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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package org.graalvm.compiler.hotspot.nodes;

import static org.graalvm.compiler.nodeinfo.InputType.Association;
import static org.graalvm.compiler.nodeinfo.InputType.Memory;
import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_30;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_8;

import org.graalvm.compiler.core.common.LocationIdentity;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.hotspot.HotSpotNodeLIRBuilder;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.FixedWithNextNode;
import org.graalvm.compiler.nodes.StateSplit;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.java.CompareAndSwapNode;
import org.graalvm.compiler.nodes.memory.MemoryCheckpoint;
import org.graalvm.compiler.nodes.memory.address.AddressNode;
import org.graalvm.compiler.nodes.memory.address.AddressNode.Address;
import org.graalvm.compiler.nodes.spi.LIRLowerable;
import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
import org.graalvm.compiler.word.Word;

A special purpose store node that differs from CompareAndSwapNode in that it is not a StateSplit and it compareAndSwap(Address, Word, Word, LocationIdentity) returns either the expected value or the compared against value instead of a boolean. /**
 * A special purpose store node that differs from {@link CompareAndSwapNode} in that it is not a
 * {@link StateSplit} and it {@linkplain #compareAndSwap(Address, Word, Word, LocationIdentity)}
 * returns either the expected value or the compared against value instead of a boolean.
 */
@NodeInfo(allowedUsageTypes = Memory, cycles = CYCLES_30, size = SIZE_8)
public final class DirectCompareAndSwapNode extends FixedWithNextNode implements LIRLowerable, MemoryCheckpoint.Single {

    public static final NodeClass<DirectCompareAndSwapNode> TYPE = NodeClass.create(DirectCompareAndSwapNode.class);
    @Input(Association) AddressNode address;
    @Input ValueNode expectedValue;
    @Input ValueNode newValue;

    protected final LocationIdentity locationIdentity;

    public DirectCompareAndSwapNode(ValueNode address, ValueNode expected, ValueNode newValue, LocationIdentity locationIdentity) {
        super(TYPE, expected.stamp());
        this.address = (AddressNode) address;
        this.expectedValue = expected;
        this.newValue = newValue;
        this.locationIdentity = locationIdentity;
    }

    public AddressNode getAddress() {
        return address;
    }

    public ValueNode expectedValue() {
        return expectedValue;
    }

    public ValueNode newValue() {
        return newValue;
    }

    @Override
    public LocationIdentity getLocationIdentity() {
        return locationIdentity;
    }

    @Override
    public void generate(NodeLIRBuilderTool gen) {
        ((HotSpotNodeLIRBuilder) gen).visitDirectCompareAndSwap(this);
    }

    
Compares an expected value with the actual value in a location denoted by an address. Iff they are same, newValue is placed into the location and the expectedValue is returned. Otherwise, the actual value is returned. All of the above is performed in one atomic hardware transaction. 
Params:
address – the address to be atomically tested and updated
expectedValue – if this value is currently in the field, perform the swap
newValue – the new value to put into the field
Returns:
either expectedValue or the actual value/**
     * Compares an expected value with the actual value in a location denoted by an address. Iff
     * they are same, {@code newValue} is placed into the location and the {@code expectedValue} is
     * returned. Otherwise, the actual value is returned. All of the above is performed in one
     * atomic hardware transaction.
     *
     * @param address the address to be atomically tested and updated
     * @param expectedValue if this value is currently in the field, perform the swap
     * @param newValue the new value to put into the field
     * @return either {@code expectedValue} or the actual value
     */
    @NodeIntrinsic
    public static native Word compareAndSwap(Address address, Word expectedValue, Word newValue, @ConstantNodeParameter LocationIdentity locationIdentity);
}