Use NumberOfOwnDescriptors/EnumLength for counting properties on fast objects.

src/objects.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 3317 matching lines @@
 
   // The global object is always normalized.
   ASSERT(!IsGlobalObject());
   // JSGlobalProxy must never be normalized
   ASSERT(!IsJSGlobalProxy());
 
   Map* map_of_this = map();
 
   // Allocate new content.
   int real_size = map_of_this->NumberOfOwnDescriptors();
-  int property_count =
-      map_of_this->NumberOfDescribedProperties(OWN_DESCRIPTORS);
+  int property_count = real_size;
   if (expected_additional_properties > 0) {
     property_count += expected_additional_properties;
   } else {
     property_count += 2;  // Make space for two more properties.
   }
   StringDictionary* dictionary;
   MaybeObject* maybe_dictionary = StringDictionary::Allocate(property_count);
   if (!maybe_dictionary->To(&dictionary)) return maybe_dictionary;
 
   DescriptorArray* descs = map_of_this->instance_descriptors();
@@ skipping 4093 matching lines @@
 
 // Clear a possible back pointer in case the transition leads to a dead map.
 // Return true in case a back pointer has been cleared and false otherwise.
 static bool ClearBackPointer(Heap* heap, Map* target) {
   if (Marking::MarkBitFrom(target).Get()) return false;
   target->SetBackPointer(heap->undefined_value(), SKIP_WRITE_BARRIER);
   return true;
 }
 
 
+static void TrimEnumCache(Heap* heap, Map* map, DescriptorArray* descriptors) {
+  int live_enum = map->EnumLength();
+  if (live_enum == Map::kInvalidEnumCache) {
+    live_enum = map->NumberOfDescribedProperties(OWN_DESCRIPTORS, DONT_ENUM);
+  }
+  if (live_enum == 0) return descriptors->ClearEnumCache();
+  
+  FixedArray* enum_cache = descriptors->GetEnumCache();
+
+  int to_trim = enum_cache->length() - live_enum;
+  if (to_trim <= 0) return;
+  RightTrimFixedArray<FROM_GC>(heap, descriptors->GetEnumCache(), to_trim);
+
+  if (!descriptors->HasEnumIndicesCache()) return;
+  FixedArray* enum_indices_cache = descriptors->GetEnumIndicesCache();
+  RightTrimFixedArray<FROM_GC>(heap, enum_indices_cache, to_trim);
+}
+
+
+static void TrimDescriptorArray(Heap* heap,
+                                Map* map,
+                                DescriptorArray* descriptors,
+                                int number_of_own_descriptors) {
+  int number_of_descriptors = descriptors->number_of_descriptors();
+  int to_trim = number_of_descriptors - number_of_own_descriptors;
+  if (to_trim <= 0) return;
+
+  // Maximally keep 50% of unused descriptors.
+  int keep = Min(to_trim, number_of_own_descriptors / 2);
+  for (int i = number_of_own_descriptors;
+       i < number_of_own_descriptors + keep;
+       ++i) {
+    descriptors->EraseDescriptor(heap, i);
+  }
+
+  if (to_trim > keep) {
+    RightTrimFixedArray<FROM_GC>(heap, descriptors, to_trim - keep);
+  }
+  descriptors->SetNumberOfDescriptors(number_of_own_descriptors);
+
+  if (descriptors->HasEnumCache()) TrimEnumCache(heap, map, descriptors);
+  descriptors->Sort();
+}
+
+
 // TODO(mstarzinger): This method should be moved into MarkCompactCollector,
 // because it cannot be called from outside the GC and we already have methods
 // depending on the transitions layout in the GC anyways.
 void Map::ClearNonLiveTransitions(Heap* heap) {
   // If there are no transitions to be cleared, return.
   // TODO(verwaest) Should be an assert, otherwise back pointers are not
   // properly cleared.
   if (!HasTransitionArray()) return;
 
   TransitionArray* t = transitions();
@@ skipping 38 matching lines @@
     // If there are no transitions to be cleared, return.
     // TODO(verwaest) Should be an assert, otherwise back pointers are not
     // properly cleared.
     if (transition_index == t->number_of_transitions()) return;
   }
 
   int number_of_own_descriptors = NumberOfOwnDescriptors();
 
   if (descriptors_owner_died) {
     if (number_of_own_descriptors > 0) {
-      int number_of_descriptors = descriptors->number_of_descriptors();
-      int to_trim = number_of_descriptors - number_of_own_descriptors;
-      if (to_trim > 0) {
-        // Maximally keep 50% of unused descriptors.
-        int keep = Min(to_trim, number_of_own_descriptors / 2);
-        for (int i = number_of_own_descriptors;
-             i < number_of_own_descriptors + keep;
-             ++i) {
-          descriptors->EraseDescriptor(heap, i);
-        }
-        if (to_trim > keep) {
-          RightTrimFixedArray<FROM_GC>(heap, descriptors, to_trim - keep);
-        }
-        descriptors->SetNumberOfDescriptors(number_of_own_descriptors);
-        if (descriptors->HasEnumCache()) {
-          int live_enum =
-              NumberOfDescribedProperties(OWN_DESCRIPTORS, DONT_ENUM);
-          if (live_enum == 0) {
-            descriptors->ClearEnumCache();
-          } else {
-            FixedArray* enum_cache = descriptors->GetEnumCache();
-            to_trim = enum_cache->length() - live_enum;
-            if (to_trim > 0) {
-              RightTrimFixedArray<FROM_GC>(
-                  heap, descriptors->GetEnumCache(), to_trim);
-              if (descriptors->HasEnumIndicesCache()) {
-                RightTrimFixedArray<FROM_GC>(
-                    heap, descriptors->GetEnumIndicesCache(), to_trim);
-              }
-            }
-          }
-        }
-        descriptors->Sort();
-      }
+      TrimDescriptorArray(heap, this, descriptors, number_of_own_descriptors);
       ASSERT(descriptors->number_of_descriptors() == number_of_own_descriptors);
     } else {
       t->set_descriptors(heap->empty_descriptor_array());
     }
     set_owns_descriptors(true);
   }
 
   // If the final transition array does not contain any live transitions, remove
   // the transition array from the map.
   if (transition_index == 0 &&
@@ skipping 3117 matching lines @@
     }
   }
 
   LookupResult result(isolate);
   LocalLookupRealNamedProperty(key, &result);
   return result.IsPropertyCallbacks();
 }
 
 
 int JSObject::NumberOfLocalProperties(PropertyAttributes filter) {
-  return HasFastProperties() ?
-      map()->NumberOfDescribedProperties(OWN_DESCRIPTORS, filter) :
-      property_dictionary()->NumberOfElementsFilterAttributes(filter);
+  if (HasFastProperties()) {
+    Map* map = this->map();
+    if (filter == NONE) return map->NumberOfOwnDescriptors();
+    if (filter == DONT_ENUM) {
+      int result = map->EnumLength();
+      if (result != Map::kInvalidEnumCache) return result;
+    }
+    return map->NumberOfDescribedProperties(OWN_DESCRIPTORS, filter);
+  }
+  return property_dictionary()->NumberOfElementsFilterAttributes(filter);
 }
 
 
 void FixedArray::SwapPairs(FixedArray* numbers, int i, int j) {
   Object* temp = get(i);
   set(i, get(j));
   set(j, temp);
   if (this != numbers) {
     temp = numbers->get(i);
     numbers->set(i, Smi::cast(numbers->get(j)));
@@ skipping 2833 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal