Couple the enumeration index of a property to the size of the descriptor array where it first appea…

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 5783 matching lines @@
   FixedArray* result;
   if (number_of_descriptors == 0 && shared_mode == MAY_BE_SHARED) {
     return heap->empty_descriptor_array();
   }
   // Allocate the array of keys.
   { MaybeObject* maybe_array =
         heap->AllocateFixedArray(ToKeyIndex(number_of_descriptors));
     if (!maybe_array->To(&result)) return maybe_array;
   }
 
-  result->set(kLastAddedIndex, Smi::FromInt(-1));
+  result->set(kLastAddedIndex, Smi::FromInt(kNoneAdded));
   result->set(kTransitionsIndex, Smi::FromInt(0));
   return result;
 }
 
 
 void DescriptorArray::SetEnumCache(FixedArray* bridge_storage,
                                    FixedArray* new_cache,
                                    Object* new_index_cache) {
   ASSERT(bridge_storage->length() >= kEnumCacheBridgeLength);
   ASSERT(new_index_cache->IsSmi() || new_index_cache->IsFixedArray());
@@ skipping 106 matching lines @@
 
   int new_size = number_of_descriptors() + 1;
 
   DescriptorArray* new_descriptors;
   { MaybeObject* maybe_result = Allocate(new_size, MAY_BE_SHARED);
     if (!maybe_result->To(&new_descriptors)) return maybe_result;
   }
 
   FixedArray::WhitenessWitness witness(new_descriptors);
 
-  descriptor->SetEnumerationIndex(NextEnumerationIndex());
+  ASSERT(new_size == NextEnumerationIndex());
+  descriptor->SetEnumerationIndex(new_size);
 
   // Copy the descriptors, inserting or replacing a descriptor.
   int insertion_index = -1;
   int to = 0;
   for (int from = 0; from < number_of_descriptors(); ++from) {
     if (insertion_index < 0 && InsertionPointFound(GetKey(from), key)) {
       insertion_index = to++;
     }
     MaybeObject* copy_result =
         new_descriptors->CopyFrom(to++, this, from, witness);
@@ skipping 39 matching lines @@
 // We need the whiteness witness since sort will reshuffle the entries in the
 // descriptor array. If the descriptor array were to be black, the shuffling
 // would move a slot that was already recorded as pointing into an evacuation
 // candidate. This would result in missing updates upon evacuation.
 void DescriptorArray::SortUnchecked(const WhitenessWitness& witness) {
   // In-place heap sort.
   int len = number_of_descriptors();
   // Nothing to sort.
   if (len == 0) return;
 
+  ASSERT(LastAdded() == kNoneAdded ||
+         GetDetails(LastAdded()).index() == number_of_descriptors());
+
   // Bottom-up max-heap construction.
   // Index of the last node with children
   const int max_parent_index = (len / 2) - 1;
   for (int i = max_parent_index; i >= 0; --i) {
     int parent_index = i;
     const uint32_t parent_hash = GetKey(i)->Hash();
     while (parent_index <= max_parent_index) {
       int child_index = 2 * parent_index + 1;
       uint32_t child_hash = GetKey(child_index)->Hash();
       if (child_index + 1 < len) {
@@ skipping 27 matching lines @@
           child_index++;
           child_hash = right_child_hash;
         }
       }
       if (child_hash <= parent_hash) break;
       NoIncrementalWriteBarrierSwapDescriptors(parent_index, child_index);
       parent_index = child_index;
     }
   }
 
-  int last_enum_index = -1;
-  int last_added = -1;
-  for (int i = 0; i < len; ++i) {
-    int current_enum = GetDetails(i).index();
-    if (current_enum > last_enum_index) {
-      last_added = i;
-      last_enum_index = current_enum;
+#ifdef DEBUG
+  // Ensure that all enumeration indexes between 1 and length occur uniquely in
+  // the descriptor array.
+  for (int i = 1; i <= len; ++i) {
+    int j;
+    for (j = 0; j < len; ++j) {
+      if (GetDetails(j).index() == i) break;
+    }
+    ASSERT(j != len);
+    for (j++; j < len; ++j) {
+      ASSERT(GetDetails(j).index() != i);
     }
   }
-  SetLastAdded(last_added);
+#endif
 
-  ASSERT(LastAdded() != -1);
+  for (int i = 0; i < len; ++i) {
+    if (GetDetails(i).index() == len) {
+      SetLastAdded(i);
+      return;
+    }
+  }
+
+  UNREACHABLE();
 }
 
 
 void DescriptorArray::Sort(const WhitenessWitness& witness) {
   SortUnchecked(witness);
   SLOW_ASSERT(IsSortedNoDuplicates());
 }
 
 
 MaybeObject* AccessorPair::CopyWithoutTransitions() {
@@ skipping 7238 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