arch/alpha/include/asm/swab.h

   1 #ifndef _ALPHA_SWAB_H
   2 #define _ALPHA_SWAB_H
   3
   4 #include <linux/types.h>
   5 #include <linux/compiler.h>
   6 #include <asm/compiler.h>
   7
   8 #ifdef __GNUC__
   9
  10 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
  11 {
  12         /*
  13          * Unfortunately, we can't use the 6 instruction sequence
  14          * on ev6 since the latency of the UNPKBW is 3, which is
  15          * pretty hard to hide.  Just in case a future implementation
  16          * has a lower latency, here's the sequence (also by Mike Burrows)
  17          *
  18          * UNPKBW a0, v0       v0: 00AA00BB00CC00DD
  19          * SLL v0, 24, a0      a0: BB00CC00DD000000
  20          * BIS v0, a0, a0      a0: BBAACCBBDDCC00DD
  21          * EXTWL a0, 6, v0     v0: 000000000000BBAA
  22          * ZAP a0, 0xf3, a0    a0: 00000000DDCC0000
  23          * ADDL a0, v0, v0     v0: ssssssssDDCCBBAA
  24          */
  25
  26         __u64 t0, t1, t2, t3;
  27
  28         t0 = __kernel_inslh(x, 7);      /* t0 : 0000000000AABBCC */
  29         t1 = __kernel_inswl(x, 3);      /* t1 : 000000CCDD000000 */
  30         t1 |= t0;                       /* t1 : 000000CCDDAABBCC */
  31         t2 = t1 >> 16;                  /* t2 : 0000000000CCDDAA */
  32         t0 = t1 & 0xFF00FF00;           /* t0 : 00000000DD00BB00 */
  33         t3 = t2 & 0x00FF00FF;           /* t3 : 0000000000CC00AA */
  34         t1 = t0 + t3;                   /* t1 : ssssssssDDCCBBAA */
  35
  36         return t1;
  37 }
  38 #define __arch_swab32 __arch_swab32
  39
  40 #endif /* __GNUC__ */
  41
  42 #endif /* _ALPHA_SWAB_H */