re2: fast path for trailing match-all in Match#607
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When a pattern ends with greedy `.*` DotNL in one line mode, compile a second RE2 with the `.*` stripped. `Match` delegates to the stripped RE2 and extends the results to cover all remaining text, avoiding O(n) scanning of the trailing input. The prefix RE2 is a completely independent object with its own Prog, forward DFA, and reverse DFA. This avoids changing the engines as it keeps the optimization at high level. Fixes google#605.
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When a pattern ends with greedy
.*DotNL in one line mode, compilea second RE2 with the
.*stripped.Matchdelegates to the strippedRE2 and extends the results to cover all remaining text, avoiding O(n)
scanning of the trailing input.
The prefix RE2 is a completely independent object with its own Prog,
forward DFA, and reverse DFA. This avoids changing the engines as
it keeps the optimization at high level.
Fixes #605.