memcmp.S revision 135682 
1238106Sdes/*      $NetBSD: memcmp.S,v 1.3 2003/10/14 07:51:45 scw Exp $ */
2238106Sdes
3238106Sdes/*
4238106Sdes * Copyright 2003 Wasabi Systems, Inc.
5238106Sdes * All rights reserved.
6238106Sdes *
7238106Sdes * Written by Steve C. Woodford for Wasabi Systems, Inc.
8238106Sdes *
9238106Sdes * Redistribution and use in source and binary forms, with or without
10238106Sdes * modification, are permitted provided that the following conditions
11238106Sdes * are met:
12238106Sdes * 1. Redistributions of source code must retain the above copyright
13238106Sdes *    notice, this list of conditions and the following disclaimer.
14238106Sdes * 2. Redistributions in binary form must reproduce the above copyright
15238106Sdes *    notice, this list of conditions and the following disclaimer in the
16238106Sdes *    documentation and/or other materials provided with the distribution.
17238106Sdes * 3. All advertising materials mentioning features or use of this software
18238106Sdes *    must display the following acknowledgement:
19238106Sdes *      This product includes software developed for the NetBSD Project by
20238106Sdes *      Wasabi Systems, Inc.
21238106Sdes * 4. The name of Wasabi Systems, Inc. may not be used to endorse
22238106Sdes *    or promote products derived from this software without specific prior
23238106Sdes *    written permission.
24238106Sdes *
25238106Sdes * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
26238106Sdes * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
27238106Sdes * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
28238106Sdes * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
29238106Sdes * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30238106Sdes * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
31238106Sdes * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
32238106Sdes * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
33238106Sdes * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
34238106Sdes * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
35238106Sdes * POSSIBILITY OF SUCH DAMAGE.
36238106Sdes */
37238106Sdes/*
38238106Sdes * Copyright (c) 2002 ARM Ltd
39238106Sdes * All rights reserved.
40238106Sdes *
41238106Sdes * Redistribution and use in source and binary forms, with or without
42238106Sdes * modification, are permitted provided that the following conditions
43238106Sdes * are met:
44238106Sdes * 1. Redistributions of source code must retain the above copyright
45238106Sdes *    notice, this list of conditions and the following disclaimer.
46238106Sdes * 2. Redistributions in binary form must reproduce the above copyright
47238106Sdes *    notice, this list of conditions and the following disclaimer in the
48238106Sdes *    documentation and/or other materials provided with the distribution.
49238106Sdes * 3. The name of the company may not be used to endorse or promote
50238106Sdes *    products derived from this software without specific prior written
51238106Sdes *    permission.
52238106Sdes *
53238106Sdes * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
54238106Sdes * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
55238106Sdes * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
56238106Sdes * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
57238106Sdes * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
58238106Sdes * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
59238106Sdes * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
60238106Sdes * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
61238106Sdes * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
62238106Sdes * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
63238106Sdes */
64238106Sdes
65238106Sdes#include <machine/asm.h>
66238106Sdes
67238106Sdes__FBSDID("$FreeBSD: head/lib/libc/arm/string/memcmp.S 135682 2004-09-23 23:10:56Z cognet $");
68238106Sdes
69238106SdesENTRY(memcmp)
70238106Sdes	mov	ip, r0
71238106Sdes#if defined(_KERNEL) && !defined(_STANDALONE)
72238106Sdes	cmp	r2, #0x06
73238106Sdes	beq	.Lmemcmp_6bytes
74238106Sdes#endif
75238106Sdes	mov	r0, #0x00
76
77	/* Are both addresses aligned the same way? */
78	cmp	r2, #0x00
79	eornes	r3, ip, r1
80	moveq	pc, lr			/* len == 0, or same addresses! */
81	tst	r3, #0x03
82	subne	r2, r2, #0x01
83	bne	.Lmemcmp_bytewise2	/* Badly aligned. Do it the slow way */
84
85	/* Word-align the addresses, if necessary */
86	sub	r3, r1, #0x05
87	ands	r3, r3, #0x03
88	add	r3, r3, r3, lsl #1
89	addne	pc, pc, r3, lsl #3
90	nop
91
92	/* Compare up to 3 bytes */
93	ldrb	r0, [ip], #0x01
94	ldrb	r3, [r1], #0x01
95	subs	r0, r0, r3
96	movne	pc, lr
97	subs	r2, r2, #0x01
98	moveq	pc, lr
99
100	/* Compare up to 2 bytes */
101	ldrb	r0, [ip], #0x01
102	ldrb	r3, [r1], #0x01
103	subs	r0, r0, r3
104	movne	pc, lr
105	subs	r2, r2, #0x01
106	moveq	pc, lr
107
108	/* Compare 1 byte */
109	ldrb	r0, [ip], #0x01
110	ldrb	r3, [r1], #0x01
111	subs	r0, r0, r3
112	movne	pc, lr
113	subs	r2, r2, #0x01
114	moveq	pc, lr
115
116	/* Compare 4 bytes at a time, if possible */
117	subs	r2, r2, #0x04
118	bcc	.Lmemcmp_bytewise
119.Lmemcmp_word_aligned:
120	ldr	r0, [ip], #0x04
121	ldr	r3, [r1], #0x04
122	subs	r2, r2, #0x04
123	cmpcs	r0, r3
124	beq	.Lmemcmp_word_aligned
125	sub	r0, r0, r3
126
127	/* Correct for extra subtraction, and check if done */
128	adds	r2, r2, #0x04
129	cmpeq	r0, #0x00		/* If done, did all bytes match? */
130	moveq	pc, lr			/* Yup. Just return */
131
132	/* Re-do the final word byte-wise */
133	sub	ip, ip, #0x04
134	sub	r1, r1, #0x04
135
136.Lmemcmp_bytewise:
137	add	r2, r2, #0x03
138.Lmemcmp_bytewise2:
139	ldrb	r0, [ip], #0x01
140	ldrb	r3, [r1], #0x01
141	subs	r2, r2, #0x01
142	cmpcs	r0, r3
143	beq	.Lmemcmp_bytewise2
144	sub	r0, r0, r3
145	mov	pc, lr
146
147#if defined(_KERNEL) && !defined(_STANDALONE)
148	/*
149	 * 6 byte compares are very common, thanks to the network stack.
150	 * This code is hand-scheduled to reduce the number of stalls for
151	 * load results. Everything else being equal, this will be ~32%
152	 * faster than a byte-wise memcmp.
153	 */
154	.align	5
155.Lmemcmp_6bytes:
156	ldrb	r3, [r1, #0x00]		/* r3 = b2#0 */
157	ldrb	r0, [ip, #0x00]		/* r0 = b1#0 */
158	ldrb	r2, [r1, #0x01]		/* r2 = b2#1 */
159	subs	r0, r0, r3		/* r0 = b1#0 - b2#0 */
160	ldreqb	r3, [ip, #0x01]		/* r3 = b1#1 */
161	movne	pc, lr			/* Return if mismatch on #0 */
162	subs	r0, r3, r2		/* r0 = b1#1 - b2#1 */
163	ldreqb	r3, [r1, #0x02]		/* r3 = b2#2 */
164	ldreqb	r0, [ip, #0x02]		/* r0 = b1#2 */
165	movne	pc, lr			/* Return if mismatch on #1 */
166	ldrb	r2, [r1, #0x03]		/* r2 = b2#3 */
167	subs	r0, r0, r3		/* r0 = b1#2 - b2#2 */
168	ldreqb	r3, [ip, #0x03]		/* r3 = b1#3 */
169	movne	pc, lr			/* Return if mismatch on #2 */
170	subs	r0, r3, r2		/* r0 = b1#3 - b2#3 */
171	ldreqb	r3, [r1, #0x04]		/* r3 = b2#4 */
172	ldreqb	r0, [ip, #0x04]		/* r0 = b1#4 */
173	movne	pc, lr			/* Return if mismatch on #3 */
174	ldrb	r2, [r1, #0x05]		/* r2 = b2#5 */
175	subs	r0, r0, r3		/* r0 = b1#4 - b2#4 */
176	ldreqb	r3, [ip, #0x05]		/* r3 = b1#5 */
177	movne	pc, lr			/* Return if mismatch on #4 */
178	sub	r0, r3, r2		/* r0 = b1#5 - b2#5 */
179	mov	pc, lr
180#endif
181