Allow partial scanning of large arrays in order to avoid

src/objects-visiting-inl.h

 // Copyright 2012 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 244 matching lines @@
   }
 
   // When map collection is enabled we have to mark through map's
   // transitions and back pointers in a special way to make these links
   // weak.  Only maps for subclasses of JSReceiver can have transitions.
   STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE);
   if (FLAG_collect_maps &&
       map_object->instance_type() >= FIRST_JS_RECEIVER_TYPE) {
     MarkMapContents(heap, map_object);
   } else {
-    StaticVisitor::VisitPointers(heap,
-        HeapObject::RawField(object, Map::kPointerFieldsBeginOffset),
-        HeapObject::RawField(object, Map::kPointerFieldsEndOffset));
+    Object** start_slot =
+        HeapObject::RawField(object, Map::kPointerFieldsBeginOffset);
+    Object** end_slot =
+        HeapObject::RawField(object, Map::kPointerFieldsEndOffset);
+    StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
   }
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitCode(
     Map* map, HeapObject* object) {
   Heap* heap = map->GetHeap();
   Code* code = Code::cast(object);
   if (FLAG_cleanup_code_caches_at_gc) {
     code->ClearTypeFeedbackCells(heap);
   }
   code->CodeIterateBody<StaticVisitor>(heap);
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitJSRegExp(
     Map* map, HeapObject* object) {
   int last_property_offset =
       JSRegExp::kSize + kPointerSize * map->inobject_properties();
-  StaticVisitor::VisitPointers(map->GetHeap(),
-      HeapObject::RawField(object, JSRegExp::kPropertiesOffset),
-      HeapObject::RawField(object, last_property_offset));
+  Object** start_slot =
+      HeapObject::RawField(object, JSRegExp::kPropertiesOffset);
+  Object** end_slot =
+      HeapObject::RawField(object, last_property_offset);
+  StaticVisitor::VisitPointers(
+      map->GetHeap(), start_slot, start_slot, end_slot);
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::MarkMapContents(
     Heap* heap, Map* map) {
   // Make sure that the back pointer stored either in the map itself or
   // inside its transitions array is marked. Skip recording the back
   // pointer slot since map space is not compacted.
   StaticVisitor::MarkObject(heap, HeapObject::cast(map->GetBackPointer()));
 
   // Treat pointers in the transitions array as weak and also mark that
   // array to prevent visiting it later. Skip recording the transition
   // array slot, since it will be implicitly recorded when the pointer
   // fields of this map are visited.
   TransitionArray* transitions = map->unchecked_transition_array();
   if (transitions->IsTransitionArray()) {
     MarkTransitionArray(heap, transitions);
   } else {
     // Already marked by marking map->GetBackPointer() above.
     ASSERT(transitions->IsMap() || transitions->IsUndefined());
   }
 
   // Mark the pointer fields of the Map. Since the transitions array has
   // been marked already, it is fine that one of these fields contains a
   // pointer to it.
-  StaticVisitor::VisitPointers(heap,
-      HeapObject::RawField(map, Map::kPointerFieldsBeginOffset),
-      HeapObject::RawField(map, Map::kPointerFieldsEndOffset));
+  Object** start_slot =
+      HeapObject::RawField(map, Map::kPointerFieldsBeginOffset);
+  Object** end_slot =
+      HeapObject::RawField(map, Map::kPointerFieldsEndOffset);
+  StaticVisitor::VisitPointers(heap, start_slot, start_slot, end_slot);
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::MarkTransitionArray(
     Heap* heap, TransitionArray* transitions) {
   if (!StaticVisitor::MarkObjectWithoutPush(heap, transitions)) return;
 
   // Skip recording the descriptors_pointer slot since the cell space
   // is not compacted and descriptors are referenced through a cell.
@@ skipping 69 matching lines @@
   RelocIterator it(this, mode_mask);
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>(heap);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_INL_H_