Intent to Ship: WebAssembly Memory64

[Emanuel Ziegler]

Dear API owners,

We are planning to ship WebAssembly Memory64 in M133 after its phase 4 vote in the WebAssembly community on November 5 with overwhelming support (25 strongly in favor, 8 in favor, no neutral votes and no votes against).

The feature is fully implemented in V8 and Mozilla also has a working implementation. All other required reviews have been obtained on the Chrome Feature page.

If you have any further questions, let us know.

Best regards,

    Emanuel

Contact emails

s...@google.com, clem...@google.com, ecmzi...@google.com

Explainer

https://github.com/WebAssembly/memory64/blob/main/proposals/memory64/Overview.md

Specification

https://github.com/WebAssembly/memory64/blob/main/proposals/memory64/Overview.md

Summary

The memory64 proposal adds support for linear WebAssembly memories with size larger than 2^32 bits. It provides no new instructions, but instead extends the existing instructions to allow 64-bit indexes for memories and tables.

Blink component

Blink>JavaScript>WebAssembly

Search tags

Wasm, WebAssembly, Memory64

TAG review

Not required as per https://www.chromium.org/blink/guidelines/api-owners/process-exceptions/ because this feature has been voted by the WebAssembly community group to phase 4 on November 05, 2024 (https://github.com/WebAssembly/proposals?tab=readme-ov-file#phase-4---standardize-the-feature-wg).

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Gecko: Positive

WebKit: In development

Web developers: Positive

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?

Debuggability

Memory64 is fully debuggable in DevTools.

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

The proposal comes with exhaustive spec tests; we pass them.

Flag name on about://flags

enable-experimental-webassembly-features

Finch feature name

None

Non-finch justification

The feature would not change any existing behavior unless the website specifically uses the new instructions to create and access large memories. As so far no website has adopted this feature in production use, a Finch trial would provide no coverage at all.

Requires code in //chrome?

False

Launch bug

https://launch.corp.google.com/launch/4201294

Estimated milestones

Shipping on desktop	133
DevTrial on desktop	112
Shipping on Android	133
DevTrial on Android	112
Shipping on WebView	133

Anticipated spec changes

Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5070065734516736?gate=5648397937147904

This intent message was generated by Chrome Platform Status.

[Rick Byers]

LGTM1, I'm excited to see this ship!

I'm also terrified about how many of my tabs will want to use more than 4GB of RAM at once for their AI models, but of course that is not a good reason to hold back the full power of devices from web developers. Thank you for doing all the work to extend WASM memory beyond the 32-bit limit!

Rick

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[Mike Taylor]

LGTM2

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[Chris Harrelson]

LGTM3

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