Initial support for length guards on final fields.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index f9c395cd0c2c224f935a90ec88a342ab2295b797..28afd19a2b02267c7ffdf391935c1147b9cbc703 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -2896,6 +2896,12 @@ void EffectGraphVisitor::VisitStoreInstanceFieldNode(
                                        dst_name);
   }
 
+  if (!node->field().is_final()) {
+    // Disable list length guarding on non-final fields by specifying
+    // that the field doesn't have a length.

[srdjan, 2013/08/14 17:01:08]

Maybe add a 'why' to the comment, or a "for now".

[Cutch, 2013/08/15 16:39:12]

Done.

+    node->field().set_guarded_list_length(Field::kNoLength);
+  }
+
   store_value = Bind(BuildStoreExprTemp(store_value));
   GuardFieldInstr* guard =
       new GuardFieldInstr(store_value,