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1 /*
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2 * Copyright 2001-2003 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_atomic.cpp.incl"
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27
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28 jbyte Atomic::cmpxchg(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value) {
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29 assert(sizeof(jbyte) == 1, "assumption.");
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30 uintptr_t dest_addr = (uintptr_t)dest;
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31 uintptr_t offset = dest_addr % sizeof(jint);
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32 volatile jint* dest_int = (volatile jint*)(dest_addr - offset);
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33 jint cur = *dest_int;
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34 jbyte* cur_as_bytes = (jbyte*)(&cur);
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35 jint new_val = cur;
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36 jbyte* new_val_as_bytes = (jbyte*)(&new_val);
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37 new_val_as_bytes[offset] = exchange_value;
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38 while (cur_as_bytes[offset] == compare_value) {
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39 jint res = cmpxchg(new_val, dest_int, cur);
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40 if (res == cur) break;
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41 cur = res;
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42 new_val = cur;
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43 new_val_as_bytes[offset] = exchange_value;
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44 }
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45 return cur_as_bytes[offset];
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46 }
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