[xxgreg]

Yes - It's difficult to describe the difference in one sentence ;)

I agree that there are many shades of the rainbow between a JIT and an interpreter.

"V8 compiles JavaScript source code directly into machine code when it is first executed. There are no intermediate byte codes, no interpreter." https://developers.google.com/v8/design#mach_code

Have a read about V8 and the DartVM's architecture. V8, and the DartVM have a different architecture than IE's Chakra and Firefox's monkeys. They use a method JIT which initially generates very simple native machine code directly from the AST. The machine code includes instructions to identify hot code, which is re-compiled again from the AST. The optimizing compiler converts the source into an SSA form, and IR, but this is not byte/bitcode. This is what Bak et al are referring to when they call this architecture a "source code vm".

Lars Bak on channel 9: Bytecodes are a silly thing in my mind. They can be used for different things interpretation. But interpreters are really slow. But they can also be used as a wire format, for instance in .net or java where that's what you ship over the wire. In javascript the wire format is sourcecode, and for each function you have, inside the running javascript program, you have to cook up the source code again. So that is the primary representation. So we just decided why not generate native code right away because the CPU is pretty fast.

http://media.ch9.ms/ch9/e6aa/354bf580-9c93-4383-bab3-cb6a3dd...