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71 lines
2.1 KiB
71 lines
2.1 KiB
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ |
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/* |
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* include/asm-xtensa/swab.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_SWAB_H |
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#define _XTENSA_SWAB_H |
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#include <linux/types.h> |
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#include <linux/compiler.h> |
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#define __SWAB_64_THRU_32__ |
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static inline __attribute_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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#define __arch_swab32 __arch_swab32 |
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static inline __attribute_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_swab16 __arch_swab16 |
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#endif /* _XTENSA_SWAB_H */
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