Rémi Denis-Courmont: > Le lauantaina 8. kesäkuuta 2024, 9.23.48 EEST Andreas Rheinhardt a écrit : >> 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.) > > It seems that they have some heuristics not to touch assembler that they are > not sure that they "completely" understand. If you add just a dummy numeric > label, the optimisation is not done. > > My preference would be to use builtin_bswap (as riscv/ does) on all > architectures on GCC and Clang, and keep the bespoke C for other compilers > and > external header inclusion. >
Why would you not want to use the compiler builtins for external users? - Andreas _______________________________________________ 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".
