Merge experimental/gc branch to the bleeding_edge.

src/heap.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 18 matching lines @@
 
 #include "accessors.h"
 #include "api.h"
 #include "bootstrapper.h"
 #include "codegen.h"
 #include "compilation-cache.h"
 #include "debug.h"
 #include "deoptimizer.h"
 #include "global-handles.h"
 #include "heap-profiler.h"
+#include "incremental-marking.h"
 #include "liveobjectlist-inl.h"
 #include "mark-compact.h"
 #include "natives.h"
 #include "objects-visiting.h"
+#include "objects-visiting-inl.h"
 #include "runtime-profiler.h"
 #include "scopeinfo.h"
 #include "snapshot.h"
+#include "store-buffer.h"
 #include "v8threads.h"
 #include "vm-state-inl.h"
 #if V8_TARGET_ARCH_ARM && !V8_INTERPRETED_REGEXP
 #include "regexp-macro-assembler.h"
 #include "arm/regexp-macro-assembler-arm.h"
 #endif
 #if V8_TARGET_ARCH_MIPS && !V8_INTERPRETED_REGEXP
 #include "regexp-macro-assembler.h"
 #include "mips/regexp-macro-assembler-mips.h"
 #endif
 
 namespace v8 {
 namespace internal {
 
 
-static const intptr_t kMinimumPromotionLimit = 2 * MB;
-static const intptr_t kMinimumAllocationLimit = 8 * MB;
-
-
 static Mutex* gc_initializer_mutex = OS::CreateMutex();
 
 
 Heap::Heap()
     : isolate_(NULL),
 // semispace_size_ should be a power of 2 and old_generation_size_ should be
 // a multiple of Page::kPageSize.
 #if defined(ANDROID)
-      reserved_semispace_size_(2*MB),
-      max_semispace_size_(2*MB),
-      initial_semispace_size_(128*KB),
-      max_old_generation_size_(192*MB),
-      max_executable_size_(max_old_generation_size_),
+#define LUMP_OF_MEMORY (128 * KB)
       code_range_size_(0),
 #elif defined(V8_TARGET_ARCH_X64)
-      reserved_semispace_size_(16*MB),
-      max_semispace_size_(16*MB),
-      initial_semispace_size_(1*MB),
-      max_old_generation_size_(1400*MB),
-      max_executable_size_(256*MB),
+#define LUMP_OF_MEMORY (2 * MB)
       code_range_size_(512*MB),
 #else
-      reserved_semispace_size_(8*MB),
-      max_semispace_size_(8*MB),
-      initial_semispace_size_(512*KB),
-      max_old_generation_size_(700*MB),
-      max_executable_size_(128*MB),
+#define LUMP_OF_MEMORY MB
       code_range_size_(0),
 #endif
+      reserved_semispace_size_(8 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
+      max_semispace_size_(8 * Max(LUMP_OF_MEMORY, Page::kPageSize)),
+      initial_semispace_size_(Max(LUMP_OF_MEMORY, Page::kPageSize)),
+      max_old_generation_size_(1400ul * LUMP_OF_MEMORY),
+      max_executable_size_(256l * LUMP_OF_MEMORY),
+
 // Variables set based on semispace_size_ and old_generation_size_ in
 // ConfigureHeap (survived_since_last_expansion_, external_allocation_limit_)
 // Will be 4 * reserved_semispace_size_ to ensure that young
 // generation can be aligned to its size.
       survived_since_last_expansion_(0),
       sweep_generation_(0),
       always_allocate_scope_depth_(0),
       linear_allocation_scope_depth_(0),
       contexts_disposed_(0),
+      scan_on_scavenge_pages_(0),
       new_space_(this),
       old_pointer_space_(NULL),
       old_data_space_(NULL),
       code_space_(NULL),
       map_space_(NULL),
       cell_space_(NULL),
       lo_space_(NULL),
       gc_state_(NOT_IN_GC),
       gc_post_processing_depth_(0),
-      mc_count_(0),
       ms_count_(0),
       gc_count_(0),
       unflattened_strings_length_(0),
 #ifdef DEBUG
       allocation_allowed_(true),
       allocation_timeout_(0),
       disallow_allocation_failure_(false),
       debug_utils_(NULL),
 #endif  // DEBUG
       old_gen_promotion_limit_(kMinimumPromotionLimit),
       old_gen_allocation_limit_(kMinimumAllocationLimit),
+      old_gen_limit_factor_(1),
+      size_of_old_gen_at_last_old_space_gc_(0),
       external_allocation_limit_(0),
       amount_of_external_allocated_memory_(0),
       amount_of_external_allocated_memory_at_last_global_gc_(0),
       old_gen_exhausted_(false),
+      store_buffer_rebuilder_(store_buffer()),
       hidden_symbol_(NULL),
       global_gc_prologue_callback_(NULL),
       global_gc_epilogue_callback_(NULL),
       gc_safe_size_of_old_object_(NULL),
       total_regexp_code_generated_(0),
       tracer_(NULL),
       young_survivors_after_last_gc_(0),
       high_survival_rate_period_length_(0),
       survival_rate_(0),
       previous_survival_rate_trend_(Heap::STABLE),
       survival_rate_trend_(Heap::STABLE),
       max_gc_pause_(0),
       max_alive_after_gc_(0),
       min_in_mutator_(kMaxInt),
       alive_after_last_gc_(0),
       last_gc_end_timestamp_(0.0),
-      page_watermark_invalidated_mark_(1 << Page::WATERMARK_INVALIDATED),
+      store_buffer_(this),
+      marking_(this),
+      incremental_marking_(this),
       number_idle_notifications_(0),
       last_idle_notification_gc_count_(0),
       last_idle_notification_gc_count_init_(false),
       configured_(false),
-      is_safe_to_read_maps_(true) {
+      last_empty_page_was_given_back_to_the_os_(false),
+      chunks_queued_for_free_(NULL) {
   // Allow build-time customization of the max semispace size. Building
   // V8 with snapshots and a non-default max semispace size is much
   // easier if you can define it as part of the build environment.
 #if defined(V8_MAX_SEMISPACE_SIZE)
   max_semispace_size_ = reserved_semispace_size_ = V8_MAX_SEMISPACE_SIZE;
 #endif
 
   intptr_t max_virtual = OS::MaxVirtualMemory();
 
   if (max_virtual > 0) {
@@ skipping 57 matching lines @@
   return old_pointer_space_ != NULL &&
          old_data_space_ != NULL &&
          code_space_ != NULL &&
          map_space_ != NULL &&
          cell_space_ != NULL &&
          lo_space_ != NULL;
 }
 
 
 int Heap::GcSafeSizeOfOldObject(HeapObject* object) {
-  ASSERT(!HEAP->InNewSpace(object));  // Code only works for old objects.
-  ASSERT(!HEAP->mark_compact_collector()->are_map_pointers_encoded());
-  MapWord map_word = object->map_word();
-  map_word.ClearMark();
-  map_word.ClearOverflow();
-  return object->SizeFromMap(map_word.ToMap());
+  if (IntrusiveMarking::IsMarked(object)) {
+    return IntrusiveMarking::SizeOfMarkedObject(object);
+  }
+  return object->SizeFromMap(object->map());
 }
 
 
-int Heap::GcSafeSizeOfOldObjectWithEncodedMap(HeapObject* object) {
-  ASSERT(!HEAP->InNewSpace(object));  // Code only works for old objects.
-  ASSERT(HEAP->mark_compact_collector()->are_map_pointers_encoded());
-  uint32_t marker = Memory::uint32_at(object->address());
-  if (marker == MarkCompactCollector::kSingleFreeEncoding) {
-    return kIntSize;
-  } else if (marker == MarkCompactCollector::kMultiFreeEncoding) {
-    return Memory::int_at(object->address() + kIntSize);
-  } else {
-    MapWord map_word = object->map_word();
-    Address map_address = map_word.DecodeMapAddress(HEAP->map_space());
-    Map* map = reinterpret_cast<Map*>(HeapObject::FromAddress(map_address));
-    return object->SizeFromMap(map);
-  }
-}
-
-
 GarbageCollector Heap::SelectGarbageCollector(AllocationSpace space) {
   // Is global GC requested?
   if (space != NEW_SPACE || FLAG_gc_global) {
     isolate_->counters()->gc_compactor_caused_by_request()->Increment();
     return MARK_COMPACTOR;
   }
 
   // Is enough data promoted to justify a global GC?
   if (OldGenerationPromotionLimitReached()) {
     isolate_->counters()->gc_compactor_caused_by_promoted_data()->Increment();
@@ skipping 130 matching lines @@
   }
 
   if (FLAG_gc_verbose) Print();
 #endif  // DEBUG
 
 #if defined(DEBUG)
   ReportStatisticsBeforeGC();
 #endif  // DEBUG
 
   LiveObjectList::GCPrologue();
+  store_buffer()->GCPrologue();
 }
 
 intptr_t Heap::SizeOfObjects() {
   intptr_t total = 0;
   AllSpaces spaces;
   for (Space* space = spaces.next(); space != NULL; space = spaces.next()) {
     total += space->SizeOfObjects();
   }
   return total;
 }
 
 void Heap::GarbageCollectionEpilogue() {
+  store_buffer()->GCEpilogue();
   LiveObjectList::GCEpilogue();
 #ifdef DEBUG
   allow_allocation(true);
   ZapFromSpace();
 
   if (FLAG_verify_heap) {
     Verify();
   }
 
   if (FLAG_print_global_handles) isolate_->global_handles()->Print();
@@ skipping 11 matching lines @@
       symbol_table()->NumberOfElements());
 #if defined(DEBUG)
   ReportStatisticsAfterGC();
 #endif  // DEBUG
 #ifdef ENABLE_DEBUGGER_SUPPORT
   isolate_->debug()->AfterGarbageCollection();
 #endif  // ENABLE_DEBUGGER_SUPPORT
 }
 
 
-void Heap::CollectAllGarbage(bool force_compaction) {
+void Heap::CollectAllGarbage(int flags) {
   // Since we are ignoring the return value, the exact choice of space does
   // not matter, so long as we do not specify NEW_SPACE, which would not
   // cause a full GC.
-  mark_compact_collector_.SetForceCompaction(force_compaction);
+  mark_compact_collector_.SetFlags(flags);
   CollectGarbage(OLD_POINTER_SPACE);
-  mark_compact_collector_.SetForceCompaction(false);
+  mark_compact_collector_.SetFlags(kNoGCFlags);
 }
 
 
 void Heap::CollectAllAvailableGarbage() {
   // Since we are ignoring the return value, the exact choice of space does
   // not matter, so long as we do not specify NEW_SPACE, which would not
   // cause a full GC.
-  mark_compact_collector()->SetForceCompaction(true);
-
   // Major GC would invoke weak handle callbacks on weakly reachable
   // handles, but won't collect weakly reachable objects until next
   // major GC.  Therefore if we collect aggressively and weak handle callback
   // has been invoked, we rerun major GC to release objects which become
   // garbage.
   // Note: as weak callbacks can execute arbitrary code, we cannot
   // hope that eventually there will be no weak callbacks invocations.
   // Therefore stop recollecting after several attempts.
+  mark_compact_collector()->SetFlags(kMakeHeapIterableMask);
   const int kMaxNumberOfAttempts = 7;
   for (int attempt = 0; attempt < kMaxNumberOfAttempts; attempt++) {
     if (!CollectGarbage(OLD_POINTER_SPACE, MARK_COMPACTOR)) {
       break;
     }
   }
-  mark_compact_collector()->SetForceCompaction(false);
+  mark_compact_collector()->SetFlags(kNoGCFlags);
 }
 
 
 bool Heap::CollectGarbage(AllocationSpace space, GarbageCollector collector) {
   // The VM is in the GC state until exiting this function.
   VMState state(isolate_, GC);
 
 #ifdef DEBUG
   // Reset the allocation timeout to the GC interval, but make sure to
   // allow at least a few allocations after a collection. The reason
   // for this is that we have a lot of allocation sequences and we
   // assume that a garbage collection will allow the subsequent
   // allocation attempts to go through.
   allocation_timeout_ = Max(6, FLAG_gc_interval);
 #endif
 
+  if (collector == SCAVENGER && !incremental_marking()->IsStopped()) {
+    if (FLAG_trace_incremental_marking) {
+      PrintF("[IncrementalMarking] Scavenge during marking.\n");
+    }
+  }
+
+  if (collector == MARK_COMPACTOR &&
+      !mark_compact_collector()->PreciseSweepingRequired() &&
+      !incremental_marking()->IsStopped() &&
+      !incremental_marking()->should_hurry() &&
+      FLAG_incremental_marking_steps) {
+    if (FLAG_trace_incremental_marking) {
+      PrintF("[IncrementalMarking] Delaying MarkSweep.\n");
+    }
+    collector = SCAVENGER;
+  }
+
   bool next_gc_likely_to_collect_more = false;
 
   { GCTracer tracer(this);
     GarbageCollectionPrologue();
     // The GC count was incremented in the prologue.  Tell the tracer about
     // it.
     tracer.set_gc_count(gc_count_);
 
     // Tell the tracer which collector we've selected.
     tracer.set_collector(collector);
 
     HistogramTimer* rate = (collector == SCAVENGER)
         ? isolate_->counters()->gc_scavenger()
         : isolate_->counters()->gc_compactor();
     rate->Start();
     next_gc_likely_to_collect_more =
         PerformGarbageCollection(collector, &tracer);
     rate->Stop();
 
     GarbageCollectionEpilogue();
   }
 
+  ASSERT(collector == SCAVENGER || incremental_marking()->IsStopped());
+  if (incremental_marking()->IsStopped()) {
+    if (incremental_marking()->WorthActivating() && NextGCIsLikelyToBeFull()) {
+      incremental_marking()->Start();
+    }
+  }
+
   return next_gc_likely_to_collect_more;
 }
 
 
 void Heap::PerformScavenge() {
   GCTracer tracer(this);
-  PerformGarbageCollection(SCAVENGER, &tracer);
+  if (incremental_marking()->IsStopped()) {
+    PerformGarbageCollection(SCAVENGER, &tracer);
+  } else {
+    PerformGarbageCollection(MARK_COMPACTOR, &tracer);
+  }
 }
 
 
 #ifdef DEBUG
 // Helper class for verifying the symbol table.
 class SymbolTableVerifier : public ObjectVisitor {
  public:
   void VisitPointers(Object** start, Object** end) {
     // Visit all HeapObject pointers in [start, end).
     for (Object** p = start; p < end; p++) {
@@ skipping 71 matching lines @@
     }
   }
 }
 
 
 void Heap::EnsureFromSpaceIsCommitted() {
   if (new_space_.CommitFromSpaceIfNeeded()) return;
 
   // Committing memory to from space failed.
   // Try shrinking and try again.
-  PagedSpaces spaces;
-  for (PagedSpace* space = spaces.next();
-       space != NULL;
-       space = spaces.next()) {
-    space->RelinkPageListInChunkOrder(true);
-  }
-
   Shrink();
   if (new_space_.CommitFromSpaceIfNeeded()) return;
 
   // Committing memory to from space failed again.
   // Memory is exhausted and we will die.
   V8::FatalProcessOutOfMemory("Committing semi space failed.");
 }
 
 
 void Heap::ClearJSFunctionResultCaches() {
@@ skipping 10 matching lines @@
       JSFunctionResultCache::cast(caches->get(i))->Clear();
     }
     // Get the next context:
     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
   }
 }
 
 
 
 void Heap::ClearNormalizedMapCaches() {
-  if (isolate_->bootstrapper()->IsActive()) return;
+  if (isolate_->bootstrapper()->IsActive() &&
+      !incremental_marking()->IsMarking()) {
+    return;
+  }
 
   Object* context = global_contexts_list_;
   while (!context->IsUndefined()) {
     Context::cast(context)->normalized_map_cache()->Clear();
     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
   }
 }
 
 
-#ifdef DEBUG
-
-enum PageWatermarkValidity {
-  ALL_VALID,
-  ALL_INVALID
-};
-
-static void VerifyPageWatermarkValidity(PagedSpace* space,
-                                        PageWatermarkValidity validity) {
-  PageIterator it(space, PageIterator::PAGES_IN_USE);
-  bool expected_value = (validity == ALL_VALID);
-  while (it.has_next()) {
-    Page* page = it.next();
-    ASSERT(page->IsWatermarkValid() == expected_value);
-  }
-}
-#endif
-
 void Heap::UpdateSurvivalRateTrend(int start_new_space_size) {
   double survival_rate =
       (static_cast<double>(young_survivors_after_last_gc_) * 100) /
       start_new_space_size;
 
   if (survival_rate > kYoungSurvivalRateThreshold) {
     high_survival_rate_period_length_++;
   } else {
     high_survival_rate_period_length_ = 0;
   }
@@ skipping 32 matching lines @@
   for (int i = 0; i < gc_prologue_callbacks_.length(); ++i) {
     if (gc_type & gc_prologue_callbacks_[i].gc_type) {
       gc_prologue_callbacks_[i].callback(gc_type, kNoGCCallbackFlags);
     }
   }
 
   EnsureFromSpaceIsCommitted();
 
   int start_new_space_size = Heap::new_space()->SizeAsInt();
 
+  if (IsHighSurvivalRate()) {
+    // We speed up the incremental marker if it is running so that it
+    // does not fall behind the rate of promotion, which would cause a
+    // constantly growing old space.
+    incremental_marking()->NotifyOfHighPromotionRate();
+  }
+
   if (collector == MARK_COMPACTOR) {
     // Perform mark-sweep with optional compaction.
     MarkCompact(tracer);
     sweep_generation_++;
     bool high_survival_rate_during_scavenges = IsHighSurvivalRate() &&
         IsStableOrIncreasingSurvivalTrend();
 
     UpdateSurvivalRateTrend(start_new_space_size);
 
-    intptr_t old_gen_size = PromotedSpaceSize();
-    old_gen_promotion_limit_ =
-        old_gen_size + Max(kMinimumPromotionLimit, old_gen_size / 3);
-    old_gen_allocation_limit_ =
-        old_gen_size + Max(kMinimumAllocationLimit, old_gen_size / 2);
+    size_of_old_gen_at_last_old_space_gc_ = PromotedSpaceSize();
 
     if (high_survival_rate_during_scavenges &&
         IsStableOrIncreasingSurvivalTrend()) {
       // Stable high survival rates of young objects both during partial and
       // full collection indicate that mutator is either building or modifying
       // a structure with a long lifetime.
       // In this case we aggressively raise old generation memory limits to
       // postpone subsequent mark-sweep collection and thus trade memory
       // space for the mutation speed.
-      old_gen_promotion_limit_ *= 2;
-      old_gen_allocation_limit_ *= 2;
+      old_gen_limit_factor_ = 2;
+    } else {
+      old_gen_limit_factor_ = 1;
     }
 
+    old_gen_promotion_limit_ =
+        OldGenPromotionLimit(size_of_old_gen_at_last_old_space_gc_);
+    old_gen_allocation_limit_ =
+        OldGenAllocationLimit(size_of_old_gen_at_last_old_space_gc_);
+
     old_gen_exhausted_ = false;
   } else {
     tracer_ = tracer;
     Scavenge();
     tracer_ = NULL;
 
     UpdateSurvivalRateTrend(start_new_space_size);
   }
 
   isolate_->counters()->objs_since_last_young()->Set(0);
 
   gc_post_processing_depth_++;
   { DisableAssertNoAllocation allow_allocation;
     GCTracer::Scope scope(tracer, GCTracer::Scope::EXTERNAL);
     next_gc_likely_to_collect_more =
         isolate_->global_handles()->PostGarbageCollectionProcessing(collector);
   }
   gc_post_processing_depth_--;
 
   // Update relocatables.
   Relocatable::PostGarbageCollectionProcessing();
 
   if (collector == MARK_COMPACTOR) {
     // Register the amount of external allocated memory.
     amount_of_external_allocated_memory_at_last_global_gc_ =
         amount_of_external_allocated_memory_;
   }
 
-  GCCallbackFlags callback_flags = tracer->is_compacting()
-      ? kGCCallbackFlagCompacted
-      : kNoGCCallbackFlags;
+  GCCallbackFlags callback_flags = kNoGCCallbackFlags;
   for (int i = 0; i < gc_epilogue_callbacks_.length(); ++i) {
     if (gc_type & gc_epilogue_callbacks_[i].gc_type) {
       gc_epilogue_callbacks_[i].callback(gc_type, callback_flags);
     }
   }
 
   if (collector == MARK_COMPACTOR && global_gc_epilogue_callback_) {
     ASSERT(!allocation_allowed_);
     GCTracer::Scope scope(tracer, GCTracer::Scope::EXTERNAL);
     global_gc_epilogue_callback_();
   }
   VerifySymbolTable();
 
   return next_gc_likely_to_collect_more;
 }
 
 
 void Heap::MarkCompact(GCTracer* tracer) {
   gc_state_ = MARK_COMPACT;
   LOG(isolate_, ResourceEvent("markcompact", "begin"));
 
   mark_compact_collector_.Prepare(tracer);
 
-  bool is_compacting = mark_compact_collector_.IsCompacting();
+  ms_count_++;
+  tracer->set_full_gc_count(ms_count_);
 
-  if (is_compacting) {
-    mc_count_++;
-  } else {
-    ms_count_++;
-  }
-  tracer->set_full_gc_count(mc_count_ + ms_count_);
+  MarkCompactPrologue();
 
-  MarkCompactPrologue(is_compacting);
-
-  is_safe_to_read_maps_ = false;
   mark_compact_collector_.CollectGarbage();
-  is_safe_to_read_maps_ = true;
 
   LOG(isolate_, ResourceEvent("markcompact", "end"));
 
   gc_state_ = NOT_IN_GC;
 
   Shrink();
 
   isolate_->counters()->objs_since_last_full()->Set(0);
 
   contexts_disposed_ = 0;
 }
 
 
-void Heap::MarkCompactPrologue(bool is_compacting) {
+void Heap::MarkCompactPrologue() {
   // At any old GC clear the keyed lookup cache to enable collection of unused
   // maps.
   isolate_->keyed_lookup_cache()->Clear();
   isolate_->context_slot_cache()->Clear();
   isolate_->descriptor_lookup_cache()->Clear();
   StringSplitCache::Clear(string_split_cache());
 
   isolate_->compilation_cache()->MarkCompactPrologue();
 
   CompletelyClearInstanceofCache();
 
-  if (is_compacting) FlushNumberStringCache();
+  // TODO(1605) select heuristic for flushing NumberString cache with
+  // FlushNumberStringCache
   if (FLAG_cleanup_code_caches_at_gc) {
     polymorphic_code_cache()->set_cache(undefined_value());
   }
 
   ClearNormalizedMapCaches();
 }
 
 
 Object* Heap::FindCodeObject(Address a) {
   Object* obj = NULL;  // Initialization to please compiler.
@@ skipping 43 matching lines @@
     }
   }
 };
 
 
 static void VerifyNonPointerSpacePointers() {
   // Verify that there are no pointers to new space in spaces where we
   // do not expect them.
   VerifyNonPointerSpacePointersVisitor v;
   HeapObjectIterator code_it(HEAP->code_space());
-  for (HeapObject* object = code_it.next();
-       object != NULL; object = code_it.next())
+  for (HeapObject* object = code_it.Next();
+       object != NULL; object = code_it.Next())
     object->Iterate(&v);
 
-  HeapObjectIterator data_it(HEAP->old_data_space());
-  for (HeapObject* object = data_it.next();
-       object != NULL; object = data_it.next())
-    object->Iterate(&v);
+  // The old data space was normally swept conservatively so that the iterator
+  // doesn't work, so we normally skip the next bit.
+  if (!HEAP->old_data_space()->was_swept_conservatively()) {
+    HeapObjectIterator data_it(HEAP->old_data_space());
+    for (HeapObject* object = data_it.Next();
+         object != NULL; object = data_it.Next())
+      object->Iterate(&v);
+  }
 }
 #endif
 
 
 void Heap::CheckNewSpaceExpansionCriteria() {
   if (new_space_.Capacity() < new_space_.MaximumCapacity() &&
       survived_since_last_expansion_ > new_space_.Capacity()) {
     // Grow the size of new space if there is room to grow and enough
     // data has survived scavenge since the last expansion.
     new_space_.Grow();
     survived_since_last_expansion_ = 0;
   }
 }
 
 
 static bool IsUnscavengedHeapObject(Heap* heap, Object** p) {
   return heap->InNewSpace(*p) &&
       !HeapObject::cast(*p)->map_word().IsForwardingAddress();
 }
 
 
+void Heap::ScavengeStoreBufferCallback(
+    Heap* heap,
+    MemoryChunk* page,
+    StoreBufferEvent event) {
+  heap->store_buffer_rebuilder_.Callback(page, event);
+}
+
+
+void StoreBufferRebuilder::Callback(MemoryChunk* page, StoreBufferEvent event) {
+  if (event == kStoreBufferStartScanningPagesEvent) {
+    start_of_current_page_ = NULL;
+    current_page_ = NULL;
+  } else if (event == kStoreBufferScanningPageEvent) {
+    if (current_page_ != NULL) {
+      // If this page already overflowed the store buffer during this iteration.
+      if (current_page_->scan_on_scavenge()) {
+        // Then we should wipe out the entries that have been added for it.
+        store_buffer_->SetTop(start_of_current_page_);
+      } else if (store_buffer_->Top() - start_of_current_page_ >=
+                 (store_buffer_->Limit() - store_buffer_->Top()) >> 2) {
+        // Did we find too many pointers in the previous page?  The heuristic is
+        // that no page can take more then 1/5 the remaining slots in the store
+        // buffer.
+        current_page_->set_scan_on_scavenge(true);
+        store_buffer_->SetTop(start_of_current_page_);
+      } else {
+        // In this case the page we scanned took a reasonable number of slots in
+        // the store buffer.  It has now been rehabilitated and is no longer
+        // marked scan_on_scavenge.
+        ASSERT(!current_page_->scan_on_scavenge());
+      }
+    }
+    start_of_current_page_ = store_buffer_->Top();
+    current_page_ = page;
+  } else if (event == kStoreBufferFullEvent) {
+    // The current page overflowed the store buffer again.  Wipe out its entries
+    // in the store buffer and mark it scan-on-scavenge again.  This may happen
+    // several times while scanning.
+    if (current_page_ == NULL) {
+      // Store Buffer overflowed while scanning promoted objects.  These are not
+      // in any particular page, though they are likely to be clustered by the
+      // allocation routines.
+      store_buffer_->HandleFullness();
+    } else {
+      // Store Buffer overflowed while scanning a particular old space page for
+      // pointers to new space.
+      ASSERT(current_page_ == page);
+      ASSERT(page != NULL);
+      current_page_->set_scan_on_scavenge(true);
+      ASSERT(start_of_current_page_ != store_buffer_->Top());
+      store_buffer_->SetTop(start_of_current_page_);
+    }
+  } else {
+    UNREACHABLE();
+  }
+}
+
+
 void Heap::Scavenge() {
 #ifdef DEBUG
   if (FLAG_enable_slow_asserts) VerifyNonPointerSpacePointers();
 #endif
 
   gc_state_ = SCAVENGE;
 
-  SwitchScavengingVisitorsTableIfProfilingWasEnabled();
-
-  Page::FlipMeaningOfInvalidatedWatermarkFlag(this);
-#ifdef DEBUG
-  VerifyPageWatermarkValidity(old_pointer_space_, ALL_VALID);
-  VerifyPageWatermarkValidity(map_space_, ALL_VALID);
-#endif
-
-  // We do not update an allocation watermark of the top page during linear
-  // allocation to avoid overhead. So to maintain the watermark invariant
-  // we have to manually cache the watermark and mark the top page as having an
-  // invalid watermark. This guarantees that dirty regions iteration will use a
-  // correct watermark even if a linear allocation happens.
-  old_pointer_space_->FlushTopPageWatermark();
-  map_space_->FlushTopPageWatermark();
-
   // Implements Cheney's copying algorithm
   LOG(isolate_, ResourceEvent("scavenge", "begin"));
 
   // Clear descriptor cache.
   isolate_->descriptor_lookup_cache()->Clear();
 
   // Used for updating survived_since_last_expansion_ at function end.
   intptr_t survived_watermark = PromotedSpaceSize();
 
   CheckNewSpaceExpansionCriteria();
 
+  SelectScavengingVisitorsTable();
+
+  incremental_marking()->PrepareForScavenge();
+
+  old_pointer_space()->AdvanceSweeper(new_space_.Size());
+  old_data_space()->AdvanceSweeper(new_space_.Size());
+
   // Flip the semispaces.  After flipping, to space is empty, from space has
   // live objects.
   new_space_.Flip();
   new_space_.ResetAllocationInfo();
 
   // We need to sweep newly copied objects which can be either in the
   // to space or promoted to the old generation.  For to-space
   // objects, we treat the bottom of the to space as a queue.  Newly
   // copied and unswept objects lie between a 'front' mark and the
   // allocation pointer.
   //
   // Promoted objects can go into various old-generation spaces, and
   // can be allocated internally in the spaces (from the free list).
   // We treat the top of the to space as a queue of addresses of
   // promoted objects.  The addresses of newly promoted and unswept
   // objects lie between a 'front' mark and a 'rear' mark that is
   // updated as a side effect of promoting an object.
   //
   // There is guaranteed to be enough room at the top of the to space
   // for the addresses of promoted objects: every object promoted
   // frees up its size in bytes from the top of the new space, and
   // objects are at least one pointer in size.
-  Address new_space_front = new_space_.ToSpaceLow();
-  promotion_queue_.Initialize(new_space_.ToSpaceHigh());
+  Address new_space_front = new_space_.ToSpaceStart();
+  promotion_queue_.Initialize(new_space_.ToSpaceEnd());
 
-  is_safe_to_read_maps_ = false;
+#ifdef DEBUG
+  store_buffer()->Clean();
+#endif
+
   ScavengeVisitor scavenge_visitor(this);
   // Copy roots.
   IterateRoots(&scavenge_visitor, VISIT_ALL_IN_SCAVENGE);
 
-  // Copy objects reachable from the old generation.  By definition,
-  // there are no intergenerational pointers in code or data spaces.
-  IterateDirtyRegions(old_pointer_space_,
-                      &Heap::IteratePointersInDirtyRegion,
-                      &ScavengePointer,
-                      WATERMARK_CAN_BE_INVALID);
-
-  IterateDirtyRegions(map_space_,
-                      &IteratePointersInDirtyMapsRegion,
-                      &ScavengePointer,
-                      WATERMARK_CAN_BE_INVALID);
-
-  lo_space_->IterateDirtyRegions(&ScavengePointer);
+  // Copy objects reachable from the old generation.
+  {
+    StoreBufferRebuildScope scope(this,
+                                  store_buffer(),
+                                  &ScavengeStoreBufferCallback);
+    store_buffer()->IteratePointersToNewSpace(&ScavengeObject);
+  }
 
   // Copy objects reachable from cells by scavenging cell values directly.
   HeapObjectIterator cell_iterator(cell_space_);
-  for (HeapObject* cell = cell_iterator.next();
-       cell != NULL; cell = cell_iterator.next()) {
+  for (HeapObject* cell = cell_iterator.Next();
+       cell != NULL; cell = cell_iterator.Next()) {
     if (cell->IsJSGlobalPropertyCell()) {
       Address value_address =
           reinterpret_cast<Address>(cell) +
           (JSGlobalPropertyCell::kValueOffset - kHeapObjectTag);
       scavenge_visitor.VisitPointer(reinterpret_cast<Object**>(value_address));
     }
   }
 
   // Scavenge object reachable from the global contexts list directly.
   scavenge_visitor.VisitPointer(BitCast<Object**>(&global_contexts_list_));
 
   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
   isolate_->global_handles()->IdentifyNewSpaceWeakIndependentHandles(
       &IsUnscavengedHeapObject);
   isolate_->global_handles()->IterateNewSpaceWeakIndependentRoots(
       &scavenge_visitor);
   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
 
 
   UpdateNewSpaceReferencesInExternalStringTable(
       &UpdateNewSpaceReferenceInExternalStringTableEntry);
 
   LiveObjectList::UpdateReferencesForScavengeGC();
   isolate()->runtime_profiler()->UpdateSamplesAfterScavenge();
+  incremental_marking()->UpdateMarkingDequeAfterScavenge();
 
   ASSERT(new_space_front == new_space_.top());
 
-  is_safe_to_read_maps_ = true;
-
   // Set age mark.
   new_space_.set_age_mark(new_space_.top());
 
+  new_space_.LowerInlineAllocationLimit(
+      new_space_.inline_allocation_limit_step());
+
   // Update how much has survived scavenge.
   IncrementYoungSurvivorsCounter(static_cast<int>(
       (PromotedSpaceSize() - survived_watermark) + new_space_.Size()));
 
   LOG(isolate_, ResourceEvent("scavenge", "end"));
 
   gc_state_ = NOT_IN_GC;
 }
 
 
@@ skipping 38 matching lines @@
       // String got promoted.  Move it to the old string list.
       external_string_table_.AddOldString(target);
     }
   }
 
   ASSERT(last <= end);
   external_string_table_.ShrinkNewStrings(static_cast<int>(last - start));
 }
 
 
+void Heap::UpdateReferencesInExternalStringTable(
+    ExternalStringTableUpdaterCallback updater_func) {
+
+  // Update old space string references.
+  if (external_string_table_.old_space_strings_.length() > 0) {
+    Object** start = &external_string_table_.old_space_strings_[0];
+    Object** end = start + external_string_table_.old_space_strings_.length();
+    for (Object** p = start; p < end; ++p) *p = updater_func(this, p);
+  }
+
+  UpdateNewSpaceReferencesInExternalStringTable(updater_func);
+}
+
+
 static Object* ProcessFunctionWeakReferences(Heap* heap,
                                              Object* function,
                                              WeakObjectRetainer* retainer) {
-  Object* head = heap->undefined_value();
+  Object* undefined = heap->undefined_value();
+  Object* head = undefined;
   JSFunction* tail = NULL;
   Object* candidate = function;
-  while (candidate != heap->undefined_value()) {
+  while (candidate != undefined) {
     // Check whether to keep the candidate in the list.
     JSFunction* candidate_function = reinterpret_cast<JSFunction*>(candidate);
     Object* retain = retainer->RetainAs(candidate);
     if (retain != NULL) {
-      if (head == heap->undefined_value()) {
+      if (head == undefined) {
         // First element in the list.
-        head = candidate_function;
+        head = retain;
       } else {
         // Subsequent elements in the list.
         ASSERT(tail != NULL);
-        tail->set_next_function_link(candidate_function);
+        tail->set_next_function_link(retain);
       }
       // Retained function is new tail.
+      candidate_function = reinterpret_cast<JSFunction*>(retain);
       tail = candidate_function;
+
+      ASSERT(retain->IsUndefined() || retain->IsJSFunction());
+
+      if (retain == undefined) break;
     }
+
     // Move to next element in the list.
     candidate = candidate_function->next_function_link();
   }
 
   // Terminate the list if there is one or more elements.
   if (tail != NULL) {
-    tail->set_next_function_link(heap->undefined_value());
+    tail->set_next_function_link(undefined);
   }
 
   return head;
 }
 
 
 void Heap::ProcessWeakReferences(WeakObjectRetainer* retainer) {
-  Object* head = undefined_value();
+  Object* undefined = undefined_value();
+  Object* head = undefined;
   Context* tail = NULL;
   Object* candidate = global_contexts_list_;
-  while (candidate != undefined_value()) {
+  while (candidate != undefined) {
     // Check whether to keep the candidate in the list.
     Context* candidate_context = reinterpret_cast<Context*>(candidate);
     Object* retain = retainer->RetainAs(candidate);
     if (retain != NULL) {
-      if (head == undefined_value()) {
+      if (head == undefined) {
         // First element in the list.
-        head = candidate_context;
+        head = retain;
       } else {
         // Subsequent elements in the list.
         ASSERT(tail != NULL);
         tail->set_unchecked(this,
                             Context::NEXT_CONTEXT_LINK,
-                            candidate_context,
+                            retain,
                             UPDATE_WRITE_BARRIER);
       }
       // Retained context is new tail.
+      candidate_context = reinterpret_cast<Context*>(retain);
       tail = candidate_context;
 
+      if (retain == undefined) break;
+
       // Process the weak list of optimized functions for the context.
       Object* function_list_head =
           ProcessFunctionWeakReferences(
               this,
               candidate_context->get(Context::OPTIMIZED_FUNCTIONS_LIST),
               retainer);
       candidate_context->set_unchecked(this,
                                        Context::OPTIMIZED_FUNCTIONS_LIST,
                                        function_list_head,
                                        UPDATE_WRITE_BARRIER);
     }
+
     // Move to next element in the list.
     candidate = candidate_context->get(Context::NEXT_CONTEXT_LINK);
   }
 
   // Terminate the list if there is one or more elements.
   if (tail != NULL) {
     tail->set_unchecked(this,
                         Context::NEXT_CONTEXT_LINK,
                         Heap::undefined_value(),
                         UPDATE_WRITE_BARRIER);
@@ skipping 11 matching lines @@
     if (!heap->InNewSpace(object)) return;
     Heap::ScavengeObject(reinterpret_cast<HeapObject**>(p),
                          reinterpret_cast<HeapObject*>(object));
   }
 };
 
 
 Address Heap::DoScavenge(ObjectVisitor* scavenge_visitor,
                          Address new_space_front) {
   do {
-    ASSERT(new_space_front <= new_space_.top());
-
+    SemiSpace::AssertValidRange(new_space_front, new_space_.top());
     // The addresses new_space_front and new_space_.top() define a
     // queue of unprocessed copied objects.  Process them until the
     // queue is empty.
-    while (new_space_front < new_space_.top()) {
-      HeapObject* object = HeapObject::FromAddress(new_space_front);
-      new_space_front += NewSpaceScavenger::IterateBody(object->map(), object);
+    while (new_space_front != new_space_.top()) {
+      if (!NewSpacePage::IsAtEnd(new_space_front)) {
+        HeapObject* object = HeapObject::FromAddress(new_space_front);
+        new_space_front +=
+          NewSpaceScavenger::IterateBody(object->map(), object);
+      } else {
+        new_space_front =
+            NewSpacePage::FromLimit(new_space_front)->next_page()->body();
+      }
     }
 
     // Promote and process all the to-be-promoted objects.
-    while (!promotion_queue_.is_empty()) {
-      HeapObject* target;
-      int size;
-      promotion_queue_.remove(&target, &size);
+    {
+      StoreBufferRebuildScope scope(this,
+                                    store_buffer(),
+                                    &ScavengeStoreBufferCallback);
+      while (!promotion_queue()->is_empty()) {
+        HeapObject* target;
+        int size;
+        promotion_queue()->remove(&target, &size);
 
-      // Promoted object might be already partially visited
-      // during dirty regions iteration. Thus we search specificly
-      // for pointers to from semispace instead of looking for pointers
-      // to new space.
-      ASSERT(!target->IsMap());
-      IterateAndMarkPointersToFromSpace(target->address(),
-                                        target->address() + size,
-                                        &ScavengePointer);
+        // Promoted object might be already partially visited
+        // during old space pointer iteration. Thus we search specificly
+        // for pointers to from semispace instead of looking for pointers
+        // to new space.
+        ASSERT(!target->IsMap());
+        IterateAndMarkPointersToFromSpace(target->address(),
+                                          target->address() + size,
+                                          &ScavengeObject);
+      }
     }
 
     // Take another spin if there are now unswept objects in new space
     // (there are currently no more unswept promoted objects).
-  } while (new_space_front < new_space_.top());
+  } while (new_space_front != new_space_.top());
 
   return new_space_front;
 }
 
 
 enum LoggingAndProfiling {
   LOGGING_AND_PROFILING_ENABLED,
   LOGGING_AND_PROFILING_DISABLED
 };
 
 
-typedef void (*ScavengingCallback)(Map* map,
-                                   HeapObject** slot,
-                                   HeapObject* object);
+enum MarksHandling { TRANSFER_MARKS, IGNORE_MARKS };
 
 
-static Atomic32 scavenging_visitors_table_mode_;
-static VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
-
-
-INLINE(static void DoScavengeObject(Map* map,
-                                    HeapObject** slot,
-                                    HeapObject* obj));
-
-
-void DoScavengeObject(Map* map, HeapObject** slot, HeapObject* obj) {
-  scavenging_visitors_table_.GetVisitor(map)(map, slot, obj);
-}
-
-
-template<LoggingAndProfiling logging_and_profiling_mode>
+template<MarksHandling marks_handling,
+         LoggingAndProfiling logging_and_profiling_mode>
 class ScavengingVisitor : public StaticVisitorBase {
  public:
   static void Initialize() {
     table_.Register(kVisitSeqAsciiString, &EvacuateSeqAsciiString);
     table_.Register(kVisitSeqTwoByteString, &EvacuateSeqTwoByteString);
     table_.Register(kVisitShortcutCandidate, &EvacuateShortcutCandidate);
     table_.Register(kVisitByteArray, &EvacuateByteArray);
     table_.Register(kVisitFixedArray, &EvacuateFixedArray);
     table_.Register(kVisitFixedDoubleArray, &EvacuateFixedDoubleArray);
 
@@ skipping 14 matching lines @@
                         template VisitSpecialized<SharedFunctionInfo::kSize>);
 
     table_.Register(kVisitJSWeakMap,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
                     Visit);
 
     table_.Register(kVisitJSRegExp,
                     &ObjectEvacuationStrategy<POINTER_OBJECT>::
                     Visit);
 
-    table_.Register(kVisitJSFunction,
-                    &ObjectEvacuationStrategy<POINTER_OBJECT>::
-                        template VisitSpecialized<JSFunction::kSize>);
+    if (marks_handling == IGNORE_MARKS) {
+      table_.Register(kVisitJSFunction,
+                      &ObjectEvacuationStrategy<POINTER_OBJECT>::
+                          template VisitSpecialized<JSFunction::kSize>);
+    } else {
+      table_.Register(kVisitJSFunction, &EvacuateJSFunction);
+    }
 
     table_.RegisterSpecializations<ObjectEvacuationStrategy<DATA_OBJECT>,
                                    kVisitDataObject,
                                    kVisitDataObjectGeneric>();
 
     table_.RegisterSpecializations<ObjectEvacuationStrategy<POINTER_OBJECT>,
                                    kVisitJSObject,
                                    kVisitJSObjectGeneric>();
 
     table_.RegisterSpecializations<ObjectEvacuationStrategy<POINTER_OBJECT>,
@@ skipping 44 matching lines @@
       Isolate* isolate = heap->isolate();
       if (isolate->logger()->is_logging() ||
           CpuProfiler::is_profiling(isolate)) {
         if (target->IsSharedFunctionInfo()) {
           PROFILE(isolate, SharedFunctionInfoMoveEvent(
               source->address(), target->address()));
         }
       }
     }
 
+    if (marks_handling == TRANSFER_MARKS) {
+      if (Marking::TransferColor(source, target)) {
+        MemoryChunk::IncrementLiveBytes(target->address(), size);
+      }
+    }
+
     return target;
   }
 
-
   template<ObjectContents object_contents, SizeRestriction size_restriction>
   static inline void EvacuateObject(Map* map,
                                     HeapObject** slot,
                                     HeapObject* object,
                                     int object_size) {
     ASSERT((size_restriction != SMALL) ||
            (object_size <= Page::kMaxHeapObjectSize));
     ASSERT(object->Size() == object_size);
 
-    Heap* heap = map->heap();
+    Heap* heap = map->GetHeap();
     if (heap->ShouldBePromoted(object->address(), object_size)) {
       MaybeObject* maybe_result;
 
       if ((size_restriction != SMALL) &&
           (object_size > Page::kMaxHeapObjectSize)) {
-        maybe_result = heap->lo_space()->AllocateRawFixedArray(object_size);
+        maybe_result = heap->lo_space()->AllocateRaw(object_size,
+                                                     NOT_EXECUTABLE);
       } else {
         if (object_contents == DATA_OBJECT) {
           maybe_result = heap->old_data_space()->AllocateRaw(object_size);
         } else {
           maybe_result = heap->old_pointer_space()->AllocateRaw(object_size);
         }
       }
 
       Object* result = NULL;  // Initialization to please compiler.
       if (maybe_result->ToObject(&result)) {
         HeapObject* target = HeapObject::cast(result);
         *slot = MigrateObject(heap, object , target, object_size);
 
         if (object_contents == POINTER_OBJECT) {
           heap->promotion_queue()->insert(target, object_size);
         }
 
         heap->tracer()->increment_promoted_objects_size(object_size);
         return;
       }
     }
-    Object* result =
-        heap->new_space()->AllocateRaw(object_size)->ToObjectUnchecked();
+    MaybeObject* allocation = heap->new_space()->AllocateRaw(object_size);
+    Object* result = allocation->ToObjectUnchecked();
+
     *slot = MigrateObject(heap, object, HeapObject::cast(result), object_size);
     return;
   }
 
 
+  static inline void EvacuateJSFunction(Map* map,
+                                        HeapObject** slot,
+                                        HeapObject* object) {
+    ObjectEvacuationStrategy<POINTER_OBJECT>::
+        template VisitSpecialized<JSFunction::kSize>(map, slot, object);
+
+    HeapObject* target = *slot;
+    MarkBit mark_bit = Marking::MarkBitFrom(target);
+    if (Marking::IsBlack(mark_bit)) {
+      // This object is black and it might not be rescanned by marker.
+      // We should explicitly record code entry slot for compaction because
+      // promotion queue processing (IterateAndMarkPointersToFromSpace) will
+      // miss it as it is not HeapObject-tagged.
+      Address code_entry_slot =
+          target->address() + JSFunction::kCodeEntryOffset;
+      Code* code = Code::cast(Code::GetObjectFromEntryAddress(code_entry_slot));
+      map->GetHeap()->mark_compact_collector()->
+          RecordCodeEntrySlot(code_entry_slot, code);
+    }
+  }
+
+
   static inline void EvacuateFixedArray(Map* map,
                                         HeapObject** slot,
                                         HeapObject* object) {
     int object_size = FixedArray::BodyDescriptor::SizeOf(map, object);
     EvacuateObject<POINTER_OBJECT, UNKNOWN_SIZE>(map,
                                                  slot,
                                                  object,
                                                  object_size);
   }
 
@@ skipping 38 matching lines @@
 
   static inline bool IsShortcutCandidate(int type) {
     return ((type & kShortcutTypeMask) == kShortcutTypeTag);
   }
 
   static inline void EvacuateShortcutCandidate(Map* map,
                                                HeapObject** slot,
                                                HeapObject* object) {
     ASSERT(IsShortcutCandidate(map->instance_type()));
 
-    if (ConsString::cast(object)->unchecked_second() ==
-        map->heap()->empty_string()) {
+    Heap* heap = map->GetHeap();
+
+    if (marks_handling == IGNORE_MARKS &&
+        ConsString::cast(object)->unchecked_second() ==
+        heap->empty_string()) {
       HeapObject* first =
           HeapObject::cast(ConsString::cast(object)->unchecked_first());
 
       *slot = first;
 
-      if (!map->heap()->InNewSpace(first)) {
+      if (!heap->InNewSpace(first)) {
         object->set_map_word(MapWord::FromForwardingAddress(first));
         return;
       }
 
       MapWord first_word = first->map_word();
       if (first_word.IsForwardingAddress()) {
         HeapObject* target = first_word.ToForwardingAddress();
 
         *slot = target;
         object->set_map_word(MapWord::FromForwardingAddress(target));
         return;
       }
 
-      DoScavengeObject(first->map(), slot, first);
+      heap->DoScavengeObject(first->map(), slot, first);
       object->set_map_word(MapWord::FromForwardingAddress(*slot));
       return;
     }
 
     int object_size = ConsString::kSize;
     EvacuateObject<POINTER_OBJECT, SMALL>(map, slot, object, object_size);
   }
 
   template<ObjectContents object_contents>
   class ObjectEvacuationStrategy {
@@ skipping 10 matching lines @@
                              HeapObject* object) {
       int object_size = map->instance_size();
       EvacuateObject<object_contents, SMALL>(map, slot, object, object_size);
     }
   };
 
   static VisitorDispatchTable<ScavengingCallback> table_;
 };
 
 
-template<LoggingAndProfiling logging_and_profiling_mode>
+template<MarksHandling marks_handling,
+         LoggingAndProfiling logging_and_profiling_mode>
 VisitorDispatchTable<ScavengingCallback>
-    ScavengingVisitor<logging_and_profiling_mode>::table_;
+    ScavengingVisitor<marks_handling, logging_and_profiling_mode>::table_;
 
 
 static void InitializeScavengingVisitorsTables() {
-  ScavengingVisitor<LOGGING_AND_PROFILING_DISABLED>::Initialize();
-  ScavengingVisitor<LOGGING_AND_PROFILING_ENABLED>::Initialize();
-  scavenging_visitors_table_.CopyFrom(
-      ScavengingVisitor<LOGGING_AND_PROFILING_DISABLED>::GetTable());
-  scavenging_visitors_table_mode_ = LOGGING_AND_PROFILING_DISABLED;
+  ScavengingVisitor<TRANSFER_MARKS,
+                    LOGGING_AND_PROFILING_DISABLED>::Initialize();
+  ScavengingVisitor<IGNORE_MARKS, LOGGING_AND_PROFILING_DISABLED>::Initialize();
+  ScavengingVisitor<TRANSFER_MARKS,
+                    LOGGING_AND_PROFILING_ENABLED>::Initialize();
+  ScavengingVisitor<IGNORE_MARKS, LOGGING_AND_PROFILING_ENABLED>::Initialize();
 }
 
 
-void Heap::SwitchScavengingVisitorsTableIfProfilingWasEnabled() {
-  if (scavenging_visitors_table_mode_ == LOGGING_AND_PROFILING_ENABLED) {
-    // Table was already updated by some isolate.
-    return;
-  }
-
-  if (isolate()->logger()->is_logging() |
+void Heap::SelectScavengingVisitorsTable() {
+  bool logging_and_profiling =
+      isolate()->logger()->is_logging() ||
       CpuProfiler::is_profiling(isolate()) ||
       (isolate()->heap_profiler() != NULL &&
-       isolate()->heap_profiler()->is_profiling())) {
-    // If one of the isolates is doing scavenge at this moment of time
-    // it might see this table in an inconsitent state when
-    // some of the callbacks point to
-    // ScavengingVisitor<LOGGING_AND_PROFILING_ENABLED> and others
-    // to ScavengingVisitor<LOGGING_AND_PROFILING_DISABLED>.
-    // However this does not lead to any bugs as such isolate does not have
-    // profiling enabled and any isolate with enabled profiling is guaranteed
-    // to see the table in the consistent state.
-    scavenging_visitors_table_.CopyFrom(
-        ScavengingVisitor<LOGGING_AND_PROFILING_ENABLED>::GetTable());
+       isolate()->heap_profiler()->is_profiling());
 
-    // We use Release_Store to prevent reordering of this write before writes
-    // to the table.
-    Release_Store(&scavenging_visitors_table_mode_,
-                  LOGGING_AND_PROFILING_ENABLED);
+  if (!incremental_marking()->IsMarking()) {
+    if (!logging_and_profiling) {
+      scavenging_visitors_table_.CopyFrom(
+          ScavengingVisitor<IGNORE_MARKS,
+                            LOGGING_AND_PROFILING_DISABLED>::GetTable());
+    } else {
+      scavenging_visitors_table_.CopyFrom(
+          ScavengingVisitor<IGNORE_MARKS,
+                            LOGGING_AND_PROFILING_ENABLED>::GetTable());
+    }
+  } else {
+    if (!logging_and_profiling) {
+      scavenging_visitors_table_.CopyFrom(
+          ScavengingVisitor<TRANSFER_MARKS,
+                            LOGGING_AND_PROFILING_DISABLED>::GetTable());
+    } else {
+      scavenging_visitors_table_.CopyFrom(
+          ScavengingVisitor<TRANSFER_MARKS,
+                            LOGGING_AND_PROFILING_ENABLED>::GetTable());
+    }
   }
 }
 
 
 void Heap::ScavengeObjectSlow(HeapObject** p, HeapObject* object) {
   ASSERT(HEAP->InFromSpace(object));
   MapWord first_word = object->map_word();
   ASSERT(!first_word.IsForwardingAddress());
   Map* map = first_word.ToMap();
-  DoScavengeObject(map, p, object);
+  map->GetHeap()->DoScavengeObject(map, p, object);
 }
 
 
 MaybeObject* Heap::AllocatePartialMap(InstanceType instance_type,
                                       int instance_size) {
   Object* result;
   { MaybeObject* maybe_result = AllocateRawMap();
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
 
@@ skipping 107 matching lines @@
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_oddball_map(Map::cast(obj));
 
   // Allocate the empty array.
   { MaybeObject* maybe_obj = AllocateEmptyFixedArray();
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_empty_fixed_array(FixedArray::cast(obj));
 
-  { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_DATA_SPACE);
+  { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_POINTER_SPACE);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_null_value(obj);
   Oddball::cast(obj)->set_kind(Oddball::kNull);
 
   // Allocate the empty descriptor array.
   { MaybeObject* maybe_obj = AllocateEmptyFixedArray();
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_empty_descriptor_array(DescriptorArray::cast(obj));
@@ skipping 70 matching lines @@
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_fixed_double_array_map(Map::cast(obj));
 
   { MaybeObject* maybe_obj =
         AllocateMap(BYTE_ARRAY_TYPE, kVariableSizeSentinel);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_byte_array_map(Map::cast(obj));
 
+  { MaybeObject* maybe_obj =
+        AllocateMap(FREE_SPACE_TYPE, kVariableSizeSentinel);
+    if (!maybe_obj->ToObject(&obj)) return false;
+  }
+  set_free_space_map(Map::cast(obj));
+
   { MaybeObject* maybe_obj = AllocateByteArray(0, TENURED);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_empty_byte_array(ByteArray::cast(obj));
 
   { MaybeObject* maybe_obj =
         AllocateMap(EXTERNAL_PIXEL_ARRAY_TYPE, ExternalArray::kAlignedSize);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_external_pixel_array_map(Map::cast(obj));
@@ skipping 180 matching lines @@
   HeapObject::cast(result)->set_map(global_property_cell_map());
   JSGlobalPropertyCell::cast(result)->set_value(value);
   return result;
 }
 
 
 MaybeObject* Heap::CreateOddball(const char* to_string,
                                  Object* to_number,
                                  byte kind) {
   Object* result;
-  { MaybeObject* maybe_result = Allocate(oddball_map(), OLD_DATA_SPACE);
+  { MaybeObject* maybe_result = Allocate(oddball_map(), OLD_POINTER_SPACE);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   return Oddball::cast(result)->Initialize(to_string, to_number, kind);
 }
 
 
 bool Heap::CreateApiObjects() {
   Object* obj;
 
   { MaybeObject* maybe_obj = AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
@@ skipping 64 matching lines @@
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_minus_zero_value(obj);
   ASSERT(signbit(minus_zero_value()->Number()) != 0);
 
   { MaybeObject* maybe_obj = AllocateHeapNumber(OS::nan_value(), TENURED);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_nan_value(obj);
 
-  { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_DATA_SPACE);
+  { MaybeObject* maybe_obj = Allocate(oddball_map(), OLD_POINTER_SPACE);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_undefined_value(obj);
   Oddball::cast(obj)->set_kind(Oddball::kUndefined);
   ASSERT(!InNewSpace(undefined_value()));
 
   // Allocate initial symbol table.
   { MaybeObject* maybe_obj = SymbolTable::Allocate(kInitialSymbolTableSize);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
@@ skipping 801 matching lines @@
   if (length < 0 || length > ByteArray::kMaxLength) {
     return Failure::OutOfMemoryException();
   }
   if (pretenure == NOT_TENURED) {
     return AllocateByteArray(length);
   }
   int size = ByteArray::SizeFor(length);
   Object* result;
   { MaybeObject* maybe_result = (size <= MaxObjectSizeInPagedSpace())
                    ? old_data_space_->AllocateRaw(size)
-                   : lo_space_->AllocateRaw(size);
+                   : lo_space_->AllocateRaw(size, NOT_EXECUTABLE);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
 
   reinterpret_cast<ByteArray*>(result)->set_map(byte_array_map());
   reinterpret_cast<ByteArray*>(result)->set_length(length);
   return result;
 }
 
 
 MaybeObject* Heap::AllocateByteArray(int length) {
@@ skipping 15 matching lines @@
 
 
 void Heap::CreateFillerObjectAt(Address addr, int size) {
   if (size == 0) return;
   HeapObject* filler = HeapObject::FromAddress(addr);
   if (size == kPointerSize) {
     filler->set_map(one_pointer_filler_map());
   } else if (size == 2 * kPointerSize) {
     filler->set_map(two_pointer_filler_map());
   } else {
-    filler->set_map(byte_array_map());
-    ByteArray::cast(filler)->set_length(ByteArray::LengthFor(size));
+    filler->set_map(free_space_map());
+    FreeSpace::cast(filler)->set_size(size);
   }
 }
 
 
 MaybeObject* Heap::AllocateExternalArray(int length,
                                          ExternalArrayType array_type,
                                          void* external_pointer,
                                          PretenureFlag pretenure) {
   AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
   Object* result;
@@ skipping 25 matching lines @@
   }
 
   // Compute size.
   int body_size = RoundUp(desc.instr_size, kObjectAlignment);
   int obj_size = Code::SizeFor(body_size);
   ASSERT(IsAligned(static_cast<intptr_t>(obj_size), kCodeAlignment));
   MaybeObject* maybe_result;
   // Large code objects and code objects which should stay at a fixed address
   // are allocated in large object space.
   if (obj_size > MaxObjectSizeInPagedSpace() || immovable) {
-    maybe_result = lo_space_->AllocateRawCode(obj_size);
+    maybe_result = lo_space_->AllocateRaw(obj_size, EXECUTABLE);
   } else {
     maybe_result = code_space_->AllocateRaw(obj_size);
   }
 
   Object* result;
   if (!maybe_result->ToObject(&result)) return maybe_result;
 
   // Initialize the object
   HeapObject::cast(result)->set_map(code_map());
   Code* code = Code::cast(result);
@@ skipping 24 matching lines @@
 #endif
   return code;
 }
 
 
 MaybeObject* Heap::CopyCode(Code* code) {
   // Allocate an object the same size as the code object.
   int obj_size = code->Size();
   MaybeObject* maybe_result;
   if (obj_size > MaxObjectSizeInPagedSpace()) {
-    maybe_result = lo_space_->AllocateRawCode(obj_size);
+    maybe_result = lo_space_->AllocateRaw(obj_size, EXECUTABLE);
   } else {
     maybe_result = code_space_->AllocateRaw(obj_size);
   }
 
   Object* result;
   if (!maybe_result->ToObject(&result)) return maybe_result;
 
   // Copy code object.
   Address old_addr = code->address();
   Address new_addr = reinterpret_cast<HeapObject*>(result)->address();
@@ skipping 22 matching lines @@
 
   int new_obj_size = Code::SizeFor(new_body_size);
 
   Address old_addr = code->address();
 
   size_t relocation_offset =
       static_cast<size_t>(code->instruction_end() - old_addr);
 
   MaybeObject* maybe_result;
   if (new_obj_size > MaxObjectSizeInPagedSpace()) {
-    maybe_result = lo_space_->AllocateRawCode(new_obj_size);
+    maybe_result = lo_space_->AllocateRaw(new_obj_size, EXECUTABLE);
   } else {
     maybe_result = code_space_->AllocateRaw(new_obj_size);
   }
 
   Object* result;
   if (!maybe_result->ToObject(&result)) return maybe_result;
 
   // Copy code object.
   Address new_addr = reinterpret_cast<HeapObject*>(result)->address();
 
@@ skipping 731 matching lines @@
     if (chars > SeqTwoByteString::kMaxLength) {
       return Failure::OutOfMemoryException();
     }
     map = symbol_map();
     size = SeqTwoByteString::SizeFor(chars);
   }
 
   // Allocate string.
   Object* result;
   { MaybeObject* maybe_result = (size > MaxObjectSizeInPagedSpace())
-                   ? lo_space_->AllocateRaw(size)
+                   ? lo_space_->AllocateRaw(size, NOT_EXECUTABLE)
                    : old_data_space_->AllocateRaw(size);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
 
   reinterpret_cast<HeapObject*>(result)->set_map(map);
   // Set length and hash fields of the allocated string.
   String* answer = String::cast(result);
   answer->set_length(chars);
   answer->set_hash_field(hash_field);
 
@@ skipping 96 matching lines @@
   if (length < 0 || length > FixedArray::kMaxLength) {
     return Failure::OutOfMemoryException();
   }
   ASSERT(length > 0);
   // Use the general function if we're forced to always allocate.
   if (always_allocate()) return AllocateFixedArray(length, TENURED);
   // Allocate the raw data for a fixed array.
   int size = FixedArray::SizeFor(length);
   return size <= kMaxObjectSizeInNewSpace
       ? new_space_.AllocateRaw(size)
-      : lo_space_->AllocateRawFixedArray(size);
+      : lo_space_->AllocateRaw(size, NOT_EXECUTABLE);
 }
 
 
 MaybeObject* Heap::CopyFixedArrayWithMap(FixedArray* src, Map* map) {
   int len = src->length();
   Object* obj;
   { MaybeObject* maybe_obj = AllocateRawFixedArray(len);
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   }
   if (InNewSpace(obj)) {
@@ skipping 310 matching lines @@
       (size > MaxObjectSizeInPagedSpace()) ? LO_SPACE : OLD_POINTER_SPACE;
   Object* result;
   { MaybeObject* maybe_result = Allocate(map, space);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   Struct::cast(result)->InitializeBody(size);
   return result;
 }
 
 
+bool Heap::IsHeapIterable() {
+  return (!old_pointer_space()->was_swept_conservatively() &&
+          !old_data_space()->was_swept_conservatively());
+}
+
+
+void Heap::EnsureHeapIsIterable() {
+  ASSERT(IsAllocationAllowed());
+  if (!IsHeapIterable()) {
+    CollectAllGarbage(kMakeHeapIterableMask);
+  }
+  ASSERT(IsHeapIterable());
+}
+
+
 bool Heap::IdleNotification() {
   static const int kIdlesBeforeScavenge = 4;
   static const int kIdlesBeforeMarkSweep = 7;
   static const int kIdlesBeforeMarkCompact = 8;
   static const int kMaxIdleCount = kIdlesBeforeMarkCompact + 1;
   static const unsigned int kGCsBetweenCleanup = 4;
 
   if (!last_idle_notification_gc_count_init_) {
     last_idle_notification_gc_count_ = gc_count_;
     last_idle_notification_gc_count_init_ = true;
@@ skipping 10 matching lines @@
     number_idle_notifications_ =
         Min(number_idle_notifications_ + 1, kMaxIdleCount);
   } else {
     number_idle_notifications_ = 0;
     last_idle_notification_gc_count_ = gc_count_;
   }
 
   if (number_idle_notifications_ == kIdlesBeforeScavenge) {
     if (contexts_disposed_ > 0) {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
-      CollectAllGarbage(false);
+      CollectAllGarbage(kNoGCFlags);
     } else {
       CollectGarbage(NEW_SPACE);
     }
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
   } else if (number_idle_notifications_ == kIdlesBeforeMarkSweep) {
     // Before doing the mark-sweep collections we clear the
     // compilation cache to avoid hanging on to source code and
     // generated code for cached functions.
     isolate_->compilation_cache()->Clear();
 
-    CollectAllGarbage(false);
+    CollectAllGarbage(kNoGCFlags);
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
 
   } else if (number_idle_notifications_ == kIdlesBeforeMarkCompact) {
-    CollectAllGarbage(true);
+    CollectAllGarbage(kNoGCFlags);
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
     number_idle_notifications_ = 0;
     finished = true;
   } else if (contexts_disposed_ > 0) {
     if (FLAG_expose_gc) {
       contexts_disposed_ = 0;
     } else {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
-      CollectAllGarbage(false);
+      CollectAllGarbage(kNoGCFlags);
       last_idle_notification_gc_count_ = gc_count_;
     }
     // If this is the first idle notification, we reset the
     // notification count to avoid letting idle notifications for
     // context disposal garbage collections start a potentially too
     // aggressive idle GC cycle.
     if (number_idle_notifications_ <= 1) {
       number_idle_notifications_ = 0;
       uncommit = false;
     }
   } else if (number_idle_notifications_ > kIdlesBeforeMarkCompact) {
     // If we have received more than kIdlesBeforeMarkCompact idle
     // notifications we do not perform any cleanup because we don't
     // expect to gain much by doing so.
     finished = true;
   }
 
   // Make sure that we have no pending context disposals and
   // conditionally uncommit from space.
-  ASSERT(contexts_disposed_ == 0);
+  ASSERT((contexts_disposed_ == 0) || incremental_marking()->IsMarking());
   if (uncommit) UncommitFromSpace();
   return finished;
 }
 
 
 #ifdef DEBUG
 
 void Heap::Print() {
   if (!HasBeenSetup()) return;
   isolate()->PrintStack();
@@ skipping 14 matching lines @@
 }
 
 
 // This function expects that NewSpace's allocated objects histogram is
 // populated (via a call to CollectStatistics or else as a side effect of a
 // just-completed scavenge collection).
 void Heap::ReportHeapStatistics(const char* title) {
   USE(title);
   PrintF(">>>>>> =============== %s (%d) =============== >>>>>>\n",
          title, gc_count_);
-  PrintF("mark-compact GC : %d\n", mc_count_);
   PrintF("old_gen_promotion_limit_ %" V8_PTR_PREFIX "d\n",
          old_gen_promotion_limit_);
   PrintF("old_gen_allocation_limit_ %" V8_PTR_PREFIX "d\n",
          old_gen_allocation_limit_);
+  PrintF("old_gen_limit_factor_ %d\n", old_gen_limit_factor_);
 
   PrintF("\n");
   PrintF("Number of handles : %d\n", HandleScope::NumberOfHandles());
   isolate_->global_handles()->PrintStats();
   PrintF("\n");
 
   PrintF("Heap statistics : ");
   isolate_->memory_allocator()->ReportStatistics();
   PrintF("To space : ");
   new_space_.ReportStatistics();
@@ skipping 56 matching lines @@
       return cell_space_->Contains(addr);
     case LO_SPACE:
       return lo_space_->SlowContains(addr);
   }
 
   return false;
 }
 
 
 #ifdef DEBUG
-static void DummyScavengePointer(HeapObject** p) {
-}
-
-
-static void VerifyPointersUnderWatermark(
-    PagedSpace* space,
-    DirtyRegionCallback visit_dirty_region) {
-  PageIterator it(space, PageIterator::PAGES_IN_USE);
-
-  while (it.has_next()) {
-    Page* page = it.next();
-    Address start = page->ObjectAreaStart();
-    Address end = page->AllocationWatermark();
-
-    HEAP->IterateDirtyRegions(Page::kAllRegionsDirtyMarks,
-                              start,
-                              end,
-                              visit_dirty_region,
-                              &DummyScavengePointer);
-  }
-}
-
-
-static void VerifyPointersUnderWatermark(LargeObjectSpace* space) {
-  LargeObjectIterator it(space);
-  for (HeapObject* object = it.next(); object != NULL; object = it.next()) {
-    if (object->IsFixedArray()) {
-      Address slot_address = object->address();
-      Address end = object->address() + object->Size();
-
-      while (slot_address < end) {
-        HeapObject** slot = reinterpret_cast<HeapObject**>(slot_address);
-        // When we are not in GC the Heap::InNewSpace() predicate
-        // checks that pointers which satisfy predicate point into
-        // the active semispace.
-        HEAP->InNewSpace(*slot);
-        slot_address += kPointerSize;
-      }
-    }
-  }
-}
-
-
 void Heap::Verify() {
   ASSERT(HasBeenSetup());
 
+  store_buffer()->Verify();
+
   VerifyPointersVisitor visitor;
   IterateRoots(&visitor, VISIT_ONLY_STRONG);
 
   new_space_.Verify();
 
-  VerifyPointersAndDirtyRegionsVisitor dirty_regions_visitor;
-  old_pointer_space_->Verify(&dirty_regions_visitor);
-  map_space_->Verify(&dirty_regions_visitor);
-
-  VerifyPointersUnderWatermark(old_pointer_space_,
-                               &IteratePointersInDirtyRegion);
-  VerifyPointersUnderWatermark(map_space_,
-                               &IteratePointersInDirtyMapsRegion);
-  VerifyPointersUnderWatermark(lo_space_);
-
-  VerifyPageWatermarkValidity(old_pointer_space_, ALL_INVALID);
-  VerifyPageWatermarkValidity(map_space_, ALL_INVALID);
+  old_pointer_space_->Verify(&visitor);
+  map_space_->Verify(&visitor);
 
   VerifyPointersVisitor no_dirty_regions_visitor;
   old_data_space_->Verify(&no_dirty_regions_visitor);
   code_space_->Verify(&no_dirty_regions_visitor);
   cell_space_->Verify(&no_dirty_regions_visitor);
 
   lo_space_->Verify();
 }
+
 #endif  // DEBUG
 
 
 MaybeObject* Heap::LookupSymbol(Vector<const char> string) {
   Object* symbol = NULL;
   Object* new_table;
   { MaybeObject* maybe_new_table =
         symbol_table()->LookupSymbol(string, &symbol);
     if (!maybe_new_table->ToObject(&new_table)) return maybe_new_table;
   }
@@ skipping 75 matching lines @@
   if (string->IsSymbol()) {
     *symbol = string;
     return true;
   }
   return symbol_table()->LookupSymbolIfExists(string, symbol);
 }
 
 
 #ifdef DEBUG
 void Heap::ZapFromSpace() {
-  ASSERT(reinterpret_cast<Object*>(kFromSpaceZapValue)->IsFailure());
-  for (Address a = new_space_.FromSpaceLow();
-       a < new_space_.FromSpaceHigh();
-       a += kPointerSize) {
-    Memory::Address_at(a) = kFromSpaceZapValue;
+  NewSpacePageIterator it(new_space_.FromSpaceStart(),
+                          new_space_.FromSpaceEnd());
+  while (it.has_next()) {
+    NewSpacePage* page = it.next();
+    for (Address cursor = page->body(), limit = page->body_limit();
+         cursor < limit;
+         cursor += kPointerSize) {
+      Memory::Address_at(cursor) = kFromSpaceZapValue;
+    }
   }
 }
 #endif  // DEBUG
 
 
-bool Heap::IteratePointersInDirtyRegion(Heap* heap,
-                                        Address start,
-                                        Address end,
-                                        ObjectSlotCallback copy_object_func) {
-  Address slot_address = start;
-  bool pointers_to_new_space_found = false;
-
-  while (slot_address < end) {
-    Object** slot = reinterpret_cast<Object**>(slot_address);
-    if (heap->InNewSpace(*slot)) {
-      ASSERT((*slot)->IsHeapObject());
-      copy_object_func(reinterpret_cast<HeapObject**>(slot));
-      if (heap->InNewSpace(*slot)) {
-        ASSERT((*slot)->IsHeapObject());
-        pointers_to_new_space_found = true;
-      }
-    }
-    slot_address += kPointerSize;
-  }
-  return pointers_to_new_space_found;
-}
-
-
-// Compute start address of the first map following given addr.
-static inline Address MapStartAlign(Address addr) {
-  Address page = Page::FromAddress(addr)->ObjectAreaStart();
-  return page + (((addr - page) + (Map::kSize - 1)) / Map::kSize * Map::kSize);
-}
-
-
-// Compute end address of the first map preceding given addr.
-static inline Address MapEndAlign(Address addr) {
-  Address page = Page::FromAllocationTop(addr)->ObjectAreaStart();
-  return page + ((addr - page) / Map::kSize * Map::kSize);
-}
-
-
-static bool IteratePointersInDirtyMaps(Address start,
-                                       Address end,
-                                       ObjectSlotCallback copy_object_func) {
-  ASSERT(MapStartAlign(start) == start);
-  ASSERT(MapEndAlign(end) == end);
-
-  Address map_address = start;
-  bool pointers_to_new_space_found = false;
-
-  Heap* heap = HEAP;
-  while (map_address < end) {
-    ASSERT(!heap->InNewSpace(Memory::Object_at(map_address)));
-    ASSERT(Memory::Object_at(map_address)->IsMap());
-
-    Address pointer_fields_start = map_address + Map::kPointerFieldsBeginOffset;
-    Address pointer_fields_end = map_address + Map::kPointerFieldsEndOffset;
-
-    if (Heap::IteratePointersInDirtyRegion(heap,
-                                           pointer_fields_start,
-                                           pointer_fields_end,
-                                           copy_object_func)) {
-      pointers_to_new_space_found = true;
-    }
-
-    map_address += Map::kSize;
-  }
-
-  return pointers_to_new_space_found;
-}
-
-
-bool Heap::IteratePointersInDirtyMapsRegion(
-    Heap* heap,
-    Address start,
-    Address end,
-    ObjectSlotCallback copy_object_func) {
-  Address map_aligned_start = MapStartAlign(start);
-  Address map_aligned_end   = MapEndAlign(end);
-
-  bool contains_pointers_to_new_space = false;
-
-  if (map_aligned_start != start) {
-    Address prev_map = map_aligned_start - Map::kSize;
-    ASSERT(Memory::Object_at(prev_map)->IsMap());
-
-    Address pointer_fields_start =
-        Max(start, prev_map + Map::kPointerFieldsBeginOffset);
-
-    Address pointer_fields_end =
-        Min(prev_map + Map::kPointerFieldsEndOffset, end);
-
-    contains_pointers_to_new_space =
-      IteratePointersInDirtyRegion(heap,
-                                   pointer_fields_start,
-                                   pointer_fields_end,
-                                   copy_object_func)
-        || contains_pointers_to_new_space;
-  }
-
-  contains_pointers_to_new_space =
-    IteratePointersInDirtyMaps(map_aligned_start,
-                               map_aligned_end,
-                               copy_object_func)
-      || contains_pointers_to_new_space;
-
-  if (map_aligned_end != end) {
-    ASSERT(Memory::Object_at(map_aligned_end)->IsMap());
-
-    Address pointer_fields_start =
-        map_aligned_end + Map::kPointerFieldsBeginOffset;
-
-    Address pointer_fields_end =
-        Min(end, map_aligned_end + Map::kPointerFieldsEndOffset);
-
-    contains_pointers_to_new_space =
-      IteratePointersInDirtyRegion(heap,
-                                   pointer_fields_start,
-                                   pointer_fields_end,
-                                   copy_object_func)
-        || contains_pointers_to_new_space;
-  }
-
-  return contains_pointers_to_new_space;
-}
-
-
 void Heap::IterateAndMarkPointersToFromSpace(Address start,
                                              Address end,
                                              ObjectSlotCallback callback) {
   Address slot_address = start;
-  Page* page = Page::FromAddress(start);
-
-  uint32_t marks = page->GetRegionMarks();
+
+  // We are not collecting slots on new space objects during mutation
+  // thus we have to scan for pointers to evacuation candidates when we
+  // promote objects. But we should not record any slots in non-black
+  // objects. Grey object's slots would be rescanned.
+  // White object might not survive until the end of collection
+  // it would be a violation of the invariant to record it's slots.
+  bool record_slots = false;
+  if (incremental_marking()->IsCompacting()) {
+    MarkBit mark_bit = Marking::MarkBitFrom(HeapObject::FromAddress(start));
+    record_slots = Marking::IsBlack(mark_bit);
+  }
 
   while (slot_address < end) {
     Object** slot = reinterpret_cast<Object**>(slot_address);
-    if (InFromSpace(*slot)) {
-      ASSERT((*slot)->IsHeapObject());
-      callback(reinterpret_cast<HeapObject**>(slot));
-      if (InNewSpace(*slot)) {
-        ASSERT((*slot)->IsHeapObject());
-        marks |= page->GetRegionMaskForAddress(slot_address);
+    Object* object = *slot;
+    // If the store buffer becomes overfull we mark pages as being exempt from
+    // the store buffer.  These pages are scanned to find pointers that point
+    // to the new space.  In that case we may hit newly promoted objects and
+    // fix the pointers before the promotion queue gets to them.  Thus the 'if'.
+    if (object->IsHeapObject()) {
+      if (Heap::InFromSpace(object)) {
+        callback(reinterpret_cast<HeapObject**>(slot),
+                 HeapObject::cast(object));
+        Object* new_object = *slot;
+        if (InNewSpace(new_object)) {
+          ASSERT(Heap::InToSpace(new_object));
+          ASSERT(new_object->IsHeapObject());
+          store_buffer_.EnterDirectlyIntoStoreBuffer(
+              reinterpret_cast<Address>(slot));
+        }
+        ASSERT(!MarkCompactCollector::IsOnEvacuationCandidate(new_object));
+      } else if (record_slots &&
+                 MarkCompactCollector::IsOnEvacuationCandidate(object)) {
+        mark_compact_collector()->RecordSlot(slot, slot, object);
       }
     }
     slot_address += kPointerSize;
   }
-
-  page->SetRegionMarks(marks);
-}
-
-
-uint32_t Heap::IterateDirtyRegions(
-    uint32_t marks,
-    Address area_start,
-    Address area_end,
-    DirtyRegionCallback visit_dirty_region,
-    ObjectSlotCallback copy_object_func) {
-  uint32_t newmarks = 0;
-  uint32_t mask = 1;
-
-  if (area_start >= area_end) {
-    return newmarks;
-  }
-
-  Address region_start = area_start;
-
-  // area_start does not necessarily coincide with start of the first region.
-  // Thus to calculate the beginning of the next region we have to align
-  // area_start by Page::kRegionSize.
-  Address second_region =
-      reinterpret_cast<Address>(
-          reinterpret_cast<intptr_t>(area_start + Page::kRegionSize) &
-          ~Page::kRegionAlignmentMask);
-
-  // Next region might be beyond area_end.
-  Address region_end = Min(second_region, area_end);
-
-  if (marks & mask) {
-    if (visit_dirty_region(this, region_start, region_end, copy_object_func)) {
-      newmarks |= mask;
-    }
-  }
-  mask <<= 1;
-
-  // Iterate subsequent regions which fully lay inside [area_start, area_end[.
-  region_start = region_end;
-  region_end = region_start + Page::kRegionSize;
-
-  while (region_end <= area_end) {
-    if (marks & mask) {
-      if (visit_dirty_region(this,
-                             region_start,
-                             region_end,
-                             copy_object_func)) {
-        newmarks |= mask;
-      }
-    }
-
-    region_start = region_end;
-    region_end = region_start + Page::kRegionSize;
-
-    mask <<= 1;
-  }
-
-  if (region_start != area_end) {
-    // A small piece of area left uniterated because area_end does not coincide
-    // with region end. Check whether region covering last part of area is
-    // dirty.
-    if (marks & mask) {
-      if (visit_dirty_region(this, region_start, area_end, copy_object_func)) {
-        newmarks |= mask;
-      }
-    }
-  }
-
-  return newmarks;
-}
-
-
-
-void Heap::IterateDirtyRegions(
-    PagedSpace* space,
-    DirtyRegionCallback visit_dirty_region,
-    ObjectSlotCallback copy_object_func,
-    ExpectedPageWatermarkState expected_page_watermark_state) {
-
-  PageIterator it(space, PageIterator::PAGES_IN_USE);
-
-  while (it.has_next()) {
-    Page* page = it.next();
-    uint32_t marks = page->GetRegionMarks();
-
-    if (marks != Page::kAllRegionsCleanMarks) {
-      Address start = page->ObjectAreaStart();
-
-      // Do not try to visit pointers beyond page allocation watermark.
-      // Page can contain garbage pointers there.
-      Address end;
-
-      if ((expected_page_watermark_state == WATERMARK_SHOULD_BE_VALID) ||
-          page->IsWatermarkValid()) {
-        end = page->AllocationWatermark();
-      } else {
-        end = page->CachedAllocationWatermark();
-      }
-
-      ASSERT(space == old_pointer_space_ ||
-             (space == map_space_ &&
-              ((page->ObjectAreaStart() - end) % Map::kSize == 0)));
-
-      page->SetRegionMarks(IterateDirtyRegions(marks,
-                                               start,
-                                               end,
-                                               visit_dirty_region,
-                                               copy_object_func));
-    }
-
-    // Mark page watermark as invalid to maintain watermark validity invariant.
-    // See Page::FlipMeaningOfInvalidatedWatermarkFlag() for details.
-    page->InvalidateWatermark(true);
-  }
-}
+}
+
+
+#ifdef DEBUG
+typedef bool (*CheckStoreBufferFilter)(Object** addr);
+
+
+bool IsAMapPointerAddress(Object** addr) {
+  uintptr_t a = reinterpret_cast<uintptr_t>(addr);
+  int mod = a % Map::kSize;
+  return mod >= Map::kPointerFieldsBeginOffset &&
+         mod < Map::kPointerFieldsEndOffset;
+}
+
+
+bool EverythingsAPointer(Object** addr) {
+  return true;
+}
+
+
+static void CheckStoreBuffer(Heap* heap,
+                             Object** current,
+                             Object** limit,
+                             Object**** store_buffer_position,
+                             Object*** store_buffer_top,
+                             CheckStoreBufferFilter filter,
+                             Address special_garbage_start,
+                             Address special_garbage_end) {
+  Map* free_space_map = heap->free_space_map();
+  for ( ; current < limit; current++) {
+    Object* o = *current;
+    Address current_address = reinterpret_cast<Address>(current);
+    // Skip free space.
+    if (o == free_space_map) {
+      Address current_address = reinterpret_cast<Address>(current);
+      FreeSpace* free_space =
+          FreeSpace::cast(HeapObject::FromAddress(current_address));
+      int skip = free_space->Size();
+      ASSERT(current_address + skip <= reinterpret_cast<Address>(limit));
+      ASSERT(skip > 0);
+      current_address += skip - kPointerSize;
+      current = reinterpret_cast<Object**>(current_address);
+      continue;
+    }
+    // Skip the current linear allocation space between top and limit which is
+    // unmarked with the free space map, but can contain junk.
+    if (current_address == special_garbage_start &&
+        special_garbage_end != special_garbage_start) {
+      current_address = special_garbage_end - kPointerSize;
+      current = reinterpret_cast<Object**>(current_address);
+      continue;
+    }
+    if (!(*filter)(current)) continue;
+    ASSERT(current_address < special_garbage_start ||
+           current_address >= special_garbage_end);
+    ASSERT(reinterpret_cast<uintptr_t>(o) != kFreeListZapValue);
+    // We have to check that the pointer does not point into new space
+    // without trying to cast it to a heap object since the hash field of
+    // a string can contain values like 1 and 3 which are tagged null
+    // pointers.
+    if (!heap->InNewSpace(o)) continue;
+    while (**store_buffer_position < current &&
+           *store_buffer_position < store_buffer_top) {
+      (*store_buffer_position)++;
+    }
+    if (**store_buffer_position != current ||
+        *store_buffer_position == store_buffer_top) {
+      Object** obj_start = current;
+      while (!(*obj_start)->IsMap()) obj_start--;
+      UNREACHABLE();
+    }
+  }
+}
+
+
+// Check that the store buffer contains all intergenerational pointers by
+// scanning a page and ensuring that all pointers to young space are in the
+// store buffer.
+void Heap::OldPointerSpaceCheckStoreBuffer() {
+  OldSpace* space = old_pointer_space();
+  PageIterator pages(space);
+
+  store_buffer()->SortUniq();
+
+  while (pages.has_next()) {
+    Page* page = pages.next();
+    Object** current = reinterpret_cast<Object**>(page->ObjectAreaStart());
+
+    Address end = page->ObjectAreaEnd();
+
+    Object*** store_buffer_position = store_buffer()->Start();
+    Object*** store_buffer_top = store_buffer()->Top();
+
+    Object** limit = reinterpret_cast<Object**>(end);
+    CheckStoreBuffer(this,
+                     current,
+                     limit,
+                     &store_buffer_position,
+                     store_buffer_top,
+                     &EverythingsAPointer,
+                     space->top(),
+                     space->limit());
+  }
+}
+
+
+void Heap::MapSpaceCheckStoreBuffer() {
+  MapSpace* space = map_space();
+  PageIterator pages(space);
+
+  store_buffer()->SortUniq();
+
+  while (pages.has_next()) {
+    Page* page = pages.next();
+    Object** current = reinterpret_cast<Object**>(page->ObjectAreaStart());
+
+    Address end = page->ObjectAreaEnd();
+
+    Object*** store_buffer_position = store_buffer()->Start();
+    Object*** store_buffer_top = store_buffer()->Top();
+
+    Object** limit = reinterpret_cast<Object**>(end);
+    CheckStoreBuffer(this,
+                     current,
+                     limit,
+                     &store_buffer_position,
+                     store_buffer_top,
+                     &IsAMapPointerAddress,
+                     space->top(),
+                     space->limit());
+  }
+}
+
+
+void Heap::LargeObjectSpaceCheckStoreBuffer() {
+  LargeObjectIterator it(lo_space());
+  for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
+    // We only have code, sequential strings, or fixed arrays in large
+    // object space, and only fixed arrays can possibly contain pointers to
+    // the young generation.
+    if (object->IsFixedArray()) {
+      Object*** store_buffer_position = store_buffer()->Start();
+      Object*** store_buffer_top = store_buffer()->Top();
+      Object** current = reinterpret_cast<Object**>(object->address());
+      Object** limit =
+          reinterpret_cast<Object**>(object->address() + object->Size());
+      CheckStoreBuffer(this,
+                       current,
+                       limit,
+                       &store_buffer_position,
+                       store_buffer_top,
+                       &EverythingsAPointer,
+                       NULL,
+                       NULL);
+    }
+  }
+}
+#endif
 
 
 void Heap::IterateRoots(ObjectVisitor* v, VisitMode mode) {
   IterateStrongRoots(v, mode);
   IterateWeakRoots(v, mode);
 }
 
 
 void Heap::IterateWeakRoots(ObjectVisitor* v, VisitMode mode) {
   v->VisitPointer(reinterpret_cast<Object**>(&roots_[kSymbolTableRootIndex]));
@@ skipping 31 matching lines @@
   isolate_->compilation_cache()->Iterate(v);
   v->Synchronize("compilationcache");
 
   // Iterate over local handles in handle scopes.
   isolate_->handle_scope_implementer()->Iterate(v);
   v->Synchronize("handlescope");
 
   // Iterate over the builtin code objects and code stubs in the
   // heap. Note that it is not necessary to iterate over code objects
   // on scavenge collections.
-  if (mode != VISIT_ALL_IN_SCAVENGE &&
-      mode != VISIT_ALL_IN_SWEEP_NEWSPACE) {
+  if (mode != VISIT_ALL_IN_SCAVENGE) {
     isolate_->builtins()->IterateBuiltins(v);
   }
   v->Synchronize("builtins");
 
   // Iterate over global handles.
   switch (mode) {
     case VISIT_ONLY_STRONG:
       isolate_->global_handles()->IterateStrongRoots(v);
       break;
     case VISIT_ALL_IN_SCAVENGE:
@@ skipping 23 matching lines @@
   // output a flag to the snapshot.  However at this point the serializer and
   // deserializer are deliberately a little unsynchronized (see above) so the
   // checking of the sync flag in the snapshot would fail.
 }
 
 
 // TODO(1236194): Since the heap size is configurable on the command line
 // and through the API, we should gracefully handle the case that the heap
 // size is not big enough to fit all the initial objects.
 bool Heap::ConfigureHeap(int max_semispace_size,
-                         int max_old_gen_size,
-                         int max_executable_size) {
+                         intptr_t max_old_gen_size,
+                         intptr_t max_executable_size) {
   if (HasBeenSetup()) return false;
 
-  if (max_semispace_size > 0) max_semispace_size_ = max_semispace_size;
+  if (max_semispace_size > 0) {
+    if (max_semispace_size < Page::kPageSize) {
+      max_semispace_size = Page::kPageSize;
+      if (FLAG_trace_gc) {
+        PrintF("Max semispace size cannot be less than %dkbytes",
+               Page::kPageSize >> 10);
+      }
+    }
+    max_semispace_size_ = max_semispace_size;
+  }
 
   if (Snapshot::IsEnabled()) {
     // If we are using a snapshot we always reserve the default amount
     // of memory for each semispace because code in the snapshot has
     // write-barrier code that relies on the size and alignment of new
     // space.  We therefore cannot use a larger max semispace size
     // than the default reserved semispace size.
     if (max_semispace_size_ > reserved_semispace_size_) {
       max_semispace_size_ = reserved_semispace_size_;
+      if (FLAG_trace_gc) {
+        PrintF("Max semispace size cannot be more than %dkbytes",
+               reserved_semispace_size_ >> 10);
+      }
     }
   } else {
     // If we are not using snapshots we reserve space for the actual
     // max semispace size.
     reserved_semispace_size_ = max_semispace_size_;
   }
 
   if (max_old_gen_size > 0) max_old_generation_size_ = max_old_gen_size;
   if (max_executable_size > 0) {
     max_executable_size_ = RoundUp(max_executable_size, Page::kPageSize);
   }
 
   // The max executable size must be less than or equal to the max old
   // generation size.
   if (max_executable_size_ > max_old_generation_size_) {
     max_executable_size_ = max_old_generation_size_;
   }
 
   // The new space size must be a power of two to support single-bit testing
   // for containment.
   max_semispace_size_ = RoundUpToPowerOf2(max_semispace_size_);
   reserved_semispace_size_ = RoundUpToPowerOf2(reserved_semispace_size_);
   initial_semispace_size_ = Min(initial_semispace_size_, max_semispace_size_);
   external_allocation_limit_ = 10 * max_semispace_size_;
 
-  // The old generation is paged.
-  max_old_generation_size_ = RoundUp(max_old_generation_size_, Page::kPageSize);
+  // The old generation is paged and needs at least one page for each space.
+  int paged_space_count = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1;
+  max_old_generation_size_ = Max(static_cast<intptr_t>(paged_space_count *
+                                                       Page::kPageSize),
+                                 RoundUp(max_old_generation_size_,
+                                         Page::kPageSize));
 
   configured_ = true;
   return true;
 }
 
 
 bool Heap::ConfigureHeapDefault() {
-  return ConfigureHeap(FLAG_max_new_space_size / 2 * KB,
-                       FLAG_max_old_space_size * MB,
-                       FLAG_max_executable_size * MB);
+  return ConfigureHeap(static_cast<intptr_t>(FLAG_max_new_space_size / 2) * KB,
+                       static_cast<intptr_t>(FLAG_max_old_space_size) * MB,
+                       static_cast<intptr_t>(FLAG_max_executable_size) * MB);
 }
 
 
 void Heap::RecordStats(HeapStats* stats, bool take_snapshot) {
   *stats->start_marker = HeapStats::kStartMarker;
   *stats->end_marker = HeapStats::kEndMarker;
   *stats->new_space_size = new_space_.SizeAsInt();
   *stats->new_space_capacity = static_cast<int>(new_space_.Capacity());
   *stats->old_pointer_space_size = old_pointer_space_->Size();
   *stats->old_pointer_space_capacity = old_pointer_space_->Capacity();
   *stats->old_data_space_size = old_data_space_->Size();
   *stats->old_data_space_capacity = old_data_space_->Capacity();
   *stats->code_space_size = code_space_->Size();
   *stats->code_space_capacity = code_space_->Capacity();
   *stats->map_space_size = map_space_->Size();
   *stats->map_space_capacity = map_space_->Capacity();
   *stats->cell_space_size = cell_space_->Size();
   *stats->cell_space_capacity = cell_space_->Capacity();
   *stats->lo_space_size = lo_space_->Size();
   isolate_->global_handles()->RecordStats(stats);
   *stats->memory_allocator_size = isolate()->memory_allocator()->Size();
   *stats->memory_allocator_capacity =
       isolate()->memory_allocator()->Size() +
       isolate()->memory_allocator()->Available();
   *stats->os_error = OS::GetLastError();
       isolate()->memory_allocator()->Available();
   if (take_snapshot) {
-    HeapIterator iterator(HeapIterator::kFilterFreeListNodes);
+    HeapIterator iterator;
     for (HeapObject* obj = iterator.next();
          obj != NULL;
          obj = iterator.next()) {
       InstanceType type = obj->map()->instance_type();
       ASSERT(0 <= type && type <= LAST_TYPE);
       stats->objects_per_type[type]++;
       stats->size_per_type[type] += obj->Size();
     }
   }
 }
@@ skipping 195 matching lines @@
   // Configuration is based on the flags new-space-size (really the semispace
   // size) and old-space-size if set or the initial values of semispace_size_
   // and old_generation_size_ otherwise.
   if (!configured_) {
     if (!ConfigureHeapDefault()) return false;
   }
 
   gc_initializer_mutex->Lock();
   static bool initialized_gc = false;
   if (!initialized_gc) {
-    initialized_gc = true;
-    InitializeScavengingVisitorsTables();
-    NewSpaceScavenger::Initialize();
-    MarkCompactCollector::Initialize();
+      initialized_gc = true;
+      InitializeScavengingVisitorsTables();
+      NewSpaceScavenger::Initialize();
+      MarkCompactCollector::Initialize();
   }
   gc_initializer_mutex->Unlock();
 
   MarkMapPointersAsEncoded(false);
 
-  // Setup memory allocator and reserve a chunk of memory for new
-  // space.  The chunk is double the size of the requested reserved
-  // new space size to ensure that we can find a pair of semispaces that
-  // are contiguous and aligned to their size.
+  // Setup memory allocator.
   if (!isolate_->memory_allocator()->Setup(MaxReserved(), MaxExecutableSize()))
       return false;
-  void* chunk =
-      isolate_->memory_allocator()->ReserveInitialChunk(
-          4 * reserved_semispace_size_);
-  if (chunk == NULL) return false;
 
-  // Align the pair of semispaces to their size, which must be a power
-  // of 2.
-  Address new_space_start =
-      RoundUp(reinterpret_cast<byte*>(chunk), 2 * reserved_semispace_size_);
-  if (!new_space_.Setup(new_space_start, 2 * reserved_semispace_size_)) {
+  // Setup new space.
+  if (!new_space_.Setup(reserved_semispace_size_, max_semispace_size_)) {
     return false;
   }
 
   // Initialize old pointer space.
   old_pointer_space_ =
       new OldSpace(this,
                    max_old_generation_size_,
                    OLD_POINTER_SPACE,
                    NOT_EXECUTABLE);
   if (old_pointer_space_ == NULL) return false;
-  if (!old_pointer_space_->Setup(NULL, 0)) return false;
+  if (!old_pointer_space_->Setup()) return false;
 
   // Initialize old data space.
   old_data_space_ =
       new OldSpace(this,
                    max_old_generation_size_,
                    OLD_DATA_SPACE,
                    NOT_EXECUTABLE);
   if (old_data_space_ == NULL) return false;
-  if (!old_data_space_->Setup(NULL, 0)) return false;
+  if (!old_data_space_->Setup()) return false;
 
   // Initialize the code space, set its maximum capacity to the old
   // generation size. It needs executable memory.
   // On 64-bit platform(s), we put all code objects in a 2 GB range of
   // virtual address space, so that they can call each other with near calls.
   if (code_range_size_ > 0) {
     if (!isolate_->code_range()->Setup(code_range_size_)) {
       return false;
     }
   }
 
   code_space_ =
       new OldSpace(this, max_old_generation_size_, CODE_SPACE, EXECUTABLE);
   if (code_space_ == NULL) return false;
-  if (!code_space_->Setup(NULL, 0)) return false;
+  if (!code_space_->Setup()) return false;
 
   // Initialize map space.
-  map_space_ = new MapSpace(this, FLAG_use_big_map_space
-      ? max_old_generation_size_
-      : MapSpace::kMaxMapPageIndex * Page::kPageSize,
-      FLAG_max_map_space_pages,
-      MAP_SPACE);
+  map_space_ = new MapSpace(this,
+                            max_old_generation_size_,
+                            FLAG_max_map_space_pages,
+                            MAP_SPACE);
   if (map_space_ == NULL) return false;
-  if (!map_space_->Setup(NULL, 0)) return false;
+  if (!map_space_->Setup()) return false;
 
   // Initialize global property cell space.
   cell_space_ = new CellSpace(this, max_old_generation_size_, CELL_SPACE);
   if (cell_space_ == NULL) return false;
-  if (!cell_space_->Setup(NULL, 0)) return false;
+  if (!cell_space_->Setup()) return false;
 
   // The large object code space may contain code or data.  We set the memory
   // to be non-executable here for safety, but this means we need to enable it
   // explicitly when allocating large code objects.
   lo_space_ = new LargeObjectSpace(this, LO_SPACE);
   if (lo_space_ == NULL) return false;
   if (!lo_space_->Setup()) return false;
-
   if (create_heap_objects) {
     // Create initial maps.
     if (!CreateInitialMaps()) return false;
     if (!CreateApiObjects()) return false;
 
     // Create initial objects
     if (!CreateInitialObjects()) return false;
 
     global_contexts_list_ = undefined_value();
   }
 
   LOG(isolate_, IntPtrTEvent("heap-capacity", Capacity()));
   LOG(isolate_, IntPtrTEvent("heap-available", Available()));
 
+  store_buffer()->Setup();
+
   return true;
 }
 
 
 void Heap::SetStackLimits() {
   ASSERT(isolate_ != NULL);
   ASSERT(isolate_ == isolate());
   // On 64 bit machines, pointers are generally out of range of Smis.  We write
   // something that looks like an out of range Smi to the GC.
 
   // Set up the special root array entries containing the stack limits.
   // These are actually addresses, but the tag makes the GC ignore it.
   roots_[kStackLimitRootIndex] =
       reinterpret_cast<Object*>(
           (isolate_->stack_guard()->jslimit() & ~kSmiTagMask) | kSmiTag);
   roots_[kRealStackLimitRootIndex] =
       reinterpret_cast<Object*>(
           (isolate_->stack_guard()->real_jslimit() & ~kSmiTagMask) | kSmiTag);
 }
 
 
 void Heap::TearDown() {
   if (FLAG_print_cumulative_gc_stat) {
     PrintF("\n\n");
     PrintF("gc_count=%d ", gc_count_);
     PrintF("mark_sweep_count=%d ", ms_count_);
-    PrintF("mark_compact_count=%d ", mc_count_);
     PrintF("max_gc_pause=%d ", get_max_gc_pause());
     PrintF("min_in_mutator=%d ", get_min_in_mutator());
     PrintF("max_alive_after_gc=%" V8_PTR_PREFIX "d ",
            get_max_alive_after_gc());
     PrintF("\n\n");
   }
 
   isolate_->global_handles()->TearDown();
 
   external_string_table_.TearDown();
@@ skipping 29 matching lines @@
     delete cell_space_;
     cell_space_ = NULL;
   }
 
   if (lo_space_ != NULL) {
     lo_space_->TearDown();
     delete lo_space_;
     lo_space_ = NULL;
   }
 
+  store_buffer()->TearDown();
+  incremental_marking()->TearDown();
+
   isolate_->memory_allocator()->TearDown();
 
 #ifdef DEBUG
   delete debug_utils_;
   debug_utils_ = NULL;
 #endif
 }
 
 
 void Heap::Shrink() {
@@ skipping 196 matching lines @@
 }
 
 
 class HeapObjectsFilter {
  public:
   virtual ~HeapObjectsFilter() {}
   virtual bool SkipObject(HeapObject* object) = 0;
 };
 
 
-class FreeListNodesFilter : public HeapObjectsFilter {
- public:
-  FreeListNodesFilter() {
-    MarkFreeListNodes();
-  }
-
-  bool SkipObject(HeapObject* object) {
-    if (object->IsMarked()) {
-      object->ClearMark();
-      return true;
-    } else {
-      return false;
-    }
-  }
-
- private:
-  void MarkFreeListNodes() {
-    Heap* heap = HEAP;
-    heap->old_pointer_space()->MarkFreeListNodes();
-    heap->old_data_space()->MarkFreeListNodes();
-    MarkCodeSpaceFreeListNodes(heap);
-    heap->map_space()->MarkFreeListNodes();
-    heap->cell_space()->MarkFreeListNodes();
-  }
-
-  void MarkCodeSpaceFreeListNodes(Heap* heap) {
-    // For code space, using FreeListNode::IsFreeListNode is OK.
-    HeapObjectIterator iter(heap->code_space());
-    for (HeapObject* obj = iter.next_object();
-         obj != NULL;
-         obj = iter.next_object()) {
-      if (FreeListNode::IsFreeListNode(obj)) obj->SetMark();
-    }
-  }
-
-  AssertNoAllocation no_alloc;
-};
-
-
 class UnreachableObjectsFilter : public HeapObjectsFilter {
  public:
   UnreachableObjectsFilter() {
     MarkUnreachableObjects();
   }
 
   bool SkipObject(HeapObject* object) {
-    if (object->IsMarked()) {
-      object->ClearMark();
+    if (IntrusiveMarking::IsMarked(object)) {
+      IntrusiveMarking::ClearMark(object);
       return true;
     } else {
       return false;
     }
   }
 
  private:
   class UnmarkingVisitor : public ObjectVisitor {
    public:
     UnmarkingVisitor() : list_(10) {}
 
     void VisitPointers(Object** start, Object** end) {
       for (Object** p = start; p < end; p++) {
         if (!(*p)->IsHeapObject()) continue;
         HeapObject* obj = HeapObject::cast(*p);
-        if (obj->IsMarked()) {
-          obj->ClearMark();
+        if (IntrusiveMarking::IsMarked(obj)) {
+          IntrusiveMarking::ClearMark(obj);
           list_.Add(obj);
         }
       }
     }
 
     bool can_process() { return !list_.is_empty(); }
 
     void ProcessNext() {
       HeapObject* obj = list_.RemoveLast();
       obj->Iterate(this);
     }
 
    private:
     List<HeapObject*> list_;
   };
 
   void MarkUnreachableObjects() {
     HeapIterator iterator;
     for (HeapObject* obj = iterator.next();
          obj != NULL;
          obj = iterator.next()) {
-      obj->SetMark();
+      IntrusiveMarking::SetMark(obj);
     }
     UnmarkingVisitor visitor;
     HEAP->IterateRoots(&visitor, VISIT_ALL);
     while (visitor.can_process())
       visitor.ProcessNext();
   }
 
   AssertNoAllocation no_alloc;
 };
 
@@ skipping 13 matching lines @@
 
 
 HeapIterator::~HeapIterator() {
   Shutdown();
 }
 
 
 void HeapIterator::Init() {
   // Start the iteration.
   space_iterator_ = filtering_ == kNoFiltering ? new SpaceIterator :
-      new SpaceIterator(MarkCompactCollector::SizeOfMarkedObject);
+      new SpaceIterator(Isolate::Current()->heap()->
+                        GcSafeSizeOfOldObjectFunction());
   switch (filtering_) {
     case kFilterFreeListNodes:
-      filter_ = new FreeListNodesFilter;
+      // TODO(gc): Not handled.
       break;
     case kFilterUnreachable:
       filter_ = new UnreachableObjectsFilter;
       break;
     default:
       break;
   }
   object_iterator_ = space_iterator_->next();
 }
 
@@ skipping 116 matching lines @@
   MarkVisitor mark_visitor(this);
   MarkRecursively(root, &mark_visitor);
 
   UnmarkVisitor unmark_visitor(this);
   UnmarkRecursively(root, &unmark_visitor);
 
   ProcessResults();
 }
 
 
+static bool SafeIsGlobalContext(HeapObject* obj) {
+  return obj->map() == obj->GetHeap()->raw_unchecked_global_context_map();
+}
+
+
 void PathTracer::MarkRecursively(Object** p, MarkVisitor* mark_visitor) {
   if (!(*p)->IsHeapObject()) return;
 
   HeapObject* obj = HeapObject::cast(*p);
 
   Object* map = obj->map();
 
   if (!map->IsHeapObject()) return;  // visited before
 
   if (found_target_in_trace_) return;  // stop if target found
   object_stack_.Add(obj);
   if (((search_target_ == kAnyGlobalObject) && obj->IsJSGlobalObject()) ||
       (obj == search_target_)) {
     found_target_in_trace_ = true;
     found_target_ = true;
     return;
   }
 
-  bool is_global_context = obj->IsGlobalContext();
+  bool is_global_context = SafeIsGlobalContext(obj);
 
   // not visited yet
   Map* map_p = reinterpret_cast<Map*>(HeapObject::cast(map));
 
   Address map_addr = map_p->address();
 
   obj->set_map(reinterpret_cast<Map*>(map_addr + kMarkTag));
 
   // Scan the object body.
   if (is_global_context && (visit_mode_ == VISIT_ONLY_STRONG)) {
@@ skipping 87 matching lines @@
 }
 #endif
 
 
 static intptr_t CountTotalHolesSize() {
   intptr_t holes_size = 0;
   OldSpaces spaces;
   for (OldSpace* space = spaces.next();
        space != NULL;
        space = spaces.next()) {
-    holes_size += space->Waste() + space->AvailableFree();
+    holes_size += space->Waste() + space->Available();
   }
   return holes_size;
 }
 
 
 GCTracer::GCTracer(Heap* heap)
     : start_time_(0.0),
       start_size_(0),
       gc_count_(0),
       full_gc_count_(0),
-      is_compacting_(false),
-      marked_count_(0),
       allocated_since_last_gc_(0),
       spent_in_mutator_(0),
       promoted_objects_size_(0),
       heap_(heap) {
-  // These two fields reflect the state of the previous full collection.
-  // Set them before they are changed by the collector.
-  previous_has_compacted_ = heap_->mark_compact_collector_.HasCompacted();
-  previous_marked_count_ =
-      heap_->mark_compact_collector_.previous_marked_count();
   if (!FLAG_trace_gc && !FLAG_print_cumulative_gc_stat) return;
   start_time_ = OS::TimeCurrentMillis();
   start_size_ = heap_->SizeOfObjects();
 
   for (int i = 0; i < Scope::kNumberOfScopes; i++) {
     scopes_[i] = 0;
   }
 
   in_free_list_or_wasted_before_gc_ = CountTotalHolesSize();
 
   allocated_since_last_gc_ =
       heap_->SizeOfObjects() - heap_->alive_after_last_gc_;
 
   if (heap_->last_gc_end_timestamp_ > 0) {
     spent_in_mutator_ = Max(start_time_ - heap_->last_gc_end_timestamp_, 0.0);
   }
+
+  steps_count_ = heap_->incremental_marking()->steps_count();
+  steps_took_ = heap_->incremental_marking()->steps_took();
+  longest_step_ = heap_->incremental_marking()->longest_step();
+  steps_count_since_last_gc_ =
+      heap_->incremental_marking()->steps_count_since_last_gc();
+  steps_took_since_last_gc_ =
+      heap_->incremental_marking()->steps_took_since_last_gc();
 }
 
 
 GCTracer::~GCTracer() {
   // Printf ONE line iff flag is set.
   if (!FLAG_trace_gc && !FLAG_print_cumulative_gc_stat) return;
 
   bool first_gc = (heap_->last_gc_end_timestamp_ == 0);
 
   heap_->alive_after_last_gc_ = heap_->SizeOfObjects();
@@ skipping 14 matching lines @@
 
   if (!FLAG_trace_gc_nvp) {
     int external_time = static_cast<int>(scopes_[Scope::EXTERNAL]);
 
     PrintF("%s %.1f -> %.1f MB, ",
            CollectorString(),
            static_cast<double>(start_size_) / MB,
            SizeOfHeapObjects());
 
     if (external_time > 0) PrintF("%d / ", external_time);
-    PrintF("%d ms.\n", time);
+    PrintF("%d ms", time);
+    if (steps_count_ > 0) {
+      if (collector_ == SCAVENGER) {
+        PrintF(" (+ %d ms in %d steps since last GC)",
+               static_cast<int>(steps_took_since_last_gc_),
+               steps_count_since_last_gc_);
+      } else {
+        PrintF(" (+ %d ms in %d steps since start of marking, "
+                   "biggest step %f ms)",
+               static_cast<int>(steps_took_),
+               steps_count_,
+               longest_step_);
+      }
+    }
+    PrintF(".\n");
   } else {
     PrintF("pause=%d ", time);
     PrintF("mutator=%d ",
            static_cast<int>(spent_in_mutator_));
 
     PrintF("gc=");
     switch (collector_) {
       case SCAVENGER:
         PrintF("s");
         break;
       case MARK_COMPACTOR:
-        PrintF("%s",
-               heap_->mark_compact_collector_.HasCompacted() ? "mc" : "ms");
+        PrintF("ms");
         break;
       default:
         UNREACHABLE();
     }
     PrintF(" ");
 
     PrintF("external=%d ", static_cast<int>(scopes_[Scope::EXTERNAL]));
     PrintF("mark=%d ", static_cast<int>(scopes_[Scope::MC_MARK]));
     PrintF("sweep=%d ", static_cast<int>(scopes_[Scope::MC_SWEEP]));
     PrintF("sweepns=%d ", static_cast<int>(scopes_[Scope::MC_SWEEP_NEWSPACE]));
     PrintF("compact=%d ", static_cast<int>(scopes_[Scope::MC_COMPACT]));
 
     PrintF("total_size_before=%" V8_PTR_PREFIX "d ", start_size_);
     PrintF("total_size_after=%" V8_PTR_PREFIX "d ", heap_->SizeOfObjects());
     PrintF("holes_size_before=%" V8_PTR_PREFIX "d ",
            in_free_list_or_wasted_before_gc_);
     PrintF("holes_size_after=%" V8_PTR_PREFIX "d ", CountTotalHolesSize());
 
     PrintF("allocated=%" V8_PTR_PREFIX "d ", allocated_since_last_gc_);
     PrintF("promoted=%" V8_PTR_PREFIX "d ", promoted_objects_size_);
 
+    if (collector_ == SCAVENGER) {
+      PrintF("stepscount=%d ", steps_count_since_last_gc_);
+      PrintF("stepstook=%d ", static_cast<int>(steps_took_since_last_gc_));
+    } else {
+      PrintF("stepscount=%d ", steps_count_);
+      PrintF("stepstook=%d ", static_cast<int>(steps_took_));
+    }
+
     PrintF("\n");
   }
 
   heap_->PrintShortHeapStatistics();
 }
 
 
 const char* GCTracer::CollectorString() {
   switch (collector_) {
     case SCAVENGER:
       return "Scavenge";
     case MARK_COMPACTOR:
-      return heap_->mark_compact_collector_.HasCompacted() ? "Mark-compact"
-                                                           : "Mark-sweep";
+      return "Mark-sweep";
   }
   return "Unknown GC";
 }
 
 
 int KeyedLookupCache::Hash(Map* map, String* name) {
   // Uses only lower 32 bits if pointers are larger.
   uintptr_t addr_hash =
       static_cast<uint32_t>(reinterpret_cast<uintptr_t>(map)) >> kMapHashShift;
   return static_cast<uint32_t>((addr_hash ^ name->Hash()) & kCapacityMask);
@@ skipping 86 matching lines @@
   Verify();
 }
 
 
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
+void Heap::QueueMemoryChunkForFree(MemoryChunk* chunk) {
+  chunk->set_next_chunk(chunks_queued_for_free_);
+  chunks_queued_for_free_ = chunk;
+}
+
+
+void Heap::FreeQueuedChunks() {
+  if (chunks_queued_for_free_ == NULL) return;
+  MemoryChunk* next;
+  MemoryChunk* chunk;
+  for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
+    next = chunk->next_chunk();
+    chunk->SetFlag(MemoryChunk::ABOUT_TO_BE_FREED);
+
+    if (chunk->owner()->identity() == LO_SPACE) {
+      // StoreBuffer::Filter relies on MemoryChunk::FromAnyPointerAddress.
+      // If FromAnyPointerAddress encounters a slot that belongs to a large
+      // chunk queued for deletion it will fail to find the chunk because
+      // it try to perform a search in the list of pages owned by of the large
+      // object space and queued chunks were detached from that list.
+      // To work around this we split large chunk into normal kPageSize aligned
+      // pieces and initialize owner field and flags of every piece.
+      // If FromAnyPointerAddress encounteres a slot that belongs to one of
+      // these smaller pieces it will treat it as a slot on a normal Page.
+      MemoryChunk* inner = MemoryChunk::FromAddress(
+          chunk->address() + Page::kPageSize);
+      MemoryChunk* inner_last = MemoryChunk::FromAddress(
+          chunk->address() + chunk->size() - 1);
+      while (inner <= inner_last) {
+        // Size of a large chunk is always a multiple of
+        // OS::AllocationAlignment() so there is always
+        // enough space for a fake MemoryChunk header.
+        inner->set_owner(lo_space());
+        inner->SetFlag(MemoryChunk::ABOUT_TO_BE_FREED);
+        inner = MemoryChunk::FromAddress(
+            inner->address() + Page::kPageSize);
+      }
+    }
+  }
+  isolate_->heap()->store_buffer()->Filter(MemoryChunk::ABOUT_TO_BE_FREED);
+  for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
+    next = chunk->next_chunk();
+    isolate_->memory_allocator()->Free(chunk);
+  }
+  chunks_queued_for_free_ = NULL;
+}
+
 } }  // namespace v8::internal