Ensure newly allocated empty Arrays are transitioned to FAST_ELEMENT

src/flag-definitions.h

 // Copyright 2011 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 102 matching lines @@
 DEFINE_bool(harmony_collections, false,
             "enable harmony collections (sets, maps, and weak maps)")
 DEFINE_bool(harmony, false, "enable all harmony features")
 DEFINE_implication(harmony, harmony_typeof)
 DEFINE_implication(harmony, harmony_scoping)
 DEFINE_implication(harmony, harmony_proxies)
 DEFINE_implication(harmony, harmony_collections)
 
 // Flags for experimental implementation features.
 DEFINE_bool(unbox_double_arrays, true, "automatically unbox arrays of doubles")
-DEFINE_bool(smi_only_arrays, false, "tracks arrays with only smi values")
+DEFINE_bool(smi_only_arrays, true, "tracks arrays with only smi values")

[Jakob Kummerow, 2012/01/04 20:55:17]

Is this change intentional?

 DEFINE_bool(string_slices, true, "use string slices")
 
 DEFINE_bool(clever_optimizations,
             true,
             "Optimize object size, Array shift, DOM strings and string +")
 
 // Flags for Crankshaft.
 DEFINE_bool(crankshaft, true, "use crankshaft")
 DEFINE_string(hydrogen_filter, "", "hydrogen use/trace filter")
 DEFINE_bool(use_hydrogen, true, "use generated hydrogen for compilation")
@@ skipping 444 matching lines @@
 #undef DEFINE_bool
 #undef DEFINE_int
 #undef DEFINE_string
 #undef DEFINE_implication
 
 #undef FLAG_MODE_DECLARE
 #undef FLAG_MODE_DEFINE
 #undef FLAG_MODE_DEFINE_DEFAULTS
 #undef FLAG_MODE_META
 #undef FLAG_MODE_DEFINE_IMPLICATIONS