[WIP] New GC related APIs.

src/global-handles.cc

 // Copyright 2009 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 "api.h"
 #include "global-handles.h"
 
 #include "vm-state-inl.h"
 
 namespace v8 {
 namespace internal {
 
 
-ObjectGroup::~ObjectGroup() {
-  if (info_ != NULL) info_->Dispose();
-}
-
-
 class GlobalHandles::Node {
  public:
   // State transition diagram:
   // FREE -> NORMAL <-> WEAK -> PENDING -> NEAR_DEATH -> { NORMAL, WEAK, FREE }
   enum State {
     FREE = 0,
     NORMAL,     // Normal global handle.
     WEAK,       // Flagged as weak but not yet finalized.
     PENDING,    // Has been recognized as only reachable by weak handles.
     NEAR_DEATH  // Callback has informed the handle is near death.
@@ skipping 517 matching lines @@
     if ((node->is_independent() || node->is_partially_dependent()) &&
         node->IsWeakRetainer()) {
       v->VisitPointer(node->location());
     }
   }
 }
 
 
 bool GlobalHandles::IterateObjectGroups(ObjectVisitor* v,
                                         WeakSlotCallbackWithHeap can_skip) {
-  int last = 0;
+  if (object_groups_.length() == 0)
+    return false;
+
+  object_groups_.Sort();

[Michael Starzinger, 2013/04/10 10:54:16]

Isn't there a sort call to the retained_object_infos list missing here?

[marja, 2013/04/10 13:14:51]

Yes! Thanks for pointing that out.

+
+  // During the iteration, some of the elements of object_groups are
+  // deleted. This is done by moving surviving elements at the front of the list
+  // and deleting from the end. This index tracks where the next surviving
+  // element should be moved.
+  int surviving_element_ix = 0;

[Michael Starzinger, 2013/04/10 10:54:16]

nit: Can we spell out the "index" in these variables?

[marja, 2013/04/10 13:14:51]

Done.

+  int info_ix = 0; // For iterating retained_object_infos_.
+  int surviving_info_ix = 0;
+
+  UniqueId current_group_id;
+  size_t current_group_start = 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;
+  for (int i = 0; i <= object_groups_.length(); ++i) {
+    if (i == 0)
+      current_group_id = object_groups_[i].id;
+    if (i == object_groups_.length() ||
+        current_group_id != object_groups_[i].id) {
+      // Group detected: objects in indices [current_group_start, i[.
+      bool group_should_be_visited = false;
+      for (int j = current_group_start; j < i; ++j) {
+        Object* object = *(object_groups_[j].object);
+        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;
+      if (!group_should_be_visited) {

[Michael Starzinger, 2013/04/10 10:54:16]

nit: Can we add an empty newline in front of this if, IMHO that makes all of
this easier to read.

[marja, 2013/04/10 13:14:51]

Done.

+        for (int j = current_group_start; j < i; ++j)
+          object_groups_[surviving_element_ix++] = object_groups_[j];
+      } else {
+        // An object in the group requires visiting, so iterate over all
+        // objects in the group.
+        for (int j = current_group_start; j < i; ++j) {
+          Object* object = *(object_groups_[j].object);
+          if (object->IsHeapObject()) {
+            v->VisitPointer(&object);
+            any_group_was_visited = true;
+          }
+        }
+      }
+      if (info_ix < retained_object_infos_.length() &&

[Michael Starzinger, 2013/04/10 10:54:16]

Likewise for this if.

[marja, 2013/04/10 13:14:51]

Done.

+          retained_object_infos_[info_ix].id ==
+          object_groups_[current_group_start].id) {
+        // This object group has an associated GroupRetainedObjectInfo.
+        if (!group_should_be_visited) {
+          retained_object_infos_[surviving_info_ix++] =
+              retained_object_infos_[info_ix];
+        } else if (retained_object_infos_[info_ix].info != NULL) {
+          retained_object_infos_[info_ix].info->Dispose();
+          retained_object_infos_[info_ix].info = NULL;
+        }
+        ++info_ix;
+      }
+      if (i < object_groups_.length()) {
+        current_group_id = object_groups_[i].id;
+        current_group_start = i;
       }
     }
-
-    // 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);
+  object_groups_.Rewind(surviving_element_ix);
+  retained_object_infos_.Rewind(surviving_info_ix);
   return any_group_was_visited;
 }
 
 
 bool GlobalHandles::PostGarbageCollectionProcessing(
     GarbageCollector collector, GCTracer* tracer) {
   // Process weak global handle callbacks. This must be done after the
   // GC is completely done, because the callbacks may invoke arbitrary
   // API functions.
   ASSERT(isolate_->heap()->gc_state() == Heap::NOT_IN_GC);
@@ skipping 187 matching lines @@
                                    v8::RetainedObjectInfo* info) {
 #ifdef DEBUG
   for (size_t i = 0; i < length; ++i) {
     ASSERT(!Node::FromLocation(handles[i])->is_independent());
   }
 #endif
   if (length == 0) {
     if (info != NULL) info->Dispose();
     return;
   }
-  object_groups_.Add(ObjectGroup::New(handles, length, info));
+  for (size_t i = 0; i < length; ++i) {
+    object_groups_.Add(
+        ObjectGroupConnection(UniqueId((intptr_t)handles[0]), handles[i]));

[Michael Starzinger, 2013/04/10 10:54:16]

nit: Use "static_cast<intptr_t>" instead of the C-style cast.

[marja, 2013/04/10 13:14:51]

Done.

+  }
+  retained_object_infos_.Add(
+      GroupRetainedObjectInfo(UniqueId((intptr_t)handles[0]), info));

[Michael Starzinger, 2013/04/10 10:54:16]

Likewise.

[marja, 2013/04/10 13:14:51]

Done.

 }
 
 
+void GlobalHandles::SetObjectGroupId(Object** handle,
+                                     UniqueId id) {
+  object_groups_.Add(ObjectGroupConnection(id, handle));
+}
+
+
+void GlobalHandles::SetRetainedObjectInfo(UniqueId id,
+                                          RetainedObjectInfo* info) {
+  retained_object_infos_.Add(GroupRetainedObjectInfo(id, info));
+}
+
+
 void GlobalHandles::AddImplicitReferences(HeapObject** parent,
                                           Object*** children,
                                           size_t length) {
 #ifdef DEBUG
   ASSERT(!Node::FromLocation(BitCast<Object**>(parent))->is_independent());
   for (size_t i = 0; i < length; ++i) {
     ASSERT(!Node::FromLocation(children[i])->is_independent());
   }
 #endif
   if (length == 0) return;
   implicit_ref_groups_.Add(ImplicitRefGroup::New(parent, children, length));
 }
 
 
 void GlobalHandles::RemoveObjectGroups() {
-  for (int i = 0; i < object_groups_.length(); i++) {
-    object_groups_.at(i)->Dispose();
+  object_groups_.Clear();
+  for (int i = 0; i < retained_object_infos_.length(); ++i) {
+    if (retained_object_infos_[i].info != NULL)
+      retained_object_infos_[i].info->Dispose();
   }
-  object_groups_.Clear();
+  retained_object_infos_.Clear();
 }
 
 
 void GlobalHandles::RemoveImplicitRefGroups() {
   for (int i = 0; i < implicit_ref_groups_.length(); i++) {
     implicit_ref_groups_.at(i)->Dispose();
   }
   implicit_ref_groups_.Clear();
 }
 
 
 void GlobalHandles::TearDown() {
   // TODO(1428): invoke weak callbacks.
 }
 
 
 } }  // namespace v8::internal