Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 01ea2a8eb95530c8af1ba9596658bc3acbfefc9e
https://github.com/WebKit/WebKit/commit/01ea2a8eb95530c8af1ba9596658bc3acbfefc9e
Author: Sosuke Suzuki <[email protected]>
Date: 2026-08-06 (Thu, 06 Aug 2026)
Changed paths:
A JSTests/microbenchmarks/string-split-non-atom-subject.js
M Source/JavaScriptCore/runtime/StringPrototype.cpp
Log Message:
-----------
[JSC] `String#split` should not atomize the results of a non-atom subject
https://bugs.webkit.org/show_bug.cgi?id=320966
Reviewed by Yusuke Suzuki.
Splitting strings built at runtime (e.g. parsing CSV/log rows) is common, and
such
subjects are not atom strings. stringSplitFast still atomized every
identifier-like
result string and built an atom-strings array for them, even though the split
cache
only accepts atom subjects, so the atomization was pure waste.
Only take the atomize-and-cache path when the subject is an atom, matching what
regExpSplitFast already does. Non-atom subjects now produce plain substrings.
With this change, elements of the result array are no longer atom strings when
the
subject is not an atom. That being a performance regression is not a common
case; we
confirmed that no such case exists in JetStream.
base patched
string-split-non-atom-subject 156.1447+-4.6023 ^ 41.2708+-0.7647
^ definitely 3.7834x faster
Test: JSTests/microbenchmarks/string-split-non-atom-subject.js
* JSTests/microbenchmarks/string-split-non-atom-subject.js: Added.
(parseRow):
* Source/JavaScriptCore/runtime/StringPrototype.cpp:
(JSC::stringSplitFast):
Canonical link: https://commits.webkit.org/318764@main
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