This content originally appeared on V8 and was authored by Ingvar Stepanyan (@RReverser)
Every four weeks, we create a new branch of V8 as part of our release process. Each version is branched from V8’s Git master immediately before a Chrome Beta milestone. Today we’re pleased to announce our newest branch, V8 version 9.5, which is in beta until its release in coordination with Chrome 95 Stable in several weeks. V8 v9.5 is filled with all sorts of developer-facing goodies. This post provides a preview of some of the highlights in anticipation of the release.
JavaScript #
Intl.DisplayNames v2 #
In v8.1 we launched the Intl.DisplayNames API API in Chrome 81, with supported types “language”, “region”, “script”, and “currency”. With v9.5, we now have added two new supported types: “calendar” and “dateTimeField”. They return the display names of different calendar types and date time fields correspondingly:
const esCalendarNames = new Intl.DisplayNames(['es'], { type: 'calendar' });
const frDateTimeFieldNames = new Intl.DisplayNames(['fr'], { type: 'dateTimeField' });
esCalendarNames.of('roc'); // "calendario de la República de China"
frDateTimeFieldNames.of('month'); // "mois"We also enhanced the support for the “language” type with a new languageDisplay option, which could be either “standard” or “dialect” (as the default value if not specified):
const jaDialectLanguageNames = new Intl.DisplayNames(['ja'], { type: 'language' });
const jaStandardLanguageNames = new Intl.DisplayNames(['ja'], { type: 'language' , languageDisplay: 'standard'});
jaDialectLanguageNames.of('en-US') // "アメリカ英語"
jaDialectLanguageNames.of('en-AU') // "オーストラリア英語"
jaDialectLanguageNames.of('en-GB') // "イギリス英語"
jaStandardLanguageNames.of('en-US') // "英語 (アメリカ合衆国)"
jaStandardLanguageNames.of('en-AU') // "英語 (オーストラリア)"
jaStandardLanguageNames.of('en-GB') // "英語 (イギリス)"Extended timeZoneName option #
Intl.DateTimeFormat API in v9.5 now supports four new values for the timeZoneName option:
- “shortGeneric” to output the name of the time zone as in a short generic non-location format, such as “PT”, “ET”, without indicating whether it is under daylight saving time.
- “longGeneric” to output the name of the time zone as in a short generic non-location format, such as “Pacific Time”, “Mountain Time”, without indicating whether it is under daylight saving time.
- “shortOffset” to output the name of the time zone as in the short localized GMT format, such as “GMT-8”.
- “longOffset” to output the name of the time zone as in the long localized GMT format, such as “GMT-0800”.
WebAssembly #
Exception Handling #
V8 now supports the WebAssembly Exception Handling (Wasm EH) proposal so that modules compiled with a compatible toolchain (e.g. Emscripten) can be executed in V8. The proposal is designed to keep the overhead low compared to the previous workarounds using JavaScript.
For example, we compiled the Binaryen optimizer to WebAssembly with old and new exception handling implementations.
When exception handling is enabled, the code size increase goes down from about 43% for the old JavaScript-based exception handling to only 9% for the new Wasm EH feature.
When we ran wasm-opt.wasm -O3 on a few big test files, Wasm EH's version showed no performance loss compared to the baseline without exceptions, while JavaScript-based EH version took around 30% longer.
However, Binaryen uses exception checking sparsely. In exception-heavy workloads the performance difference is expected to be even larger.
V8 API #
The main v8.h header file has been split into several parts which can be included separately. For instance v8-isolate.h now contains the v8::Isolate class. Many header files that declare methods passing v8::Local<T> can now import v8-forward.h to get the definition of v8::Local and all v8 heap object types.
Please use git log branch-heads/9.4..branch-heads/9.5 include/v8\*.h to get a list of the API changes.
Developers with an active V8 checkout can use git checkout -b 9.5 -t branch-heads/9.5 to experiment with the new features in V8 v9.5. Alternatively you can subscribe to Chrome’s Beta channel and try the new features out yourself soon.
This content originally appeared on V8 and was authored by Ingvar Stepanyan (@RReverser)
Ingvar Stepanyan (@RReverser) | Sciencx (2021-09-21T00:00:00+00:00) V8 release v9.5. Retrieved from https://www.scien.cx/2021/09/21/v8-release-v9-5/
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