10000 bpo-46055: Speed up binary shifting operators by xuxinhang · Pull Request #30044 · python/cpython · GitHub
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bpo-46055: Speed up binary shifting operators #30044

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Merged
merged 18 commits into from
Dec 27, 2021
Merged

bpo-46055: Speed up binary shifting operators #30044

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7b11d7d
Perf: Accelerate binary shift op.
xuxinhang Dec 11, 2021
403652a
Fix: Ubuntu gcc segment fault.
xuxinhang Dec 12, 2021
dcd2796
Let PyLong_New accept a negtive size.
xuxinhang Dec 12, 2021
25bbf4d
Fix: Use Py_ARITHMETIC_RIGHT_SHIFT to avoid the undefined padding bah…
xuxinhang Dec 12, 2021
b2ef93d
Style: PEP7: add braces.
xuxinhang Dec 12, 2021
7d2203f
Fix: Bypass undefined shift operator behavior
xuxinhang Dec 13, 2021
932ad87
Revert "Let PyLong_New accept a negtive size."
xuxinhang Dec 22, 2021
596b8cf
Revert: Remove additional inline keywords.
xuxinhang Dec 22, 2021
6545e9a
Refactor: Simpilify code by using _PyLong_FromSTwoDigit
xuxinhang Dec 23, 2021
7f80cd9
Fix: Wrong rshift result.
xuxinhang Dec 23, 2021
b24c7dc
Test: More testcases.
xuxinhang Dec 23, 2021
c00a963
Refactor: Clean code.
xuxinhang Dec 23, 2021
b7ad599
Revert: Revert unrelated code.
xuxinhang Dec 23, 2021
c359521
Docs: A couple more things.
xuxinhang Dec 24, 2021
241da4c
Revert: medium_value
xuxinhang Dec 24, 2021
9ed09aa
Add attribution; fix typo
mdickinson Dec 27, 2021
c24ad0a
Merge branch 'main' into feat/binary_shift_optimization
mdickinson Dec 27, 2021
59672cf
Merge remote-tracking branch 'upstream/main' into feat/binary_shift_o…
mdickinson Dec 27, 2021
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Refactor: Clean code.
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@xuxinhang
xuxinhang committed Dec 23, 2021
commit c00a963661a9a48a9b29119b5f7eded570a37d77
17 changes: 8 additions & 9 deletions Objects/longobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4496,11 +4496,11 @@ long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
digit lomask, himask, omitmark;

if (IS_MEDIUM_VALUE(a)) {
stwodigits x;
if (wordshift > 0) {
return get_small_int(-(Py_SIZE(a) < 0));
}
x = Py_ARITHMETIC_RIGHT_SHIFT(stwodigits, medium_value(a), remshift);
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);
}

Expand Down Expand Up @@ -4590,14 +4590,13 @@ long_lshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
Py_ssize_t oldsize, newsize, i, j;
twodigits accum;

if (wordshift == 0 && IS_MEDIUM_VALUE(a) &&
(a->ob_digit[0] & ~(PyLong_MASK >> remshift)) == 0) {
if (wordshift == 0 && IS_MEDIUM_VALUE(a)) {
stwodigits m = medium_value(a);
// bypass undefined shift operator behavior
stwodigits x = (stwodigits)((twodigits)medium_value(a) << remshift);
stwodigits x = m < 0 ? -(-m << remshift) : m << remshift;
return _PyLong_FromSTwoDigits(x);
}

/* This version due to Tim Peters */
oldsize = Py_ABS(Py_SIZE(a));
newsize = oldsize + wordshift;
if (remshift)
Expand Down
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