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

On Ter, 2016-07-26 at 16:54 +0100, Sérgio Basto wrote: > On Ter, 2016-07-26 at 14:28 +0200, Nicolas Chauvet wrote: > > > > 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. > yeah , so at least doesn't crash and I was right about x264 have > fallback code for pentium3 (so the runtime cpu detection work > starting > with sse1), which makes me think because of pentium2 we don't have > full > features ... , but OK, for now, makes sense disable asm on i686 ... > BTW and for 10b ? (compile with --bit-depth=10 ) make sense also make > 2 > builds or can I enable asm there ? or just leave as is (one build > without asm). > > I also read yesterday, about http://emmabuntus.sourceforge.net/, This > distribution was originally designed to facilitate the reconditioning > of computers, given to humanitarian organizations ... > Thinking betterm since doesn't crash , and in pentium 2 we have a message to disable-asm , I think we should enable asm by default , and at most drop a note in wiki , that PII are not supported or something like that .