Fix bug with mint unboxing on non-SSE 4.1 machines.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2012, 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/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 1068 matching lines @@
           Definition::kEffect);
       comp->set_receiver_class_id(kSmiCid);
     } else if ((class_ids[0] == kDoubleCid) && (class_ids[1] == kDoubleCid)) {
       comp->set_receiver_class_id(kDoubleCid);
     } else if (HasTwoMintOrSmi(*comp->ic_data()) &&
                FlowGraphCompiler::SupportsUnboxedMints()) {
       comp->set_receiver_class_id(kMintCid);
     } else {
       ASSERT(comp->receiver_class_id() == kIllegalCid);
     }
-  } else if (HasTwoMintOrSmi(*comp->ic_data())) {
+  } else if (HasTwoMintOrSmi(*comp->ic_data()) &&
+             FlowGraphCompiler::SupportsUnboxedMints()) {
     comp->set_receiver_class_id(kMintCid);
   } else if (comp->ic_data()->AllReceiversAreNumbers()) {
     comp->set_receiver_class_id(kNumberCid);
   }
 }
 
 
 void FlowGraphOptimizer::VisitEqualityCompare(EqualityCompareInstr* instr) {
   HandleEqualityCompare(this, instr, instr, current_iterator());
 }
@@ skipping 2049 matching lines @@
 
   if (FLAG_trace_constant_propagation) {
     OS::Print("\n==== After constant propagation ====\n");
     FlowGraphPrinter printer(*graph_);
     printer.PrintBlocks();
   }
 }
 
 
 }  // namespace dart