[MPlayer-dev-eng] [PATCH] bswap.h which takes care of cpu's > 386 by using different asm commands

[Falk Hueffner]

Dirk <noisyb at gmx.net> writes:

> +  unsigned char *ptr = (unsigned char *) &x, tmp;
> +  tmp = ptr[0];
> +  ptr[0] = ptr[7];
> +  ptr[7] = tmp;
> +  tmp = ptr[1];
> +  ptr[1] = ptr[6];
> +  ptr[6] = tmp;
> +  tmp = ptr[2];
> +  ptr[2] = ptr[5];
> +  ptr[5] = tmp;
> +  tmp = ptr[3];
> +  ptr[3] = ptr[4];
> +  ptr[4] = tmp;

This is going to be horrendously slow on Alpha, and probably on most
other RISC architectures. Besides, I don't see any reason to touch
this code unless you can measure an improvement for some platform.

> -#define bswap_64(x) \
> -     (__extension__						\
> -      ({ union { __extension__ unsigned long long int __ll;	\
> -                 unsigned long int __l[2]; } __w, __r;		\
> -         __w.__ll = (x);					\
> -         __r.__l[0] = bswap_32 (__w.__l[1]);			\
> -         __r.__l[1] = bswap_32 (__w.__l[0]);			\
> -         __r.__ll; }))
> -#endif	/* !ARCH_X86 */

By the way, this is broken, too, since long int is 64 bit on some
architectures (It was fixed in glibc some years ago). Please somebody
s/unsigned long int/unsigned int/.

        Falk