had to switch from am3+ cpu to am3 cpu. ffmpeg "illegal instruction"

whansard · 07-06-2021, 09:28 AM

this is in 2 seperate funtoo linux installs, but gentoo is very close. i've been haveing constant crashes on my main box, and i've switched back to my previous. fx-4100 cpu back to adx640 athlon 2. i've spend a ton of time trying to find what libs or whatever have the newer fx-4100 instructions, and i'm failing. i've already rebuild world twice. i made a list of all installed apps with qlist, and rebuilt everything i could that still existed from that list. i custom emerged ffmpeg with -(everthing) that would still build, with the same results. i ran ldd ffmpeg, and everything in that list i checked and has been rebuilt. the 2 installs had cflags -march=native. luckily, my gentoo install had -mtune=native and no -march command. it's still fine. if i compile ffmpeg and mplayer by hand with configure and make, it works, so emerge is pulling in something with illegal instructions in it? that i can't find. how should i proceed?

syg00 · 07-07-2021, 04:37 AM

Have you asked on gentoo's own fora ?.
Been a good few years since I partook, but the ricers there were seriously committed to trying every option known to mankind to wring out that extra grain of performance. I'm sure someone there has had to travel this path and will have some ideas for you.

whansard · 08-09-2021, 04:55 AM

i'm not sure, but in the past day after revisiting this and a couple of rebuilds with --deep for mplayer and ffmpeg, they are working. i don't know what did it really.

Brains · 08-22-2021, 04:56 PM

Code:

cat /proc/cpuinfo

In /etc/portage/make.conf you should have: CPU_FLAGS_X86=
Changing cpu likely requires changing some of these flags.
I had a set of flags I found on the net someone was using with similar processor, then I decided to check what my cpus flags are and the list was a lot bigger. Granted many need not be in make.conf as they have no bearing on anything. For the Halibut I commented out the first CPU_FLAGS_X86= and added a new one with all flags found in the output of: cat /proc/cpuinfo and ran: emerge -avD --changed-use @world and adjusted them based on complaints till it was happy and ffmpeg was the only package needing rebuild. Everything appears normal so far.