Intent to ship: WebAssembly 64-bit mode (memory64)

[Ben Visness]

We intend to enable WebAssembly Memory64 by default in Firefox 134.

Summary: WebAssembly memory currently uses 32-bit pointers and is restricted to a maximum size of 4GiB. The Memory64 proposal adds a 64-bit addressing mode to both memories and tables, allowing for larger memories (currently up to 8GiB, soon up to 16GiB).

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1677586

Bug to enable by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1929590

Specification: https://github.com/WebAssembly/memory64

Standards Body: WebAssembly CG at the W3C

Platform coverage: All platforms

Preference: javascript.options.wasm_memory64

DevTools bug: N/A

Other browsers:

• Blink: Behind a flag, estimated to ship in 113 (https://chromestatus.com/feature/5070065734516736)
• WebKit: No status

web-platform-tests: The JS API is covered by WPT tests here: https://github.com/WebAssembly/memory64/tree/main/test/js-api. These tests are not yet upstreamed into mozilla-central but have been manually verified. The rest of the proposal is covered by our own JS tests and the official WebAssembly spec tests (https://github.com/WebAssembly/memory64/tree/main/test/core).

[Ben Visness]

Correction: Blink expects to ship Memory64 in version 133, not 113.