[FFmpeg-trac] #3048(undetermined:new): ICL and HAVE_INLINE_ASM

[FFmpeg]

#3048: ICL and HAVE_INLINE_ASM
-------------------------------------+-------------------------------------
             Reporter:  nikolaynnov  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:  icl          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 I have old version of ffmpeg (0.8) with was compiled with ICL compiler
 manually. Manually means what only required c-files (for 2-3 required for
 me codecs) was included in my icproj. Now I see that ffmpeg has native
 support for icl  (through --toolchain=icl). So I have compiled last ffmpeg
 (2.0.1) with standard instructions. Then I have notice that encoding to
 MPEG4/AV_CODEC_ID_MSMPEG4V2 with new ffmpeg take too much time. I have
 some tests: old ffmpeg encode test video for a 0:55 and new ffmpeg encode
 the same video for a 1:19 - it is slowly on 43%!!! It is unacceptable in
 real applications.

 I make some investigation and found that problem is that some
 optimizations are disabled for icl by default. The main degradation is
 that some high optimized asm code is not included in icl. HAVE_INLINE_ASM
 is 0 by default. I have defined HAVE_INLINE_ASM to 1, make code compilable
 and linkable with some minor changes and now the test video is encoded for
 0:55 min as expected.

 I believe that icl build of ffmpeg have to be fully optimized by default.
 I have attached some example of how to change code to make it compilable
 with ICL and HAVE_INLINE_ASM. Please note that I have disabled some asm
 code as I don't need it for my set of codecs.
 Typically, there are 2 kind of changes:
 1) icl doesn't know non ia32 - cltd instruction. It has to be replaced
 with cdq instruction instead.
 example:
 #ifdef __ICL
 #define MASK_ABS(mask, level)                   \
     __asm__ ("cdq                   \n\t"      \
              "xorl %1, %0            \n\t"      \
              "subl %1, %0            \n\t"      \
              : "+a"(level), "=&d"(mask))
 #else
 #define MASK_ABS(mask, level)                   \
     __asm__ ("cltd                   \n\t"      \
              "xorl %1, %0            \n\t"      \
              "subl %1, %0            \n\t"      \
              : "+a"(level), "=&d"(mask))
 #endif
 2)
 #ifdef __ICL
     __asm__ volatile(
         ...
         "movq %N, %%mm5     \n\t"
         ...
         : "m"(var)
     );
 #else
     __asm__ volatile(
         ...
         "movq "MANGLE(var)", %%mm5     \n\t"
         ...
     );
 #endif
 I believe that icl syntax will work with gcc as well. So may be the best
 solution will be to rewrite code to don't use MANGLE in movq.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/3048>
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