Fix bug in double unboxing.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 3537 matching lines @@
     const Function& getter =
         Function::Handle(owner.LookupGetterFunction(field_name));
     const Function& setter =
         Function::Handle(owner.LookupSetterFunction(field_name));
     bool result = !getter.IsNull()
                && !setter.IsNull()
                && (setter.usage_counter() > 0)
                && (FLAG_getter_setter_ratio * setter.usage_counter() >
                    getter.usage_counter());
     if (!result) {
+      if (FLAG_trace_optimization) {
+        OS::Print("Disabling unboxing of %s\n", field.ToCString());
+      }
       field.set_is_unboxing_candidate(false);
       field.DeoptimizeDependentCode();
     } else {
       FlowGraph::AddToGuardedFields(flow_graph_->guarded_fields(), &field);
     }
   }
 }
 
 
 bool FlowGraphOptimizer::TryInlineInstanceSetter(InstanceCallInstr* instr,
@@ skipping 4545 matching lines @@
   }
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, alloc->cls(), *fields);
   }
 }
 
 
 }  // namespace dart