[RFC] Optimize swab operations on mips_r2 cpu

[Franck <vagabon.xyz@gmail.com>]

Here is a little patch to optimize swab operations by using "wsbh"
instruction available on mips revision 2 cpus. I do not know what
condition I should use to compile this only for mips r2 cpu though.

Comments ?

Thanks
--
               Franck

--- linux.git/include/asm-mips/byteorder.h~old  2006-01-25
09:39:33.000000000 +0100
+++ linux.git/include/asm-mips/byteorder.h      2006-01-25 10:30:10.000000000 
+0100
@@ -8,15 +8,39 @@
 #ifndef _ASM_BYTEORDER_H
 #define _ASM_BYTEORDER_H

+#include <linux/compiler.h>
 #include <asm/types.h>

 #ifdef __GNUC__

+/* FIXME: MIPS_R2 only */
+static __inline__ __attribute_const__ __u16 ___arch__swab16(__u16 x)
+{
+       __asm__(
+               "wsbh   %0, %1\n"
+               : "=r" (x)
+               : "r" (x));
+       return x;
+}
+
+static __inline__ __attribute_const__ __u32 ___arch__swab32(__u32 x)
+{
+       __asm__(
+               "wsbh   %0, %1\n\t"
+               "rotr   %0, %0, 16\n"
+               : "=r" (x)
+               : "r" (x));
+       return x;
+}
+
 #if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
 #  define __BYTEORDER_HAS_U64__
 #  define __SWAB_64_THRU_32__
 #endif

+#define __arch__swab16(x)      ___arch__swab16(x)
+#define __arch__swab32(x)      ___arch__swab32(x)
+
 #endif /* __GNUC__ */

 #if defined (__MIPSEB__)