Add support to the JSCallReducer to recognize JSConstruct nodes where
the target is the Object constructor, and reduce them to JSCreate
nodes if either
(a) no value is passed to the Object constructor, or
(b) the target and new.target are definitely not identical, by checking
whether both target and new.target are different HeapConstants
(if they are not, then the JSCreateLowering will not be able to
do a lot with the JSCreate anyways).
This should cover the relevant cases for subclassing appropriately. It
fixes the 3-4x slowdown on the micro-benchmark mentioned in the linked
bug,
baseNoExtends: 752 ms.
baseExtendsObject: 752 ms.
baseExtendsViaFactory: 751 ms.
and thus removes the performance cliff.
R=jarin@chromium.org
Bug: v8:6801
Change-Id: Id265fd1399302a67b5790a6d0156679920c58bdd
Reviewed-on: https://chromium-review.googlesource.com/657019
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47913}
When calling
Object(value)
where the value is known to be a JSReceiver, we can just replace it with
value, as the Object constructor call is a no-op in that case. Otherwise
when value is known to be not null or undefined then we can replace the
Object constructor call with an invocation of ToObject.
This covers the common pattern found in bundles generated by Webpack,
where the Object constructor is used to call imported functions, i.e.
Object(module.foo)(1, 2, 3)
There's a lot of detail in https://github.com/webpack/webpack/issues/5600
on this matter and why this pattern was chosen.
Bug: v8:6772
Change-Id: I2b4f0b4542b68b97b337ce571d6d79946c73d8bb
Reviewed-on: https://chromium-review.googlesource.com/643868
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47728}
