/*

 * Copyright (c) 2012, 2014, 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.nodes.extended;

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

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

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.graph.iterators.NodePredicates;

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

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

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.FixedGuardNode;

import org.graalvm.compiler.nodes.IfNode;

import org.graalvm.compiler.nodes.NodeView;

import org.graalvm.compiler.nodes.ReturnNode;

import org.graalvm.compiler.nodes.ValueNode;

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

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

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

import org.graalvm.compiler.nodes.spi.Lowerable;

import org.graalvm.compiler.nodes.spi.LoweringTool;

/**

 * Instances of this node class will look for a preceding if node and put the given probability into

 * the if node's taken probability. Then the branch probability node will be removed. This node is

 * intended primarily for snippets, so that they can define their fast and slow paths.

 */

@NodeInfo(cycles = CYCLES_0, cyclesRationale = "Artificial Node", size = SIZE_0)

public final class BranchProbabilityNode extends FloatingNode implements Simplifiable, Lowerable {

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

    public static final double LIKELY_PROBABILITY = 0.6;

    public static final double NOT_LIKELY_PROBABILITY = 1 - LIKELY_PROBABILITY;

    public static final double FREQUENT_PROBABILITY = 0.9;

    public static final double NOT_FREQUENT_PROBABILITY = 1 - FREQUENT_PROBABILITY;

    public static final double FAST_PATH_PROBABILITY = 0.99;

    public static final double SLOW_PATH_PROBABILITY = 1 - FAST_PATH_PROBABILITY;

    public static final double VERY_FAST_PATH_PROBABILITY = 0.999;

    public static final double VERY_SLOW_PATH_PROBABILITY = 1 - VERY_FAST_PATH_PROBABILITY;

    @Input ValueNode probability;

    @Input ValueNode condition;

    public BranchProbabilityNode(ValueNode probability, ValueNode condition) {

        super(TYPE, condition.stamp(NodeView.DEFAULT));

        this.probability = probability;

        this.condition = condition;

    }

    public ValueNode getProbability() {

        return probability;

    }

    public ValueNode getCondition() {

        return condition;

    }

    @Override

    public void simplify(SimplifierTool tool) {

        if (!hasUsages()) {

            return;

        }

        if (probability.isConstant()) {

            double probabilityValue = probability.asJavaConstant().asDouble();

            if (probabilityValue < 0.0) {

                throw new GraalError("A negative probability of " + probabilityValue + " is not allowed!");

            } else if (probabilityValue > 1.0) {

                throw new GraalError("A probability of more than 1.0 (" + probabilityValue + ") is not allowed!");

            } else if (Double.isNaN(probabilityValue)) {

                /*

                 * We allow NaN if the node is in unreachable code that will eventually fall away,

                 * or else an error will be thrown during lowering since we keep the node around.

                 */

                return;

            }

            boolean usageFound = false;

            for (IntegerEqualsNode node : this.usages().filter(IntegerEqualsNode.class)) {

                ValueNode other = node.getX();

                if (node.getX() == this) {

                    other = node.getY();

                }

                if (other.isConstant()) {

                    double probabilityToSet = probabilityValue;

                    if (other.asJavaConstant().asInt() == 0) {

                        probabilityToSet = 1.0 - probabilityToSet;

                    }

                    for (IfNode ifNodeUsages : node.usages().filter(IfNode.class)) {

                        usageFound = true;

                        ifNodeUsages.setTrueSuccessorProbability(probabilityToSet);

                    }

                    if (!usageFound) {

                        usageFound = node.usages().filter(NodePredicates.isA(FixedGuardNode.class).or(ConditionalNode.class)).isNotEmpty();

                    }

                }

            }

            if (usageFound) {

                ValueNode currentCondition = condition;

                replaceAndDelete(currentCondition);

                if (tool != null) {

                    tool.addToWorkList(currentCondition.usages());

                }

            } else {

                if (!isSubstitutionGraph()) {

                    throw new GraalError("Wrong usage of branch probability injection!");

                }

            }

        }

    }

    private boolean isSubstitutionGraph() {

        return hasExactlyOneUsage() && usages().first() instanceof ReturnNode;

    }

    /**

     * This intrinsic should only be used for the condition of an if statement. The parameter

     * condition should also only denote a simple condition and not a combined condition involving

     * && or || operators. It injects the probability of the condition into the if

     * statement.

     *

     * @param probability the probability that the given condition is true as a double value between

     *            0.0 and 1.0.

     * @param condition the simple condition without any && or || operators

     * @return the condition

     */

    @NodeIntrinsic

    public static native boolean probability(double probability, boolean condition);

    @Override

    public void lower(LoweringTool tool) {

        throw new GraalError("Branch probability could not be injected, because the probability value did not reduce to a constant value.");

    }

}