Start porting fast typechecks to x64.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 7716)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -46,14 +46,20 @@
 
 // ==== Per-instruction input counts.
 intptr_t AssertAssignableComp::InputCount() const {
-  // Value and optional instantiator type arguments.
-  return (instantiator_type_arguments() == NULL) ? 1 : 2;
+  // Value and optional instantiator and instantiator type arguments.
+  intptr_t count = 1;
+  if (instantiator() != NULL) count++;
+  if (instantiator_type_arguments() != NULL) count++;
+  return count;
 }
 
 
 intptr_t InstanceOfComp::InputCount() const {
-  // Value and optional type_arguments.
-  return (type_arguments() == NULL) ? 1 : 2;
+  // Value and optional instantiator and instantiator type_arguments.
+  intptr_t count = 1;
+  if (instantiator() != NULL) count++;
+  if (type_arguments() != NULL) count++;
+  return count;
 }