Intent to prototype and ship: WebAssembly Wide Arithmetic proposal

[Ben Visness]

As of Firefox 155, we intend to enable the WebAssembly wide arithmetic proposal by default on all platforms.

Summary: 

This proposal adds four new numeric instructions to WebAssembly that perform 128-bit integer arithmetic: `i64.add128`, `i64.sub128`, `i64.mul_wide_s`, and `i64.mul_wide_u`. These instructions are useful for improving the performance of some workloads.

Bugs:

Tracker: https://bugzilla.mozilla.org/show_bug.cgi?id=wasm-wide-arithmetic
Enable by default: https://bugzilla.mozilla.org/show_bug.cgi?id=2062374

Specification:

https://github.com/WebAssembly/wide-arithmetic/

Standards Body:

W3C (WebAssembly CG & WG)

Platform Coverage:

All platforms

Preference:

javascript.options.wasm_wide_arithmetic

DevTools Bug:

N/A

Extensions Bug:

N/A

Use Counter:

N/A

Standards-Position Discussion:

None, covered by our blanket policy for Wasm proposals.

Other Browsers:

- Blink: Implemented, not yet shipped (https://chromium-review.googlesource.com/c/v8/v8/+/7639297)
- WebKit: Implemented, not yet shipped (https://bugs.webkit.org/show_bug.cgi?id=312213)

web-platform-tests:

None yet, but we run the official spec tests that will eventually be upstreamed into WPT.