[vm] Implement gradual refinement of types

runtime/vm/redundancy_elimination.cc

Index: runtime/vm/redundancy_elimination.cc
diff --git a/runtime/vm/redundancy_elimination.cc b/runtime/vm/redundancy_elimination.cc
index 1b83ace2a2986971eb099243e9d7288ffb0696ef..4d2b9b1e1f2797ba0832cc050f1473484dd18bb4 100644
--- a/runtime/vm/redundancy_elimination.cc
+++ b/runtime/vm/redundancy_elimination.cc
@@ -1323,6 +1323,7 @@ void LICM::TrySpecializeSmiPhi(PhiInstr* phi,
 
   // Replace value we are checking with phi's input.
   check->value()->BindTo(phi->InputAt(non_smi_input)->definition());
+  check->value()->SetReachingType(phi->InputAt(non_smi_input)->Type());
 
   phi->UpdateType(CompileType::FromCid(kSmiCid));
 }