Box values of LoadCodeUnits that fall outside of smi range on 32bit platforms.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index 26083848b24ed174dacea037dcde88b01996095f..1f1802cfb7042c23b211223b873a0b03f1db2626 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -4618,6 +4618,15 @@ void FlowGraphOptimizer::VisitAllocateContext(AllocateContextInstr* instr) {
 }
 
 
+void FlowGraphOptimizer::VisitLoadCodeUnits(LoadCodeUnitsInstr* instr) {
+  // TODO(zerny): Use kUnboxedUint32 once it is fully supported/optimized.
+#if defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_ARM)
+  if (!instr->can_pack_into_smi())
+    instr->set_representation(kUnboxedMint);
+#endif
+}
+
+
 bool FlowGraphOptimizer::TryInlineInstanceSetter(InstanceCallInstr* instr,
                                                  const ICData& unary_ic_data) {
   ASSERT((unary_ic_data.NumberOfChecks() > 0) &&