Variation of patch # 1624059 to speed up checking if an object is a subclass

of some of the common builtin types.

Use a bit in tp_flags for each common builtin type.  Check the bit
to determine if any instance is a subclass of these common types.
The check avoids a function call and O(n) search of the base classes.
The check is done in the various Py*_Check macros rather than calling
PyType_IsSubtype().

All the bits are set in tp_flags when the type is declared
in the Objects/*object.c files because PyType_Ready() is not called
for all the types.  Should PyType_Ready() be called for all types?
If so and the change is made, the changes to the Objects/*object.c files
can be reverted (remove setting the tp_flags).  Objects/typeobject.c
would also have to be modified to add conditions
for Py*_CheckExact() in addition to each the PyType_IsSubtype check.

1 files changed, 2 insertions, 1 deletions

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 0cd819c5a1..c6ea6a40c4 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -300,7 +300,8 @@ static PyTypeObject _PyExc_BaseException = {
     PyObject_GenericGetAttr,    /*tp_getattro*/
     PyObject_GenericSetAttr,    /*tp_setattro*/
     0,                          /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,  /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
+    	Py_TPFLAGS_BASE_EXC_SUBCLASS,  /*tp_flags*/
     PyDoc_STR("Common base class for all exceptions"), /* tp_doc */
     (traverseproc)BaseException_traverse, /* tp_traverse */
     (inquiry)BaseException_clear, /* tp_clear */