Limit the number of transitions allowed per hidden class.

src/objects.cc

 // Copyright 2013 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.
 
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
@@ skipping 6576 matching lines @@
 
   Handle<Map> result = CopyDropDescriptors(map);
   Handle<Name> name = descriptor->GetKey();
 
   // Ensure there's space for the new descriptor in the shared descriptor array.
   if (descriptors->NumberOfSlackDescriptors() == 0) {
     int old_size = descriptors->number_of_descriptors();
     if (old_size == 0) {
       descriptors = DescriptorArray::Allocate(map->GetIsolate(), 0, 1);
     } else {
-      EnsureDescriptorSlack(map, old_size < 4 ? 1 : old_size / 2);
+      EnsureDescriptorSlack(
+          map, SlackForArraySize(old_size, kMaxNumberOfDescriptors));
       descriptors = handle(map->instance_descriptors());
     }
   }
 
   {
     DisallowHeapAllocation no_gc;
     descriptors->Append(descriptor);
     result->InitializeDescriptors(*descriptors);
   }
 
   DCHECK(result->NumberOfOwnDescriptors() == map->NumberOfOwnDescriptors() + 1);
   ConnectTransition(map, result, name, SIMPLE_TRANSITION);
 
   return result;
 }
 
 
 void Map::ConnectTransition(Handle<Map> parent, Handle<Map> child,
                             Handle<Name> name, SimpleTransitionFlag flag) {
   parent->set_owns_descriptors(false);
   if (parent->is_prototype_map()) {
     DCHECK(child->is_prototype_map());
   } else {
     Handle<TransitionArray> transitions =
-        TransitionArray::CopyInsert(parent, name, child, flag);
-    parent->set_transitions(*transitions);
+        TransitionArray::Insert(parent, name, child, flag);
+    if (!parent->HasTransitionArray() ||
+        *transitions != parent->transitions()) {
+      parent->set_transitions(*transitions);
+    }
     child->SetBackPointer(*parent);
   }
 }
 
 
 Handle<Map> Map::CopyReplaceDescriptors(Handle<Map> map,
                                         Handle<DescriptorArray> descriptors,
                                         TransitionFlag flag,
                                         MaybeHandle<Name> maybe_name,
                                         SimpleTransitionFlag simple_flag) {
@@ skipping 9835 matching lines @@
   Handle<DependentCode> codes =
       DependentCode::Insert(handle(cell->dependent_code(), info->isolate()),
                             DependentCode::kPropertyCellChangedGroup,
                             info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal