[Python-Dev] A new JIT compiler for a faster CPython? (original) (raw)

Cesare Di Mauro cesare.di.mauro at gmail.com
Wed Jul 18 07:50:23 CEST 2012

2012/7/18 Victor Stinner <victor.stinner at gmail.com>

I don't expect to run a program 10x faster, but I would be happy if I can run arbitrary Python code 25% faster.

If that's your target, you don't need to resort to a bytecode-to-binary-equivalent compiler. WPython already gave similar results with Python 2.6.

The idea behind is that using an hybrid stack-register VM, you'll spend less time on the ceval loop "constant stuff" (checking for events / GIL release, etc.). That's because superinstructions aggregates more bytecodes into a single "wordcode", which requires only one decoding phase, avoids many pushes/pops, and some unnecessary inc/decr reference counting. A better peephole optimizer is provided, and some other optimizations as well.

There's also room for more optimizations. I have many ideas to improve both WPython or just the ceval loop. For example, at the last EuroPython sprint I was working to a ceval optimization that gave about 10% speed improvement for the CPython 3.3 beta trunk (on my old MacBook Air, running 32-bit Windows 8 preview), but still needs to be checked for correctness (I'm spending much more time running and checking the standard tests than for its implementation ;-)

In the end, I think that a lot can be done to improve the good old CPython VM, without resorting to a JIT compiler. Lack of time is the enemy...

Regards, Cesare

--

Specialization / tracing JIT can be seen as another project, or at least added later. Victor

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