<regex>: Optimize skip heuristic for searches of patterns with initial dot wildcards#6189
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StephanTLavavej merged 2 commits intomicrosoft:mainfrom Mar 31, 2026
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Towards #5468.
This closes one of the remaining gaps in the skip heuristic. It doesn't really make sense to use the dot wildcard itself as the basis for skipping ahead, as it essentially matches everything (except for newlines in ECMAScript or NUL in POSIX grammars). So instead, this uses the following NFA node to compute the skip.
Benchmark
Relevant changes highlighted.
Note that there is some observable slowdown for the regular expressions
(?=....)bibe"and(?=bibe)..... This is because the new logic keeps analyzing the regex beyond the first dot wildcard, so more time is spent on the subpattern..... This additional analysis turns out to be not helpful on this specific subpattern. But this subpattern is also not realistic for an assertion because it doesn't actually restrict the set of strings the regex can match, and I think this slight slowdown in some cases is worth it given the potential huge acceleration in more realistic regular expressions.