350884: KeyedStoreIC miss didn't handle a transitioning case.

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 1417 matching lines @@
   }
 
   // There are several special cases where an IC that is MONOMORPHIC can still
   // transition to a different GetNonTransitioningStoreMode IC that handles a
   // superset of the original IC. Handle those here if the receiver map hasn't
   // changed or it has transitioned to a more general kind.
   KeyedAccessStoreMode old_store_mode =
       KeyedStoreIC::GetKeyedAccessStoreMode(target()->extra_ic_state());
   Handle<Map> previous_receiver_map = target_receiver_maps.at(0);
   if (state() == MONOMORPHIC) {
-      // If the "old" and "new" maps are in the same elements map family, stay
-      // MONOMORPHIC and use the map for the most generic ElementsKind.
-    Handle<Map> transitioned_receiver_map = receiver_map;
     if (IsTransitionStoreMode(store_mode)) {
-      transitioned_receiver_map =
+      // If the "old" and "new" maps are in the same elements map family, or
+      // if they at least come from the same origin for a transitioning store,
+      // stay MONOMORPHIC and use the map for the most generic ElementsKind.
+      Handle<Map> transitioned_receiver_map =
           ComputeTransitionedMap(receiver, store_mode);
-    }
-    if (IsTransitionOfMonomorphicTarget(
-            MapToType<HeapType>(transitioned_receiver_map, isolate()))) {
-      // Element family is the same, use the "worst" case map.
-      store_mode = GetNonTransitioningStoreMode(store_mode);
-      return isolate()->stub_cache()->ComputeKeyedStoreElement(
-          transitioned_receiver_map, strict_mode(), store_mode);
+      if (*previous_receiver_map == receiver->map() ||
+          IsTransitionOfMonomorphicTarget(
+              MapToType<HeapType>(transitioned_receiver_map, isolate()))) {
+        store_mode = GetNonTransitioningStoreMode(store_mode);
+        return isolate()->stub_cache()->ComputeKeyedStoreElement(
+            transitioned_receiver_map, strict_mode(), store_mode);
+      }
     } else if (*previous_receiver_map == receiver->map() &&
                old_store_mode == STANDARD_STORE &&
                (IsGrowStoreMode(store_mode) ||
                 store_mode == STORE_NO_TRANSITION_IGNORE_OUT_OF_BOUNDS ||
                 store_mode == STORE_NO_TRANSITION_HANDLE_COW)) {
       // A "normal" IC that handles stores can switch to a version that can
       // grow at the end of the array, handle OOB accesses or copy COW arrays
       // and still stay MONOMORPHIC.
       return isolate()->stub_cache()->ComputeKeyedStoreElement(
           receiver_map, strict_mode(), store_mode);
@@ skipping 1356 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal