1456137 - JIT code seems to spend a lot of time checking to see whether objects have getters or setters

Status: RESOLVED INCOMPLETE

(Core :: JavaScript Engine: JIT, enhancement, P3)

Description

[Mike Conley (:mconley) (:⚙️)]

Noticed during The Joy of Profiling Episode 24[1].

Here's a profile:

https://perfht.ml/2vDrkNB

This is from YouTube, where we're getting polyfilled with Polymer. Over a range of about 5s, we spend about 291ms checking to see if objects have getters or setters in js::jit::ObjectHasGetterSetter.

[1]: https://air.mozilla.org/the-joy-of-profiling-episode-24/

Comment 1

[Jan de Mooij [:jandem]]

This might be bug 1389159, but would have to investigate.

Comment 2

[Kannan Vijayan [:djvj]]

If this is the bug that jan links to, it seems like a larger project than a [qf] targeted work, unless we can guarantee a resource allocation for this.  Changing where accessors are stored, and updating all the relevant other info (e.g. baseline jits and ion etc.) is a mid-term task.

Comment 3

[Mike Conley (:mconley) (:⚙️)]

YouTube has moved off of Polymer since WebComponents v1 shipped, so I don't think this is an issue anymore. If anything, it's probably wildly out of date and a new bug can be filed with newer information if there's still a problem here.