Rémi Denis-Courmont: > Le lauantaina 8. kesäkuuta 2024, 0.26.21 EEST Andreas Rheinhardt a écrit : >> (Also: IIRC Clang actually parses inline assembler and optimize it; > > That sounds sketchy. While FFmpeg only uses inline assembler as intrinsic > ersatz, other projects can and definitely do use them for weirder stuff. That > will fail miserably if the compiler modifies the sequence.
See https://godbolt.org/z/ozeGoWzK7: Clang is smart enough to know that the x86-inline asm version of av_bswap32 is self-inverse. (It can also evaluate it for constants at compile-time.) > > The Linux kernel for instance pushes/pops sections or patches the byte > sequence at load time or even run time. Some code also assumes exact byte > offsets between instructions (not sure Linux specifically). So, AFAICT, the > only > thing the compiler can sanely do is move, and maybe eliminate/replicate, the > entire assembler block. > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
