[Python-Dev] opcode dispatch optimization (original) (raw)

Nicolas Trangez nicolas at qlayer.com
Fri Jan 2 09:25:34 CET 2009

On Wed, 2008-12-31 at 12:51 -0600, Jason Orendorff wrote:

On Wed, Dec 31, 2008 at 11:44 AM, Christian Heimes <lists at cheimes.de> wrote: > The patch makes use of a GCC feature where labels can be used as values: > http://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html . I didn't know > about the feature and got confused by the unary && operator.

Right. SpiderMonkey (Mozilla's JavaScript interpreter) does this, and it was good for a similar win on platforms that use GCC. (It took me a while to figure out why it was so much faster, so I think this patch would be better with a few very specific comments!) SpiderMonkey calls this optimization "threaded code" too, but this isn't the standard meaning of that term. See: http://en.wikipedia.org/wiki/Threadedcode

FWIW, it's also explained pretty well in the first pages of [1]. WebKit's SquirrelFish is direct-threaded as well [2].

Nicolas

[1] http://citeseer.ist.psu.edu/cache/papers/cs/32018/http:zSzzSzwww.jilp.orgzSzvol5zSzv5paper12.pdf/ertl03structure.pdf [2] http://webkit.org/blog/189/announcing-squirrelfish/

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