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Diffstat (limited to 'sysdeps/i386/bits/byteswap.h')
-rw-r--r--sysdeps/i386/bits/byteswap.h23
1 files changed, 19 insertions, 4 deletions
diff --git a/sysdeps/i386/bits/byteswap.h b/sysdeps/i386/bits/byteswap.h
index a1ba6b8748..64fc56ada2 100644
--- a/sysdeps/i386/bits/byteswap.h
+++ b/sysdeps/i386/bits/byteswap.h
@@ -1,5 +1,5 @@
/* Macros to swap the order of bytes in integer values.
- Copyright (C) 1997, 1998 Free Software Foundation, Inc.
+ Copyright (C) 1997, 1998, 2000 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
@@ -84,12 +84,27 @@
#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))
+
# define __bswap_64(x) \
(__extension__ \
({ union { __extension__ unsigned long long int __ll; \
unsigned long int __l[2]; } __w, __r; \
- __w.__ll = (x); \
- __r.__l[0] = __bswap_32 (__w.__l[1]); \
- __r.__l[1] = __bswap_32 (__w.__l[0]); \
+ 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