| Summary: | Evaluation order broken for empty alternatives in subpatterns | ||
|---|---|---|---|
| Product: | WebKit | Reporter: | Gavin Barraclough <barraclough> |
| Component: | JavaScriptCore | Assignee: | Gavin Barraclough <barraclough> |
| Status: | RESOLVED FIXED | ||
| Severity: | Normal | CC: | ggaren, pvarga, zherczeg |
| Priority: | P2 | ||
| Version: | 528+ (Nightly build) | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Bug Depends on: | 60860 | ||
| Bug Blocks: | |||
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. rs=me to roll out that optimization with a layout test for
/(|a)/.exec("a")
/(a|)/.exec("b")
Perhaps a non-greedy conversion? (|a) == a?? (a|) == a? 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. |
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).