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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.calc;

import org.graalvm.compiler.core.common.calc.CanonicalCondition;

import org.graalvm.compiler.core.common.type.AbstractPointerStamp;

import org.graalvm.compiler.core.common.type.ObjectStamp;

import org.graalvm.compiler.core.common.type.Stamp;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.graph.spi.Canonicalizable.BinaryCommutative;

import org.graalvm.compiler.graph.spi.CanonicalizerTool;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.LogicConstantNode;

import org.graalvm.compiler.nodes.LogicNode;

import org.graalvm.compiler.nodes.NodeView;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.extended.LoadHubNode;

import org.graalvm.compiler.nodes.extended.LoadMethodNode;

import org.graalvm.compiler.nodes.type.StampTool;

import org.graalvm.compiler.nodes.util.GraphUtil;

import org.graalvm.compiler.options.OptionValues;

import jdk.vm.ci.meta.ConstantReflectionProvider;

import jdk.vm.ci.meta.MetaAccessProvider;

import jdk.vm.ci.meta.ResolvedJavaMethod;

import jdk.vm.ci.meta.ResolvedJavaType;

import jdk.vm.ci.meta.TriState;

@NodeInfo(shortName = "==")

public class PointerEqualsNode extends CompareNode implements BinaryCommutative<ValueNode> {

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

    private static final PointerEqualsOp OP = new PointerEqualsOp();

    public PointerEqualsNode(ValueNode x, ValueNode y) {

        this(TYPE, x, y);

    }

    public static LogicNode create(ValueNode x, ValueNode y, NodeView view) {

        LogicNode result = findSynonym(x, y, view);

        if (result != null) {

            return result;

        }

        return new PointerEqualsNode(x, y);

    }

    protected PointerEqualsNode(NodeClass<? extends PointerEqualsNode> c, ValueNode x, ValueNode y) {

        super(c, CanonicalCondition.EQ, false, x, y);

        assert x.stamp(NodeView.DEFAULT) instanceof AbstractPointerStamp;

        assert y.stamp(NodeView.DEFAULT) instanceof AbstractPointerStamp;

    }

    @Override

    public Node canonical(CanonicalizerTool tool, ValueNode forX, ValueNode forY) {

        NodeView view = NodeView.from(tool);

        ValueNode value = OP.canonical(tool.getConstantReflection(), tool.getMetaAccess(), tool.getOptions(), tool.smallestCompareWidth(), CanonicalCondition.EQ, false, forX, forY, view);

        if (value != null) {

            return value;

        }

        return this;

    }

    public static class PointerEqualsOp extends CompareOp {

        /**

         * Determines if this is a comparison used to determine whether dispatching on a receiver

         * could select a certain method and if so, returns {@code true} if the answer is guaranteed

         * to be false. Otherwise, returns {@code false}.

         */

        private static boolean isAlwaysFailingVirtualDispatchTest(CanonicalCondition condition, ValueNode forX, ValueNode forY) {

            if (forY.isConstant()) {

                if (forX instanceof LoadMethodNode && condition == CanonicalCondition.EQ) {

                    LoadMethodNode lm = ((LoadMethodNode) forX);

                    if (lm.getMethod().getEncoding().equals(forY.asConstant())) {

                        if (lm.getHub() instanceof LoadHubNode) {

                            ValueNode object = ((LoadHubNode) lm.getHub()).getValue();

                            ResolvedJavaType type = StampTool.typeOrNull(object);

                            ResolvedJavaType declaringClass = lm.getMethod().getDeclaringClass();

                            if (type != null && !type.equals(declaringClass) && declaringClass.isAssignableFrom(type)) {

                                ResolvedJavaMethod override = type.resolveMethod(lm.getMethod(), lm.getCallerType());

                                if (override != null && !override.equals(lm.getMethod())) {

                                    assert declaringClass.isAssignableFrom(override.getDeclaringClass());

                                    return true;

                                }

                            }

                        }

                    }

                }

            }

            return false;

        }

        @Override

        public LogicNode canonical(ConstantReflectionProvider constantReflection, MetaAccessProvider metaAccess, OptionValues options, Integer smallestCompareWidth, CanonicalCondition condition,

                        boolean unorderedIsTrue, ValueNode forX, ValueNode forY, NodeView view) {

            LogicNode result = findSynonym(forX, forY, view);

            if (result != null) {

                return result;

            }

            if (isAlwaysFailingVirtualDispatchTest(condition, forX, forY)) {

                return LogicConstantNode.contradiction();

            }

            return super.canonical(constantReflection, metaAccess, options, smallestCompareWidth, condition, unorderedIsTrue, forX, forY, view);

        }

        @Override

        protected CompareNode duplicateModified(ValueNode newX, ValueNode newY, boolean unorderedIsTrue, NodeView view) {

            return new PointerEqualsNode(newX, newY);

        }

    }

    public static LogicNode findSynonym(ValueNode forX, ValueNode forY, NodeView view) {

        if (GraphUtil.unproxify(forX) == GraphUtil.unproxify(forY)) {

            return LogicConstantNode.tautology();

        } else if (forX.stamp(view).alwaysDistinct(forY.stamp(view))) {

            return LogicConstantNode.contradiction();

        } else if (((AbstractPointerStamp) forX.stamp(view)).alwaysNull()) {

        } else if (((AbstractPointerStamp) forY.stamp(view)).alwaysNull()) {

        } else {

            return null;

        }

    }

    @Override

    public Stamp getSucceedingStampForX(boolean negated, Stamp xStamp, Stamp yStamp) {

        if (!negated) {

            Stamp newStamp = xStamp.join(yStamp);

            if (!newStamp.equals(xStamp)) {

                return newStamp;

            }

        }

        return null;

    }

    @Override

    public Stamp getSucceedingStampForY(boolean negated, Stamp xStamp, Stamp yStamp) {

        if (!negated) {

            Stamp newStamp = yStamp.join(xStamp);

            if (!newStamp.equals(yStamp)) {

                return newStamp;

            }

        }

        return null;

    }

    @Override

    public TriState tryFold(Stamp xStampGeneric, Stamp yStampGeneric) {

        if (xStampGeneric instanceof ObjectStamp && yStampGeneric instanceof ObjectStamp) {

            ObjectStamp xStamp = (ObjectStamp) xStampGeneric;

            ObjectStamp yStamp = (ObjectStamp) yStampGeneric;

            if (xStamp.alwaysDistinct(yStamp)) {

                return TriState.FALSE;

            } else if (xStamp.neverDistinct(yStamp)) {

                return TriState.TRUE;

            }

        }

        return TriState.UNKNOWN;

    }

}