Streamline IL for instantiating type arguments.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
===================================================================
--- runtime/vm/flow_graph_builder.cc	(revision 23201)
+++ runtime/vm/flow_graph_builder.cc	(working copy)
@@ -2299,10 +2299,16 @@
       owner()->parsed_function().function().Owner());
   Value* instantiator_value =
       BuildInstantiatorTypeArguments(token_pos, instantiator_class, NULL);
-  return Bind(new InstantiateTypeArgumentsInstr(token_pos,
-                                                type_arguments,
-                                                instantiator_class,
-                                                instantiator_value));
+  const bool use_instantiator_type_args =
+      type_arguments.IsUninstantiatedIdentity() ||

[Kevin Millikin (Google), 2013/05/27 09:22:03]

This predicate or its negation appears over and over.  Do you think it deserves
to be a named predicate on the AbstractTypeArguments?

[Florian Schneider, 2013/05/27 10:20:11]

Possibly. I don't have a really good name for such a predicate though.

+      type_arguments.CanShareInstantiatorTypeArguments(
+          instantiator_class);
+  return use_instantiator_type_args
+      ? instantiator_value
+      : Bind(new InstantiateTypeArgumentsInstr(token_pos,
+                                               type_arguments,
+                                               instantiator_class,
+                                               instantiator_value));
 }