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/*
* include/asm-xtensa/swab.h
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2001 - 2005 Tensilica Inc.
*/
#ifndef _XTENSA_SWAB_H
#define _XTENSA_SWAB_H
#include <linux/types.h>
#include <linux/compiler.h>
#define __SWAB_64_THRU_32__
static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
{
__u32 res;
/* instruction sequence from Xtensa ISA release 2/2000 */
__asm__("ssai 8 \n\t"
"srli %0, %1, 16 \n\t"
"src %0, %0, %1 \n\t"
"src %0, %0, %0 \n\t"
"src %0, %1, %0 \n"
: "=&a" (res)
: "a" (x)
);
return res;
}
#define __arch_swab32 __arch_swab32
static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
{
/* Given that 'short' values are signed (i.e., can be negative),
* we cannot assume that the upper 16-bits of the register are
* zero. We are careful to mask values after shifting.
*/
/* There exists an anomaly between xt-gcc and xt-xcc. xt-gcc
* inserts an extui instruction after putting this function inline
* to ensure that it uses only the least-significant 16 bits of
* the result. xt-xcc doesn't use an extui, but assumes the
* __asm__ macro follows convention that the upper 16 bits of an
* 'unsigned short' result are still zero. This macro doesn't
* follow convention; indeed, it leaves garbage in the upport 16
* bits of the register.
* Declaring the temporary variables 'res' and 'tmp' to be 32-bit
* types while the return type of the function is a 16-bit type
* forces both compilers to insert exactly one extui instruction
* (or equivalent) to mask off the upper 16 bits. */
__u32 res;
__u32 tmp;
__asm__("extui %1, %2, 8, 8\n\t"
"slli %0, %2, 8 \n\t"
"or %0, %0, %1 \n"
: "=&a" (res), "=&a" (tmp)
: "a" (x)
);
return res;
}
#define __arch_swab16 __arch_swab16
#endif /* _XTENSA_SWAB_H */
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