Separating transitions from descriptors.

src/objects-debug.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 285 matching lines @@
 
 void Map::MapVerify() {
   ASSERT(!HEAP->InNewSpace(this));
   ASSERT(FIRST_TYPE <= instance_type() && instance_type() <= LAST_TYPE);
   ASSERT(instance_size() == kVariableSizeSentinel ||
          (kPointerSize <= instance_size() &&
           instance_size() < HEAP->Capacity()));
   VerifyHeapPointer(prototype());
   VerifyHeapPointer(instance_descriptors());
   SLOW_ASSERT(instance_descriptors()->IsSortedNoDuplicates());
-  SLOW_ASSERT(instance_descriptors()->IsConsistentWithBackPointers(this));
+  SLOW_ASSERT(transitions()->IsSortedNoDuplicates());
+  SLOW_ASSERT(transitions()->IsConsistentWithBackPointers(this));
 }
 
 
 void Map::SharedMapVerify() {
   MapVerify();
   ASSERT(is_shared());
   ASSERT(instance_descriptors()->IsEmpty());
   ASSERT_EQ(0, pre_allocated_property_fields());
   ASSERT_EQ(0, unused_property_fields());
   ASSERT_EQ(StaticVisitorBase::GetVisitorId(instance_type(), instance_size()),
@@ skipping 592 matching lines @@
     if (hash < current) {
       PrintDescriptors();
       return false;
     }
     current = hash;
   }
   return true;
 }
 
 
+bool TransitionArray::IsSortedNoDuplicates() {
+  if (!IsTransitionArray()) return true;

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

Can this really happen? If not, drop this line.

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

Done.

+  String* current_key = NULL;
+  uint32_t current = 0;
+  for (int i = 0; i < number_of_transitions(); i++) {
+    String* key = GetKey(i);
+    if (key == current_key) {
+      PrintTransitions();
+      return false;
+    }
+    current_key = key;
+    uint32_t hash = GetKey(i)->Hash();
+    if (hash < current) {
+      PrintTransitions();
+      return false;
+    }
+    current = hash;
+  }
+  return true;
+}
+
+
 static bool CheckOneBackPointer(Map* current_map, Object* target) {
   return !target->IsMap() || Map::cast(target)->GetBackPointer() == current_map;
 }
 
 
-bool DescriptorArray::IsConsistentWithBackPointers(Map* current_map) {
-  Map* elements_transition = elements_transition_map();
-  if (elements_transition != NULL &&
-      !CheckOneBackPointer(current_map, elements_transition)) {
-    return false;
-  }
-  for (int i = 0; i < number_of_descriptors(); ++i) {
-    switch (GetType(i)) {
-      case MAP_TRANSITION:
-      case CONSTANT_TRANSITION:
-        if (!CheckOneBackPointer(current_map, GetValue(i))) {
-          return false;
-        }
-        break;
-      case CALLBACKS: {
-        Object* object = GetValue(i);
-        if (object->IsAccessorPair()) {
-          AccessorPair* accessors = AccessorPair::cast(object);
-          if (!CheckOneBackPointer(current_map, accessors->getter())) {
-            return false;
-          }
-          if (!CheckOneBackPointer(current_map, accessors->setter())) {
-            return false;
-          }
-        }
-        break;
-      }
-      case NORMAL:
-      case FIELD:
-      case CONSTANT_FUNCTION:
-      case HANDLER:
-      case INTERCEPTOR:
-        break;
-      case NONEXISTENT:
-        UNREACHABLE();
-        break;
+bool TransitionArray::IsConsistentWithBackPointers(Map* current_map) {
+  if (this == NULL) return true;

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

Can "this" really be NULL? If not, drop this line.

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

Done.

+  if (!CheckOneBackPointer(current_map, elements())) return false;
+  for (int i = 0; i < number_of_transitions(); ++i) {
+    Object* value = GetValue(i);
+    if (value->IsAccessorPair()) {
+      AccessorPair* accessors = AccessorPair::cast(value);
+      if (!CheckOneBackPointer(current_map, accessors->getter())) return false;
+      if (!CheckOneBackPointer(current_map, accessors->setter())) return false;
+      continue;

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

Drop the continue.

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

Done.

     }
+    if (!CheckOneBackPointer(current_map, value)) return false;

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

Can we turn this into a proper "else" branch and also assert that it actually is
a map in the else branch?

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

Done.

   }
   return true;
 }
 
 
 void JSFunctionResultCache::JSFunctionResultCacheVerify() {
   JSFunction::cast(get(kFactoryIndex))->Verify();
 
   int size = Smi::cast(get(kCacheSizeIndex))->value();
   ASSERT(kEntriesIndex <= size);
@@ skipping 26 matching lines @@
       if (e->IsMap()) {
         Map::cast(e)->SharedMapVerify();
       } else {
         ASSERT(e->IsUndefined());
       }
     }
   }
 }
 
 
-void Map::ZapInstanceDescriptors() {
-  DescriptorArray* descriptors = instance_descriptors();
-  if (descriptors == GetHeap()->empty_descriptor_array()) return;
-  MemsetPointer(descriptors->data_start(),
+void Map::ZapTransitions() {
+  TransitionArray* transition_array = transitions();
+  if (transition_array == NULL) return;
+  MemsetPointer(transition_array->data_start(),
                 GetHeap()->the_hole_value(),
-                descriptors->length());
+                transition_array->length());
 }
 
 
 void Map::ZapPrototypeTransitions() {
   FixedArray* proto_transitions = prototype_transitions();
   MemsetPointer(proto_transitions->data_start(),
                 GetHeap()->the_hole_value(),
                 proto_transitions->length());
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal