Re: SIMD vs no SIMD on i686 (was: [Bug 3975] executable stack flag prevents use of libx264.so.148 with selinux in enforcing mode)

2016-07-25 4:36 GMT+02:00 Sérgio Basto <sergio(a)serjux.com&gt;: > > On Seg, 2016-07-25 at 04:02 +0200, Kevin Kofler wrote: > > > > So for those stuck with such an old machine, it > > is better to have a library that works (slowly) than one that > > just > > crashes > > with a SIGILL (illegal instruction). > I think x264 , detects if have the cpu instructions and if not, > have > one fall back code, don't crash. Okay to put an end to this thread, here are the tests: # x264 -o out.mp4  BigBuckBunny_320x180.mp4 lavf [info]: 320x180p 1:1 @ 24/1 fps (vfr) x264 [error]: your cpu does not support SSE1, but x264 was compiled with asm x264 [error]: to run x264, recompile without asm (configure -- disable-asm) x264 [error]: x264_encoder_open failed # mv /usr/lib/libx264.so.148 /usr/lib/sse2/ # mv /tmp/libx264.so.148 /usr/lib/ # ldconfig # x264 -o out.mp4  BigBuckBunny_320x180.mp4 lavf [info]: 320x180p 1:1 @ 24/1 fps (vfr) x264 [info]: using SAR=1/1 x264 [info]: using cpu capabilities: none! x264 [info]: profile High, level 1.2 x264 [info]: frame I:5     Avg QP:17.11  size: 13610 This was tested on KVM guest with pentium 2 cpu emulated. Here are the relevant cpuinfo flags there: flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr eagerfpu x2apic hypervisor vmmcall (no mmx, or sse1/2 here). Actually, I've tested on pentium3 which has sse1 but not sse2 and the asm version worked there, so the runtime cpu detection work starting with sse1, but not sse2. The last cpuinfo case which is relevant to the thread is either this work on AMD geode (probably one of the last produced 32bit only x86 cpu) As seen here the result might be random: http://wiki.laptop.org/go/Geode_instruction_set#supported_SSE1, but sse is unlikely to be advertised by cpuinfo This last is specially relevant for the OLPC project. At the end, I think it's urgent not to move anything already working fine in legacy architecture.

Thx