64 lines
2.6 KiB
ArmAsm
64 lines
2.6 KiB
ArmAsm
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/* $NetBSD: atomic_cas_8.S,v 1.1 2008/11/18 15:22:56 matt Exp $ */
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/*-
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* Copyright (c) 2008 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Matt Thomas <matt@3am-software.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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RCSID("$NetBSD: atomic_cas_8.S,v 1.1 2008/11/18 15:22:56 matt Exp $")
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ENTRY(atomic_cas_8)
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XPUSH {r4,r5} /* we need some more registers */
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and r3, r0, #3 /* which byte do we replace? */
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#if __ARMEB__
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eor r3, r3, #3 /* bytes are reversed on BE */
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#endif
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mov r3, r3, lsl #3 /* multiply by 8 */
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mov r1, r1, lsl r3 /* mov old value to correct byte */
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eor r2, r1, r2, lsl r3 /* move new value to correct byte */
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/* eor r2, r2, r1 */ /* new value is now (old ^ new) */
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mov r5, #0xff /* load mask */
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mov r5, r5, lsl r3 /* and move to correct byte */
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mov r3, r0 /* move pointer */
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1: ldrex r4, [r3] /* load 32bit value */
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and r0, r4, r5 /* clear other bytes */
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teq r0, r1 /* equal old value? */
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bne 2f /* nope, bail. */
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eor r4, r4, r2 /* new == old ^ (old ^ new) */
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strex ip, r4, [r3] /* attempt to store it */
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cmp ip, #0 /* succeed? */
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bne 1b /* nope, try again. */
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2: XPOP {r4,r5} /* don't need these anymore */
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and r1, r3, #3
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#if __ARMEB__
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eor r1, r1, #3
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#endif
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mov r0, r0, lsr r1 /* shift it back to lsb byte */
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RET
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