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gh-94673: Recover Weaklist Lookup Performance (gh-95544)

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gh-95302 seems to have introduced a small performance regression. Here we make some minor changes to recover that lost performance.
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Eric Snow 2022-08-04 11:28:15 -06:00 • committed by GitHub
parent 60f54d9485
commit bdbadb905a
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3 changed files with 47 additions and 7 deletions
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33
Include/internal/pycore_object.h
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@ -217,6 +217,16 @@ extern void _Py_PrintReferences(FILE *);
extern void _Py_PrintReferenceAddresses(FILE *);
#endif
/* Return the *address* of the object's weaklist. The address may be
* dereferenced to get the current head of the weaklist. This is useful
* for iterating over the linked list of weakrefs, especially when the
* list is being modified externally (e.g. refs getting removed).
*
* The returned pointer should not be used to change the head of the list
* nor should it be used to add, remove, or swap any refs in the list.
* That is the sole responsibility of the code in weakrefobject.c.
*/
static inline PyObject **
_PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)
{
@ -226,10 +236,33 @@ _PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)
(PyTypeObject *)op);
return _PyStaticType_GET_WEAKREFS_LISTPTR(state);
}
// Essentially _PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET():
Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset;
return (PyObject **)((char *)op + offset);
}
/* This is a special case of _PyObject_GET_WEAKREFS_LISTPTR().
* Only the most fundamental lookup path is used.
* Consequently, static types should not be used.
*
* For static builtin types the returned pointer will always point
* to a NULL tp_weaklist. This is fine for any deallocation cases,
* since static types are never deallocated and static builtin types
* are only finalized at the end of runtime finalization.
*
* If the weaklist for static types is actually needed then use
* _PyObject_GET_WEAKREFS_LISTPTR().
*/
static inline PyWeakReference **
_PyObject_GET_WEAKREFS_LISTPTR_FROM_OFFSET(PyObject *op)
{
assert(!PyType_Check(op) ||
((PyTypeObject *)op)->tp_flags & Py_TPFLAGS_HEAPTYPE);
Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset;
return (PyWeakReference **)((char *)op + offset);
}
// Fast inlined version of PyObject_IS_GC()
static inline int
_PyObject_IS_GC(PyObject *obj)