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Allow the compiler to micro-optimize byte swapping functions by

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evaluating them at compile time rather than at run time.  As for x86
and amd64, this requires GCC and it's enabled only if __OPTIMIZE__ is
defined (ie, if at least -O is used).

Reviewed by:	jake
This commit is contained in:
Maxime Henrion 2003-09-30 22:35:27 +00:00
parent d68d22ba52
commit 4e513b7a01
1 changed files with 24 additions and 15 deletions
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39
sys/sparc64/include/endian.h
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@ -67,17 +67,30 @@
#define BYTE_ORDER _BYTE_ORDER
#endif
#ifdef __GNUC__
#if defined(__GNUC__) && defined(__OPTIMIZE__)
#define __is_constant(x) __builtin_constant_p(x)
#else
#define __is_constant(x) 0
#endif
#define __bswap16_const(x) ((x >> 8) | ((x << 8) & 0xff00))
#define __bswap32_const(x) ((x >> 24) | ((x >> 8) & 0xff00) | \
((x << 8) & 0xff0000) | ((x << 24) & 0xff000000))
#define __bswap64_const(x) ((x >> 56) | ((x >> 40) & 0xff00) | \
((x >> 24) & 0xff0000) | ((x >> 8) & 0xff000000) | \
((x << 8) & ((__uint64_t)0xff << 32)) | \
((x << 24) & ((__uint64_t)0xff << 40)) | \
((x << 40) & ((__uint64_t)0xff << 48)) | ((x << 56)))
static __inline __uint16_t
__bswap16(__uint16_t _x)
__bswap16_var(__uint16_t _x)
{
return ((_x >> 8) | ((_x << 8) & 0xff00));
}
static __inline __uint32_t
__bswap32(__uint32_t _x)
__bswap32_var(__uint32_t _x)
{
return ((_x >> 24) | ((_x >> 8) & 0xff00) | ((_x << 8) & 0xff0000) |
@ -85,7 +98,7 @@ __bswap32(__uint32_t _x)
}
static __inline __uint64_t
__bswap64(__uint64_t _x)
__bswap64_var(__uint64_t _x)
{
return ((_x >> 56) | ((_x >> 40) & 0xff00) | ((_x >> 24) & 0xff0000) |
@ -94,20 +107,16 @@ __bswap64(__uint64_t _x)
((_x << 40) & ((__uint64_t)0xff << 48)) | ((_x << 56)));
}
#define __bswap16(x) (__is_constant(x) ? __bswap16_const(x) : \
__bswap16_var(x))
#define __bswap32(x) (__is_constant(x) ? __bswap32_const(x) : \
__bswap32_var(x))
#define __bswap64(x) (__is_constant(x) ? __bswap64_const(x) : \
__bswap64_var(x))
#define __htonl(x) ((__uint32_t)(x))
#define __htons(x) ((__uint16_t)(x))
#define __ntohl(x) ((__uint32_t)(x))
#define __ntohs(x) ((__uint16_t)(x))
#else /* !__GNUC__ */
/*
* No optimizations are available for this compiler. Fall back to
* non-optimized functions by defining the constant usually used to prevent
* redefinition.
*/
#define _BYTEORDER_FUNC_DEFINED
#endif /* __GNUC__ */
#endif /* !_MACHINE_ENDIAN_H_ */