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gh-90213: Speed up right shifts of negative integers #30277

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Merged
markshannon merged 15 commits into from
May 2, 2022
Merged

gh-90213: Speed up right shifts of negative integers #30277

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9bf9dcd
bpo-46055: Speed up right shifts of negative integers
mdickinson Dec 27, 2021
ad69e48
Rework to remove duplication and move the shift==0 check earlier.
mdickinson Dec 28, 2021
cf7de3b
Update NEWS.d entry
mdickinson Dec 28, 2021
41de654
Revert unrelated spacing change
mdickinson Dec 28, 2021
27843b1
Fix unidiomatic decrement
mdickinson Dec 28, 2021
53a4e24
Don't handle the shift==0 special-case until we need to
mdickinson Dec 28, 2021
b3a1a8f
Fix incompatible types
mdickinson Dec 28, 2021
fd4ce81
Comment updates
mdickinson Jan 9, 2022
447e508
Updates from review
mdickinson Apr 12, 2022
1bf4063
Clean up loop declarations
mdickinson Apr 12, 2022
cfe47ac
Fix comment
mdickinson Apr 12, 2022
68e10a3
Remove an unnecessary 'else' branch
mdickinson Apr 12, 2022
5d8d8ef
New news entry
mdickinson Apr 12, 2022
c5e3f81
Merge remote-tracking branch 'upstream/main' into faster-rshift-of-ne…
mdickinson Apr 12, 2022
82c5ccd
One more assert
mdickinson Apr 12, 2022
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Clean up loop declarations
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@mdickinson
mdickinson committed Apr 12, 2022
commit 1bf40635e705cec8a47e5cf33b98000a0ecb78d1
7 changes: 3 additions & 4 deletions Objects/longobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4494,7 +4494,7 @@ static PyObject *
long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
{
PyLongObject *z = NULL;
Py_ssize_t newsize, hishift, i, j, size_a;
Py_ssize_t newsize, hishift, size_a;
twodigits accum;
int a_negative;

Expand Down Expand Up @@ -4566,14 +4566,13 @@ long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
}

accum >>= remshift;
for (i = 0, j = wordshift + 1; j < size_a; i++, j++) {
for (Py_ssize_t i = 0, j = wordshift + 1; j < size_a; i++, j++) {
accum += (twodigits)a->ob_digit[j] << hishift;
z->ob_digit[i] = (digit)(accum & PyLong_MASK);
accum >>= PyLong_SHIFT;
}
assert(i == newsize - 1);
assert(accum <= PyLong_MASK);
z->ob_digit[i] = (digit)accum;
z->ob_digit[newsize - 1] = (digit)accum;
z = maybe_small_long(long_normalize(z));
return (PyObject *)z;
}
Expand Down