1644403 - Do not use Clone on CloneableAutoTArray

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Simon Giesecke [:sg] [he/him]]

As was mentioned in https://bugzilla.mozilla.org/show_bug.cgi?id=1626570#c118, there were some performance regressions in connection with the introduction of CopyableAutoTArray, in particular with WebAudio.

This is likely to be caused by missed optimization / copy elision opportunities due to the calling of the base class' Clone method which returns an AutoTArray instead of a CopyableAutoTArray. Changing this to an ordinary copy reverts the performance regression as can be observed here:

https://treeherder.mozilla.org/perf.html#/comparesubtest?originalProject=mozilla-central&newProject=try&newRevision=85724fd24502163650b7e5e4378d15d52baa3b88&originalSignature=1931866&newSignature=1904634&framework=10&selectedTimeRange=172800

CopyableAutoTArray should be deleted to avoid doing this accidentally as in this case.

Comment 1

[Simon Giesecke [:sg] [he/him]]

Attachment: Bug 1644403 - Fix inconsistent uses of CopyableAutoTArray and Clone. r=froydnj

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug is a defect, but please change it back in case of error.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1626570

Comment 4

[Simon Giesecke [:sg] [he/him]]

I am not sure if this should be regarded a defect. It does not fix a functional issue, but reverts a performance regression, which I am not sure is significant enough to be regarded a defect.

Comment 5

[(Away)]

Nice find, thanks for looking into this!

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/53776f985a81
Fix inconsistent uses of CopyableAutoTArray and Clone. r=froydnj

Comment 7

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/53776f985a81