So Firefox 106 triggered a bug on 1st gen Ryzen processors. We found this by noticing a bunch of nonsensical crashes in the painting code that only happened on these processors.
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How did we fix it? By rebuilding the exact same code as 106. The timing differences caused by using a new profile when doing PGO were enough to cause the generated code to be different enough to avoid triggering the processor bug.
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Sigh.
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Unclear. We haven't been able to get a useful analysis of the problem out of AMD yet. We were able to reproduce the problem internally, but not reliably or reproducibly.