byteswap: unify common definitions

The majority of the byteswap functions are the same across all arches, so
setup a common header to provide definitions if they don't exist.  This
allows arches to override only the ones they actually want to implement
with inline assembly.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 31 insertions, 96 deletions

diff --git a/libc/sysdeps/linux/x86_64/bits/byteswap.h b/libc/sysdeps/linux/x86_64/bits/byteswap.h
index e1c861c75..a9cf23d75 100644
--- a/libc/sysdeps/linux/x86_64/bits/byteswap.h
+++ b/libc/sysdeps/linux/x86_64/bits/byteswap.h
@@ -17,117 +17,52 @@
    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
+#ifndef _ASM_BITS_BYTESWAP_H
+#define _ASM_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) \
+#define __bswap_non_constant_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");						      \
+      ({ register unsigned short int __v;				      \
+	 __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__)
+#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) \
+# define __bswap_non_constant_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));		      \
+      ({ register unsigned int __v;					      \
+	 __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) \
+# define __bswap_non_constant_32(x) \
      (__extension__							      \
-      ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
+      ({ register unsigned int __v;					      \
+	 __asm__ ("rorw $8, %w0;"					      \
+		  "rorl $16, %0;"					      \
+		  "rorw $8, %w0"					      \
+		  : "=r" (__v)						      \
+		  : "0" (x)						      \
+		  : "cc");						      \
+	 __v; }))
 #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) \
+#if __WORDSIZE == 64
+# define __bswap_non_constant_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));		      \
+      ({ register unsigned long __v;					      \
+	 __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 */
+#endif
+
+#include <bits/byteswap-common.h>