if (steps_count_ > 0) {
6996       if (collector_ == SCAVENGER) {
6997         PrintF(" (+ %d ms in %d steps since last GC)",
6998                static_cast<int>(steps_took_since_last_gc_),
6999                steps_count_since_last_gc_);
7000       } else {
7001         PrintF(" (+ %d ms in %d steps since start of marking, "
7002                    "biggest step %f ms)",
7003                static_cast<int>(steps_took_),
7004                steps_count_,
7005                longest_step_);
7006       }
7007     }
7008
7009     if (gc_reason_ != NULL) {
7010       PrintF(" [%s]", gc_reason_);
7011     }
7012
7013     if (collector_reason_ != NULL) {
7014       PrintF(" [%s]", collector_reason_);
7015     }
7016
7017     PrintF(".\n");
7018   } else {
7019     PrintF("pause=%d ", time);
7020     PrintF("mutator=%d ", static_cast<int>(spent_in_mutator_));
7021     PrintF("gc=");
7022     switch (collector_) {
7023       case SCAVENGER:
7024         PrintF("s");
7025         break;
7026       case MARK_COMPACTOR:
7027         PrintF("ms");
7028         break;
7029       default:
7030         UNREACHABLE();
7031     }
7032     PrintF(" ");
7033
7034     PrintF("external=%d ", static_cast<int>(scopes_[Scope::EXTERNAL]));
7035     PrintF("mark=%d ", static_cast<int>(scopes_[Scope::MC_MARK]));
7036     PrintF("sweep=%d ", static_cast<int>(scopes_[Scope::MC_SWEEP]));
7037     PrintF("sweepns=%d ", static_cast<int>(scopes_[Scope::MC_SWEEP_NEWSPACE]));
7038     PrintF("evacuate=%d ", static_cast<int>(scopes_[Scope::MC_EVACUATE_PAGES]));
7039     PrintF("new_new=%d ",
7040            static_cast<int>(scopes_[Scope::MC_UPDATE_NEW_TO_NEW_POINTERS]));
7041     PrintF("root_new=%d ",
7042            static_cast<int>(scopes_[Scope::MC_UPDATE_ROOT_TO_NEW_POINTERS]));
7043     PrintF("old_new=%d ",
7044            static_cast<int>(scopes_[Scope::MC_UPDATE_OLD_TO_NEW_POINTERS]));
7045     PrintF("compaction_ptrs=%d ",
7046            static_cast<int>(scopes_[Scope::MC_UPDATE_POINTERS_TO_EVACUATED]));
7047     PrintF("intracompaction_ptrs=%d ", static_cast<int>(scopes_[
7048         Scope::MC_UPDATE_POINTERS_BETWEEN_EVACUATED]));
7049     PrintF("misc_compaction=%d ",
7050            static_cast<int>(scopes_[Scope::MC_UPDATE_MISC_POINTERS]));
7051
7052     PrintF("total_size_before=%" V8_PTR_PREFIX "d ", start_object_size_);
7053     PrintF("total_size_after=%" V8_PTR_PREFIX "d ", heap_->SizeOfObjects());
7054     PrintF("holes_size_before=%" V8_PTR_PREFIX "d ",
7055            in_free_list_or_wasted_before_gc_);
7056     PrintF("holes_size_after=%" V8_PTR_PREFIX "d ", CountTotalHolesSize());
7057
7058     PrintF("allocated=%" V8_PTR_PREFIX "d ", allocated_since_last_gc_);
7059     PrintF("promoted=%" V8_PTR_PREFIX "d ", promoted_objects_size_);
7060
7061     if (collector_ == SCAVENGER) {
7062       PrintF("stepscount=%d ", steps_count_since_last_gc_);
7063       PrintF("stepstook=%d ", static_cast<int>(steps_took_since_last_gc_));
7064     } else {
7065       PrintF("stepscount=%d ", steps_count_);
7066       PrintF("stepstook=%d ", static_cast<int>(steps_took_));
7067     }
7068
7069     PrintF("\n");
7070   }
7071
7072   heap_->PrintShortHeapStatistics();
7073 }
7074
7075
7076 const char* GCTracer::CollectorString() {
7077   switch (collector_) {
7078     case SCAVENGER:
7079       return "Scavenge";
7080     case MARK_COMPACTOR:
7081       return "Mark-sweep";
7082   }
7083   return "Unknown GC";
7084 }
7085
7086
7087 int KeyedLookupCache::Hash(Map* map, String* name) {
7088   // Uses only lower 32 bits if pointers are larger.
7089   uintptr_t addr_hash =
7090       static_cast<uint32_t>(reinterpret_cast<uintptr_t>(map)) >> kMapHashShift;
7091   return static_cast<uint32_t>((addr_hash ^ name->Hash()) & kCapacityMask);
7092 }
7093
7094
7095 int KeyedLookupCache::Lookup(Map* map, String* name) {
7096   int index = (Hash(map, name) & kHashMask);
7097   for (int i = 0; i < kEntriesPerBucket; i++) {
7098     Key& key = keys_[index + i];
7099     if ((key.map == map) && key.name->Equals(name)) {
7100       return field_offsets_[index + i];
7101     }
7102   }
7103   return kNotFound;
7104 }
7105
7106
7107 void KeyedLookupCache::Update(Map* map, String* name, int field_offset) {
7108   String* symbol;
7109   if (HEAP->LookupSymbolIfExists(name, &symbol)) {
7110     int index = (Hash(map, symbol) & kHashMask);
7111     // After a GC there will be free slots, so we use them in order (this may
7112     // help to get the most frequently used one in position 0).
7113     for (int i = 0; i< kEntriesPerBucket; i++) {
7114       Key& key = keys_[index];
7115       Object* free_entry_indicator = NULL;
7116       if (key.map == free_entry_indicator) {
7117         key.map = map;
7118         key.name = symbol;
7119         field_offsets_[index + i] = field_offset;
7120         return;
7121       }
7122     }
7123     // No free entry found in this bucket, so we move them all down one and
7124     // put the new entry at position zero.
7125     for (int i = kEntriesPerBucket - 1; i > 0; i--) {
7126       Key& key = keys_[index + i];
7127       Key& key2 = keys_[index + i - 1];
7128       key = key2;
7129       field_offsets_[index + i] = field_offsets_[index + i - 1];
7130     }
7131
7132     // Write the new first entry.
7133     Key& key = keys_[index];
7134     key.map = map;
7135     key.name = symbol;
7136     field_offsets_[index] = field_offset;
7137   }
7138 }
7139
7140
7141 void KeyedLookupCache::Clear() {
7142   for (int index = 0; index < kLength; index++) keys_[index].map = NULL;
7143 }
7144
7145
7146 void DescriptorLookupCache::Clear() {
7147   for (int index = 0; index < kLength; index++) keys_[index].source = NULL;
7148 }
7149
7150
7151 #ifdef DEBUG
7152 void Heap::GarbageCollectionGreedyCheck() {
7153   ASSERT(FLAG_gc_greedy);
7154   if (isolate_->bootstrapper()->IsActive()) return;
7155   if (disallow_allocation_failure()) return;
7156   CollectGarbage(NEW_SPACE);
7157 }
7158 #endif
7159
7160
7161 TranscendentalCache::SubCache::SubCache(Type t)
7162   : type_(t),
7163     isolate_(Isolate::Current()) {
7164   uint32_t in0 = 0xffffffffu;  // Bit-pattern for a NaN that isn't
7165   uint32_t in1 = 0xffffffffu;  // generated by the FPU.
7166   for (int i = 0; i < kCacheSize; i++) {
7167     elements_[i].in[0] = in0;
7168     elements_[i].in[1] = in1;
7169     elements_[i].output = NULL;
7170   }
7171 }
7172
7173
7174 void TranscendentalCache::Clear() {
7175   for (int i = 0; i < kNumberOfCaches; i++) {
7176     if (caches_[i] != NULL) {
7177       delete caches_[i];
7178       caches_[i] = NULL;
7179     }
7180   }
7181 }
7182
7183
7184 void ExternalStringTable::CleanUp() {
7185   int last = 0;
7186   for (int i = 0; i < new_space_strings_.length(); ++i) {
7187     if (new_space_strings_[i] == heap_->raw_unchecked_the_hole_value()) {
7188       continue;
7189     }
7190     if (heap_->InNewSpace(new_space_strings_[i])) {
7191       new_space_strings_[last++] = new_space_strings_[i];
7192     } else {
7193       old_space_strings_.Add(new_space_strings_[i]);
7194     }
7195   }
7196   new_space_strings_.Rewind(last);
7197   last = 0;
7198   for (int i = 0; i < old_space_strings_.length(); ++i) {
7199     if (old_space_strings_[i] == heap_->raw_unchecked_the_hole_value()) {
7200       continue;
7201     }
7202     ASSERT(!heap_->InNewSpace(old_space_strings_[i]));
7203     old_space_strings_[last++] = old_space_strings_[i];
7204   }
7205   old_space_strings_.Rewind(last);
7206 #ifdef VERIFY_HEAP
7207   if (FLAG_verify_heap) {
7208     Verify();
7209   }
7210 #endif
7211 }
7212
7213
7214 void ExternalStringTable::TearDown() {
7215   new_space_strings_.Free();
7216   old_space_strings_.Free();
7217 }
7218
7219
7220 void Heap::QueueMemoryChunkForFree(MemoryChunk* chunk) {
7221   chunk->set_next_chunk(chunks_queued_for_free_);
7222   chunks_queued_for_free_ = chunk;
7223 }
7224
7225
7226 void Heap::FreeQueuedChunks() {
7227   if (chunks_queued_for_free_ == NULL) return;
7228   MemoryChunk* next;
7229   MemoryChunk* chunk;
7230   for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
7231     next = chunk->next_chunk();
7232     chunk->SetFlag(MemoryChunk::ABOUT_TO_BE_FREED);
7233
7234     if (chunk->owner()->identity() == LO_SPACE) {
7235       // StoreBuffer::Filter relies on MemoryChunk::FromAnyPointerAddress.
7236       // If FromAnyPointerAddress encounters a slot that belongs to a large
7237       // chunk queued for deletion it will fail to find the chunk because
7238       // it try to perform a search in the list of pages owned by of the large
7239       // object space and queued chunks were detached from that list.
7240       // To work around this we split large chunk into normal kPageSize aligned
7241       // pieces and initialize size, owner and flags field of every piece.
7242       // If FromAnyPointerAddress encounters a slot that belongs to one of
7243       // these smaller pieces it will treat it as a slot on a normal Page.
7244       Address chunk_end = chunk->address() + chunk->size();
7245       MemoryChunk* inner = MemoryChunk::FromAddress(
7246           chunk->address() + Page::kPageSize);
7247       MemoryChunk* inner_last = MemoryChunk::FromAddress(chunk_end - 1);
7248       while (inner <= inner_last) {
7249         // Size of a large chunk is always a multiple of
7250         // OS::AllocateAlignment() so there is always
7251         // enough space for a fake MemoryChunk header.
7252         Address area_end = Min(inner->address() + Page::kPageSize, chunk_end);
7253         // Guard against overflow.
7254         if (area_end < inner->address()) area_end = chunk_end;
7255         inner->SetArea(inner->address(), area_end);
7256         inner->set_size(Page::kPageSize);
7257         inner->set_owner(lo_space());
7258         inner->SetFlag(MemoryChunk::ABOUT_TO_BE_FREED);
7259         inner = MemoryChunk::FromAddress(
7260             inner->address() + Page::kPageSize);
7261       }
7262     }
7263   }
7264   isolate_->heap()->store_buffer()->Compact();
7265   isolate_->heap()->store_buffer()->Filter(MemoryChunk::ABOUT_TO_BE_FREED);
7266   for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
7267     next = chunk->next_chunk();
7268     isolate_->memory_allocator()->Free(chunk);
7269   }
7270   chunks_queued_for_free_ = NULL;
7271 }
7272
7273
7274 void Heap::RememberUnmappedPage(Address page, bool compacted) {
7275   uintptr_t p = reinterpret_cast<uintptr_t>(page);
7276   // Tag the page pointer to make it findable in the dump file.
7277   if (compacted) {
7278     p ^= 0xc1ead & (Page::kPageSize - 1);  // Cleared.
7279   } else {
7280     p ^= 0x1d1ed & (Page::kPageSize - 1);  // I died.
7281   }
7282   remembered_unmapped_pages_[remembered_unmapped_pages_index_] =
7283       reinterpret_cast<Address>(p);
7284   remembered_unmapped_pages_index_++;
7285   remembered_unmapped_pages_index_ %= kRememberedUnmappedPages;
7286 }
7287
7288
7289 void Heap::ClearObjectStats(bool clear_last_time_stats) {
7290   memset(object_counts_, 0, sizeof(object_counts_));
7291   memset(object_sizes_, 0, sizeof(object_sizes_));
7292   if (clear_last_time_stats) {
7293     memset(object_counts_last_time_, 0, sizeof(object_counts_last_time_));
7294     memset(object_sizes_last_time_, 0, sizeof(object_sizes_last_time_));
7295   }
7296 }
7297
7298
7299 static LazyMutex checkpoint_object_stats_mutex = LAZY_MUTEX_INITIALIZER;
7300
7301
7302 void Heap::CheckpointObjectStats() {
7303   ScopedLock lock(checkpoint_object_stats_mutex.Pointer());
7304   Counters* counters = isolate()->counters();
7305 #define ADJUST_LAST_TIME_OBJECT_COUNT(name)                                    \
7306   counters->count_of_##name()->Increment(                                      \
7307       static_cast<int>(object_counts_[name]));                                 \
7308   counters->count_of_##name()->Decrement(                                      \
7309       static_cast<int>(object_counts_last_time_[name]));                       \
7310   counters->size_of_##name()->Increment(                                       \
7311       static_cast<int>(object_sizes_[name]));                                  \
7312   counters->size_of_##name()->Decrement(                                       \
7313       static_cast<int>(object_sizes_last_time_[name]));
7314   INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
7315 #undef ADJUST_LAST_TIME_OBJECT_COUNT
7316   int index;
7317 #define ADJUST_LAST_TIME_OBJECT_COUNT(name)               \
7318   index = FIRST_CODE_KIND_SUB_TYPE + Code::name;          \
7319   counters->count_of_CODE_TYPE_##name()->Increment(       \
7320       static_cast<int>(object_counts_[index]));           \
7321   counters->count_of_CODE_TYPE_##name()->Decrement(       \
7322       static_cast<int>(object_counts_last_time_[index])); \
7323   counters->size_of_CODE_TYPE_##name()->Increment(        \
7324       static_cast<int>(object_sizes_[index]));            \
7325   counters->size_of_CODE_TYPE_##name()->Decrement(        \
7326       static_cast<int>(object_sizes_last_time_[index]));
7327   CODE_KIND_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
7328 #undef ADJUST_LAST_TIME_OBJECT_COUNT
7329 #define ADJUST_LAST_TIME_OBJECT_COUNT(name)               \
7330   index = FIRST_FIXED_ARRAY_SUB_TYPE + name;              \
7331   counters->count_of_FIXED_ARRAY_##name()->Increment(     \
7332       static_cast<int>(object_counts_[index]));           \
7333   counters->count_of_FIXED_ARRAY_##name()->Decrement(     \
7334       static_cast<int>(object_counts_last_time_[index])); \
7335   counters->size_of_FIXED_ARRAY_##name()->Increment(      \
7336       static_cast<int>(object_sizes_[index]));            \
7337   counters->size_of_FIXED_ARRAY_##name()->Decrement(      \
7338       static_cast<int>(object_sizes_last_time_[index]));
7339   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
7340 #undef ADJUST_LAST_TIME_OBJECT_COUNT
7341
7342   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
7343   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
7344   ClearObjectStats();
7345 }
7346
7347 } }  // namespace v8::internal