Use off-heap data for class check instructions

runtime/vm/flow_graph.cc

Index: runtime/vm/flow_graph.cc
diff --git a/runtime/vm/flow_graph.cc b/runtime/vm/flow_graph.cc
index dff1c08e5882e639e8d8bd3dea9548902818261f..f7e9228f677d0df402b48eb9d6a48086cf5b8e37 100644
--- a/runtime/vm/flow_graph.cc
+++ b/runtime/vm/flow_graph.cc
@@ -468,6 +468,19 @@ bool FlowGraph::InstanceCallNeedsClassCheck(InstanceCallInstr* call,
 }
 
 
+Instruction* FlowGraph::GetCheckClass(Definition* to_check,
+                                      const CallTargets& targets,
+                                      intptr_t deopt_id,
+                                      TokenPosition token_pos) {
+  if (targets.IsMonomorphic() && targets.MonomorphicReceiverCid() == kSmiCid) {
+    return new (zone())
+        CheckSmiInstr(new (zone()) Value(to_check), deopt_id, token_pos);
+  }
+  return new (zone()) CheckClassInstr(new (zone()) Value(to_check), deopt_id,
+                                      targets, token_pos);
+}
+
+
 bool FlowGraph::VerifyUseLists() {
   // Verify the initial definitions.
   for (intptr_t i = 0; i < graph_entry_->initial_definitions()->length(); ++i) {