Mere r4172 to trunk. The new version is 2.1.6.1.

src/rewriter.cc

 // Copyright 2006-2008 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 229 matching lines @@
     } else if (node->type()->IsLikelySmi()) {
       var->type()->SetAsLikelySmi();
     }
 
     if (!var->is_this() &&
         !Heap::result_symbol()->Equals(*var->name())) {
       func_name_inferrer_.PushName(var->name());
     }
 
     if (FLAG_safe_int32_compiler) {
-      if (var->IsStackAllocated() && !var->is_arguments()) {
+      if (var->IsStackAllocated() &&
+          !var->is_arguments() &&
+          var->mode() != Variable::CONST) {
         node->set_side_effect_free(true);
       }
     }
   }
 }
 
 
 void AstOptimizer::VisitLiteral(Literal* node) {
   Handle<Object> literal = node->handle();
   if (literal->IsSmi()) {
@@ skipping 689 matching lines @@
     optimizer.Optimize(body);
     if (optimizer.HasStackOverflow()) {
       return false;
     }
   }
   return true;
 }
 
 
 } }  // namespace v8::internal