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gh-158790: Improve performance for list.insert() and del list[i] free-threaded builds (gh-158791)

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he_tao authored and GitHub committed 2026-10-07 21:21:00 +09:00
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commit c120cae880
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Misc/NEWS.d/next/Core_and_Builtins/2026-10-04-01-40-31.gh-issue-158790.F3kQ7z.rst
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@@ -0,0 +1 @@
Speed up :meth:`list.insert` and item deletion via :keyword:`del` in free-threaded builds by using :manpage:`memmove(3)`.
Objects/listobject.c
+39 -5
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@@ -478,10 +478,43 @@ end:;
return ret;
}
static void ptr_wise_atomic_memmove(PyListObject *a, PyObject **dest,
PyObject **src, Py_ssize_t n);
static inline void
list_shift_items_right_lock_held(PyListObject *self, Py_ssize_t first,
Py_ssize_t last)
{
#ifdef Py_GIL_DISABLED
ptr_wise_atomic_memmove(self, &self->ob_item[first + 1],
&self->ob_item[first], last - first);
#else
PyObject **items = self->ob_item;
for (Py_ssize_t i = last; --i >= first; ) {
items[i + 1] = items[i];
}
#endif
}
static inline void
list_shift_items_left_lock_held(PyListObject *self, Py_ssize_t first,
Py_ssize_t last)
{
#ifdef Py_GIL_DISABLED
ptr_wise_atomic_memmove(self, &self->ob_item[first],
&self->ob_item[first + 1], last - first);
#else
PyObject **items = self->ob_item;
for (Py_ssize_t i = first; i < last; i++) {
items[i] = items[i + 1];
}
#endif
}
static int
ins1(PyListObject *self, Py_ssize_t where, PyObject *v)
{
Py_ssize_t i, n = Py_SIZE(self);
Py_ssize_t n = Py_SIZE(self);
PyObject **items;
if (v == NULL) {
PyErr_BadInternalCall();
@@ -500,8 +533,9 @@ ins1(PyListObject *self, Py_ssize_t where, PyObject *v)
if (where > n)
where = n;
items = self->ob_item;
for (i = n; --i >= where; )
FT_ATOMIC_STORE_PTR_RELEASE(items[i+1], items[i]);
if (where < n) {
list_shift_items_right_lock_held(self, where, n);
}
FT_ATOMIC_STORE_PTR_RELEASE(items[where], Py_NewRef(v));
return 0;
}
@@ -1145,8 +1179,8 @@ list_ass_item_lock_held(PyListObject *a, Py_ssize_t i, PyObject *v)
PyObject *tmp = a->ob_item[i];
if (v == NULL) {
Py_ssize_t size = Py_SIZE(a);
for (Py_ssize_t idx = i; idx < size - 1; idx++) {
FT_ATOMIC_STORE_PTR_RELEASE(a->ob_item[idx], a->ob_item[idx + 1]);
if (i < size - 1) {
list_shift_items_left_lock_held(a, i, size - 1);
}
Py_SET_SIZE(a, size - 1);
}