1/* 2 * Written by J.T. Conklin <jtc@NetBSD.org>. 3 * Public domain. 4 */ 5 6#include <machine/asm.h> 7 8#if defined(LIBC_SCCS) 9 RCSID("$NetBSD: swab.S,v 1.4 2014/05/22 15:01:57 uebayasi Exp $") 10#endif 11 12#define LOAD_SWAP_STORE_WORD \ 13 lodsw ; \ 14 xchgb %al,%ah ; \ 15 stosw 16 17ENTRY(swab) 18 xchgq %rdi,%rsi 19 cld # set direction forward 20 21 shrq $1,%rdx 22 testq $7,%rdx # copy first group of 1 to 7 words 23 jz L2 # while swapping alternate bytes. 24L1: lodsw 25 rorw $8,%ax 26 stosw 27 decq %rdx 28 testq $7,%rdx 29 jnz L1 30 31L2: shrq $3,%rdx # copy remainder 8 words at a time 32 jz L4 # while swapping alternate bytes. 33L3: 34 LOAD_SWAP_STORE_WORD 35 LOAD_SWAP_STORE_WORD 36 LOAD_SWAP_STORE_WORD 37 LOAD_SWAP_STORE_WORD 38 LOAD_SWAP_STORE_WORD 39 LOAD_SWAP_STORE_WORD 40 LOAD_SWAP_STORE_WORD 41 LOAD_SWAP_STORE_WORD 42 43 decq %rdx 44 jnz L3 45L4: 46 ret 47END(swab) 48