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 * Copyright (c) 2011, 2018, 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;

import org.graalvm.compiler.core.common.type.Stamp;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.spi.Canonicalizable;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.spi.LIRLowerable;
import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
import org.graalvm.compiler.nodes.spi.ValueProxy;

import jdk.vm.ci.meta.TriState;

@NodeInfo
public abstract class UnaryOpLogicNode extends LogicNode implements LIRLowerable, Canonicalizable.Unary<ValueNode> {

    public static final NodeClass<UnaryOpLogicNode> TYPE = NodeClass.create(UnaryOpLogicNode.class);
    @Input protected ValueNode value;

    @Override
    public ValueNode getValue() {
        return value;
    }

    public UnaryOpLogicNode(NodeClass<? extends UnaryOpLogicNode> c, ValueNode value) {
        super(c);
        assert value != null;
        this.value = value;
    }

    @Override
    public void generate(NodeLIRBuilderTool gen) {
    }

    
In general the input stamp cannot be trusted, this method is reserved for the cases when it's "safe" to use the input stamp. To ensure safety use getSucceedingStampForValue(boolean) instead. /**
     * In general the input stamp cannot be trusted, this method is reserved for the cases when it's
     * "safe" to use the input stamp. To ensure safety use
     * {@link #getSucceedingStampForValue(boolean)} instead.
     */
    public Stamp getSucceedingStampForValue(boolean negated, Stamp valueStamp) {
        Stamp succStamp = getSucceedingStampForValue(negated);
        if (succStamp != null) {
            succStamp = succStamp.join(valueStamp);
        }
        return succStamp;
    }

    
The input stamp cannot be trusted, the returned stamp cannot use the input stamp to narrow itself or derive any assumptions. This method does not use the input stamp and is considered safe. It's responsibility of the caller to determine when it's "safe" to "trust" the input stamp and use getSucceedingStampForValue(boolean, Stamp) instead. /**
     * The input stamp cannot be trusted, the returned stamp cannot use the input stamp to narrow
     * itself or derive any assumptions. This method does not use the input stamp and is considered
     * safe.
     *
     * It's responsibility of the caller to determine when it's "safe" to "trust" the input stamp
     * and use {@link #getSucceedingStampForValue(boolean, Stamp)} instead.
     */
    public abstract Stamp getSucceedingStampForValue(boolean negated);

    public abstract TriState tryFold(Stamp valueStamp);

    @Override
    public TriState implies(boolean thisNegated, LogicNode other) {
        if (other instanceof UnaryOpLogicNode) {
            UnaryOpLogicNode unaryY = (UnaryOpLogicNode) other;
            if (this.getValue() == unaryY.getValue() || // fast path
                            skipThroughPisAndProxies(this.getValue()) == skipThroughPisAndProxies(unaryY.getValue())) {
                Stamp succStamp = this.getSucceedingStampForValue(thisNegated);
                TriState fold = unaryY.tryFold(succStamp);
                if (fold.isKnown()) {
                    return fold;
                }
            }
        }
        return super.implies(thisNegated, other);
    }

    private static ValueNode skipThroughPisAndProxies(ValueNode node) {
        ValueNode n = node;
        while (n != null) {
            if (n instanceof PiNode) {
                n = ((PiNode) n).getOriginalNode();
            } else if (n instanceof ValueProxy) {
                n = ((ValueProxy) n).getOriginalNode();
            } else {
                break;
            }
        }
        return n;
    }
}