1363929 - nsIFrame::In3DContextAndBackfaceIsHidden could be faster

Status: RESOLVED FIXED

(Core :: Web Painting, enhancement)

Description

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

I just profiled scrolling my facebook timeline.  I noticed about 0.15% of the time being spent in nsIFrame::Combines3DTransformWithAncestors being called from nsIFrame::In3DContextAndBackfaceIsHidden.

So In3DContextAndBackfaceIsHidden does two tests, both of which are likely to fail the vast majority of the time, separated by an &&.  I think the one that's currently *second* is likely to be the faster test, because BackfaceIsHidden() initially tests style data on the frame itself, whereas Combines3DTransformWithAncestors initially walks up to the parent frame and tests style data on it.  So I think the BackfaceIsHidden test is likely to fail faster simply due to less pointer chasing.

Comment 1

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Attachment: Swap the order of tests in nsIFrame::In3DContextAndBackfaceIsHidden so that the faster-to-fail one is first

MozReview-Commit-ID: E8uj0vQMlti

Comment 2

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/0515ebda07af3263ab124ba1a6eabe212e9e1b89
Bug 1363929 - Swap the order of tests in nsIFrame::In3DContextAndBackfaceIsHidden so that the faster-to-fail one is first.  r=mattwoodrow

Comment 3

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/0515ebda07af