Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 13a1f2916933547024ee020d94031096a41eb7cb
https://github.com/WebKit/WebKit/commit/13a1f2916933547024ee020d94031096a41eb7cb
Author: Sosuke Suzuki <[email protected]>
Date: 2026-10-03 (Sat, 03 Oct 2026)
Changed paths:
M Source/JavaScriptCore/runtime/JSBigInt.cpp
Log Message:
-----------
[JSC] `JSBigInt::divideSchoolbook` should not allocate for Burnikel-Ziegler
leaves
https://bugs.webkit.org/show_bug.cgi?id=326174
Reviewed by Yusuke Suzuki.
divideSchoolbook copies the dividend into a Vector<Digit, 16> that is one
digit longer than the dividend. Burnikel-Ziegler division, added in
322437@main, calls it once per leaf of its recursion. A leaf has a divisor of
8 to 15 digits and a dividend of up to twice that, so the copy has 17 to 31
digits and is allocated on the heap every time: 32 times for 512 / 256 digits,
4 times for 71 / 24.
Give the Vector an inline capacity of 32, which covers every leaf. A
schoolbook division with a dividend of 16 to 31 digits, which does not go
through Burnikel-Ziegler division, no longer allocates either.
x % y in nanoseconds, median of 15 runs on x86-64:
digits Before After
71 / 24 2467.1 2414.7 (-2.1%)
200 / 24 9199.8 8972.7 (-2.5%)
2000 / 24 111833.7 108852.7 (-2.7%)
2000 / 40 148339.3 144653.4 (-2.5%)
8000 / 24 471837.7 460385.6 (-2.4%)
512 / 256 70299.3 69657.7 (-0.9%)
4096 / 2048 1842756.3 1836428.6 (-0.3%)
24 / 12 406.8 385.4 (-5.3%)
30 / 8 494.2 475.9 (-3.7%)
12 / 6 152.5 152.9 (+0.3%)
* Source/JavaScriptCore/runtime/JSBigInt.cpp:
(JSC::JSBigInt::divideSchoolbook):
(JSC::JSBigInt::burnikelZieglerBasecase):
Canonical link: https://commits.webkit.org/322597@main
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