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bpo-47009: Streamline list.append for the common case (GH-31864)

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Dennis Sweeney 2022-04-01 06:23:42 -04:00 • committed by GitHub
parent f877b40e3f
commit a0ea7a116c
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 41 additions and 27 deletions
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18
Include/internal/pycore_list.h
View file

@ -37,6 +37,24 @@ struct _Py_list_state {
#define _PyList_ITEMS(op) (_PyList_CAST(op)->ob_item) #define _PyList_ITEMS(op) (_PyList_CAST(op)->ob_item)
extern int
_PyList_AppendTakeRefListResize(PyListObject *self, PyObject *newitem);
static inline int
_PyList_AppendTakeRef(PyListObject *self, PyObject *newitem)
{
assert(self != NULL && newitem != NULL);
assert(PyList_Check(self));
Py_ssize_t len = PyList_GET_SIZE(self);
Py_ssize_t allocated = self->allocated;
assert((size_t)len + 1 < PY_SSIZE_T_MAX);
if (allocated > len) {
PyList_SET_ITEM(self, len, newitem);
Py_SET_SIZE(self, len + 1);
return 0;
}
return _PyList_AppendTakeRefListResize(self, newitem);
}
#ifdef __cplusplus #ifdef __cplusplus
} }

1
Misc/NEWS.d/next/Core and Builtins/2022-03-14-09-45-10.bpo-47009.ZI05b5.rst Normal file
View file

@ -0,0 +1 @@
Improved the performance of :meth:`list.append()` and list comprehensions by optimizing for the common case, where no resize is needed. Patch by Dennis Sweeney.

36
Objects/listobject.c
View file

@ -301,26 +301,27 @@ PyList_Insert(PyObject *op, Py_ssize_t where, PyObject *newitem)
return ins1((PyListObject *)op, where, newitem); return ins1((PyListObject *)op, where, newitem);
} }
static int /* internal, used by _PyList_AppendTakeRef */
app1(PyListObject *self, PyObject *v) int
_PyList_AppendTakeRefListResize(PyListObject *self, PyObject *newitem)
{ {
Py_ssize_t n = PyList_GET_SIZE(self); Py_ssize_t len = PyList_GET_SIZE(self);
assert(self->allocated == -1 || self->allocated == len);
assert (v != NULL); if (list_resize(self, len + 1) < 0) {
assert((size_t)n + 1 < PY_SSIZE_T_MAX); Py_DECREF(newitem);
if (list_resize(self, n+1) < 0)
return -1; return -1;
}
Py_INCREF(v); PyList_SET_ITEM(self, len, newitem);
PyList_SET_ITEM(self, n, v);
return 0; return 0;
} }
int int
PyList_Append(PyObject *op, PyObject *newitem) PyList_Append(PyObject *op, PyObject *newitem)
{ {
if (PyList_Check(op) && (newitem != NULL)) if (PyList_Check(op) && (newitem != NULL)) {
return app1((PyListObject *)op, newitem); Py_INCREF(newitem);
return _PyList_AppendTakeRef((PyListObject *)op, newitem);
}
PyErr_BadInternalCall(); PyErr_BadInternalCall();
return -1; return -1;
} }
@ -844,9 +845,10 @@ static PyObject *
list_append(PyListObject *self, PyObject *object) list_append(PyListObject *self, PyObject *object)
/*[clinic end generated code: output=7c096003a29c0eae input=43a3fe48a7066e91]*/ /*[clinic end generated code: output=7c096003a29c0eae input=43a3fe48a7066e91]*/
{ {
if (app1(self, object) == 0) if (_PyList_AppendTakeRef(self, Py_NewRef(object)) < 0) {
Py_RETURN_NONE; return NULL;
return NULL; }
Py_RETURN_NONE;
} }
/*[clinic input] /*[clinic input]
@ -963,9 +965,7 @@ list_extend(PyListObject *self, PyObject *iterable)
Py_SET_SIZE(self, Py_SIZE(self) + 1); Py_SET_SIZE(self, Py_SIZE(self) + 1);
} }
else { else {
int status = app1(self, item); if (_PyList_AppendTakeRef(self, item) < 0)
Py_DECREF(item); /* append creates a new ref */
if (status < 0)
goto error; goto error;
} }
} }

13
Python/ceval.c
View file

@ -2213,10 +2213,7 @@ handle_eval_breaker:
TARGET(LIST_APPEND) { TARGET(LIST_APPEND) {
PyObject *v = POP(); PyObject *v = POP();
PyObject *list = PEEK(oparg); PyObject *list = PEEK(oparg);
int err; if (_PyList_AppendTakeRef((PyListObject *)list, v) < 0)
err = PyList_Append(list, v);
Py_DECREF(v);
if (err != 0)
goto error; goto error;
PREDICT(JUMP_BACKWARD_QUICK); PREDICT(JUMP_BACKWARD_QUICK);
DISPATCH(); DISPATCH();
@ -5044,14 +5041,12 @@ handle_eval_breaker:
DEOPT_IF(!PyList_Check(list), PRECALL); DEOPT_IF(!PyList_Check(list), PRECALL);
STAT_INC(PRECALL, hit); STAT_INC(PRECALL, hit);
SKIP_CALL(); SKIP_CALL();
PyObject *arg = TOP(); PyObject *arg = POP();
int err = PyList_Append(list, arg); if (_PyList_AppendTakeRef((PyListObject *)list, arg) < 0) {
if (err) {
goto error; goto error;
} }
Py_DECREF(arg);
Py_DECREF(list); Py_DECREF(list);
STACK_SHRINK(2); STACK_SHRINK(1);
Py_INCREF(Py_None); Py_INCREF(Py_None);
SET_TOP(Py_None); SET_TOP(Py_None);
Py_DECREF(callable); Py_DECREF(callable);