[Bug 1930982]

Walter ZAMBOTTI 1930982 at bugs.launchpad.net
Mon Jun 14 23:58:07 UTC 2021

(In reply to Lee Salzman [:lsalzman] from comment #25)
> The circumstantial evidence "seems like" something in the function here (https://searchfox.org/mozilla-central/source/gfx/wr/swgl/src/composite.h#534) is underflowing. But I would need someone who can reliably reproduce the issue to find out where in those math equations are actually doing so. I tried testing in my patch if the additions were the culprit, but that seems unlikely.
> It's possible the multiplications "rbCoeffs * uv" or "gCoeffs * uv" are underflowing based on whatever values the ARM video codecs seem to be supplying. However, this is not happening on x86 at all, which is strange, and it is also happening on ARM across platform, which is further strange, since there isn't really much in the way of platform specific code here.
> Sotaro, might you be able to investigate this?

Taking a step back.  If a certain function is suspected what are the
diff's with this code between the working 88.0 and non working 89.0

Since the issue affects all ARM regardless of platform the only culprit
not eliminated is Firefox.

If you have a downloaded executable for me to test I'm happy to do so.
My platforms are :

aarch64 Ubuntu 18.04 LTS
aarch64 Ubuntu 20.10

I can only test on one of these platforms!

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