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gh-91247: Use memcpy for list and tuple repeat (#91482)

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* Add _Py_memory_repeat function to pycore_list

* Add _Py_RefcntAdd function to pycore_object

* Use the new functions in tuplerepeat, list_repeat, and list_inplace_repeat
This commit is contained in:
Pieter Eendebak 2022-07-26 04:10:23 +02:00 • committed by GitHub
parent 27055d766a
commit 2ef73be891
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GPG key ID: 4AEE18F83AFDEB23
5 changed files with 73 additions and 65 deletions
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73
Objects/listobject.c
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@ -551,47 +551,41 @@ list_concat(PyListObject *a, PyObject *bb)
static PyObject *
list_repeat(PyListObject *a, Py_ssize_t n)
{
Py_ssize_t size;
PyListObject *np;
if (n < 0)
n = 0;
if (n > 0 && Py_SIZE(a) > PY_SSIZE_T_MAX / n)
return PyErr_NoMemory();
size = Py_SIZE(a) * n;
if (size == 0)
const Py_ssize_t input_size = Py_SIZE(a);
if (input_size == 0 || n <= 0)
return PyList_New(0);
np = (PyListObject *) list_new_prealloc(size);
assert(n > 0);
if (input_size > PY_SSIZE_T_MAX / n)
return PyErr_NoMemory();
Py_ssize_t output_size = input_size * n;
PyListObject *np = (PyListObject *) list_new_prealloc(output_size);
if (np == NULL)
return NULL;
PyObject **dest = np->ob_item;
PyObject **dest_end = dest + size;
if (Py_SIZE(a) == 1) {
if (input_size == 1) {
PyObject *elem = a->ob_item[0];
Py_SET_REFCNT(elem, Py_REFCNT(elem) + n);
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
_Py_RefcntAdd(elem, n);
PyObject **dest_end = dest + output_size;
while (dest < dest_end) {
*dest++ = elem;
}
}
else {
PyObject **src = a->ob_item;
PyObject **src_end = src + Py_SIZE(a);
PyObject **src_end = src + input_size;
while (src < src_end) {
Py_SET_REFCNT(*src, Py_REFCNT(*src) + n);
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
*dest++ = *src++;
}
// Now src chases after dest in the same buffer
src = np->ob_item;
while (dest < dest_end) {
_Py_RefcntAdd(*src, n);
*dest++ = *src++;
}
_Py_memory_repeat((char *)np->ob_item, sizeof(PyObject *)*output_size,
sizeof(PyObject *)*input_size);
}
Py_SET_SIZE(np, size);
Py_SET_SIZE(np, output_size);
return (PyObject *) np;
}
@ -743,12 +737,8 @@ PyList_SetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
static PyObject *
list_inplace_repeat(PyListObject *self, Py_ssize_t n)
{
PyObject **items;
Py_ssize_t size, i, j, p;
size = PyList_GET_SIZE(self);
if (size == 0 || n == 1) {
Py_ssize_t input_size = PyList_GET_SIZE(self);
if (input_size == 0 || n == 1) {
Py_INCREF(self);
return (PyObject *)self;
}
@ -759,22 +749,21 @@ list_inplace_repeat(PyListObject *self, Py_ssize_t n)
return (PyObject *)self;
}
if (size > PY_SSIZE_T_MAX / n) {
if (input_size > PY_SSIZE_T_MAX / n) {
return PyErr_NoMemory();
}
Py_ssize_t output_size = input_size * n;
if (list_resize(self, size*n) < 0)
if (list_resize(self, output_size) < 0)
return NULL;
p = size;
items = self->ob_item;
for (i = 1; i < n; i++) { /* Start counting at 1, not 0 */
for (j = 0; j < size; j++) {
PyObject *o = items[j];
Py_INCREF(o);
items[p++] = o;
}
PyObject **items = self->ob_item;
for (Py_ssize_t j = 0; j < input_size; j++) {
_Py_RefcntAdd(items[j], n-1);
}
_Py_memory_repeat((char *)items, sizeof(PyObject *)*output_size,
sizeof(PyObject *)*input_size);
Py_INCREF(self);
return (PyObject *)self;
}