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-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