[Python-checkins] bpo-42161: mathmodule.c: move _PyLong_GetOne() loop invariant (GH-26391) (GH-26393)
vstinner
webhook-mailer at python.org
Wed May 26 19:13:25 EDT 2021
https://github.com/python/cpython/commit/4115996342278de7c2a1b59ac348322e7a4e9072
commit: 4115996342278de7c2a1b59ac348322e7a4e9072
branch: 3.10
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: vstinner <vstinner at python.org>
date: 2021-05-27T01:13:17+02:00
summary:
bpo-42161: mathmodule.c: move _PyLong_GetOne() loop invariant (GH-26391) (GH-26393)
Move _PyLong_GetZero() and _PyLong_GetOne() loop invariants outside
loops in functions:
* math.comb()
* math.gcd()
* math.lcm()
* math.perm()
(cherry picked from commit 3e7ee02327db13e4337374597cdc4458ecb9e3ad)
Co-authored-by: Victor Stinner <vstinner at python.org>
files:
M Modules/mathmodule.c
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index d0dd12d25966a..a2a2db29be343 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -845,13 +845,15 @@ math_gcd(PyObject *module, PyObject * const *args, Py_ssize_t nargs)
Py_SETREF(res, PyNumber_Absolute(res));
return res;
}
+
+ PyObject *one = _PyLong_GetOne(); // borrowed ref
for (i = 1; i < nargs; i++) {
x = _PyNumber_Index(args[i]);
if (x == NULL) {
Py_DECREF(res);
return NULL;
}
- if (res == _PyLong_GetOne()) {
+ if (res == one) {
/* Fast path: just check arguments.
It is okay to use identity comparison here. */
Py_DECREF(x);
@@ -918,13 +920,15 @@ math_lcm(PyObject *module, PyObject * const *args, Py_ssize_t nargs)
Py_SETREF(res, PyNumber_Absolute(res));
return res;
}
+
+ PyObject *zero = _PyLong_GetZero(); // borrowed ref
for (i = 1; i < nargs; i++) {
x = PyNumber_Index(args[i]);
if (x == NULL) {
Py_DECREF(res);
return NULL;
}
- if (res == _PyLong_GetZero()) {
+ if (res == zero) {
/* Fast path: just check arguments.
It is okay to use identity comparison here. */
Py_DECREF(x);
@@ -3293,10 +3297,10 @@ math_perm_impl(PyObject *module, PyObject *n, PyObject *k)
goto done;
}
- factor = n;
- Py_INCREF(factor);
+ factor = Py_NewRef(n);
+ PyObject *one = _PyLong_GetOne(); // borrowed ref
for (i = 1; i < factors; ++i) {
- Py_SETREF(factor, PyNumber_Subtract(factor, _PyLong_GetOne()));
+ Py_SETREF(factor, PyNumber_Subtract(factor, one));
if (factor == NULL) {
goto error;
}
@@ -3415,10 +3419,10 @@ math_comb_impl(PyObject *module, PyObject *n, PyObject *k)
goto done;
}
- factor = n;
- Py_INCREF(factor);
+ factor = Py_NewRef(n);
+ PyObject *one = _PyLong_GetOne(); // borrowed ref
for (i = 1; i < factors; ++i) {
- Py_SETREF(factor, PyNumber_Subtract(factor, _PyLong_GetOne()));
+ Py_SETREF(factor, PyNumber_Subtract(factor, one));
if (factor == NULL) {
goto error;
}
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