• Martin Möhrmann's avatar
    regexp: add ASCII fast path for context methods · e74c6cd3
    Martin Möhrmann authored
    The step method implementations check directly if the next rune
    only needs one byte to be decoded and avoid calling utf8.DecodeRune
    for such ASCII characters.
    
    Introduce the same fast path optimization for rune decoding
    for the context methods.
    
    Results for regexp benchmarks that use the context methods:
    
    name                            old time/op  new time/op  delta
    AnchoredLiteralShortNonMatch-4  97.5ns ± 1%  94.8ns ± 2%  -2.80%  (p=0.000 n=45+43)
    AnchoredShortMatch-4             163ns ± 1%   160ns ± 1%  -1.84%  (p=0.000 n=46+47)
    NotOnePassShortA-4               742ns ± 2%   742ns ± 2%    ~     (p=0.440 n=49+50)
    NotOnePassShortB-4               535ns ± 1%   533ns ± 2%  -0.37%  (p=0.005 n=46+48)
    OnePassLongPrefix-4              169ns ± 2%   166ns ± 2%  -2.06%  (p=0.000 n=50+49)
    
    Change-Id: Ib302d9e8c63333f02695369fcf9963974362e335
    Reviewed-on: https://go-review.googlesource.com/38256Reviewed-by: 's avatarBrad Fitzpatrick <bradfitz@golang.org>
    Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    e74c6cd3
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