1705446 - WASM simd pref is not read correctly in Firefox (was: WASM SIMD support is broken)

Status: RESOLVED FIXED

(Core :: JavaScript: WebAssembly, defect, P1)

Description

[Gian-Carlo Pascutto [:gcp]]

8:22.16 INFO: Last good revision: d5390c04b7ba6c977f704306a4b5bf6fab16248f
8:22.16 INFO: First bad revision: f89e1e839debb71ee6a3f49fee146a0d03c6a537
8:22.16 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=d5390c04b7ba6c977f704306a4b5bf6fab16248f&tochange=f89e1e839debb71ee6a3f49fee146a0d03c6a537

STR:

1. Make sure javascript.options.wasm_simd = true
2. Go to lichess.org
3. Tools->Analysis board
4. The pane on the right should say "Stockfish 13 NNUE". If WASM SIMD is broken, it will say "Stockfish 11+HCE".

Background: https://lichess.org/blog/YDOKRxQAACgAREB3/stockfish-13-nnue-on-lichess

Comment 1

[Lars T Hansen [:lth]]

OK, something fishy here.

This is the program lichess uses to detect SIMD:

(module
  (type (;0;) (func (result v128)))
  (func (;0;) (type 0) (result v128)
    i32.const 0
    i32x4.splat
    i32.const 0
    i32x4.splat
    i32x4.dot_i16x8_s)
  (export "test" (func 0)))

This validates as it should in the spidermonkey shell, but not in Firefox when I step through the lichess detection code in the debugger. So something is definitely up.

Comment 2

[Lars T Hansen [:lth]]

Attachment: nnue.html

Test case for browser. With SIMD enabled, this should print 'true' but it prints 'false' (current Nightly).

Comment 3

[Lars T Hansen [:lth]]

Attachment: Bug 1705446 - Fix Firefox pref names in WasmFeatures. r?rhunt

The features rewrite got the names of the Firefox wasm prefs wrong, they
all have a wasm_ prefix that got chopped off. We could discuss whether the
prefix should be added in XPCJSContext.cpp or in the WasmFeatures list,
but I think the latter is clearer.

It sucks that we don't have meaningful test cases for this. A manual
test case (see bug) is easy, but how to automate it?

Comment 4

[Lars T Hansen [:lth]]

Patch fixes the problem on lichess.

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1677204

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/cb26d49c9f18
Fix Firefox pref names in WasmFeatures.  r=rhunt

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/cb26d49c9f18