1/*	$NetBSD: sync_bool_compare_and_swap_8.S,v 1.2 2013/11/30 21:09:11 joerg Exp $	*/
2/*-
3 * Copyright (c) 2012 The NetBSD Foundation, Inc.
4 * All rights reserved.
5 *
6 * This code is derived from software contributed to The NetBSD Foundation
7 * by Matt Thomas <matt@3am-software.com>
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 *
18 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
19 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
22 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#include "atomic_op_asm.h"
32
33#if defined(_ARM_ARCH_6)
34/*
35 * ARMv6 has load-exclusive/store-exclusive which works for both user
36 * and kernel.
37 */
38ENTRY_NP(__sync_bool_compare_and_swap_8)
39	push	{r4-r7}			/* save temporaries */
40	mov	ip, r0			/* we need r0 for return value */
41	movs	r0, #0			/* assume failure */
42#ifdef __ARM_EABI__
43	ldrd	r4, r5, [sp]		/* fetch new value from stack */
44#else
45	ldr	r4, [sp, #0]		/* fetch new value from stack */
46	ldr	r5, [sp, #4]		/* fetch new value from stack */
47	mov	r3, r2			/* r2 will be overwritten by r1 which ... */
48	mov	r2, r1			/* r1 will be overwritten by ldrexd */
49#endif
501:
51	ldrexd	r6, r7, [ip]		/* load current value */
52	cmp	r6, r2			/*   compare to old? 1st half */
53#ifdef __thumb__
54	bne	2f			/*     jump to return if different */
55	cmp	r7, r3			/*   compare to old? 2nd half */
56#else
57	cmpeq	r7, r3			/*   compare to old? 2nd half */
58#endif
59	bne	2f			/*     jump to return if different */
60	strexd	r0, r4, r5, [ip]	/* store new value */
61	cmp	r0, #0			/*   succeed? */
62	bne	1b			/*     nope, try again. */
63	movs	r0, #1			/* indicate success */
64#ifdef _ARM_ARCH_7
65	dsb
66#else
67	mcr	p15, 0, ip, c7, c10, 4	/* data synchronization barrier */
68#endif
692:	pop	{r4-r7}			/* restore temporaries */
70	RET				/* return. */
71END(__sync_bool_compare_and_swap_8)
72
73#endif /* _ARM_ARCH_6 */
74