1/*	$OpenBSD: memset.S,v 1.4 2015/06/08 14:22:05 jsg Exp $	*/
2/*	$NetBSD: memset.S,v 1.1 2000/12/29 20:51:57 bjh21 Exp $	*/
3
4/*
5 * Copyright (c) 1995 Mark Brinicombe.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by Mark Brinicombe.
19 * 4. The name of the company nor the name of the author may be used to
20 *    endorse or promote products derived from this software without specific
21 *    prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
24 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
25 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
26 * IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
27 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
28 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
29 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36#include <machine/asm.h>
37
38/*
39 * Sets a block of memory to the specified value
40 *
41 * On entry:
42 *   r0 - dest address
43 *   r1 - byte to write
44 *   r2 - number of bytes to write
45 *
46 * On exit:
47 *   r0 - dest address
48 */
49
50.syntax unified
51
52ENTRY(memset)
53	stmfd	sp!, {r0}		/* Remember address for return value */
54	and	r1, r1, #0x000000ff	/* We write bytes */
55
56	cmp	r2, #0x00000004		/* Do we have less than 4 bytes */
57	blt	Lmemset_lessthanfour
58
59	/* Ok first we will word align the address */
60
61	ands	r3, r0, #0x00000003	/* Get the bottom two bits */
62	beq	Lmemset_addraligned	/* The address is word aligned */
63
64	rsb	r3, r3, #0x00000004
65	sub	r2, r2, r3
66	cmp	r3, #0x00000002
67	strb	r1, [r0], #0x0001	/* Set 1 byte */
68	strbge	r1, [r0], #0x0001	/* Set another byte */
69	strbgt	r1, [r0], #0x0001	/* and a third */
70
71	cmp	r2, #0x00000004
72	blt	Lmemset_lessthanfour
73
74	/* Now we must be word aligned */
75
76Lmemset_addraligned:
77
78	orr	r3, r1, r1, lsl #8	/* Repeat the byte into a word */
79	orr	r3, r3, r3, lsl #16
80
81	/* We know we have at least 4 bytes ... */
82
83	cmp	r2, #0x00000020		/* If less than 32 then use words */
84	blt	Lmemset_lessthan32
85
86	/* We have at least 32 so lets use quad words */
87
88	stmfd	sp!, {r4-r6}		/* Store registers */
89	mov	r4, r3			/* Duplicate data */
90	mov	r5, r3
91	mov	r6, r3
92
93Lmemset_loop16:
94	stmia	r0!, {r3-r6}		/* Store 16 bytes */
95	sub	r2, r2, #0x00000010	/* Adjust count */
96	cmp	r2, #0x00000010		/* Still got at least 16 bytes ? */
97	bgt	Lmemset_loop16
98
99	ldmfd	sp!, {r4-r6}		/* Restore registers */
100
101	/* Do we need to set some words as well ? */
102
103	cmp	r2, #0x00000004
104	blt	Lmemset_lessthanfour
105
106	/* Have either less than 16 or less than 32 depending on route taken */
107
108Lmemset_lessthan32:
109
110	/* We have at least 4 bytes so copy as words */
111
112Lmemset_loop4:
113	str	r3, [r0], #0x0004
114	sub	r2, r2, #0x0004
115	cmp	r2, #0x00000004
116	bge	Lmemset_loop4
117
118Lmemset_lessthanfour:
119	cmp	r2, #0x00000000
120	ldmfdeq	sp!, {r0}
121	moveq	pc, lr			/* Zero length so exit */
122
123	cmp	r2, #0x00000002
124	strb	r1, [r0], #0x0001	/* Set 1 byte */
125	strbge	r1, [r0], #0x0001	/* Set another byte */
126	strbgt	r1, [r0], #0x0001	/* and a third */
127
128	ldmfd	sp!, {r0}
129	mov	pc, lr			/* Exit */
130