Bug 16503 – match limit takes at least 13% of the time on the SunSpider regexp-dna test

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Darin Adler]

The match limit inside the regular expression execution engine slows down the regexp-dna test by about 13%. If we can find some more efficient way of preventing complex regular expressions from causing a hang, then we could get a substantial speed-up.

See bug 16458 for some history.

[Alexey Proskuryakov]

Created attachment 21408 [details]
2.3% improvement

Removing the check altogether is a 9.5% win on my machine.

I guess this micro-optimization is unnecessary if someone has a real fix in mind, but I thought it was worth posting anyway.

[Darin Adler]

Comment on attachment 21408 [details]
2.3% improvement

r=me

I'm not sure anyone has a handle on a "real fix".

[Cameron Zwarich (cpst)]

Alexey, are you going to land this?

[Alexey Proskuryakov]

I'm trying to land this periodically, but random code generation changes elsewhere cause it to be a regression overall now. One of these days, I'll get lucky and have it landed.

[Alexey Proskuryakov]

Comment on attachment 21408 [details]
2.3% improvement

Landed in r34480, clearing review flag. Today, the win on regexp-dna was only 0.6%, but the total win was huge (0.5%), apparently due to random code generation changes.

[Alexey Proskuryakov]

Something was landed here, so marking fixed. The rest of the bug is likely long obsolete.