sim: Rename the SimObject cxx_bases field to cxx_extra_bases.

cxx_bases adds in additional c++ base classes beyond those implied by
the python SimObject inheritance hierarchy. To imply the fact that
these are additional bases, and to disambiguate a future mechanism
which changes the implied bases, this flag/field is being renamed from
cxx_bases to cxx_extra_bases.

As far as I can tell, this field was only used internally in
SimObject.py.

Change-Id: Ie7cc3d0107ff71cc31424d6e20c9a2f430022ab9
Reviewed-on: https://gem5-review.googlesource.com/10661
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
diff --git a/src/python/m5/SimObject.py b/src/python/m5/SimObject.py
index 6e61961..e051a97 100644
--- a/src/python/m5/SimObject.py
+++ b/src/python/m5/SimObject.py
@@ -407,7 +407,7 @@
         'cxx_type' : str,
         'cxx_header' : str,
         'type' : str,
-        'cxx_bases' : list,
+        'cxx_extra_bases' : list,
         'cxx_exports' : list,
         'cxx_param_exports' : list,
     }
@@ -441,8 +441,8 @@
                 value_dict[key] = val
         if 'abstract' not in value_dict:
             value_dict['abstract'] = False
-        if 'cxx_bases' not in value_dict:
-            value_dict['cxx_bases'] = []
+        if 'cxx_extra_bases' not in value_dict:
+            value_dict['cxx_extra_bases'] = []
         if 'cxx_exports' not in value_dict:
             value_dict['cxx_exports'] = cxx_exports
         else:
@@ -734,8 +734,8 @@
         code()
         code.dedent()
 
-        bases = [ cls._base.cxx_class ] + cls.cxx_bases if cls._base else \
-                cls.cxx_bases
+        bases = [ cls._base.cxx_class ] + cls.cxx_extra_bases if \
+                cls._base else cls.cxx_extra_bases
         if bases:
             base_str = ", ".join(bases)
             code('py::class_<${{cls.cxx_class}}, ${base_str}, ' \
@@ -933,7 +933,7 @@
     abstract = True
 
     cxx_header = "sim/sim_object.hh"
-    cxx_bases = [ "Drainable", "Serializable" ]
+    cxx_extra_bases = [ "Drainable", "Serializable" ]
     eventq_index = Param.UInt32(Parent.eventq_index, "Event Queue Index")
 
     cxx_exports = [