minix/lib/nbsd_libc/arch/i386/string/swab.S
Gianluca Guida b6cbf7203b Import unmodified NetBSD libc in trunk
This patch imports the unmodified current version of NetBSD libc.
The NetBSD includes are in /nbsd_include, while the libc code itself is 
split between lib/nbsd_libc and common/lib/libc.
2011-02-14 19:36:03 +00:00

68 lines
1 KiB
ArmAsm

/*
* Written by J.T. Conklin <jtc@NetBSD.org>.
* Public domain.
*/
#include <machine/asm.h>
#if defined(LIBC_SCCS)
RCSID("$NetBSD: swab.S,v 1.13 2007/11/12 18:42:00 ad Exp $")
#endif
/*
* On the i486, this code is negligibly faster than the code generated
* by gcc at about half the size. If my i386 databook is correct, it
* should be considerably faster than the gcc code on a i386.
*/
ENTRY(swab)
pushl %esi
pushl %edi
movl 12(%esp),%esi
movl 16(%esp),%edi
movl 20(%esp),%ecx
shrl $1,%ecx
testl $7,%ecx # copy first group of 1 to 7 words
jz L2 # while swapping alternate bytes.
_ALIGN_TEXT,0x90
L1: lodsw
rorw $8,%ax
stosw
decl %ecx
testl $7,%ecx
jnz L1
L2: shrl $3,%ecx # copy remainder 8 words at a time
jz L4 # while swapping alternate bytes.
_ALIGN_TEXT,0x90
L3: lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
lodsw
rorw $8,%ax
stosw
decl %ecx
jnz L3
L4: popl %edi
popl %esi
ret