1/*	$OpenBSD: bcopy.S,v 1.5 2015/08/31 02:53:56 guenther Exp $ */
2/*-
3 * Copyright (c) 1991, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Ralph Campbell.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include "SYS.h"
35
36/* bcopy(s1, s2, n) */
37
38
39LEAF(bcopy, 0)
40	.set	noreorder
41	daddu	t0, a0, a2		# t0 = end of s1 region
42	sltu	t1, a1, t0
43	sltu	t2, a0, a1
44	and	t1, t1, t2		# t1 = true if from < to < (from+len)
45	beq	t1, zero, forward	# non overlapping, do forward copy
46	slt	t2, a2, 12		# check for small copy
47
48	ble	a2, zero, 2f
49	daddu	t1, a1, a2		# t1 = end of to region
501:
51	lb	v0, -1(t0)		# copy bytes backwards,
52	dsubu	t0, t0, 1		#  does not happen often so do slow way
53	dsubu	t1, t1, 1
54	bne	t0, a0, 1b
55	sb	v0, 0(t1)
562:
57	j	ra
58	nop
59forward:
60	bne	t2, zero, smallcpy	# do a small bcopy
61	xor	v0, a0, a1		# compare low two bits of addresses
62	and	v0, v0, 3
63	dsubu	a3, zero, a1		# compute # bytes to word align address
64	beq	v0, zero, aligned	# addresses can be word aligned
65	and	a3, a3, 3
66
67	beq	a3, zero, 1f
68	dsubu	a2, a2, a3		# subtract from remaining count
69	LWHI	v0, 0(a0)		# get next 4 bytes (unaligned)
70	LWLO	v0, 3(a0)
71	daddu	a0, a0, a3
72	SWHI	v0, 0(a1)		# store 1, 2, or 3 bytes to align a1
73	daddu	a1, a1, a3
741:
75	and	v0, a2, 3		# compute number of words left
76	dsubu	a3, a2, v0
77	move	a2, v0
78	daddu	a3, a3, a0		# compute ending address
792:
80	LWHI	v0, 0(a0)		# copy words a0 unaligned, a1 aligned
81	LWLO	v0, 3(a0)
82	daddu	a0, a0, 4
83	daddu	a1, a1, 4
84	bne	a0, a3, 2b
85	sw	v0, -4(a1)
86	b	smallcpy
87	nop
88aligned:
89	beq	a3, zero, 1f
90	dsubu	a2, a2, a3		# subtract from remaining count
91	LWHI	v0, 0(a0)		# copy 1, 2, or 3 bytes to align
92	daddu	a0, a0, a3
93	SWHI	v0, 0(a1)
94	daddu	a1, a1, a3
951:
96	and	v0, a2, 3		# compute number of whole words left
97	dsubu	a3, a2, v0
98	move	a2, v0
99	daddu	a3, a3, a0		# compute ending address
1002:
101	lw	v0, 0(a0)		# copy words
102	daddu	a0, a0, 4
103	daddu	a1, a1, 4
104	bne	a0, a3, 2b
105	sw	v0, -4(a1)
106smallcpy:
107	ble	a2, zero, 2f
108	daddu	a3, a2, a0		# compute ending address
1091:
110	lbu	v0, 0(a0)		# copy bytes
111	daddu	a0, a0, 1
112	daddu	a1, a1, 1
113	bne	a0, a3, 1b
114	sb	v0, -1(a1)
1152:
116	j	ra
117	nop
118	.set	reorder
119END_WEAK(bcopy)
120