Don't replace initializing smi stores during store elimination.

src/hydrogen-store-elimination.cc

 // Copyright 2013 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 "hydrogen-store-elimination.h"
 #include "hydrogen-instructions.h"
 
 namespace v8 {
 namespace internal {
 
@@ skipping 40 matching lines @@
   }
 }
 
 
 void HStoreEliminationPhase::ProcessStore(HStoreNamedField* store) {
   HValue* object = store->object()->ActualValue();
   int i = 0;
   while (i < unobserved_.length()) {
     HStoreNamedField* prev = unobserved_.at(i);
     if (aliasing_->MustAlias(object, prev->object()->ActualValue()) &&
-        store->access().Equals(prev->access())) {
+        prev->CanBeReplacedWith(store)) {
       // This store is guaranteed to overwrite the previous store.
       prev->DeleteAndReplaceWith(NULL);
       TRACE(("++ Unobserved store S%d overwritten by S%d\n",
              prev->id(), store->id()));
       unobserved_.Remove(i);
     } else {
       // TODO(titzer): remove map word clearing from folded allocations.
       i++;
     }
   }
@@ skipping 35 matching lines @@
     return;
   }
   if (instr->DependsOnFlags().ContainsAnyOf(flags)) {
     TRACE(("-- Observed stores at I%d (GVN flags)\n", instr->id()));
     unobserved_.Rewind(0);
     return;
   }
 }
 
 } }  // namespace v8::internal