https://github.com/python/cpython/commit/360fedc2d2ce6ccb0dab554ef45fe83f7ae... commit: 360fedc2d2ce6ccb0dab554ef45fe83f7aea1862 branch: main author: Mark Dickinson <mdickinson@enthought.com> committer: mdickinson <dickinsm@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;