• Peter Marshall's avatar
    [typedarray] Use fast path for Float32Array.from(float_64_array) and similar · c7c0e110
    Peter Marshall authored
    Currently, because the source float_64_array has an iterator, it hits
    the code in the "check_iterator" section of TypedArrayFrom which calls
    IterableToList. This builds a temporary PACKED_ELEMENTS array (and boxes
    all of the numeric values as HeapNumbers), then uses this as the source
    array.
    
    This patch checks if the source array is a TypedArray, and if the iterator
    is the built-in one (where we know the iterator's behaviour). If both are
    true then it bypasses the creation of this temporary array and uses the
    original TypedArray as the source.
    
    This allows it to take advantage of the existing fast code for copying one
    typed array to another.
    
    R=hablich@chromium.org, petermarshall@chromium.org
    
    Bug: chromium:884671
    Change-Id: I19a944c9d6d5d07699c7dc3ad7196fc871200b62
    Reviewed-on: https://chromium-review.googlesource.com/c/1297312Reviewed-by: 's avatarPeter Marshall <petermarshall@chromium.org>
    Reviewed-by: 's avatarBenedikt Meurer <bmeurer@chromium.org>
    Commit-Queue: Peter Marshall <petermarshall@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#57022}
    c7c0e110
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