Rewrite the byte swapping macros.

The clever pointer tricks were actually not working, and we were doing
the byte-by-byte moves in general.  By just doing the memcpy and
obvious byte swap code, we end up generating actual byte swap
instructions, thanks to optimizing compilers.

         text	   data	    bss	    dec	    hex	filename
before: 2240807	  51552	 132016	2424375	 24fe37	hw/xfree86/Xorg
after:  2215167	  51552	 132016	2398735	 249a0f	hw/xfree86/Xorg

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Keith Packard <keithp@keithp.com>

doc/Xserver-spec.xml

@@ -600,7 +600,7 @@ are: REQUEST, REQUEST_SIZE_MATCH, REQUEST_AT_LEAST_SIZE,
 REQUEST_FIXED_SIZE, LEGAL_NEW_RESOURCE, and
 VALIDATE_DRAWABLE_AND_GC. Useful byte swapping macros can be found
 in Xserver/include/dix.h: WriteReplyToClient and WriteSwappedDataToClient; and
-in Xserver/include/misc.h: lswapl, lswaps, LengthRestB, LengthRestS,
+in Xserver/include/misc.h: bswap_64, bswap_32, bswap_16, LengthRestB, LengthRestS,
 LengthRestL, SwapRestS, SwapRestL, swapl, swaps, cpswapl, and cpswaps.</para>
 </section>
 </section>

glx/glxbyteorder.h

@@ -37,25 +37,4 @@
 
 #include "misc.h"
 
-static inline uint16_t
-bswap_16(uint16_t val)
-{
-    swap_uint16(&val);
-    return val;
-}
-
-static inline uint32_t
-bswap_32(uint32_t val)
-{
-    swap_uint32(&val);
-    return val;
-}
-
-static inline uint64_t
-bswap_64(uint64_t val)
-{
-    swap_uint64(&val);
-    return val;
-}
-
 #endif                          /* !defined(__GLXBYTEORDER_H__) */

include/misc.h

@@ -128,21 +128,6 @@ typedef struct _xReq *xReqPtr;
 #define USE_BACKGROUND_PIXEL 3
 #define USE_BORDER_PIXEL 3
 
-/* byte swap a 32-bit literal */
-static inline uint32_t
-lswapl(uint32_t x)
-{
-    return ((x & 0xff) << 24) |
-        ((x & 0xff00) << 8) | ((x & 0xff0000) >> 8) | ((x >> 24) & 0xff);
-}
-
-/* byte swap a 16-bit literal */
-static inline uint16_t
-lswaps(uint16_t x)
-{
-    return (uint16_t)((x & 0xff) << 8) | ((x >> 8) & 0xff);
-}
-
 #undef min
 #undef max
 
@@ -311,88 +296,74 @@ __builtin_constant_p(int x)
 }
 #endif
 
-/* byte swap a 64-bit value */
-static inline void
-swap_uint64(uint64_t *x)
+static inline uint64_t
+bswap_64(uint64_t x)
 {
-    char n;
-
-    n = ((char *) x)[0];
-    ((char *) x)[0] = ((char *) x)[7];
-    ((char *) x)[7] = n;
-
-    n = ((char *) x)[1];
-    ((char *) x)[1] = ((char *) x)[6];
-    ((char *) x)[6] = n;
-
-    n = ((char *) x)[2];
-    ((char *) x)[2] = ((char *) x)[5];
-    ((char *) x)[5] = n;
-
-    n = ((char *) x)[3];
-    ((char *) x)[3] = ((char *) x)[4];
-    ((char *) x)[4] = n;
+    return (((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 swapll(x) do { \
+		uint64_t temp; \
 		if (sizeof(*(x)) != 8) \
 			wrong_size(); \
-                swap_uint64((uint64_t *)(x));   \
+		memcpy(&temp, x, 8); \
+		temp = bswap_64(temp); \
+		memcpy(x, &temp, 8); \
 	} while (0)
 
-/* byte swap a 32-bit value */
-static inline void
-swap_uint32(uint32_t * x)
+static inline uint32_t
+bswap_32(uint32_t x)
 {
-    char n = ((char *) x)[0];
-
-    ((char *) x)[0] = ((char *) x)[3];
-    ((char *) x)[3] = n;
-    n = ((char *) x)[1];
-    ((char *) x)[1] = ((char *) x)[2];
-    ((char *) x)[2] = n;
+    return (((x & 0xFF000000) >> 24) |
+            ((x & 0x00FF0000) >> 8) |
+            ((x & 0x0000FF00) << 8) |
+            ((x & 0x000000FF) << 24));
 }
 
 #define swapl(x) do { \
+		uint32_t temp; \
 		if (sizeof(*(x)) != 4) \
 			wrong_size(); \
-		if (__builtin_constant_p((uintptr_t)(x) & 3) && ((uintptr_t)(x) & 3) == 0) \
-			*(x) = lswapl(*(x)); \
-		else \
-			swap_uint32((uint32_t *)(x)); \
+		memcpy(&temp, x, 4); \
+		temp = bswap_32(temp); \
+		memcpy(x, &temp, 4); \
 	} while (0)
 
-/* byte swap a 16-bit value */
-static inline void
-swap_uint16(uint16_t * x)
+static inline uint16_t
+bswap_16(uint16_t x)
 {
-    char n = ((char *) x)[0];
-
-    ((char *) x)[0] = ((char *) x)[1];
-    ((char *) x)[1] = n;
+    return (((x & 0xFF00) >> 8) |
+            ((x & 0x00FF) << 8));
 }
 
 #define swaps(x) do { \
+		uint16_t temp; \
 		if (sizeof(*(x)) != 2) \
 			wrong_size(); \
-		if (__builtin_constant_p((uintptr_t)(x) & 1) && ((uintptr_t)(x) & 1) == 0) \
-			*(x) = lswaps(*(x)); \
-		else \
-			swap_uint16((uint16_t *)(x)); \
+		memcpy(&temp, x, 2); \
+		temp = bswap_16(temp); \
+		memcpy(x, &temp, 2); \
 	} while (0)
 
 /* copy 32-bit value from src to dst byteswapping on the way */
 #define cpswapl(src, dst) do { \
 		if (sizeof((src)) != 4 || sizeof((dst)) != 4) \
 			wrong_size(); \
-		(dst) = lswapl((src)); \
+		(dst) = bswap_32((src)); \
 	} while (0)
 
 /* copy short from src to dst byteswapping on the way */
 #define cpswaps(src, dst) do { \
 		if (sizeof((src)) != 2 || sizeof((dst)) != 2) \
 			wrong_size(); \
-		(dst) = lswaps((src)); \
+		(dst) = bswap_16((src)); \
 	} while (0)
 
 extern _X_EXPORT void SwapLongs(CARD32 *list, unsigned long count);

os/io.c

@@ -108,12 +108,12 @@ static ConnectionOutputPtr FreeOutputs = (ConnectionOutputPtr) NULL;
 static OsCommPtr AvailableInput = (OsCommPtr) NULL;
 
 #define get_req_len(req,cli) ((cli)->swapped ? \
-			      lswaps((req)->length) : (req)->length)
+			      bswap_16((req)->length) : (req)->length)
 
 #include <X11/extensions/bigreqsproto.h>
 
 #define get_big_req_len(req,cli) ((cli)->swapped ? \
-				  lswapl(((xBigReq *)(req))->length) : \
+				  bswap_32(((xBigReq *)(req))->length) : \
 				  ((xBigReq *)(req))->length)
 
 #define BUFSIZE 16384