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 * Copyright (c) 2011, 2020, Oracle and/or its affiliates. All rights reserved.
 * 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.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package org.graalvm.compiler.nodes.extended;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_0;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_0;

import org.graalvm.compiler.graph.Node;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.spi.Canonicalizable;
import org.graalvm.compiler.graph.spi.CanonicalizerTool;
import org.graalvm.compiler.nodeinfo.InputType;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.FrameState;
import org.graalvm.compiler.nodes.StateSplit;
import org.graalvm.compiler.nodes.ValueNode;

This node provides a state split along with the functionality of FixedValueAnchorNode. This is used to capture a state for deoptimization when a node has side effects which aren't easily represented. The anchored value is usually part of the FrameState since this forces uses of the value below this node so they will consume this frame state instead of an earlier one. /**
 * This node provides a state split along with the functionality of {@link FixedValueAnchorNode}.
 * This is used to capture a state for deoptimization when a node has side effects which aren't
 * easily represented. The anchored value is usually part of the FrameState since this forces uses
 * of the value below this node so they will consume this frame state instead of an earlier one.
 */
@NodeInfo(cycles = CYCLES_0, size = SIZE_0)
public final class StateSplitProxyNode extends FixedValueAnchorNode implements Canonicalizable, StateSplit {

    public static final NodeClass<StateSplitProxyNode> TYPE = NodeClass.create(StateSplitProxyNode.class);

    @OptionalInput(InputType.State) FrameState stateAfter;
    
Disallows elimination of this node until after the FrameState has been consumed.
/**
     * Disallows elimination of this node until after the FrameState has been consumed.
     */
    private final boolean delayElimination;

    public StateSplitProxyNode(ValueNode object) {
        this(object, false);
    }

    public StateSplitProxyNode(ValueNode object, boolean delayElimination) {
        super(TYPE, object);
        this.delayElimination = delayElimination;
    }

    @Override
    public FrameState stateAfter() {
        return stateAfter;
    }

    @Override
    public void setStateAfter(FrameState x) {
        assert x == null || x.isAlive() : "frame state must be in a graph";
        updateUsages(stateAfter, x);
        stateAfter = x;
    }

    @Override
    public boolean hasSideEffect() {
        return true;
    }

    @Override
    public Node canonical(CanonicalizerTool tool) {
        if (!delayElimination && (object != null && object.isConstant()) || stateAfter == null) {
            return object;
        }
        return this;
    }

}