/*
* Written by J.T. Conklin <[email protected]>.
* Public domain.
*/

#include <machine/asm.h>

#if defined(LIBC_SCCS)
       RCSID("$NetBSD: swab.S,v 1.4 2014/05/22 15:01:57 uebayasi Exp $")
#endif

#define LOAD_SWAP_STORE_WORD \
       lodsw   ; \
       xchgb   %al,%ah ; \
       stosw

ENTRY(swab)
       xchgq   %rdi,%rsi
       cld                             # set direction forward

       shrq    $1,%rdx
       testq   $7,%rdx                 # copy first group of 1 to 7 words
       jz      L2                      # while swapping alternate bytes.
L1:     lodsw
       rorw    $8,%ax
       stosw
       decq    %rdx
       testq   $7,%rdx
       jnz     L1

L2:     shrq    $3,%rdx                 # copy remainder 8 words at a time
       jz      L4                      # while swapping alternate bytes.
L3:
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD
       LOAD_SWAP_STORE_WORD

       decq    %rdx
       jnz     L3
L4:
       ret
END(swab)

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