Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 2b8c08245ca45124187a717bd6b26c4604f8b961
https://github.com/WebKit/WebKit/commit/2b8c08245ca45124187a717bd6b26c4604f8b961
Author: Sosuke Suzuki <[email protected]>
Date: 2026-06-18 (Thu, 18 Jun 2026)
Changed paths:
A JSTests/microbenchmarks/temporal-instant-to-locale-string.js
A JSTests/microbenchmarks/temporal-plain-date-time-to-locale-string.js
A JSTests/microbenchmarks/temporal-plain-date-to-locale-string.js
A JSTests/microbenchmarks/temporal-plain-time-to-locale-string.js
A JSTests/stress/temporal-tolocalestring-default-formatter.js
M Source/JavaScriptCore/runtime/TemporalInstantPrototype.cpp
M Source/JavaScriptCore/runtime/TemporalPlainDatePrototype.cpp
M Source/JavaScriptCore/runtime/TemporalPlainDateTimePrototype.cpp
M Source/JavaScriptCore/runtime/TemporalPlainMonthDayPrototype.cpp
M Source/JavaScriptCore/runtime/TemporalPlainTimePrototype.cpp
M Source/JavaScriptCore/runtime/TemporalPlainYearMonthPrototype.cpp
Log Message:
-----------
[JSC][Temporal] `toLocaleString` should reuse the per-globalObject default
`IntlDateTimeFormat` when locales/options are undefined
https://bugs.webkit.org/show_bug.cgi?id=315974
Reviewed by Yusuke Suzuki.
All six Temporal toLocaleString implementations created and initialized a fresh
IntlDateTimeFormat on every call, even in the most common case where both
locales
and options are undefined. initializeDateTimeFormat is the most expensive Intl
constructor (~100us per call), and because the formatter was discarded after
each
call, its internal per-TemporalFieldKind formatter cache
(m_temporalFormatterCache)
was rebuilt every time as well.
Follow the same approach as Date.prototype.toLocaleString / toLocaleDateString /
toLocaleTimeString: when both locales and options are undefined, reuse the
per-globalObject default formatters. The (RequiredComponent, Defaults) pairs
used
by each Temporal type match the existing defaults exactly, so no new
globalObject
members are needed:
- PlainDate, PlainMonthDay, PlainYearMonth -> defaultDateFormat() (Date, Date)
- PlainTime -> defaultTimeFormat() (Time, Time)
- PlainDateTime, Instant -> defaultDateTimeFormat() (Any, All)
This is unobservable: with undefined arguments, initializeDateTimeFormat runs no
user code, so the resulting configuration is deterministic. Sharing is also safe
because the legacy Date path formats through m_dateFormat while the Temporal
path
formats through m_temporalFormatterCache, which are disjoint. As a bonus, the
Temporal formatter cache now survives across calls.
temporal-plain-date-to-locale-string 87.4065+-0.6976 ^
0.6863+-0.0602 ^ definitely 127.3515x faster
temporal-plain-time-to-locale-string 87.8948+-1.6492 ^
0.7042+-0.0537 ^ definitely 124.8110x faster
temporal-plain-date-time-to-locale-string 95.9008+-0.7969 ^
0.9443+-0.0996 ^ definitely 101.5602x faster
temporal-instant-to-locale-string 99.6770+-1.3693 ^
1.0900+-0.0762 ^ definitely 91.4445x faster
date-to-locale-string, date-to-locale-date-string, and
date-to-locale-time-string
remain neutral.
Tests: JSTests/microbenchmarks/temporal-instant-to-locale-string.js
JSTests/microbenchmarks/temporal-plain-date-time-to-locale-string.js
JSTests/microbenchmarks/temporal-plain-date-to-locale-string.js
JSTests/microbenchmarks/temporal-plain-time-to-locale-string.js
JSTests/stress/temporal-tolocalestring-default-formatter.js
* JSTests/microbenchmarks/temporal-instant-to-locale-string.js: Added.
* JSTests/microbenchmarks/temporal-plain-date-time-to-locale-string.js: Added.
* JSTests/microbenchmarks/temporal-plain-date-to-locale-string.js: Added.
* JSTests/microbenchmarks/temporal-plain-time-to-locale-string.js: Added.
* JSTests/stress/temporal-tolocalestring-default-formatter.js: Added.
(shouldBe):
(const.object.of.formattable.object.toLocaleString):
(i.formattable.forEach):
* Source/JavaScriptCore/runtime/TemporalInstantPrototype.cpp:
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/TemporalPlainDatePrototype.cpp:
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/TemporalPlainDateTimePrototype.cpp:
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/TemporalPlainMonthDayPrototype.cpp:
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/TemporalPlainTimePrototype.cpp:
(JSC::JSC_DEFINE_HOST_FUNCTION):
* Source/JavaScriptCore/runtime/TemporalPlainYearMonthPrototype.cpp:
(JSC::JSC_DEFINE_HOST_FUNCTION):
Canonical link: https://commits.webkit.org/315508@main
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