New hydrogen instruction to reduce cost of growing an array on keyed stores.

src/runtime/runtime-array.cc

 // Copyright 2014 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/arguments.h"
 #include "src/messages.h"
 #include "src/runtime/runtime-utils.h"
 
@@ skipping 1223 matching lines @@
                  !array->HasFixedTypedArrayElements() &&
                  !array->IsJSGlobalProxy());
   JSObject::NormalizeElements(array);
   return *array;
 }
 
 
 // GrowArrayElements returns a sentinel Smi if the object was normalized.
 RUNTIME_FUNCTION(Runtime_GrowArrayElements) {
   HandleScope scope(isolate);
-  DCHECK(args.length() == 3);
+  DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
   CONVERT_NUMBER_CHECKED(int, key, Int32, args[1]);
 
   if (key < 0) {
     return object->elements();
   }
 
   uint32_t capacity = static_cast<uint32_t>(object->elements()->length());
   uint32_t index = static_cast<uint32_t>(key);
 
@@ skipping 157 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_FastOneByteArrayJoin) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 2);
   // Returning undefined means that this fast path fails and one has to resort
   // to a slow path.
   return isolate->heap()->undefined_value();
 }
 }
 }  // namespace v8::internal