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-rw-r--r--bits/byteswap.h24
1 files changed, 21 insertions, 3 deletions
diff --git a/bits/byteswap.h b/bits/byteswap.h
index 6e3ed3ffae..d818293a4c 100644
--- a/bits/byteswap.h
+++ b/bits/byteswap.h
@@ -23,6 +23,8 @@
#ifndef _BITS_BYTESWAP_H
#define _BITS_BYTESWAP_H 1
+#include <features.h>
+
/* Swap bytes in 16 bit value. */
#define __bswap_constant_16(x) \
((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
@@ -36,9 +38,17 @@
(((x) & 0x0000ff00u) << 8) | (((x) & 0x000000ffu) << 24))
#ifdef __GNUC__
-# define __bswap_32(x) \
+# if __GNUC_PREREQ (4, 2)
+static __inline unsigned int
+__bswap_32 (unsigned int __bsx)
+{
+ return __builtin_bswap32 (__bsx);
+}
+# else
+# define __bswap_32(x) \
(__extension__ \
({ register unsigned int __bsx = (x); __bswap_constant_32 (__bsx); }))
+# endif
#else
static __inline unsigned int
__bswap_32 (unsigned int __bsx)
@@ -47,8 +57,8 @@ __bswap_32 (unsigned int __bsx)
}
#endif
-#if defined __GNUC__ && __GNUC__ >= 2
/* Swap bytes in 64 bit value. */
+#if __GNUC_PREREQ (2, 0)
# define __bswap_constant_64(x) \
(__extension__ ((((x) & 0xff00000000000000ull) >> 56) \
| (((x) & 0x00ff000000000000ull) >> 40) \
@@ -59,7 +69,14 @@ __bswap_32 (unsigned int __bsx)
| (((x) & 0x000000000000ff00ull) << 40) \
| (((x) & 0x00000000000000ffull) << 56)))
-# define __bswap_64(x) \
+# if __GNUC_PREREQ (4, 2)
+static __inline unsigned long long int
+__bswap_64 (unsigned long long int __bsx)
+{
+ return __builtin_bswap64 (__bsx);
+}
+# else
+# define __bswap_64(x) \
(__extension__ \
({ union { __extension__ unsigned long long int __ll; \
unsigned int __l[2]; } __w, __r; \
@@ -72,6 +89,7 @@ __bswap_32 (unsigned int __bsx)
__r.__l[1] = __bswap_32 (__w.__l[0]); \
} \
__r.__ll; }))
+# endif
#elif __GLIBC_HAVE_LONG_LONG
# define __bswap_constant_64(x) \
((((x) & 0xff00000000000000ull) >> 56) \