1/*	$NetBSD: memset.S,v 1.3 2007/11/12 18:41:59 ad Exp $	*/
2
3/*-
4 * Copyright (c) 2003 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by David Laight.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include <machine/asm.h>
33
34#if defined(LIBC_SCCS)
35	RCSID("$NetBSD: memset.S,v 1.3 2007/11/12 18:41:59 ad Exp $")
36#endif
37
38#ifdef BZERO
39ENTRY(bzero)
40#else
41ENTRY(memset)
42#endif
43#ifdef BZERO
44	movl	8(%esp),%ecx
45	xor	%eax,%eax
46#else
47	movl	12(%esp),%ecx
48	movzbl	8(%esp),%eax		/* unsigned char, zero extend */
49#endif
50	cmpl	$0x0f,%ecx		/* avoid mispredicted branch... */
51
52	pushl	%edi
53	movl	8(%esp),%edi
54
55	/*
56	 * if the string is too short, it's really not worth the overhead
57	 * of aligning to word boundries, etc.  So we jump to a plain
58	 * unaligned set.
59	 *
60	 * NB aligning the transfer is actually pointless on my athlon 700,
61	 * It does make a difference to a PII though.
62	 *
63	 * The PII, PIII and PIV all seem to have a massive performance
64	 * drop when the initial target address is an odd multiple of 4.
65	 */
66	jbe	.Lby_bytes
67
68#ifndef BZERO
69	movb	%al,%ah			/* copy char to all bytes in word */
70	movl	%eax,%edx
71	sall	$16,%eax
72	orl	%edx,%eax
73#endif
74
75	movl	%edi,%edx		/* detect misalignment */
76	neg	%edx
77	andl	$7,%edx
78	jnz	.Lalign
79.Laligned:
80	movl	%eax,-4(%edi,%ecx)	/* zap last 4 bytes */
81	shrl	$2,%ecx			/* zero by words */
82	rep
83	stosl
84.Ldone:
85#ifndef BZERO
86	movl	8(%esp),%eax		/* return address of buffer */
87#endif
88	pop	%edi
89	ret
90
91.Lalign:
92	movl	%eax,(%edi)		/* zap first 8 bytes */
93	movl	%eax,4(%edi)
94	subl	%edx,%ecx		/* remove from main count */
95	add	%edx,%edi
96	jmp	.Laligned
97
98.Lby_bytes:
99	rep
100	stosb
101
102#ifndef BZERO
103	movl	8(%esp),%eax		/* return address of buffer */
104#endif
105	popl	%edi
106	ret
107