Update gc branch to bleeding_edge revision 8862.

src/mark-compact.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 55 matching lines @@
       live_young_objects_size_(0),
       live_old_pointer_objects_size_(0),
       live_old_data_objects_size_(0),
       live_code_objects_size_(0),
       live_map_objects_size_(0),
       live_cell_objects_size_(0),
       live_lo_objects_size_(0),
       live_bytes_(0),
 #endif
       heap_(NULL),
-      code_flusher_(NULL) { }
+      code_flusher_(NULL),
+      encountered_weak_maps_(NULL) { }
 
 
 #ifdef DEBUG
 class VerifyMarkingVisitor: public ObjectVisitor {
  public:
   void VisitPointers(Object** start, Object** end) {
     for (Object** current = start; current < end; current++) {
       if ((*current)->IsHeapObject()) {
         HeapObject* object = HeapObject::cast(*current);
         ASSERT(HEAP->mark_compact_collector()->IsMarked(object));
@@ skipping 157 matching lines @@
   }
 
   return compacting_;
 }
 
 
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
   ASSERT(state_ == PREPARE_GC);
+  ASSERT(encountered_weak_maps_ == Smi::FromInt(0));
 
   MarkLiveObjects();
   ASSERT(heap_->incremental_marking()->IsStopped());
 
   if (collect_maps_) ClearNonLiveTransitions();
 
+  ClearWeakMaps();
+
 #ifdef DEBUG
   if (FLAG_verify_heap) {
     VerifyMarking(heap_);
   }
 #endif
 
   SweepSpaces();
 
   if (!collect_maps_) ReattachInitialMaps();
 
@@ skipping 414 matching lines @@
 
     table_.Register(kVisitGlobalContext, &VisitGlobalContext);
 
     table_.Register(kVisitFixedDoubleArray, DataObjectVisitor::Visit);
 
     table_.Register(kVisitByteArray, &DataObjectVisitor::Visit);
     table_.Register(kVisitFreeSpace, &DataObjectVisitor::Visit);
     table_.Register(kVisitSeqAsciiString, &DataObjectVisitor::Visit);
     table_.Register(kVisitSeqTwoByteString, &DataObjectVisitor::Visit);
 
+    table_.Register(kVisitJSWeakMap, &VisitJSWeakMap);
+
     table_.Register(kVisitOddball,
                     &FixedBodyVisitor<StaticMarkingVisitor,
                                       Oddball::BodyDescriptor,
                                       void>::Visit);
     table_.Register(kVisitMap,
                     &FixedBodyVisitor<StaticMarkingVisitor,
                                       Map::BodyDescriptor,
                                       void>::Visit);
 
     table_.Register(kVisitCode, &VisitCode);
@@ skipping 143 matching lines @@
   };
 
   typedef FlexibleBodyVisitor<StaticMarkingVisitor,
                               JSObject::BodyDescriptor,
                               void> JSObjectVisitor;
 
   typedef FlexibleBodyVisitor<StaticMarkingVisitor,
                               StructBodyDescriptor,
                               void> StructObjectVisitor;
 
+  static void VisitJSWeakMap(Map* map, HeapObject* object) {
+    MarkCompactCollector* collector = map->GetHeap()->mark_compact_collector();
+    JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(object);
+
+    // Enqueue weak map in linked list of encountered weak maps.
+    ASSERT(weak_map->next() == Smi::FromInt(0));
+    weak_map->set_next(collector->encountered_weak_maps());
+    collector->set_encountered_weak_maps(weak_map);
+
+    // Skip visiting the backing hash table containing the mappings.
+    int object_size = JSWeakMap::BodyDescriptor::SizeOf(map, object);
+    BodyVisitorBase<StaticMarkingVisitor>::IteratePointers(
+        map->GetHeap(),
+        object,
+        JSWeakMap::BodyDescriptor::kStartOffset,
+        JSWeakMap::kTableOffset);
+    BodyVisitorBase<StaticMarkingVisitor>::IteratePointers(
+        map->GetHeap(),
+        object,
+        JSWeakMap::kTableOffset + kPointerSize,
+        object_size);
+
+    // Mark the backing hash table without pushing it on the marking stack.
+    ASSERT(!MarkCompactCollector::IsMarked(weak_map->unchecked_table()));
+    ASSERT(MarkCompactCollector::IsMarked(weak_map->unchecked_table()->map()));
+
+    HeapObject* unchecked_table = weak_map->unchecked_table();
+    MarkBit mark_bit = Marking::MarkBitFrom(unchecked_table);
+    collector->SetMark(unchecked_table, mark_bit);
+  }
+
   static void VisitCode(Map* map, HeapObject* object) {
     reinterpret_cast<Code*>(object)->CodeIterateBody<StaticMarkingVisitor>(
         map->GetHeap());
   }
 
   // Code flushing support.
 
   // How many collections newly compiled code object will survive before being
   // flushed.
   static const int kCodeAgeThreshold = 5;
@@ skipping 893 matching lines @@
   ref_groups->Rewind(last);
 }
 
 
 // Mark all objects reachable from the objects on the marking stack.
 // Before: the marking stack contains zero or more heap object pointers.
 // After: the marking stack is empty, and all objects reachable from the
 // marking stack have been marked, or are overflowed in the heap.
 void MarkCompactCollector::EmptyMarkingDeque() {
   while (!marking_deque_.IsEmpty()) {
-    HeapObject* object = marking_deque_.Pop();
-    ASSERT(object->IsHeapObject());
-    ASSERT(heap()->Contains(object));
-    ASSERT(Marking::IsBlack(Marking::MarkBitFrom(object)));
+    while (!marking_deque_.IsEmpty()) {
+      HeapObject* object = marking_deque_.Pop();
+      ASSERT(object->IsHeapObject());
+      ASSERT(heap()->Contains(object));
+      ASSERT(Marking::IsBlack(Marking::MarkBitFrom(object)));
 
-    Map* map = object->map();
-    MarkBit map_mark = Marking::MarkBitFrom(map);
-    MarkObject(map, map_mark);
+      Map* map = object->map();
+      MarkBit map_mark = Marking::MarkBitFrom(map);
+      MarkObject(map, map_mark);
 
-    StaticMarkingVisitor::IterateBody(map, object);
+      StaticMarkingVisitor::IterateBody(map, object);
+    }
+
+    // Process encountered weak maps, mark objects only reachable by those
+    // weak maps and repeat until fix-point is reached.
+    ProcessWeakMaps();
   }
 }
 
 
 // Sweep the heap for overflowed objects, clear their overflow bits, and
 // push them on the marking stack.  Stop early if the marking stack fills
 // before sweeping completes.  If sweeping completes, there are no remaining
 // overflowed objects in the heap so the overflow flag on the markings stack
 // is cleared.
 void MarkCompactCollector::RefillMarkingDeque() {
@@ skipping 381 matching lines @@
       if (is_alive) {
         Object** slot = HeapObject::RawField(current, Map::kPrototypeOffset);
         RecordSlot(slot, slot, real_prototype);
       }
       current = reinterpret_cast<Map*>(next);
     }
   }
 }
 
 
+void MarkCompactCollector::ProcessWeakMaps() {
+  Object* weak_map_obj = encountered_weak_maps();
+  while (weak_map_obj != Smi::FromInt(0)) {
+    ASSERT(MarkCompactCollector::IsMarked(HeapObject::cast(weak_map_obj)));
+    JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj);
+    ObjectHashTable* table = weak_map->unchecked_table();
+    for (int i = 0; i < table->Capacity(); i++) {
+      if (MarkCompactCollector::IsMarked(HeapObject::cast(table->KeyAt(i)))) {
+        Object* value = table->get(table->EntryToValueIndex(i));
+        StaticMarkingVisitor::VisitPointer(heap(), &value);
+        table->set_unchecked(heap(),
+                             table->EntryToValueIndex(i),
+                             value,
+                             UPDATE_WRITE_BARRIER);
+      }
+    }
+    weak_map_obj = weak_map->next();
+  }
+}
+
+
+void MarkCompactCollector::ClearWeakMaps() {
+  Object* weak_map_obj = encountered_weak_maps();
+  while (weak_map_obj != Smi::FromInt(0)) {
+    ASSERT(MarkCompactCollector::IsMarked(HeapObject::cast(weak_map_obj)));
+    JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj);
+    ObjectHashTable* table = weak_map->unchecked_table();
+    for (int i = 0; i < table->Capacity(); i++) {
+      if (!MarkCompactCollector::IsMarked(HeapObject::cast(table->KeyAt(i)))) {
+        table->RemoveEntry(i, heap());
+      }
+    }
+    weak_map_obj = weak_map->next();
+    weak_map->set_next(Smi::FromInt(0));
+  }
+  set_encountered_weak_maps(Smi::FromInt(0));
+}
+
+
 // We scavange new space simultaneously with sweeping. This is done in two
 // passes.
 //
 // The first pass migrates all alive objects from one semispace to another or
 // promotes them to old space.  Forwarding address is written directly into
 // first word of object without any encoding.  If object is dead we write
 // NULL as a forwarding address.
 //
 // The second pass updates pointers to new space in all spaces.  It is possible
 // to encounter pointers to dead new space objects during traversal of pointers
@@ skipping 1154 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal