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bpo-42161: mathmodule.c: move _PyLong_GetOne() loop invariant (GH-26391)

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Move _PyLong_GetZero() and _PyLong_GetOne() loop invariants outside
loops in functions:

* math.comb()
* math.gcd()
* math.lcm()
* math.perm()
This commit is contained in:
Victor Stinner 2021-05-27 00:51:07 +02:00 • committed by GitHub
parent d8fd8c8568
commit 3e7ee02327
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 12 additions and 8 deletions
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20
Modules/mathmodule.c
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@ -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;
}