Intent to Extend Experiment: WebAssembly JS String Builtins

[Emanuel Ziegler]

Dear API owners,

We would like to request an extension of the origin trial for Wasm JS String Builtins. There were recent changes to the initialization of string constants (implicit imports) which improved startup time and binary size on local measurements.

We would like to use the experiment to verify the viability of this change in the wild (effect on load and startup times) and upcoming changes to it (variable import namespace for greater flexibility). Sheets/J2Wasm already implemented the first part and wants to roll it out to users in the next weeks as part of the origin trial.

The proposal is progressing well along the requested dimensions

• Draft spec (early draft is ok, but must be spec-like and associated with the appropriate standardization venue, or WICG)
• The proposal continues to be actively maintained and changed with plenty of community engagement.
• Recent changes mostly affected string constants and their initialization.
• TAG review (see exceptions)
• A TAG review has been requested and is scheduled for discussion.
• bit.ly/blink-signals requests
• Firefox/SpiderMonkey is actively working on their prototype and the champion behind this proposal.
• Safari/JSC expressed openness to the proposal but no official confirmation yet.
• Outreach for feedback from the spec community
• The proposal (including string constant changes) was voted to phase 3 at the on-site Wasm CG meeting on June 5 with unanimous consent.
• WPT tests
• WPTs will likely be added based on the already existing JS API tests in the proposal repository (see GitHub issue 33 on the proposal repository on this question).

More details on some of these items can be found in the updated experiment summary.

Thank you,

    Emanuel

Contact emails

ecmzi...@chromium.org, jkum...@chromium.org, ad...@chromium.org

Explainer

None

Specification

https://github.com/WebAssembly/js-string-builtins/blob/main/proposals/js-string-builtins/Overview.md

Summary

This feature exposes common JS string operations for easy import into WebAssembly and optimizations thereof. This allows creating and manipulating JS strings from WebAssembly without native support within WebAssembly while still allowing for a similar performance as native string references. The mechanism works by exposing suitably strict versions of JS string operations in the WebAssembly JS API. These can be imported by modules using externref as a generic data type for storing the strings. The engine can identify that these imports can be represented by native graph operators without the need for calling into JS. This leads to a comparable peak performance as native string operations while allowing quick interoperability with JS since no copying at the boundary is required when calling into arbitrary JS functions that consume strings.

Blink component

Blink>JavaScript>WebAssembly

TAG review

None

TAG review status

Pending

Chromium Trial Name

WebAssemblyJSStringBuiltins

Link to origin trial feedback summary

https://docs.google.com/document/d/1zL9goDsawTQUFuuQ8ddI_pUcLY1_iFOsHaDZ374dnGw/edit?usp=sharing

Origin Trial documentation link

https://github.com/WebAssembly/js-string-builtins/blob/main/proposals/js-string-builtins/Overview.md

Risks

Interoperability and Compatibility

None

Gecko: Positive

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/343)

Web developers: No signals

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

None

Goals for experimentation

Ongoing technical constraints

None

Debuggability

None

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

Is this feature fully tested by web-platform-tests?

No

Flag name on chrome://flags

None

Finch feature name

None

Non-finch justification

None

Requires code in //chrome?

False

Estimated milestones

Origin trial desktop first	119
Origin trial desktop last	127
Origin trial extension 1 end milestone	127

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6695587390423040?gate=5106659883220992

Links to previous Intent discussions

Intent to Experiment: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPAU7RyzxKa0Pj6q7B_jyfT%3DH%2BSK264%3Dx8wn1ans%3D8UjHRhctQ%40mail.gmail.com
Intent to Extend Experiment 1: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPAU7RyYPNTcmt1uHe279qW46ff3S%3DZ-M%3DHZjKn%3DK%2Bgp_0DyZw%40mail.gmail.com?utm_medium=email&utm_source=footer
Intent to Ship: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPAU7RyYPNTcmt1uHe279qW46ff3S%3DZ-M%3DHZjKn%3DK%2Bgp_0DyZw%40mail.gmail.com?utm_medium=email&utm_source=footer

This intent message was generated by Chrome Platform Status.