Separating transitions from descriptors.

src/mark-compact.cc

 // 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 1874 matching lines @@
   if (descriptors->HasEnumCache()) {
     Object** enum_cache_slot = descriptors->GetEnumCacheSlot();
     Object* enum_cache = *enum_cache_slot;
     base_marker()->MarkObjectAndPush(
         reinterpret_cast<HeapObject*>(enum_cache));
     mark_compact_collector()->RecordSlot(descriptor_start,
                                          enum_cache_slot,
                                          enum_cache);
   }
 
-  if (descriptors->elements_transition_map() != NULL) {
+  if (descriptors->HasTransitionArray()) {
     Object** transitions_slot = descriptors->GetTransitionsSlot();
     Object* transitions = *transitions_slot;
     mark_compact_collector()->RecordSlot(descriptor_start,
                                          transitions_slot,
                                          transitions);
+    MarkTransitionArray(reinterpret_cast<TransitionArray*>(transitions));
   }
 
   // If the descriptor contains a transition (value is a Map), we don't mark the
   // value as live. It might be removed by ClearNonLiveTransitions later.
   for (int i = 0; i < descriptors->number_of_descriptors(); ++i) {
     Object** key_slot = descriptors->GetKeySlot(i);
     Object* key = *key_slot;
     if (key->IsHeapObject()) {
       base_marker()->MarkObjectAndPush(reinterpret_cast<HeapObject*>(key));

[Michael Starzinger, 2012/06/28 16:02:12]

We can also use HeapObject::cast() here.

[Toon Verwaest, 2012/06/29 08:14:55]

Done.

       mark_compact_collector()->RecordSlot(descriptor_start, key_slot, key);
     }
 
     Object** value_slot = descriptors->GetValueSlot(i);
     if (!(*value_slot)->IsHeapObject()) continue;
     HeapObject* value = HeapObject::cast(*value_slot);
 
     mark_compact_collector()->RecordSlot(descriptor_start,
                                          value_slot,
                                          value);
@@ skipping 10 matching lines @@
         break;
       case CALLBACKS:
         if (!value->IsAccessorPair()) {
           base_marker()->MarkObjectAndPush(value);
         } else if (base_marker()->MarkObjectWithoutPush(value)) {
           AccessorPair* accessors = AccessorPair::cast(value);
           MarkAccessorPairSlot(accessors, AccessorPair::kGetterOffset);
           MarkAccessorPairSlot(accessors, AccessorPair::kSetterOffset);
         }
         break;
-      case MAP_TRANSITION:
-      case CONSTANT_TRANSITION:
-        break;
+      case TRANSITION:
       case NONEXISTENT:
         UNREACHABLE();
         break;
     }
   }
 }
 
+template <class T>
+void Marker<T>::MarkTransitionArray(TransitionArray* transitions) {
+  ASSERT(transitions != NULL);
+  if (!base_marker()->MarkObjectWithoutPush(transitions)) return;
+  Object** transitions_start = transitions->data_start();
+
+  if (transitions->elements() != NULL) {
+    mark_compact_collector()->RecordSlot(transitions_start,
+                                         transitions->GetElementsSlot(),
+                                         transitions->elements());
+  }
+
+  for (int i = 0; i < transitions->number_of_transitions(); ++i) {
+    Object** key_slot = transitions->GetKeySlot(i);
+    Object* key = *key_slot;
+    if (key->IsHeapObject()) {
+      base_marker()->MarkObjectAndPush(reinterpret_cast<HeapObject*>(key));

[Michael Starzinger, 2012/06/28 16:02:12]

Use HeapObject::cast() here.

[Toon Verwaest, 2012/06/29 08:14:55]

Done.

+      mark_compact_collector()->RecordSlot(transitions_start, key_slot, key);
+    }
+
+    Object** value_slot = transitions->GetValueSlot(i);
+    if (!(*value_slot)->IsHeapObject()) continue;
+    HeapObject* value = HeapObject::cast(*value_slot);
+
+    mark_compact_collector()->RecordSlot(transitions_start,
+                                         value_slot,
+                                         value);
+
+    if (value->IsAccessorPair()) {
+      base_marker()->MarkObjectWithoutPush(value);

[Michael Starzinger, 2012/06/28 16:02:12]

We only need to mark the slots if the pair itself wasn't marked. So move the
MarkObjectWithoutPush() into the condition.

[Toon Verwaest, 2012/06/29 08:14:55]

Done.

+      AccessorPair* accessors = AccessorPair::cast(value);
+      MarkAccessorPairSlot(accessors, AccessorPair::kGetterOffset);
+      MarkAccessorPairSlot(accessors, AccessorPair::kSetterOffset);
+    }
+  }
+}
+
 
 template <class T>
 void Marker<T>::MarkAccessorPairSlot(AccessorPair* accessors, int offset) {
   Object** slot = HeapObject::RawField(accessors, offset);
   HeapObject* accessor = HeapObject::cast(*slot);
   if (accessor->IsMap()) return;
   mark_compact_collector()->RecordSlot(slot, slot, accessor);
   base_marker()->MarkObjectAndPush(accessor);
 }
 
@@ skipping 2165 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal