experiment with macOS M1 runners

[RalfJung]

Try running our macOS CI on the new free M1 runners. This would mean that our 3 jobs run 3 different OSes and 3 different host CPU architectures. :)

[RalfJung]

Hm, that doesn't seem to work -- they don't have cargo?
According to this Ruts is supposed to be installed.

[RalfJung]

Oh so the problem was the cache, interesting. No idea how a bad cache would lead to that kind of error, probably because some binaries have the wrong architecture or so?

And the build was very fast, too.
@rust-lang/miri what do you think, shall we give these runners a try? It's easy to switch back to the old runners if we're getting problems.

[bors]

☔ The latest upstream changes (presumably #3436) made this pull request unmergeable. Please resolve the merge conflicts.

[RalfJung]

One point I didn't realize is that this is still a tier 2 target. So there's some risk things break as rustc CI doesn't cover everything.

But it's also easy to revert this PR in the future, should it become a problem.

[RalfJung]

Judging from this GH announcement, macos-latest will switch to M1 machines some time soon (April - June). So we have to either do something like this PR or set the runner to macos-12 to get more time to migrate.

[saethlin]

I do not think the risk is very high. If aarch64 MacOS breaks, too many of us will know because we develop on it. Speed is nice. No objection to merging this.

[RalfJung]

I do not think the risk is very high. If aarch64 MacOS breaks, too many of us will know because we develop on it. Speed is nice. No objection to merging this.

Yeah, makes sense. And additionally we can serve as a canary for Rust compiler stuff breaking on M1 hosts, which is a good service to the compiler team. This target is clearly going to become tier 1, so we may as well be part of slowly increasing test coverage.

@bors r+

Cc @shepmaster since you seem to be tracking M1 progress. :)
Cc rust-lang/rust#73908

[bors]

📌 Commit 9e7ff74 has been approved by RalfJung

It is now in the queue for this repository.

[bors]

⌛ Testing commit 9e7ff74 with merge 38ed8a8...

[RalfJung]

@bors r+

[bors]

📌 Commit a99ed29 has been approved by RalfJung

It is now in the queue for this repository.

[bors]

⌛ Testing commit a99ed29 with merge 5918da6...

[bors]

☀️ Test successful - checks-actions
Approved by: RalfJung
Pushing 5918da6 to master...

[shepmaster]

this is still a tier 2 target

To the best of my knowledge, this is in name only. Right when the M1 runners came out we enabled tests and other things that the tier 1 platforms do. It’s mostly waiting on me to do the paperwork for the promotion and I’m just waiting for a bit of stability on GitHub’s side over a medium-length time period.

switch to M1 machines some time soon (April - June)

I had missed that, so that might be the sign I was waiting for…