Perfherder has detected a raptor performance regression from push d70a9cd7bd71672181847c87599501c35726b494. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the offending patch(es) will be backed out in accordance with our regression policy.

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I'm not entirely sure which of the two changesets here caused the regression, but it could be either.

d70a9cd7bd71672181847c87599501c35726b494 disables a pref which was only ever enabled for Nightly. This definitely reduces performance for Nightly, but in a way that makes it more accurately reflect what we're actually shipping.

c927b7ad07cb89caa91b183a3af13734f441be01 disables Advanced Layers, which also might reduce performance, but is a system that we are rapidly replacing with WebRender.

Any regressions here are expected, and are changes that either won't affect release, or are reducing our maintenance burden on configurations with rapidly decreasing numbers of users.

We should WONTFIX this, and continue to push WebRender performance.