On Fri, Sep 12, 2014 at 9:49 PM, Mikulas Patocka <miku...@artax.karlin.mff.cuni.cz> wrote: > Hi > > Here I'm sending two patches to fix portability for 586-class machines > (Pentium, K6, etc.) > > > If the CPU is generic, 386, 486 or pentium, we must not use cmov in inline > assembler. > > Note that some Linux distributions are compiled for i686, and for them it is > possible to use cmov in the assembler (because gcc uses it anyway). To test > for > this case, we test for defined(__i686__) || defined(__athlon__) || > defined(__SSE__) (these macros are driven by -march flag to gcc) and use cmov > if > one of these conditions is true. > > --- > configure | 4 ++++ > libavcodec/x86/mathops.h | 2 +- > 2 files changed, 5 insertions(+), 1 deletion(-) > > Index: ffmpeg/configure > =================================================================== > --- ffmpeg.orig/configure 2014-09-12 21:46:25.710512294 +0200 > +++ ffmpeg/configure 2014-09-12 21:46:32.099587711 +0200 > @@ -3840,8 +3840,12 @@ elif enabled sparc; then > elif enabled x86; then > > case $cpu in > + generic) > + disable i686 > + ;;
i686 extensions were specifically enabled some time ago by default, since we live in a modern world. If you're building for a older system, its your responsibility to pass the appropriate option. > i[345]86|pentium) > cpuflags="-march=$cpu" > + disable i686 > disable mmx > ;; > # targets that do NOT support nopl and conditional mov (cmov) > Index: ffmpeg/libavcodec/x86/mathops.h > =================================================================== > --- ffmpeg.orig/libavcodec/x86/mathops.h 2014-09-12 21:46:05.823390224 > +0200 > +++ ffmpeg/libavcodec/x86/mathops.h 2014-09-12 21:46:32.116251966 +0200 > @@ -69,7 +69,7 @@ static av_always_inline av_const int64_t > > #endif /* ARCH_X86_32 */ > > -#if HAVE_I686 > +#if HAVE_I686 || defined(__i686__) || defined(__athlon__) || defined(__SSE__) > /* median of 3 */ > #define mid_pred mid_pred > static inline av_const int mid_pred(int a, int b, int c) I don't like this part, configure should control if the code is used, and if the i686 extensions are not enabled in configure, then they should not be built here. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
