In Rust you can probably get away with not speculating and thus having "imprecise exceptions" for overflow and maybe array reads (if you don't care about side c

In Rust you can probably get away with not speculating and thus having "imprecise exceptions" for overflow and maybe array reads (if you don't care about side channels), since panic essentially destroys all non-Mutex-protected accessible memory anyway and Mutex-protected memory is made inaccessible via poisoning (as long as they don't get moved through things like library calls and atomic ops). It would require a minor compatibility break, significant checking work and changes to unsafe code to make it work, but it should be doable. Array writes do need precise checking though, since otherwise you can write to arbitrary memory.