Properly set ElementsKind of empty FAST_DOUBLE_ELEMENTS arrays when transitioning.

src/builtins.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 394 matching lines @@
 
 
 MUST_USE_RESULT
 static inline MaybeObject* EnsureJSArrayWithWritableFastElements(
     Heap* heap, Object* receiver, Arguments* args, int first_added_arg) {
   if (!receiver->IsJSArray()) return NULL;
   JSArray* array = JSArray::cast(receiver);
   HeapObject* elms = array->elements();
   Map* map = elms->map();
   if (map == heap->fixed_array_map()) {
-    if (args == NULL || !array->HasFastSmiOnlyElements()) {
+    if (array->HasFastElements()) return elms;
+    if (args == NULL) {
+      if (array->HasFastDoubleElements()) {
+        ASSERT(elms == heap->empty_fixed_array());
+        MaybeObject* maybe_transition =
+            array->TransitionElementsKind(FAST_ELEMENTS);
+        if (maybe_transition->IsFailure()) return maybe_transition;
+      }
       return elms;
     }
   } else if (map == heap->fixed_cow_array_map()) {
     MaybeObject* maybe_writable_result = array->EnsureWritableFastElements();
-    if (args == NULL || !array->HasFastSmiOnlyElements() ||
+    if (args == NULL || array->HasFastElements() ||
         maybe_writable_result->IsFailure()) {
       return maybe_writable_result;
     }
   } else {
     return NULL;
   }
 
   // Need to ensure that the arguments passed in args can be contained in
   // the array.
   int args_length = args->length();
@@ skipping 1242 matching lines @@
   return Handle<Code>(code_address);                        \
 }
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 } }  // namespace v8::internal