[Python-checkins] bpo-46055: Streamline inner loop for right shifts (#30243)
mdickinson
webhook-mailer at python.org
Mon Dec 27 13:04:57 EST 2021
https://github.com/python/cpython/commit/360fedc2d2ce6ccb0dab554ef45fe83f7aea1862
commit: 360fedc2d2ce6ccb0dab554ef45fe83f7aea1862
branch: main
author: Mark Dickinson <mdickinson at enthought.com>
committer: mdickinson <dickinsm at gmail.com>
date: 2021-12-27T18:04:36Z
summary:
bpo-46055: Streamline inner loop for right shifts (#30243)
files:
M Objects/longobject.c
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 77434e67642f5..ddb3def402cdd 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -4491,7 +4491,7 @@ long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
{
PyLongObject *z = NULL;
Py_ssize_t newsize, hishift, i, j;
- digit lomask, himask;
+ twodigits accum;
if (Py_SIZE(a) < 0) {
/* Right shifting negative numbers is harder */
@@ -4511,16 +4511,17 @@ long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
if (newsize <= 0)
return PyLong_FromLong(0);
hishift = PyLong_SHIFT - remshift;
- lomask = ((digit)1 << hishift) - 1;
- himask = PyLong_MASK ^ lomask;
z = _PyLong_New(newsize);
if (z == NULL)
return NULL;
- for (i = 0, j = wordshift; i < newsize; i++, j++) {
- z->ob_digit[i] = (a->ob_digit[j] >> remshift) & lomask;
- if (i+1 < newsize)
- z->ob_digit[i] |= (a->ob_digit[j+1] << hishift) & himask;
+ j = wordshift;
+ accum = a->ob_digit[j++] >> remshift;
+ for (i = 0; j < Py_SIZE(a); i++, j++) {
+ accum |= (twodigits)a->ob_digit[j] << hishift;
+ z->ob_digit[i] = (digit)(accum & PyLong_MASK);
+ accum >>= PyLong_SHIFT;
}
+ z->ob_digit[i] = (digit)accum;
z = maybe_small_long(long_normalize(z));
}
return (PyObject *)z;
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