Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 459880fdd40351501295040dd219ef965256dea9
https://github.com/WebKit/WebKit/commit/459880fdd40351501295040dd219ef965256dea9
Author: Sosuke Suzuki <[email protected]>
Date: 2026-10-07 (Wed, 07 Oct 2026)
Changed paths:
A JSTests/microbenchmarks/string-iterator-for-of-16bit-ascii.js
A JSTests/stress/string-iterator-16bit-single-character.js
M Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp
M Source/JavaScriptCore/ftl/FTLLowerDFGToB3.cpp
Log Message:
-----------
[JSC] DFG / FTL `StringIteratorNext` should inline Latin-1 characters in
16-bit strings
https://bugs.webkit.org/show_bug.cgi?id=326316
Reviewed by Yusuke Suzuki.
StringIteratorNext called operationStringIteratorNext for every character of a
16-bit string. A string is 16-bit as soon as it has one non-Latin-1 character,
so its ASCII characters took the slow path too.
This patch reads the character of a 16-bit string inline. If it is
maxSingleCharacterString or less, we return the cached single-character string
as we do for 8-bit strings. Larger characters still call the operation.
ToT
Patched
string-iterator-for-of-16bit-ascii 176.0537+-1.1032 ^
80.7716+-5.3993 ^ definitely 2.1796x faster
Tests: JSTests/microbenchmarks/string-iterator-for-of-16bit-ascii.js
JSTests/stress/string-iterator-16bit-single-character.js
* JSTests/microbenchmarks/string-iterator-for-of-16bit-ascii.js: Added.
(countE):
* JSTests/stress/string-iterator-16bit-single-character.js: Added.
(shouldBe):
(collect):
(collectWithNext):
(countE):
(makeRope):
* Source/JavaScriptCore/dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::compileStringIteratorNext):
* Source/JavaScriptCore/ftl/FTLLowerDFGToB3.cpp:
(JSC::FTL::DFG::LowerDFGToB3::compileCompareStrictEq):
Canonical link: https://commits.webkit.org/323062@main
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