The test for CanTreatHoleAsUndefined on keyed element access was
checking for stability of Object.prototype and Array.prototype and
even adding stability dependencies on both, which is too restrictive
and leads to unnecessary deoptimizations (and might disable further
optimization of the keyed access depending on the state of the
prototype objects during optimization). This was not intended and
is considered a (performance) bug.
Instead use the correct approach of checking whether the receiver's
prototype is one of the current Object.prototype or Array.prototype
objects (since the Array protector works isolate-wide), and then
check the Array protector and install an appropriate code dependency
on the protector only.
Bug: v8:6607
Change-Id: I0bcfe32813ca3693e7b22de31b03edb3509d0a27
Reviewed-on: https://chromium-review.googlesource.com/574849
Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46743}
e1e35df329