Reland "Limit the number of transitions allowed per hidden class."

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 5185 matching lines @@
 
 
 Map* Map::elements_transition_map() {
   int index = transitions()->Search(GetHeap()->elements_transition_symbol());
   return transitions()->GetTarget(index);
 }
 
 
 bool Map::CanHaveMoreTransitions() {
   if (!HasTransitionArray()) return true;
-  return FixedArray::SizeFor(transitions()->length() +
-                             TransitionArray::kTransitionSize)
-      <= Page::kMaxRegularHeapObjectSize;
+  return transitions()->number_of_transitions() <
+         TransitionArray::kMaxNumberOfTransitions;
 }
 
 
 Map* Map::GetTransition(int transition_index) {
   return transitions()->GetTarget(transition_index);
 }
 
 
 int Map::SearchTransition(Name* name) {
   if (HasTransitionArray()) return transitions()->Search(name);
@@ skipping 1769 matching lines @@
 void Map::ClearCodeCache(Heap* heap) {
   // No write barrier is needed since empty_fixed_array is not in new space.
   // Please note this function is used during marking:
   //  - MarkCompactCollector::MarkUnmarkedObject
   //  - IncrementalMarking::Step
   DCHECK(!heap->InNewSpace(heap->empty_fixed_array()));
   WRITE_FIELD(this, kCodeCacheOffset, heap->empty_fixed_array());
 }
 
 
+int Map::SlackForArraySize(int old_size, int size_limit) {
+  const int max_slack = size_limit - old_size;
+  CHECK(max_slack >= 0);
+  if (old_size < 4) return Min(max_slack, 1);
+  return Min(max_slack, old_size / 2);
+}
+
+
 void JSArray::EnsureSize(Handle<JSArray> array, int required_size) {
   DCHECK(array->HasFastSmiOrObjectElements());
   Handle<FixedArray> elts = handle(FixedArray::cast(array->elements()));
   const int kArraySizeThatFitsComfortablyInNewSpace = 128;
   if (elts->length() < required_size) {
     // Doubling in size would be overkill, but leave some slack to avoid
     // constantly growing.
     Expand(array, required_size + (required_size >> 3));
     // It's a performance benefit to keep a frequently used array in new-space.
   } else if (!array->GetHeap()->new_space()->Contains(*elts) &&
@@ skipping 270 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_