I think while interesting, the semantic gap is probably too large. E.g. the machine stores machine words on the stack, but the JVM stores Java values. And the i

I think while interesting, the semantic gap is probably too large. E.g. the machine stores machine words on the stack, but the JVM stores Java values. And the instruction set of the JVM is much richer, and it knows about many more concepts (types, classes, objects, boxing/unboxing, ...). So you'll have a significant translation layer anyway. If you have to pay that cost, then doing register allocation onto a conventional set of registers is probably cheap in comparison. And you want the conventional machine for its much, much higher performance.