2016-02-01 17:54 GMT+01:00 Yury Selivanov <yselivanov.ml@gmail.com>:

Thanks for bringing this up!

IIRC wpython was about using "fat" bytecodes, i.e. using 64bits per bytecode instead of 8.

No, it used 16, 32, and 48-bit per opcode (1, 2, or 3 16-bit words).

That allows to minimize the number of bytecodes, thus having some performance increase. TBH, I don't think it was "significantly faster".

Please, take a look at the benchmarks, or compile it and check yourself. ;-)

If I were to do some big refactoring of the ceval loop, I'd probably consider implementing a register VM. While register VMs are a bit faster than stack VMs (up to 20-30%), they would also allow us to apply more optimizations, and even bolt on a simple JIT compiler.

Yury

WPython was an hybrid-VM: it supported both a stack-based and a register-based approach.

I think that it's needed, since the nature of Python, because you can have operations with intermixed operands: constants, locals, globals, names. It's quite difficult to handle all possible cases with a register-based VM.

Regards,

Cesare