It's quite common today to use Function#apply together with typed
arrays, for example to construct a String from character codes (or code
points) within a Uint8Array or Uint16Array, i.e.
String.fromCharCode.apply(undefined, uint8array)
is seen quite often on the web. But there are other interesting cases
like
Math.max.apply(undefined, float64array)
to compute the maximum value in a Float64Array, which is definitely not
the fastest implementation, but quite convenient and readable.
Unfortunately these cases hit the super-slow-path of the Function#apply
machinery in V8 currently, because Function#apply doesn't have any
fast-path for TypedArrays.
This CL adds a proper fast-path to CreateListFromArrayLike to the
ElementsAccessor, which can be used as long as the typed array that's
passed wasn't neutered. With this fast-path in place, the performance on
the micro-benchmark mentioned in the issue improves from
stringFromCharCode: 6386 ms.
stringFromCodePoint: 8752 ms.
to
stringFromCharCode: 1932 ms.
stringFromCodePoint: 4262 ms.
which corresponds to a 2.0x-3.3x improvement.
Bug: v8:2435
Change-Id: I4d39666e53644b11d5856982b005928e26f296fe
Reviewed-on: https://chromium-review.googlesource.com/657405
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47936}
