[compiler] Drop the CompareNilIC.

src/types.cc

Index: src/types.cc
diff --git a/src/types.cc b/src/types.cc
index d54826e34efc9a1c97d15a5bb3f9fbf89b74f4ae..4bf61f98b6a0c4457138f730ad462563014617a6 100644
--- a/src/types.cc
+++ b/src/types.cc
@@ -219,26 +219,16 @@ Type::bitset BitsetType::Lub(i::Map* map) {
     case JS_WEAK_SET_TYPE:
     case JS_PROMISE_TYPE:
     case JS_BOUND_FUNCTION_TYPE:
-      if (map->is_undetectable()) return kUndetectable;
+      if (map->is_undetectable()) return kOtherUndetectable;
       return kOtherObject;
     case JS_FUNCTION_TYPE:
-      if (map->is_undetectable()) return kUndetectable;
+      if (map->is_undetectable()) return kOtherUndetectable;
       return kFunction;
     case JS_REGEXP_TYPE:
       return kOtherObject;  // TODO(rossberg): there should be a RegExp type.
     case JS_PROXY_TYPE:
       return kProxy;
     case MAP_TYPE:
-      // When compiling stub templates, the meta map is used as a place holder
-      // for the actual map with which the template is later instantiated.
-      // We treat it as a kind of type variable whose upper bound is Any.
-      // TODO(rossberg): for caching of CompareNilIC stubs to work correctly,
-      // we must exclude Undetectable here. This makes no sense, really,
-      // because it means that the template isn't actually parametric.
-      // Also, it doesn't apply elsewhere. 8-(
-      // We ought to find a cleaner solution for compiling stubs parameterised
-      // over type or class variables, esp ones with bounds...
-      return kDetectable & kTaggedPointer;
     case ALLOCATION_SITE_TYPE:
     case ACCESSOR_INFO_TYPE:
     case SHARED_FUNCTION_INFO_TYPE: