Introduce one way dependencies into object grouping.

test/cctest/test-mark-compact.cc

 // Copyright 2006-2008 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 280 matching lines @@
   CHECK_EQ(gc_ends, gc_starts);
 
   Heap::CollectGarbage(OLD_POINTER_SPACE);
   CHECK_EQ(1, gc_starts);
   CHECK_EQ(gc_ends, gc_starts);
 }
 
 
 static int NumberOfWeakCalls = 0;
 static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
+  ASSERT(id == reinterpret_cast<void*>(1234));
   NumberOfWeakCalls++;
   handle.Dispose();
 }
 
 TEST(ObjectGroups) {
   InitializeVM();
 
   NumberOfWeakCalls = 0;
   v8::HandleScope handle_scope;
 
   Handle<Object> g1s1 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1)->ToObjectChecked());
   Handle<Object> g1s2 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1)->ToObjectChecked());
+  Handle<Object> g1c1 =
+    GlobalHandles::Create(Heap::AllocateFixedArray(1)->ToObjectChecked());
   GlobalHandles::MakeWeak(g1s1.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
   GlobalHandles::MakeWeak(g1s2.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
+  GlobalHandles::MakeWeak(g1c1.location(),
+                          reinterpret_cast<void*>(1234),
+                          &WeakPointerCallback);
 
   Handle<Object> g2s1 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1)->ToObjectChecked());
   Handle<Object> g2s2 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1)->ToObjectChecked());
+  Handle<Object> g2c1 =
+    GlobalHandles::Create(Heap::AllocateFixedArray(1)->ToObjectChecked());
   GlobalHandles::MakeWeak(g2s1.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
   GlobalHandles::MakeWeak(g2s2.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
+  GlobalHandles::MakeWeak(g2c1.location(),
+                          reinterpret_cast<void*>(1234),
+                          &WeakPointerCallback);
 
   Handle<Object> root = GlobalHandles::Create(*g1s1);  // make a root.
 
   // Connect group 1 and 2, make a cycle.
   Handle<FixedArray>::cast(g1s2)->set(0, *g2s2);
   Handle<FixedArray>::cast(g2s1)->set(0, *g1s1);
 
   {
     Object** g1_objects[] = { g1s1.location(), g1s2.location() };
+    Object** g1_children[] = { g1c1.location() };
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
-    GlobalHandles::AddGroup(g1_objects, 2, NULL);
-    GlobalHandles::AddGroup(g2_objects, 2, NULL);
+    Object** g2_children[] = { g2c1.location() };
+    GlobalHandles::AddObjectGroup(g1_objects, 2, NULL);
+    GlobalHandles::AddImplicitReferences(HeapObject::cast(*g1s1),
+                                         g1_children, 1);
+    GlobalHandles::AddObjectGroup(g2_objects, 2, NULL);
+    GlobalHandles::AddImplicitReferences(HeapObject::cast(*g2s2),
+                                         g2_children, 1);
   }
   // Do a full GC
   Heap::CollectGarbage(OLD_POINTER_SPACE);
 
   // All object should be alive.
   CHECK_EQ(0, NumberOfWeakCalls);
 
   // Weaken the root.
   GlobalHandles::MakeWeak(root.location(),
                           reinterpret_cast<void*>(1234),
                           &WeakPointerCallback);
+  // But make children strong roots---all the objects (except for children)
+  // should be collectable now.
+  GlobalHandles::ClearWeakness(g1c1.location());
+  GlobalHandles::ClearWeakness(g2c1.location());
 
   // Groups are deleted, rebuild groups.
   {
     Object** g1_objects[] = { g1s1.location(), g1s2.location() };
+    Object** g1_children[] = { g1c1.location() };
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
-    GlobalHandles::AddGroup(g1_objects, 2, NULL);
-    GlobalHandles::AddGroup(g2_objects, 2, NULL);
+    Object** g2_children[] = { g2c1.location() };
+    GlobalHandles::AddObjectGroup(g1_objects, 2, NULL);
+    GlobalHandles::AddImplicitReferences(HeapObject::cast(*g1s1),
+                                         g1_children, 1);
+    GlobalHandles::AddObjectGroup(g2_objects, 2, NULL);
+    GlobalHandles::AddImplicitReferences(HeapObject::cast(*g2s2),
+                                         g2_children, 1);
   }
 
   Heap::CollectGarbage(OLD_POINTER_SPACE);
 
   // All objects should be gone. 5 global handles in total.
   CHECK_EQ(5, NumberOfWeakCalls);
+
+  // And now make children weak again and collect them.
+  GlobalHandles::MakeWeak(g1c1.location(),
+                          reinterpret_cast<void*>(1234),
+                          &WeakPointerCallback);
+  GlobalHandles::MakeWeak(g2c1.location(),
+                          reinterpret_cast<void*>(1234),
+                          &WeakPointerCallback);
+
+  Heap::CollectGarbage(OLD_POINTER_SPACE);
+  CHECK_EQ(7, NumberOfWeakCalls);
 }