• Jakob Kummerow's avatar
    [bigint] Faster parsing from small strings · 7817cf1f
    Jakob Kummerow authored
    This patch significantly speeds up parsing of small BigInts. Its
    primary idea is to move the loop that's iterating over the string
    into the FromStringAccumulator API. That enables using function-
    local variables instead of member fields.
    A second optimization is to use a stack-allocated digit_t[] array
    for small sizes, before falling back to a (comparatively slow)
    std::vector.
    As a particularly fast path, when this stack-allocated storage is
    guaranteed to be enough, we can perform inlined multiply-and-add
    steps directly on that data.
    Finally, this patch changes the conversion of characters to their
    numeric values from computations to a lookup table, which is a bit
    faster for radixes <= 10 (where, in the old code, only one range
    needed to be checked), and a lot faster for radixes > 10.
    
    Bug: v8:11515
    Change-Id: Ifd8ec4799ac34447ba6d4350b7788b559307784c
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3064603
    Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
    Reviewed-by: 's avatarMaya Lekova <mslekova@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#76210}
    7817cf1f
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