[PSA] The Evergreen Public Service Announcements Thread

[bnjbvr]

This issue should serve as a central point of communication with Cranelift users / embedders, because we don't have one yet.

For the record, we have two real-time chat systems being used at the moment:

• IRC (irc.mozilla.org in channel #cranelift)
• Gitter room

In the future, it is likely that a single real-time chat system is going to be used. The choice of which one is currently deferred to Mozilla, which is in the process of switching over from IRC to something else.

If you're a Cranelift embedder / user, and want to stay aware of organizational changes / security issues, you're invited to subscribe to this issue. Also, don't hesitate to say hi! 🙂

[bnjbvr]

Starting with a mundane PSA: every pull request will now need a review before getting merged, as discussed with Dan and others. This ensures a high code quality, which is a requirement since Cranelift is embedded in Firefox and can be experimentally used (off by default) to compile wasm code.

[bnjbvr]

I've enabled the wiki so we have a place where to put tutorials / hack notes / documentation that wouldn't be well on docs.rs. Right now this only includes Spidermonkey-related information which was on private documents for no good reason, so sharing it here. Feel free to add any more content there if you'd like to!

[bnjbvr]

We'll be using Zulip for instant communication. The IRC room on Mozilla's IRC network will disappear with the rest of the IRC network (to be shut down soon), and the Gitter room is no longer an official place. Yay for a single instant communication platform!

[bjorn3]

The Cranelift repository has been merged into Wasmtime. See #1185 for more info about why.

[bnjbvr]

As #1930 may land soon, and Spectre mitigations will be enabled by default as part of this patch, embedders who are using explicit bounds checks for heaps should be aware that there's going to be a small performance cost implied by this, and that they might want to disable the spectre checks if their environment makes it safe to do so.

While we don't have precise numbers, the overhead should be pretty small (generate one immediate + one conditional move based for each heap bounds checks). It is possible to disable it, if the embedder's environment is safe under Spectre attacks (e.g. each wasm runs its own process); set the Cranelift setting enable_heap_access_spectre_mitigation to false, in this case.

[bjorn3]

The old x86 backend has been removed in #3009 in accordance with bytecodealliance/rfcs#12.