1/* $NetBSD: atomic_cas_8.S,v 1.1 2008/11/18 15:22:56 matt Exp $ */ 2/*- 3 * Copyright (c) 2008 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#include <machine/asm.h> 31 32RCSID("$NetBSD: atomic_cas_8.S,v 1.1 2008/11/18 15:22:56 matt Exp $") 33 34ENTRY(atomic_cas_8) 35 XPUSH {r4,r5} /* we need some more registers */ 36 and r3, r0, #3 /* which byte do we replace? */ 37#if __ARMEB__ 38 eor r3, r3, #3 /* bytes are reversed on BE */ 39#endif 40 mov r3, r3, lsl #3 /* multiply by 8 */ 41 mov r1, r1, lsl r3 /* mov old value to correct byte */ 42 eor r2, r1, r2, lsl r3 /* move new value to correct byte */ 43/* eor r2, r2, r1 */ /* new value is now (old ^ new) */ 44 mov r5, #0xff /* load mask */ 45 mov r5, r5, lsl r3 /* and move to correct byte */ 46 mov r3, r0 /* move pointer */ 47 481: ldrex r4, [r3] /* load 32bit value */ 49 and r0, r4, r5 /* clear other bytes */ 50 teq r0, r1 /* equal old value? */ 51 bne 2f /* nope, bail. */ 52 eor r4, r4, r2 /* new == old ^ (old ^ new) */ 53 strex ip, r4, [r3] /* attempt to store it */ 54 cmp ip, #0 /* succeed? */ 55 bne 1b /* nope, try again. */ 56 572: XPOP {r4,r5} /* don't need these anymore */ 58 and r1, r3, #3 59#if __ARMEB__ 60 eor r1, r1, #3 61#endif 62 mov r0, r0, lsr r1 /* shift it back to lsb byte */ 63 RET 64