104 lines
4.0 KiB
C++
104 lines
4.0 KiB
C++
/*
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* Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "runtime/atomic.inline.hpp"
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/*
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* This is the default implementation of byte-sized cmpxchg. It emulates jbyte-sized cmpxchg
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* in terms of jint-sized cmpxchg. Platforms may override this by defining their own inline definition
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* as well as defining VM_HAS_SPECIALIZED_CMPXCHG_BYTE. This will cause the platform specific
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* implementation to be used instead.
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*/
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jbyte Atomic::cmpxchg_general(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value) {
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assert(sizeof(jbyte) == 1, "assumption.");
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uintptr_t dest_addr = (uintptr_t)dest;
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uintptr_t offset = dest_addr % sizeof(jint);
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volatile jint* dest_int = (volatile jint*)(dest_addr - offset);
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jint cur = *dest_int;
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jbyte* cur_as_bytes = (jbyte*)(&cur);
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jint new_val = cur;
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jbyte* new_val_as_bytes = (jbyte*)(&new_val);
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new_val_as_bytes[offset] = exchange_value;
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while (cur_as_bytes[offset] == compare_value) {
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jint res = cmpxchg(new_val, dest_int, cur);
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if (res == cur) break;
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cur = res;
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new_val = cur;
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new_val_as_bytes[offset] = exchange_value;
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}
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return cur_as_bytes[offset];
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}
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unsigned Atomic::xchg(unsigned int exchange_value, volatile unsigned int* dest) {
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assert(sizeof(unsigned int) == sizeof(jint), "more work to do");
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return (unsigned int)Atomic::xchg((jint)exchange_value, (volatile jint*)dest);
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}
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unsigned Atomic::cmpxchg(unsigned int exchange_value,
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volatile unsigned int* dest, unsigned int compare_value) {
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assert(sizeof(unsigned int) == sizeof(jint), "more work to do");
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return (unsigned int)Atomic::cmpxchg((jint)exchange_value, (volatile jint*)dest,
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(jint)compare_value);
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}
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jlong Atomic::add(jlong add_value, volatile jlong* dest) {
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jlong old = load(dest);
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jlong new_value = old + add_value;
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while (old != cmpxchg(new_value, dest, old)) {
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old = load(dest);
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new_value = old + add_value;
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}
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return old;
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}
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void Atomic::inc(volatile short* dest) {
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// Most platforms do not support atomic increment on a 2-byte value. However,
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// if the value occupies the most significant 16 bits of an aligned 32-bit
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// word, then we can do this with an atomic add of 0x10000 to the 32-bit word.
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//
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// The least significant parts of this 32-bit word will never be affected, even
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// in case of overflow/underflow.
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//
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// Use the ATOMIC_SHORT_PAIR macro to get the desired alignment.
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#ifdef VM_LITTLE_ENDIAN
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assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
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(void)Atomic::add(0x10000, (volatile int*)(dest-1));
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#else
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assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
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(void)Atomic::add(0x10000, (volatile int*)(dest));
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#endif
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}
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void Atomic::dec(volatile short* dest) {
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#ifdef VM_LITTLE_ENDIAN
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assert((intx(dest) & 0x03) == 0x02, "wrong alignment");
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(void)Atomic::add(-0x10000, (volatile int*)(dest-1));
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#else
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assert((intx(dest) & 0x03) == 0x00, "wrong alignment");
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(void)Atomic::add(-0x10000, (volatile int*)(dest));
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#endif
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}
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