(__bswap_64): Handle constant argument case separately.
[kopensolaris-gnu/glibc.git] / sysdeps / generic / bits / byteswap.h
index b193ea1..ec2051a 100644 (file)
@@ -53,12 +53,27 @@ __bswap_32 (unsigned int __bsx)
 
 #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 { unsigned long long int __ll;                                \
-                unsigned int __l[2]; } __v, __r;                             \
-        __v.__ll = (x);                                                      \
-        __r.__l[0] = __bswap_32 (__v.__l[1]);                                \
-        __r.__l[1] = __bswap_32 (__v.__l[0]);                                \
+      ({ union { __extension__ unsigned long long int __ll;                  \
+                unsigned long 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