60866 2011-05-15 19:28:57 -0700 Evaluation order broken for empty alternatives in subpatterns 2011-05-23 13:51:01 -0700 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) Unspecified Unspecified RESOLVED FIXED P2 Normal --- 60860 1 barraclough barraclough ggaren pvarga zherczeg oldest_to_newest 404249 0 barraclough 2011-05-15 19:28:57 -0700 for example: /(|a)/.exec("a"); should return ["",""], but instead returns ["a","a"]. This was broken by https://bugs.webkit.org/show_bug.cgi?id=51395, which will be reverted (this unsafe optimization does not appear significant to any benchmarks we are tracking, we should reimplement in a more restricted, safe fashion only if we can demonstrate an important workload benefitting from doing so). 404251 1 barraclough 2011-05-15 19:33:28 -0700 This unsafe optimization is masking further problems in the JIT, reverting the optimization causes failures in fast/regex/parentheses. These issues are fixed by 60860. 404325 2 ggaren 2011-05-16 00:08:29 -0700 rs=me to roll out that optimization with a layout test for /(|a)/.exec("a") /(a|)/.exec("b") 404375 3 barraclough 2011-05-16 02:08:37 -0700 Fixed in r86547. 405670 4 zherczeg 2011-05-18 06:24:45 -0700 Perhaps a non-greedy conversion? (|a) == a?? (a|) == a? 408250 5 barraclough 2011-05-23 13:51:01 -0700 Conversion to an appropriately greedy quantifier would be possible, but would limit the scope of this optimization. We would consider such a patch if it were to provide a useful performance gain on an interesting workload.