Unify object groups iteration in global handles.

This unifies the iteration logic of objects groups iteration in global
handles. The scavenger as well as mark-and-compact now rely on the same
underlying logic.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/11299248

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13128 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/global-handles.cc

@@ -551,6 +551,51 @@ void GlobalHandles::IterateNewSpaceWeakIndependentRoots(ObjectVisitor* v) {
 }
 
 
+bool GlobalHandles::IterateObjectGroups(ObjectVisitor* v,
+                                        WeakSlotCallbackWithHeap can_skip) {
+  int last = 0;
+  bool any_group_was_visited = false;
+  for (int i = 0; i < object_groups_.length(); i++) {
+    ObjectGroup* entry = object_groups_.at(i);
+    ASSERT(entry != NULL);
+
+    Object*** objects = entry->objects_;
+    bool group_should_be_visited = false;
+    for (size_t j = 0; j < entry->length_; j++) {
+      Object* object = *objects[j];
+      if (object->IsHeapObject()) {
+        if (!can_skip(isolate_->heap(), &object)) {
+          group_should_be_visited = true;
+          break;
+        }
+      }
+    }
+
+    if (!group_should_be_visited) {
+      object_groups_[last++] = entry;
+      continue;
+    }
+
+    // An object in the group requires visiting, so iterate over all
+    // objects in the group.
+    for (size_t j = 0; j < entry->length_; ++j) {
+      Object* object = *objects[j];
+      if (object->IsHeapObject()) {
+        v->VisitPointer(&object);
+        any_group_was_visited = true;
+      }
+    }
+
+    // Once the entire group has been iterated over, set the object
+    // group to NULL so it won't be processed again.
+    entry->Dispose();
+    object_groups_.at(i) = NULL;
+  }
+  object_groups_.Rewind(last);
+  return any_group_was_visited;
+}
+
+
 bool GlobalHandles::PostGarbageCollectionProcessing(
     GarbageCollector collector) {
   // Process weak global handle callbacks. This must be done after the

src/global-handles.h

@@ -206,6 +206,11 @@ class GlobalHandles {
   // See the note above.
   void IterateNewSpaceWeakIndependentRoots(ObjectVisitor* v);
 
+  // Iterate over objects in object groups that have at least one object
+  // which requires visiting. The callback has to return true if objects
+  // can be skipped and false otherwise.
+  bool IterateObjectGroups(ObjectVisitor* v, WeakSlotCallbackWithHeap can_skip);
+
   // Add an object group.
   // Should be only used in GC callback function before a collection.
   // All groups are destroyed after a garbage collection.

src/heap.cc

@@ -1338,7 +1338,8 @@ void Heap::Scavenge() {
 
   new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
 
-  while (IterateObjectGroups(&scavenge_visitor)) {
+  while (isolate()->global_handles()->IterateObjectGroups(
+      &scavenge_visitor, &IsUnscavengedHeapObject)) {
     new_space_front = DoScavenge(&scavenge_visitor, new_space_front);
   }
   isolate()->global_handles()->RemoveObjectGroups();
@@ -1383,51 +1384,6 @@ void Heap::Scavenge() {
 }
 
 
-// TODO(mstarzinger): Unify this method with
-// MarkCompactCollector::MarkObjectGroups().
-bool Heap::IterateObjectGroups(ObjectVisitor* scavenge_visitor) {
-  List<ObjectGroup*>* object_groups =
-    isolate()->global_handles()->object_groups();
-
-  int last = 0;
-  bool changed = false;
-  for (int i = 0; i < object_groups->length(); i++) {
-    ObjectGroup* entry = object_groups->at(i);
-    ASSERT(entry != NULL);
-
-    Object*** objects = entry->objects_;
-    bool group_marked = false;
-    for (size_t j = 0; j < entry->length_; j++) {
-      Object* object = *objects[j];
-      if (object->IsHeapObject()) {
-        if (!IsUnscavengedHeapObject(this, &object)) {
-          group_marked = true;
-          break;
-        }
-      }
-    }
-
-    if (!group_marked) {
-      (*object_groups)[last++] = entry;
-      continue;
-    }
-
-    for (size_t j = 0; j < entry->length_; ++j) {
-      Object* object = *objects[j];
-      if (object->IsHeapObject()) {
-        scavenge_visitor->VisitPointer(&object);
-        changed = true;
-      }
-    }
-
-    entry->Dispose();
-    object_groups->at(i) = NULL;
-  }
-  object_groups->Rewind(last);
-  return changed;
-}
-
-
 String* Heap::UpdateNewSpaceReferenceInExternalStringTableEntry(Heap* heap,
                                                                 Object** p) {
   MapWord first_word = HeapObject::cast(*p)->map_word();

src/heap.h

@@ -1901,8 +1901,6 @@ class Heap {
   bool PerformGarbageCollection(GarbageCollector collector,
                                 GCTracer* tracer);
 
-  bool IterateObjectGroups(ObjectVisitor* scavenge_visitor);
-
   inline void UpdateOldSpaceLimits();
 
   // Allocate an uninitialized object in map space.  The behavior is identical

src/mark-compact.cc

@@ -1745,6 +1745,16 @@ bool MarkCompactCollector::IsUnmarkedHeapObject(Object** p) {
 }
 
 
+bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
+                                                        Object** p) {
+  Object* o = *p;
+  ASSERT(o->IsHeapObject());
+  HeapObject* heap_object = HeapObject::cast(o);
+  MarkBit mark = Marking::MarkBitFrom(heap_object);
+  return !mark.Get();
+}
+
+
 void MarkCompactCollector::MarkSymbolTable() {
   SymbolTable* symbol_table = heap()->symbol_table();
   // Mark the symbol table itself.
@@ -1773,54 +1783,6 @@ void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
 }
 
 
-void MarkCompactCollector::MarkObjectGroups() {
-  List<ObjectGroup*>* object_groups =
-      heap()->isolate()->global_handles()->object_groups();
-
-  int last = 0;
-  for (int i = 0; i < object_groups->length(); i++) {
-    ObjectGroup* entry = object_groups->at(i);
-    ASSERT(entry != NULL);
-
-    Object*** objects = entry->objects_;
-    bool group_marked = false;
-    for (size_t j = 0; j < entry->length_; j++) {
-      Object* object = *objects[j];
-      if (object->IsHeapObject()) {
-        HeapObject* heap_object = HeapObject::cast(object);
-        MarkBit mark = Marking::MarkBitFrom(heap_object);
-        if (mark.Get()) {
-          group_marked = true;
-          break;
-        }
-      }
-    }
-
-    if (!group_marked) {
-      (*object_groups)[last++] = entry;
-      continue;
-    }
-
-    // An object in the group is marked, so mark as grey all white heap
-    // objects in the group.
-    for (size_t j = 0; j < entry->length_; ++j) {
-      Object* object = *objects[j];
-      if (object->IsHeapObject()) {
-        HeapObject* heap_object = HeapObject::cast(object);
-        MarkBit mark = Marking::MarkBitFrom(heap_object);
-        MarkObject(heap_object, mark);
-      }
-    }
-
-    // Once the entire group has been colored grey, set the object group
-    // to NULL so it won't be processed again.
-    entry->Dispose();
-    object_groups->at(i) = NULL;
-  }
-  object_groups->Rewind(last);
-}
-
-
 void MarkCompactCollector::MarkImplicitRefGroups() {
   List<ImplicitRefGroup*>* ref_groups =
       heap()->isolate()->global_handles()->implicit_ref_groups();
@@ -1939,11 +1901,12 @@ void MarkCompactCollector::ProcessMarkingDeque() {
 }
 
 
-void MarkCompactCollector::ProcessExternalMarking() {
+void MarkCompactCollector::ProcessExternalMarking(RootMarkingVisitor* visitor) {
   bool work_to_do = true;
   ASSERT(marking_deque_.IsEmpty());
   while (work_to_do) {
-    MarkObjectGroups();
+    heap()->isolate()->global_handles()->IterateObjectGroups(
+        visitor, &IsUnmarkedHeapObjectWithHeap);
     MarkImplicitRefGroups();
     work_to_do = !marking_deque_.IsEmpty();
     ProcessMarkingDeque();
@@ -2022,7 +1985,7 @@ void MarkCompactCollector::MarkLiveObjects() {
   // The objects reachable from the roots are marked, yet unreachable
   // objects are unmarked.  Mark objects reachable due to host
   // application specific logic.
-  ProcessExternalMarking();
+  ProcessExternalMarking(&root_visitor);
 
   // The objects reachable from the roots or object groups are marked,
   // yet unreachable objects are unmarked.  Mark objects reachable
@@ -2041,7 +2004,7 @@ void MarkCompactCollector::MarkLiveObjects() {
 
   // Repeat host application specific marking to mark unmarked objects
   // reachable from the weak roots.
-  ProcessExternalMarking();
+  ProcessExternalMarking(&root_visitor);
 
   AfterMarking();
 }

src/mark-compact.h

@@ -756,17 +756,13 @@ class MarkCompactCollector {
   // symbol table are weak.
   void MarkSymbolTable();
 
-  // Mark objects in object groups that have at least one object in the
-  // group marked.
-  void MarkObjectGroups();
-
   // Mark objects in implicit references groups if their parent object
   // is marked.
   void MarkImplicitRefGroups();
 
   // Mark all objects which are reachable due to host application
   // logic like object groups or implicit references' groups.
-  void ProcessExternalMarking();
+  void ProcessExternalMarking(RootMarkingVisitor* visitor);
 
   // Mark objects reachable (transitively) from objects in the marking stack
   // or overflowed in the heap.
@@ -790,6 +786,7 @@ class MarkCompactCollector {
   // Callback function for telling whether the object *p is an unmarked
   // heap object.
   static bool IsUnmarkedHeapObject(Object** p);
+  static bool IsUnmarkedHeapObjectWithHeap(Heap* heap, Object** p);
 
   // Map transitions from a live map to a dead map must be killed.
   // We replace them with a null descriptor, with the same key.