https://github.com/python/cpython/commit/5f46ac97490ddfd8f7a4d01b9f765cccd00d0e72
commit: 5f46ac97490ddfd8f7a4d01b9f765cccd00d0e72
branch: main
author: XiaohongGong <[email protected]>
committer: eendebakpt <[email protected]>
date: 2026-11-07T23:18:39+01:00
summary:
gh-160872: Keep PyLong "x_divrem" inner loop carry in 64 bits (#161156)
* gh-160872: Keep PyLong "x_divrem" inner loop carry in 64 bits
---------
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-11-02-05-50-35.gh-issue-160872.x8NvzN.rst
M Objects/longobject.c
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-11-02-05-50-35.gh-issue-160872.x8NvzN.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-11-02-05-50-35.gh-issue-160872.x8NvzN.rst
new file mode 100644
index 00000000000000..2911abe2f166f1
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-11-02-05-50-35.gh-issue-160872.x8NvzN.rst
@@ -0,0 +1 @@
+Optimize division and remainder operations on large :class:`int` values.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 9d02793fdd6366..09bfe4ad464128 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -3325,8 +3325,7 @@ x_divrem(PyLongObject *v1, PyLongObject *w1, PyLongObject
**prem)
int d;
digit wm1, wm2, carry, q, r, vtop, *v0, *vk, *w0, *ak;
twodigits vv;
- sdigit zhi;
- stwodigits z;
+ stwodigits z, zhi;
/* We follow Knuth [The Art of Computer Programming, Vol. 2 (3rd
edn.), section 4.3.1, Algorithm D], except that we don't explicitly
@@ -3416,16 +3415,15 @@ x_divrem(PyLongObject *v1, PyLongObject *w1,
PyLongObject **prem)
for (i = 0; i < size_w; ++i) {
/* invariants: -PyLong_BASE <= -q <= zhi <= 0;
-PyLong_BASE * q <= z < PyLong_BASE */
- z = (sdigit)vk[i] + zhi -
+ z = (stwodigits)vk[i] + zhi -
(stwodigits)q * (stwodigits)w0[i];
vk[i] = (digit)z & PyLong_MASK;
- zhi = (sdigit)Py_ARITHMETIC_RIGHT_SHIFT(stwodigits,
- z, PyLong_SHIFT);
+ zhi = Py_ARITHMETIC_RIGHT_SHIFT(stwodigits, z, PyLong_SHIFT);
}
/* add w back if q was too large (this branch taken rarely) */
- assert((sdigit)vtop + zhi == -1 || (sdigit)vtop + zhi == 0);
- if ((sdigit)vtop + zhi < 0) {
+ assert((stwodigits)vtop + zhi == -1 || (stwodigits)vtop + zhi == 0);
+ if ((stwodigits)vtop + zhi < 0) {
carry = 0;
for (i = 0; i < size_w; ++i) {
carry += vk[i] + w0[i];
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