Hrm, interesting. First time I've heard of such a thing. Would have expected the Rust devs to have rolled back emitting noalias if it were still causing miscompiles. A quick glance through the bug tracker didn't turn up anything obvious, though I wouldn't be surprised if I just missed it.

For what it's worth, according to Godbolt the test program in your probe seems to work correctly for Clang 12.0.0 and later, which IIRC corresponds to when Rust (re-(re-?))enabled emitting noalias.