You don't need to model the timing though.

What I'm saying with the type system comment is this: the cache side effects of speculation are desirable most of the time but not always. We should find a way to model data sensitivity in the type system so that a compiler can automatically choose to generate a side-effect-free code sequence where the side effects must be avoided (this assumes a future with ISA extensions that allow telling the CPU to prevent such side effects by blocking the speculative execution).