Isn't using bottom bit is how most runtimes represent their ints taking advantage of the fact that gc pointers are aligned? This is common practice afaiu.
Sure, but for the bottom bit, 64-bit addressing doesn't come into it. If you only want to steal bits at the bottom and have pointers with greater than single byte alignment this worked just fine on a 32-bit CPU already.
I was reacting to the claim that this mitigates the overhead (larger pointer size) of 64-bit addressing. You can steal bits at the top but it's probably a bad idea.
