Bugfix for 349874: we incorrectly believe we saw a growing store

src/ic.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 1681 matching lines @@
           stub = non_strict_arguments_stub();
         } else if (key_is_smi_like &&
                    !(target().is_identical_to(non_strict_arguments_stub()))) {
           // We should go generic if receiver isn't a dictionary, but our
           // prototype chain does have dictionary elements. This ensures that
           // other non-dictionary receivers in the polymorphic case benefit
           // from fast path keyed stores.
           if (!(receiver->map()->DictionaryElementsInPrototypeChainOnly())) {
             KeyedAccessStoreMode store_mode =
                 GetStoreMode(receiver, key, value);
-            stub = StoreElementStub(receiver, store_mode);
+            // Use the generic stub if the store would send the receiver to
+            // dictionary mode.
+            if (!IsGrowStoreMode(store_mode) ||
+                !receiver->WouldConvertToSlowElements(key)) {
+              stub = StoreElementStub(receiver, store_mode);
+            }
           }
         }
       }
     }
   }
 
   if (!is_target_set()) {
     if (*stub == *generic_stub()) {
       TRACE_GENERIC_IC(isolate(), "KeyedStoreIC", "set generic");
     }
@@ skipping 1098 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal