commit 1edb46cc04912689fa6790a1e20177b1f0c8d30e
author Benedikt Meurer <bmeurer@chromium.org> Mon Jul 10 18:50:09 2017
committer Commit Bot <commit-bot@chromium.org> Mon Jul 10 19:16:38 2017
tree 78a2add2a849afdb3a66a985de05cb38b5cb48d8
parent be8983da7b014eb4abdb36a41132bc5ff4fb4e85

[turbofan] Widen the fast-path for JSCreateArray.

This improves the general Array constructor call performance (w/o
usable AllocationSite feedback) in TurboFan by ~2x, i.e. for example
invoking the Array constructor like this

  var a = Array.call(undefined, n);

instead of

  var a = Array(n);

such that the CallIC doesn't know that it's eventually calling the
Array constructor.

It also thus changes the single argument Array constructor to always
return holey arrays. Previously the single argument case for the Array
constructor was somehow trying to dynamically detect 0 and in that case
returned a packed array instead of a holey one. That adds quite a lot
of churn, and doesn't seem to be very useful, especially since this
might lead to unnecessary feedback pollution later.

R=mvstanton@chromium.org

Bug: v8:2229, v8:5269, v8:6399
Change-Id: I3d7cb9bd975ec0e491e3cdbcf1230185cfd1e3de
Reviewed-on: https://chromium-review.googlesource.com/565721
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46538}