With a couple of simple macros, the code could be fraction of its size and much more readable. Code with that property is atrocious in my mind. For example these "argument reading" bits are repeated over and over again:

ram[PC++0xfff]&0xff

((ram[PC++0xfff]&0xff)|((ram[PC++0xfff]&0xff)<<8))

Of course Notch said it has been generated, so he probably had a neat definition that barfed this garbage out. But it's strange that so many commentators here are defending the output as a reasonable coding style for a VM!