That's pretty nifty, but it seems like something a really good compiler could achieve automatically. Of course I'm not sure if any compilers actually are that good.
This is not exactly how fast bytecode interpreters are implemented. There is one next step - pre-caching the jump table straight into the bytecode. And there is absolutely no way compiler can transform your ad hoc switch-based interpreter into a threaded code interpreter automatically - it is not allowed to rewrite your data willy-nilly.
Hadn't thought of that, but it sounds interesting. I guess this means that opcodes in your bytecode need to be large enough to store a pointer, this could involve some tradeoffs in terms of minimizing instructions vs fitting in the cache, but I suppose it could fall on the right side of things often enough.
An offset from the first label, or some nearby alignment point? Makes sense.
Do you have a pointer to the relevant part of OCaml's source? The whole thing is probably worth a read, but don't think I can set aside enough time for that soon, and it could take me a while to find the right part.
This is a fairly mechanical conversion, so suppose a sufficiently smart compiler could do that.
But assuming a sufficiently smart compiler when you depend on your code being fast tends to cause issues. Especially if you expect it to run on a bunch of platforms with compilers of varying qualities. Last time I saw code last this, we certainly couldn't rely on compilers being particularly smart, and we did care about speed.
