Bug 152578 – RegExp with anchor negation and grouping performance

• Status: NEW
• Component: JavaScriptCore

reproduced here:

https://jsperf.com/regexp-negation-in-group/5

Expected: 
* Similar performance for these two regExps
* Performance for these RegExp.test should be independent of input size as they anchor to the start of the input. 
var noGroup = /^"[^\\"]+"/;
var oneGroup = /^"(:?[^\\"])+"/;

Actual:
* for oneGroup regExp the performance is much worse.
anywhere from x30 slower for a single line input
to 5 orders of magnitude for a 10000 lines input.

When running the benchmark on other browsers (chrome/firefox)
The input size does not affect the performance.

Thanks.
Shahar.

fixed the jsperf example (was using wrong syntax for none capturing groups)
http://jsperf.com/regexp-negation-in-group/6

JSPerf is down so I've added a reproducing jsfiddle instead.

https://jsfiddle.net/cbepLyum/2/

(open the console to see the results).

[Pierre-Yves Gérardy]

There is still a slowdown when using groups, but it is now by a constant factor of ~4, rather than dependent on the subject length.

Surprisingly, the RegExp with two non-capturing groups is 10-20% faster than the one with only one.