Reduce number of writes to DependentCode array when inserting dependent IC.

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 "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
 #include "src/api.h"
 #include "src/arguments.h"
@@ skipping 12043 matching lines @@
   bool marked = MarkCodeForDeoptimization(isolate, group);
 
   if (marked) Deoptimizer::DeoptimizeMarkedCode(isolate);
 }
 
 
 void DependentCode::AddToDependentICList(Handle<Code> stub) {
   DisallowHeapAllocation no_heap_allocation;
   GroupStartIndexes starts(this);
   int i = starts.at(kWeakICGroup);
-  stub->set_next_code_link(object_at(i));
-  set_object_at(i, *stub);
+  Object* head = object_at(i);
+  // Try to insert the stub after the head of the list to minimize number of
+  // writes to the DependentCode array, since a write to the array can make it
+  // strong if it was alread marked by incremental marker.
+  if (head->IsCode()) {
+    stub->set_next_code_link(Code::cast(head)->next_code_link());
+    Code::cast(head)->set_next_code_link(*stub);
+  } else {
+    stub->set_next_code_link(head);
+    set_object_at(i, *stub);
+  }
 }
 
 
 Handle<Map> Map::TransitionToPrototype(Handle<Map> map,
                                        Handle<Object> prototype) {
   Handle<Map> new_map = GetPrototypeTransition(map, prototype);
   if (new_map.is_null()) {
     new_map = Copy(map);
     PutPrototypeTransition(map, prototype, new_map);
     new_map->set_prototype(*prototype);
@@ skipping 4878 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal