83 строки
2.4 KiB
C
83 строки
2.4 KiB
C
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/*
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* include/asm-xtensa/byteorder.h
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 2001 - 2005 Tensilica Inc.
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*/
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#ifndef _XTENSA_BYTEORDER_H
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#define _XTENSA_BYTEORDER_H
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#include <asm/processor.h>
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#include <asm/types.h>
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static __inline__ __const__ __u32 ___arch__swab32(__u32 x)
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{
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__u32 res;
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/* instruction sequence from Xtensa ISA release 2/2000 */
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__asm__("ssai 8 \n\t"
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"srli %0, %1, 16 \n\t"
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"src %0, %0, %1 \n\t"
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"src %0, %0, %0 \n\t"
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"src %0, %1, %0 \n"
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: "=&a" (res)
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: "a" (x)
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);
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return res;
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}
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static __inline__ __const__ __u16 ___arch__swab16(__u16 x)
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{
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/* Given that 'short' values are signed (i.e., can be negative),
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* we cannot assume that the upper 16-bits of the register are
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* zero. We are careful to mask values after shifting.
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*/
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/* There exists an anomaly between xt-gcc and xt-xcc. xt-gcc
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* inserts an extui instruction after putting this function inline
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* to ensure that it uses only the least-significant 16 bits of
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* the result. xt-xcc doesn't use an extui, but assumes the
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* __asm__ macro follows convention that the upper 16 bits of an
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* 'unsigned short' result are still zero. This macro doesn't
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* follow convention; indeed, it leaves garbage in the upport 16
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* bits of the register.
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* Declaring the temporary variables 'res' and 'tmp' to be 32-bit
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* types while the return type of the function is a 16-bit type
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* forces both compilers to insert exactly one extui instruction
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* (or equivalent) to mask off the upper 16 bits. */
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__u32 res;
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__u32 tmp;
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__asm__("extui %1, %2, 8, 8\n\t"
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"slli %0, %2, 8 \n\t"
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"or %0, %0, %1 \n"
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: "=&a" (res), "=&a" (tmp)
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: "a" (x)
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);
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return res;
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}
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#define __arch__swab32(x) ___arch__swab32(x)
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#define __arch__swab16(x) ___arch__swab16(x)
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#if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
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# define __BYTEORDER_HAS_U64__
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# define __SWAB_64_THRU_32__
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#endif
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#ifdef __XTENSA_EL__
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# include <linux/byteorder/little_endian.h>
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#elif defined(__XTENSA_EB__)
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# include <linux/byteorder/big_endian.h>
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#else
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# error processor byte order undefined!
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#endif
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#endif /* __ASM_XTENSA_BYTEORDER_H */
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