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  "path": "/viewtopic.php?t=27873&p=275178#p275178",
  "publishedAt": "2026-06-03T18:05:11.000Z",
  "site": "http://forum.palemoon.org",
  "textContent": "> Maybe I got this wrong but wouldn't an option like ac_add_options --enable-optimize=\"-O2 -msse2 -mfpmath=sse -w\" imply the binaries are built for usage on SSE2 machines, that is without any AVX/AVX2 capability?  Otherwise there would be no point in having separate AVX and SSE2 builds (official or not).\n\nIt does, but there can be overrides for some compiler options for certain source files/their parts.\n\nAnd there is matter of inline assembly, which is common in codecs where hand optimizations are done. Ideally they are guarded by #ifs, but in case of dav1d this apparently isn't the case. Making and maintaining patches that will do just that isn't viable, and tbh isn't even very useful.\n\n\n> Now, just for clarification: while I built PM using the SSE option as above, and enabled AV1 without also enabling libaom, what would happen if I tried to view/play an AV1 video file in this browser, on my SSE2-only machine? Would it just refuse to play, would it throw a player error, or would it crash the whole browser? If it wouldn't crash then I'd rather avoid sitting idle around my notebook for another 2+ hours.\n> Not that I'm usually playing videos in browser - as previously mentioned - but one doesn't know what they may stumble upon on some random page.\n\nDue to above it will crash with illegal instruction error, but since that code is confined to av1 decoder, it will happen only when av1 playback is attempted.\n\n\n> > ... would it throw a player error, or would it crash the whole browser? If it wouldn't crash then I'd rather avoid sitting idle around my notebook for another 2+ hours.\n>\n> Isn't there a risk for **_system_** crashes (and quite the ugly ones) with CPU instruction mismatches?\n\nCpus aren't that stupid. For ages there are ways to catch attempt of executing unknown instructions.\nOn non-AVX cpu it will crash with illegal instruction error.\nIf it built into 32bit binary and run on AVX capable cpu it will either produce some incorrect results or outright crash because AVX instructions are made with assumption that they are used from 64bit mode. Why they aren't trapped as illegal in legacy(32bit) mode is anyone's guess...\n\n* * *",
  "title": "Contributed 3rd Party Builds • Re: Pale Moon x86-64 SSE2/AVX2",
  "updatedAt": "2026-06-03T18:05:11.000Z"
}