dom-query.html spends ~10% of total time in OSAtomicAdd32Barrier on my Mac

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 690 matching lines @@
     // Check access rights if needed.
     if (js_object->IsAccessCheckNeeded()) {
       Isolate* isolate = heap->isolate();
       if (!isolate->MayIndexedAccess(js_object, index, v8::ACCESS_GET)) {
         isolate->ReportFailedAccessCheck(js_object, v8::ACCESS_GET);
         return heap->undefined_value();
       }
     }
 
     if (js_object->HasIndexedInterceptor()) {
-      return js_object->GetElementWithInterceptor(receiver, index);
+      return js_object->GetElementWithInterceptor(
+          receiver, index, heap->isolate());
     }
 
     if (js_object->elements() != heap->empty_fixed_array()) {
       MaybeObject* result = js_object->GetElementsAccessor()->Get(
           receiver, js_object, index);
       if (result != heap->the_hole_value()) return result;
     }
   }
 
   return heap->undefined_value();
@@ skipping 9450 matching lines @@
           GetHeap()->NumberFromDouble(static_cast<double>(index) + 1);
       if (!maybe_len->ToObject(&len)) return maybe_len;
     }
     set_length(len);
   }
   return value;
 }
 
 
 MaybeObject* JSObject::GetElementWithInterceptor(Object* receiver,
-                                                 uint32_t index) {
-  Isolate* isolate = GetIsolate();
+                                                 uint32_t index,
+                                                 Isolate* isolate) {
   // Make sure that the top context does not change when doing
   // callbacks or interceptor calls.
   AssertNoContextChange ncc;
   HandleScope scope(isolate);
   Handle<InterceptorInfo> interceptor(GetIndexedInterceptor(), isolate);
   Handle<Object> this_handle(receiver, isolate);
   Handle<JSObject> holder_handle(this, isolate);
   if (!interceptor->getter()->IsUndefined()) {
     v8::IndexedPropertyGetter getter =
         v8::ToCData<v8::IndexedPropertyGetter>(interceptor->getter());
@@ skipping 3281 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