https://github.com/python/cpython/commit/119bcfad9cac9ac8fa5fa6c0f3ee3ccfca778fe1
commit: 119bcfad9cac9ac8fa5fa6c0f3ee3ccfca778fe1
branch: main
author: Chris Eibl <138194463+chris-e...@users.noreply.github.com>
committer: picnixz <10796600+picn...@users.noreply.github.com>
date: 2025-03-13T12:06:56+01:00
summary:
gh-129149: Add fast path for medium-sized integers in `PyLong_FromSsize_t()`
(#129301)
The implementation of `PyLong_FromLong()`, `PyLong_FromLongLong()` and
`PyLong_FromSsize_t()`
are now handled by a common macro `PYLONG_FROM_INT` which contains fast paths
depending on the
size of the integer to convert. Consequently, `PyLong_FromSsize_t()` for
medium-sized integers is faster
by roughly 25%.
---------
Co-authored-by: Sergey B Kirpichev <skirpic...@gmail.com>
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2025-01-25-20-07-03.gh-issue-129149.njeFJi.rst
M Lib/test/test_capi/test_long.py
M Objects/longobject.c
diff --git a/Lib/test/test_capi/test_long.py b/Lib/test/test_capi/test_long.py
index a371f634432b6d..d3156645eeec2d 100644
--- a/Lib/test/test_capi/test_long.py
+++ b/Lib/test/test_capi/test_long.py
@@ -168,9 +168,9 @@ def check_long_asint(self, func, min_val, max_val, *,
mask=False,
negative_value_error=OverflowError):
# round trip (object -> C integer -> object)
- values = (0, 1, 1234, max_val)
+ values = (0, 1, 512, 1234, max_val)
if min_val < 0:
- values += (-1, min_val)
+ values += (-1, -512, -1234, min_val)
for value in values:
with self.subTest(value=value):
self.assertEqual(func(value), value)
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2025-01-25-20-07-03.gh-issue-129149.njeFJi.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-25-20-07-03.gh-issue-129149.njeFJi.rst
new file mode 100644
index 00000000000000..b74607986d9a2e
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2025-01-25-20-07-03.gh-issue-129149.njeFJi.rst
@@ -0,0 +1,2 @@
+Add fast path for medium-size integers in :c:func:`PyLong_FromSsize_t`.
+Patch by Chris Eibl.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index ab5cfab74d8a34..51ecbd9e0ee0bd 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -332,49 +332,51 @@ _PyLong_Negate(PyLongObject **x_p)
Py_DECREF(x);
}
+#define PYLONG_FROM_INT(UINT_TYPE, INT_TYPE, ival)
\
+ do {
\
+ /* Handle small and medium cases. */
\
+ if (IS_SMALL_INT(ival)) {
\
+ return get_small_int((sdigit)(ival));
\
+ }
\
+ if (-(INT_TYPE)PyLong_MASK <= (ival) && (ival) <=
(INT_TYPE)PyLong_MASK) { \
+ return _PyLong_FromMedium((sdigit)(ival));
\
+ }
\
+ UINT_TYPE abs_ival = (ival) < 0 ? 0U-(UINT_TYPE)(ival) :
(UINT_TYPE)(ival); \
+ /* Do shift in two steps to avoid possible undefined behavior. */
\
+ UINT_TYPE t = abs_ival >> PyLong_SHIFT >> PyLong_SHIFT;
\
+ /* Count digits (at least two - smaller cases were handled above). */
\
+ Py_ssize_t ndigits = 2;
\
+ while (t) {
\
+ ++ndigits;
\
+ t >>= PyLong_SHIFT;
\
+ }
\
+ /* Construct output value. */
\
+ PyLongObject *v = long_alloc(ndigits);
\
+ if (v == NULL) {
\
+ return NULL;
\
+ }
\
+ digit *p = v->long_value.ob_digit;
\
+ _PyLong_SetSignAndDigitCount(v, (ival) < 0 ? -1 : 1, ndigits);
\
+ t = abs_ival;
\
+ while (t) {
\
+ *p++ = (digit)(t & PyLong_MASK);
\
+ t >>= PyLong_SHIFT;
\
+ }
\
+ return (PyObject *)v;
\
+ } while(0)
+
+
/* Create a new int object from a C long int */
PyObject *
PyLong_FromLong(long ival)
{
- PyLongObject *v;
- unsigned long abs_ival, t;
- int ndigits;
-
- /* Handle small and medium cases. */
- if (IS_SMALL_INT(ival)) {
- return get_small_int((sdigit)ival);
- }
- if (-(long)PyLong_MASK <= ival && ival <= (long)PyLong_MASK) {
- return _PyLong_FromMedium((sdigit)ival);
- }
-
- /* Count digits (at least two - smaller cases were handled above). */
- abs_ival = ival < 0 ? 0U-(unsigned long)ival : (unsigned long)ival;
- /* Do shift in two steps to avoid possible undefined behavior. */
- t = abs_ival >> PyLong_SHIFT >> PyLong_SHIFT;
- ndigits = 2;
- while (t) {
- ++ndigits;
- t >>= PyLong_SHIFT;
- }
-
- /* Construct output value. */
- v = long_alloc(ndigits);
- if (v != NULL) {
- digit *p = v->long_value.ob_digit;
- _PyLong_SetSignAndDigitCount(v, ival < 0 ? -1 : 1, ndigits);
- t = abs_ival;
- while (t) {
- *p++ = (digit)(t & PyLong_MASK);
- t >>= PyLong_SHIFT;
- }
- }
- return (PyObject *)v;
+ PYLONG_FROM_INT(unsigned long, long, ival);
}
#define PYLONG_FROM_UINT(INT_TYPE, ival) \
do { \
+ /* Handle small and medium cases. */ \
if (IS_SMALL_UINT(ival)) { \
return get_small_int((sdigit)(ival)); \
} \
@@ -383,12 +385,13 @@ PyLong_FromLong(long ival)
} \
/* Do shift in two steps to avoid possible undefined behavior. */ \
INT_TYPE t = (ival) >> PyLong_SHIFT >> PyLong_SHIFT; \
- /* Count the number of Python digits. */ \
+ /* Count digits (at least two - smaller cases were handled above). */ \
Py_ssize_t ndigits = 2; \
while (t) { \
++ndigits; \
t >>= PyLong_SHIFT; \
} \
+ /* Construct output value. */ \
PyLongObject *v = long_alloc(ndigits); \
if (v == NULL) { \
return NULL; \
@@ -1482,40 +1485,7 @@ PyLong_AsVoidPtr(PyObject *vv)
PyObject *
PyLong_FromLongLong(long long ival)
{
- PyLongObject *v;
- unsigned long long abs_ival, t;
- int ndigits;
-
- /* Handle small and medium cases. */
- if (IS_SMALL_INT(ival)) {
- return get_small_int((sdigit)ival);
- }
- if (-(long long)PyLong_MASK <= ival && ival <= (long long)PyLong_MASK) {
- return _PyLong_FromMedium((sdigit)ival);
- }
-
- /* Count digits (at least two - smaller cases were handled above). */
- abs_ival = ival < 0 ? 0U-(unsigned long long)ival : (unsigned long
long)ival;
- /* Do shift in two steps to avoid possible undefined behavior. */
- t = abs_ival >> PyLong_SHIFT >> PyLong_SHIFT;
- ndigits = 2;
- while (t) {
- ++ndigits;
- t >>= PyLong_SHIFT;
- }
-
- /* Construct output value. */
- v = long_alloc(ndigits);
- if (v != NULL) {
- digit *p = v->long_value.ob_digit;
- _PyLong_SetSignAndDigitCount(v, ival < 0 ? -1 : 1, ndigits);
- t = abs_ival;
- while (t) {
- *p++ = (digit)(t & PyLong_MASK);
- t >>= PyLong_SHIFT;
- }
- }
- return (PyObject *)v;
+ PYLONG_FROM_INT(unsigned long long, long long, ival);
}
/* Create a new int object from a C Py_ssize_t. */
@@ -1523,42 +1493,7 @@ PyLong_FromLongLong(long long ival)
PyObject *
PyLong_FromSsize_t(Py_ssize_t ival)
{
- PyLongObject *v;
- size_t abs_ival;
- size_t t; /* unsigned so >> doesn't propagate sign bit */
- int ndigits = 0;
- int negative = 0;
-
- if (IS_SMALL_INT(ival)) {
- return get_small_int((sdigit)ival);
- }
-
- if (ival < 0) {
- /* avoid signed overflow when ival = SIZE_T_MIN */
- abs_ival = (size_t)(-1-ival)+1;
- negative = 1;
- }
- else {
- abs_ival = (size_t)ival;
- }
-
- /* Count the number of Python digits. */
- t = abs_ival;
- while (t) {
- ++ndigits;
- t >>= PyLong_SHIFT;
- }
- v = long_alloc(ndigits);
- if (v != NULL) {
- digit *p = v->long_value.ob_digit;
- _PyLong_SetSignAndDigitCount(v, negative ? -1 : 1, ndigits);
- t = abs_ival;
- while (t) {
- *p++ = (digit)(t & PyLong_MASK);
- t >>= PyLong_SHIFT;
- }
- }
- return (PyObject *)v;
+ PYLONG_FROM_INT(size_t, Py_ssize_t, ival);
}
/* Get a C long long int from an int object or any object that has an
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