raptor-webaudio-firefox regression from clang 8
Categories
(Core :: Web Audio, defect, P2)
Tracking
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| Tracking | Status | |
|---|---|---|
| firefox67 | --- | fixed |
People
(Reporter: away, Assigned: away)
References
Details
Attachments
(1 file)
Continuing from bug 1522289 comment 4.
== Change summary for alert #18883 (as of Thu, 24 Jan 2019 13:10:20 GMT) ==
Regressions:
6% raptor-webaudio-firefox windows7-32 opt 209.67 -> 221.58
4% raptor-webaudio-firefox windows7-32 pgo 223.62 -> 232.67
For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=18883
The 4-6% overall regression understates the issue: one subtest (Periodic Wave with Automation) was regressing over 40%!
For some reason clang 7 was optimizing this pow(2., foo) to exp2(foo) and clang 8 stopped doing so: https://searchfox.org/mozilla-central/rev/78cd247b5d7a08832f87d786541d3e2204842e8e/dom/media/webaudio/OscillatorNode.cpp#174
I'll look into whether this was intentional from LLVM and potentially file a bug, but in the meantime, writing exp2 solves the regression.
Clang 7 was making the pow => exp2 optimization for us, and for some reason clang 8 stopped doing so. This resulted in a surprisingly large regression in raptor numbers.
Pushed by dmajor@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/f7b03b3e66cb Use exp2 instead of pow in OscillatorNode r=padenot
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Comment 4•5 years ago
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| bugherder | ||
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Comment 5•5 years ago
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The regressions seem to have been fixed. Will wait some extra data points, to properly confirm.
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Comment 6•5 years ago
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I confirm the fix! \0/
== Change summary for alert #19100 (as of Thu, 31 Jan 2019 13:22:46 GMT) ==
Improvements:
5% raptor-webaudio-firefox windows7-32 opt 222.50 -> 210.83
4% raptor-webaudio-firefox windows7-32 pgo 232.96 -> 223.33
For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=19100
Description
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