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diff --git a/sysdeps/x86_64/bits/byteswap.h b/sysdeps/x86_64/bits/byteswap.h
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+/* Macros to swap the order of bytes in integer values.
+ Copyright (C) 1997, 1998, 2000, 2002, 2003 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#if !defined _BYTESWAP_H && !defined _NETINET_IN_H
+# error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
+#endif
+
+#ifndef _BITS_BYTESWAP_H
+#define _BITS_BYTESWAP_H 1
+
+#include <bits/wordsize.h>
+
+/* Swap bytes in 16 bit value. */
+#define __bswap_constant_16(x) \
+ ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))
+
+#if defined __GNUC__ && __GNUC__ >= 2
+# define __bswap_16(x) \
+ (__extension__ \
+ ({ register unsigned short int __v, __x = (x); \
+ if (__builtin_constant_p (__x)) \
+ __v = __bswap_constant_16 (__x); \
+ else \
+ __asm__ ("rorw $8, %w0" \
+ : "=r" (__v) \
+ : "0" (__x) \
+ : "cc"); \
+ __v; }))
+#else
+/* This is better than nothing. */
+# define __bswap_16(x) \
+ (__extension__ \
+ ({ register unsigned short int __x = (x); __bswap_constant_16 (__x); }))
+#endif
+
+
+/* Swap bytes in 32 bit value. */
+#define __bswap_constant_32(x) \
+ ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >> 8) | \
+ (((x) & 0x0000ff00) << 8) | (((x) & 0x000000ff) << 24))
+
+#if defined __GNUC__ && __GNUC__ >= 2
+# if __WORDSIZE == 64 || (defined __i486__ || defined __pentium__ \
+ || defined __pentiumpro__ || defined __pentium4__ \
+ || defined __k8__ || defined __athlon__ \
+ || defined __k6__)
+/* To swap the bytes in a word the i486 processors and up provide the
+ `bswap' opcode. On i386 we have to use three instructions. */
+# define __bswap_32(x) \
+ (__extension__ \
+ ({ register unsigned int __v, __x = (x); \
+ if (__builtin_constant_p (__x)) \
+ __v = __bswap_constant_32 (__x); \
+ else \
+ __asm__ ("bswap %0" : "=r" (__v) : "0" (__x)); \
+ __v; }))
+# else
+# define __bswap_32(x) \
+ (__extension__ \
+ ({ register unsigned int __v, __x = (x); \
+ if (__builtin_constant_p (__x)) \
+ __v = __bswap_constant_32 (__x); \
+ else \
+ __asm__ ("rorw $8, %w0;" \
+ "rorl $16, %0;" \
+ "rorw $8, %w0" \
+ : "=r" (__v) \
+ : "0" (__x) \
+ : "cc"); \
+ __v; }))
+# endif
+#else
+# define __bswap_32(x) \
+ (__extension__ \
+ ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
+#endif
+
+
+#if defined __GNUC__ && __GNUC__ >= 2
+/* Swap bytes in 64 bit value. */
+# define __bswap_constant_64(x) \
+ ((((x) & 0xff00000000000000ull) >> 56) \
+ | (((x) & 0x00ff000000000000ull) >> 40) \
+ | (((x) & 0x0000ff0000000000ull) >> 24) \
+ | (((x) & 0x000000ff00000000ull) >> 8) \
+ | (((x) & 0x00000000ff000000ull) << 8) \
+ | (((x) & 0x0000000000ff0000ull) << 24) \
+ | (((x) & 0x000000000000ff00ull) << 40) \
+ | (((x) & 0x00000000000000ffull) << 56))
+
+# if __WORDSIZE == 64
+# define __bswap_64(x) \
+ (__extension__ \
+ ({ register unsigned long __v, __x = (x); \
+ if (__builtin_constant_p (__x)) \
+ __v = __bswap_constant_64 (__x); \
+ else \
+ __asm__ ("bswap %q0" : "=r" (__v) : "0" (__x)); \
+ __v; }))
+# else
+# define __bswap_64(x) \
+ (__extension__ \
+ ({ union { __extension__ unsigned long long int __ll; \
+ unsigned int __l[2]; } __w, __r; \
+ if (__builtin_constant_p (x)) \
+ __r.__ll = __bswap_constant_64 (x); \
+ else \
+ { \
+ __w.__ll = (x); \
+ __r.__l[0] = __bswap_32 (__w.__l[1]); \
+ __r.__l[1] = __bswap_32 (__w.__l[0]); \
+ } \
+ __r.__ll; }))
+# endif
+#endif
+
+#endif /* _BITS_BYTESWAP_H */