/*

 * Copyright (c) 2013, 2013, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package org.graalvm.compiler.phases.common;

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.graph.Graph;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.AbstractMergeNode;

import org.graalvm.compiler.nodes.BeginNode;

import org.graalvm.compiler.nodes.EndNode;

import org.graalvm.compiler.nodes.IfNode;

import org.graalvm.compiler.nodes.LogicNode;

import org.graalvm.compiler.nodes.MergeNode;

import org.graalvm.compiler.nodes.ShortCircuitOrNode;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.calc.ConditionalNode;

import org.graalvm.compiler.phases.Phase;

public class ExpandLogicPhase extends Phase {

    @Override

    protected void run(StructuredGraph graph) {

        for (ShortCircuitOrNode logic : graph.getNodes(ShortCircuitOrNode.TYPE)) {

            processBinary(logic);

        }

        assert graph.getNodes(ShortCircuitOrNode.TYPE).isEmpty();

    }

    private static void processBinary(ShortCircuitOrNode binary) {

        while (binary.usages().isNotEmpty()) {

            Node usage = binary.usages().first();

            if (usage instanceof ShortCircuitOrNode) {

                processBinary((ShortCircuitOrNode) usage);

            } else if (usage instanceof IfNode) {

                processIf(binary.getX(), binary.isXNegated(), binary.getY(), binary.isYNegated(), (IfNode) usage, binary.getShortCircuitProbability());

            } else if (usage instanceof ConditionalNode) {

                processConditional(binary.getX(), binary.isXNegated(), binary.getY(), binary.isYNegated(), (ConditionalNode) usage);

            } else {

                throw GraalError.shouldNotReachHere();

            }

        }

        binary.safeDelete();

    }

    private static void processIf(LogicNode x, boolean xNegated, LogicNode y, boolean yNegated, IfNode ifNode, double shortCircuitProbability) {

        AbstractBeginNode trueTarget = ifNode.trueSuccessor();

        AbstractBeginNode falseTarget = ifNode.falseSuccessor();

        double firstIfProbability = shortCircuitProbability;

        /*

         * P(Y | not(X)) = P(Y inter not(X)) / P(not(X)) = (P(X union Y) - P(X)) / (1 - P(X))

         *

         * P(X) = shortCircuitProbability

         *

         * P(X union Y) = ifNode.probability(trueTarget)

         */

        double secondIfProbability = (ifNode.probability(trueTarget) - shortCircuitProbability) / (1 - shortCircuitProbability);

        secondIfProbability = Math.min(1.0, Math.max(0.0, secondIfProbability));

        if (Double.isNaN(secondIfProbability)) {

            secondIfProbability = 0.5;

        }

        ifNode.clearSuccessors();

        Graph graph = ifNode.graph();

        AbstractMergeNode trueTargetMerge = graph.add(new MergeNode());

        trueTargetMerge.setNext(trueTarget);

        EndNode firstTrueEnd = graph.add(new EndNode());

        EndNode secondTrueEnd = graph.add(new EndNode());

        trueTargetMerge.addForwardEnd(firstTrueEnd);

        trueTargetMerge.addForwardEnd(secondTrueEnd);

        AbstractBeginNode firstTrueTarget = BeginNode.begin(firstTrueEnd);

        AbstractBeginNode secondTrueTarget = BeginNode.begin(secondTrueEnd);

        AbstractBeginNode secondIf = BeginNode.begin(graph.add(new IfNode(y, yNegated ? falseTarget : secondTrueTarget, yNegated ? secondTrueTarget : falseTarget, secondIfProbability)));

        IfNode firstIf = graph.add(new IfNode(x, xNegated ? secondIf : firstTrueTarget, xNegated ? firstTrueTarget : secondIf, firstIfProbability));

        ifNode.replaceAtPredecessor(firstIf);

        ifNode.safeDelete();

    }

    private static void processConditional(LogicNode x, boolean xNegated, LogicNode y, boolean yNegated, ConditionalNode conditional) {

        ValueNode trueTarget = conditional.trueValue();

        ValueNode falseTarget = conditional.falseValue();

        Graph graph = conditional.graph();

        ConditionalNode secondConditional = graph.unique(new ConditionalNode(y, yNegated ? falseTarget : trueTarget, yNegated ? trueTarget : falseTarget));

        ConditionalNode firstConditional = graph.unique(new ConditionalNode(x, xNegated ? secondConditional : trueTarget, xNegated ? trueTarget : secondConditional));

        conditional.replaceAndDelete(firstConditional);

    }

    @Override

    public boolean checkContract() {

        return false;

    }

}