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bpo-46055: Speed up binary shifting operators (GH-30044)

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Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
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Xinhang Xu 2021-12-28 02:36:55 +08:00 • committed by GitHub
parent 360fedc2d2
commit 3581c7abbe
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4 changed files with 80 additions and 3 deletions
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17
Objects/longobject.c
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@ -4493,6 +4493,15 @@ long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
Py_ssize_t newsize, hishift, i, j;
twodigits accum;
if (IS_MEDIUM_VALUE(a)) {
stwodigits m, x;
digit shift;
m = medium_value(a);
shift = wordshift == 0 ? remshift : PyLong_SHIFT;
x = m < 0 ? ~(~m >> shift) : m >> shift;
return _PyLong_FromSTwoDigits(x);
}
if (Py_SIZE(a) < 0) {
/* Right shifting negative numbers is harder */
PyLongObject *a1, *a2;
@ -4566,11 +4575,17 @@ _PyLong_Rshift(PyObject *a, size_t shiftby)
static PyObject *
long_lshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
{
/* This version due to Tim Peters */
PyLongObject *z = NULL;
Py_ssize_t oldsize, newsize, i, j;
twodigits accum;
if (wordshift == 0 && IS_MEDIUM_VALUE(a)) {
stwodigits m = medium_value(a);
// bypass undefined shift operator behavior
stwodigits x = m < 0 ? -(-m << remshift) : m << remshift;
return _PyLong_FromSTwoDigits(x);
}
oldsize = Py_ABS(Py_SIZE(a));
newsize = oldsize + wordshift;
if (remshift)