Pointer comparison of live non-heap allocations is suspicious

[oli-obk]

In https://github.com/solson/miri/blob/80a6e739424728d7505587ea6c53c39d6687cb59/src/operator.rs#L151 we compare pointers directly, even if they are from different allocations, as long as both are inbounds of live allocations.

Unfortunately optimizations might bite us:

&42 as *const u32 == &42 as *const u32

can be true or false depending on how these promoteds get deduplicated. Even for explicit local variables

let x = 42;
let y = 42;
&x as *const u32 == &y as *const u32

an optimizer may merge the two variables if they are guaranteed equal (especially if their types are Copy).

So we can essentially only compare live heap allocations, static items and mutable local variables, since these are guaranteed distinct in all models I know.

[RalfJung]

This is basically #131, right?

[oli-obk]

Yes