NetBSD/lib/libc/arch/x86_64/string/swab.S

47 lines
801 B
ArmAsm

/*
* Written by J.T. Conklin <jtc@netbsd.org>.
* Public domain.
*/
#include <machine/asm.h>
#if defined(LIBC_SCCS)
RCSID("$NetBSD: swab.S,v 1.1 2001/06/19 00:25:05 fvdl 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 swaping 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