I once implemented a VM in Ada and just used a large switch. I extensively benchmarked it and it was blazingly fast at -O3.

However, it was only fast when I used packages very sparingly. In contrast to the usual advice given in the Ada community, splitting up the implementation into several packages slowed down the main loop tremendously. I suspect this wouldn't happen with whole-program optimization in C, but believe that the version of gcc I was using didn't support that for Ada. Also, my Green Threads were slower than a single thread, no matter which tricks I tried.

It's an abandoned project now, since the accompanying assembler was hacked together in Racket and at some point I simply lost track of what was going on where :O