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      1 /* $NetBSD: sync_bool_compare_and_swap_2.S,v 1.4 2021/07/28 07:32:20 skrll Exp $ */
      2 /*-
      3  * Copyright (c) 2013 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 (at) 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 /*
     36  * ARMv6 has load-exclusive/store-exclusive which works for both user
     37  * and kernel.
     38  */
     39 ENTRY_NP(__sync_bool_compare_and_swap_2)
     40 	mov	ip, r0			/* we need r0 for return value */
     41 	movs	r0, #0			/* assume failure */
     42 1:
     43 	ldrexh	r3, [ip]		/* load old value */
     44 	cmp	r3, r1			/*   compare? */
     45 #ifdef __thumb__
     46 	bne	2f
     47 #else
     48 	RETc(ne)			/*     return if different */
     49 #endif
     50 	strexh	r0, r2, [ip]		/* store new value */
     51 	cmp	r0, #0			/*   succeed? */
     52 	bne	1b			/*     nope, try again. */
     53 	movs	r0, #1			/* indicate success */
     54 2:	RET				/* return. */
     55 END(__sync_bool_compare_and_swap_2)
     56 
     57 #endif /* _ARM_ARCH_6 */
     58