Hi,
I did(/am doing) something similar: a VM on a resource constrained system. I made some experiments with jump tables, ifs and such and settled with plain "switch/case".
In my VM the opcode is always the first byte of the instruction so I can branch on it easily and the C compiler(gcc) generates a nice big jumptable. The code, that jumps to the case: which executes the emulated instruction is a few instructions to create pointer and an indirect jump in assembly. No register saving and such involved.
Hope this helps,
Chris
