[toast0]

Well pre-emption only happens at function call or return, or when a NIF calls the special function to allow for it; if all the math was in a single function, with no interleaved function calls (possibly after inlining?), unbox, math away, and rebox could work.

There wouldn't need to be an indication of intent, other than writing the math separate from any function calls. I don't know how much code fits this pattern, but it's an idea that could be explored. I think that's part of what hipe is supposed to do, but I haven't looked into hipe in a long time.