Redid the slot computation. The initial slot assignments are now done

using the same algorithm as the slot updates.  The slotdefs array is
now sorted by slot offset and has an interned string object corresponding
to the name added to each item.  More can be done but I need to commit
this first as a working intermediate stage.

Objects/typeobject.c

@@ -3452,6 +3452,11 @@ slot_tp_getattr_hook(PyObject *self, PyObject *name)
 			return NULL;
 	}
 	getattr = _PyType_Lookup(tp, getattr_str);
+	if (getattr == NULL && tp->tp_getattro == slot_tp_getattr_hook) {
+		/* No __getattr__ hook: use a simpler dispatcher */
+		tp->tp_getattro = slot_tp_getattro;
+		return slot_tp_getattro(self, name);
+	}
 	getattribute = _PyType_Lookup(tp, getattribute_str);
 	if (getattribute != NULL &&
 	    getattribute->ob_type == &PyWrapperDescr_Type &&
@@ -3459,14 +3464,7 @@ slot_tp_getattr_hook(PyObject *self, PyObject *name)
 	    PyObject_GenericGetAttr)
 		    getattribute = NULL;
 	if (getattr == NULL && getattribute == NULL) {
-		/* Avoid further slowdowns */
-		/* XXX This is questionable: it means that a class that
-		   isn't born with __getattr__ or __getattribute__ cannot
-		   acquire them in later life.  But it's a relatively big
-		   speedup, so I'm keeping it in for now.  If this is
-		   removed, you can also remove the "def __getattr__" from
-		   class C (marked with another XXX comment) in dynamics()
-		   in Lib/test/test_descr.py. */
+		/* Use the default dispatcher */
 		if (tp->tp_getattro == slot_tp_getattr_hook)
 			tp->tp_getattro = PyObject_GenericGetAttr;
 		return PyObject_GenericGetAttr(self, name);
@@ -3813,7 +3811,7 @@ static slotdef slotdefs[] = {
 	TPSLOT("__cmp__", tp_compare, _PyObject_SlotCompare, wrap_cmpfunc),
 	TPSLOT("__hash__", tp_hash, slot_tp_hash, wrap_hashfunc),
 	TPSLOT("__call__", tp_call, slot_tp_call, wrap_call),
-	TPSLOT("__getattribute__", tp_getattro, slot_tp_getattro,
+	TPSLOT("__getattribute__", tp_getattro, slot_tp_getattr_hook,
 	       wrap_binaryfunc),
 	TPSLOT("__getattribute__", tp_getattr, NULL, NULL),
 	TPSLOT("__getattr__", tp_getattro, slot_tp_getattr_hook, NULL),
@@ -3864,27 +3862,27 @@ slotptr(PyTypeObject *type, int offset)
 	return (void **)ptr;
 }
 
-staticforward int recurse_down_subclasses(PyTypeObject *type, int offset);
+staticforward int recurse_down_subclasses(PyTypeObject *type, slotdef *p);
 
 static int
-update_one_slot(PyTypeObject *type, int offset)
+update_one_slot(PyTypeObject *type, slotdef *p0)
 {
-	slotdef *p;
+	slotdef *p = p0;
 	PyObject *descr;
 	PyWrapperDescrObject *d;
 	void *generic = NULL, *specific = NULL;
 	int use_generic = 0;
+	int offset;
 	void **ptr;
 
-	for (p = slotdefs; p->name; p++) {
-		if (p->offset != offset)
-			continue;
+	offset = p->offset;
+	ptr = slotptr(type, offset);
+	if (ptr == NULL)
+		return recurse_down_subclasses(type, p);
+	do {
 		descr = _PyType_Lookup(type, p->name_strobj);
 		if (descr == NULL)
 			continue;
-		ptr = slotptr(type, p->offset);
-		if (ptr == NULL)
-			continue;
 		generic = p->function;
 		if (descr->ob_type == &PyWrapperDescr_Type) {
 			d = (PyWrapperDescrObject *)descr;
@@ -3899,18 +3897,16 @@ update_one_slot(PyTypeObject *type, int offset)
 		}
 		else
 			use_generic = 1;
-		if (specific && !use_generic)
-			*ptr = specific;
-		else
-			*ptr = generic;
-	}
-	if (recurse_down_subclasses(type, offset) < 0)
-		return -1;
-	return 0;
+	} while ((++p)->offset == offset);
+	if (specific && !use_generic)
+		*ptr = specific;
+	else
+		*ptr = generic;
+	return recurse_down_subclasses(type, p0);
 }
 
 static int
-recurse_down_subclasses(PyTypeObject *type, int offset)
+recurse_down_subclasses(PyTypeObject *type, slotdef *p)
 {
 	PyTypeObject *subclass;
 	PyObject *ref, *subclasses;
@@ -3928,14 +3924,25 @@ recurse_down_subclasses(PyTypeObject *type, int offset)
 		if (subclass == NULL)
 			continue;
 		assert(PyType_Check(subclass));
-		if (update_one_slot(subclass, offset) < 0)
+		if (update_one_slot(subclass, p) < 0)
 			return -1;
 	}
 	return 0;
 }
 
+static int
+slotdef_cmp(const void *aa, const void *bb)
+{
+	const slotdef *a = (const slotdef *)aa, *b = (const slotdef *)bb;
+	int c = a->offset - b->offset;
+	if (c != 0)
+		return c;
+	else
+		return a - b;
+}
+
 static void
-init_name_strobj(void)
+init_slotdefs(void)
 {
 	slotdef *p;
 	static int initialized = 0;
@@ -3947,31 +3954,36 @@ init_name_strobj(void)
 		if (!p->name_strobj)
 			Py_FatalError("XXX ouch");
 	}
+	qsort((void *)slotdefs, (size_t)(p-slotdefs), sizeof(slotdef), slotdef_cmp);
 	initialized = 1;
 }
 
 static void
-collect_offsets(PyObject *name, int offsets[])
+collect_ptrs(PyObject *name, slotdef *ptrs[])
 {
 	slotdef *p;
 
-	init_name_strobj();
+	init_slotdefs();
 	for (p = slotdefs; p->name; p++) {
 		if (name == p->name_strobj)
-			*offsets++ = p->offset;
+			*ptrs++ = p;
 	}
-	*offsets = 0;
+	*ptrs = NULL;
 }
 
 static int
 update_slot(PyTypeObject *type, PyObject *name)
 {
-	int offsets[10];
-	int *ip;
-
-	collect_offsets(name, offsets);
-	for (ip = offsets; *ip; ip++) {
-		if (update_one_slot(type, *ip) < 0)
+	slotdef *ptrs[10];
+	slotdef *p;
+	slotdef **pp;
+
+	collect_ptrs(name, ptrs);
+	for (pp = ptrs; *pp; pp++) {
+		p = *pp;
+		while (p > slotdefs && p->offset == (p-1)->offset)
+			--p;
+		if (update_one_slot(type, p) < 0)
 			return -1;
 	}
 	return 0;
@@ -3984,42 +3996,57 @@ fixup_slot_dispatchers(PyTypeObject *type)
 	PyObject *mro, *descr;
 	PyTypeObject *base;
 	PyWrapperDescrObject *d;
-	int i, n;
+	int i, n, offset;
 	void **ptr;
+	void *generic, *specific;
+	int use_generic;
 
-	for (p = slotdefs; p->name; p++) {
-		ptr = slotptr(type, p->offset);
-		if (ptr)
-			*ptr = NULL;
-	}
+	init_slotdefs();
 	mro = type->tp_mro;
 	assert(PyTuple_Check(mro));
 	n = PyTuple_GET_SIZE(mro);
-	for (p = slotdefs; p->name; p++) {
-		for (i = 0; i < n; i++) {
-			base = (PyTypeObject *)PyTuple_GET_ITEM(mro, i);
-			assert(PyType_Check(base));
-			descr = PyDict_GetItemString(
-				base->tp_defined, p->name);
+	for (p = slotdefs; p->name; ) {
+		offset = p->offset;
+		ptr = slotptr(type, offset);
+		if (!ptr) {
+			do {
+				++p;
+			} while (p->offset == offset);
+			continue;
+		}
+		generic = specific = NULL;
+		use_generic = 0;
+		do {
+			descr = NULL;
+			for (i = 0; i < n; i++) {
+				base = (PyTypeObject *)PyTuple_GET_ITEM(mro, i);
+				assert(PyType_Check(base));
+				descr = PyDict_GetItem(
+					base->tp_defined, p->name_strobj);
+				if (descr != NULL)
+					break;
+			}
 			if (descr == NULL)
 				continue;
-			ptr = slotptr(type, p->offset);
-			if (ptr == NULL)
-				continue;
+			generic = p->function;
 			if (descr->ob_type == &PyWrapperDescr_Type) {
 				d = (PyWrapperDescrObject *)descr;
-				if (d->d_base->wrapper == p->wrapper) {
-					if (*ptr == NULL) {
-						*ptr = d->d_wrapped;
-						continue;
-					}
-					if (p->wrapper == wrap_binaryfunc_r)
-						continue;
+				if (d->d_base->wrapper == p->wrapper &&
+					PyType_IsSubtype(type, d->d_type)) {
+					if (specific == NULL ||
+						specific == d->d_wrapped)
+						specific = d->d_wrapped;
+					else
+						use_generic = 1;
 				}
 			}
-			*ptr = p->function;
-			break;
-		}
+			else
+				use_generic = 1;
+		} while ((++p)->offset == offset);
+		if (specific && !use_generic)
+			*ptr = specific;
+		else
+			*ptr = generic;
 	}
 }