Bug #81424 [Ver]: PCRE2 10.35 JIT performance regression

Edit report at https://bugs.php.net/bug.php?id=81424&edit=1 ID: 81424 Updated by: cmb@php.net Reported by: nospam at briat dot org Summary: PCRE2 10.35 JIT performance regression Status: Verified Type: Bug Package: PCRE related Operating System: * PHP Version: 7.4 Assigned To: cmb Block user comment: N Private report: N New Comment: > […] I think that your regex is maybe equivalent for matching but > not for replacing […] Oh, right. Maybe some other improvement can be made for that. Anyway, let's wait on the upstream decision. :) Previous Comments: ------------------------------------------------------------------------ [2021-09-08 14:41:14] nospam at briat dot org Here the issue https://github.com/tubalmartin/YUI-CSS-compressor-PHP-port/issues/63 For the record, I think that your regex is maybe equivalent for matching but not for replacing: $css = preg_replace('/[^{};\/\n]+\{\}/S', '', $css); => match and replace the whole css declaration. ------------------------------------------------------------------------ [2021-09-08 13:47:02] nospam at briat dot org Thanks for the analysis. I will also fill an issue on https://github.com/tubalmartin/YUI-CSS-compressor-PHP-port. ------------------------------------------------------------------------ [2021-09-08 12:34:28] cmb@php.net Anyhow, I filed <https://github.com/PhilipHazel/pcre2/issues/16>. ------------------------------------------------------------------------ [2021-09-08 12:16:29] cmb@php.net Simpler reproducer: <?php $data = file_get_contents("lorem.css.txt"); $time_start = hrtime(true); var_dump(preg_match('/[^{};\/\n]+\{\}/S', $data)); var_dump( strlen($data), (hrtime(true) - $time_start) / 100000 ); ?> Yields a performance regression by more than factor 100 for me. I'm not sure, though, whether the PCRE2 maintainers would fix this, since the regex appears to be suboptimal. Using a look behind assertion var_dump(preg_match('/(?<![{};\/\n]+)\{\}/S', $data)); instead, makes almost no performance difference. ------------------------------------------------------------------------ [2021-09-08 11:09:59] cmb@php.net I can confirm the serious performance regression, and that it is caused by the update to PCRE2 10.35. The issue persists with current master, which has PCRE2 10.37. It is possible that the issue has been fixed in PCRE2 10.38-RC1, but I haven't verified that yet. Just in case the issue has not been fixed upstream, we'd need a simpler reproducer before reporting upstream. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=81424 -- Edit this bug report at https://bugs.php.net/bug.php?id=81424&edit=1