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The GraalVM compiler and the Graal-truffle optimizer.
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/*
 * Copyright (c) 2009, 2021, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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 jdk.graal.compiler.nodes;

import jdk.graal.compiler.core.common.type.Stamp;
import jdk.graal.compiler.debug.Assertions;
import jdk.graal.compiler.graph.Node;
import jdk.graal.compiler.graph.NodeClass;
import jdk.graal.compiler.nodeinfo.NodeInfo;

/**
 * The {@code ControlSplitNode} is a base class for all instructions that split the control flow
 * (i.e., have more than one successor).
 */
@NodeInfo
public abstract class ControlSplitNode extends FixedNode {
    public static final NodeClass TYPE = NodeClass.create(ControlSplitNode.class);

    protected ControlSplitNode(NodeClass c, Stamp stamp) {
        super(c, stamp);
    }

    public abstract double probability(AbstractBeginNode successor);

    /**
     * Attempts to set the probability for the given successor to the passed value (which has to be
     * in the range of 0.0 and 1.0). Returns whether setting the probability was successful. When
     * successful, sets the source of the knowledge about probabilities according to the
     * {@code profileData}'s profile source.
     */
    public abstract boolean setProbability(AbstractBeginNode successor, ProfileData.BranchProbabilityData profileData);

    /**
     * Returns an array containing the successors' probabilities. The positions in the array
     * correspond to the order of iteration over the successors.
     *
     * @return the array of successor probabilities
     */
    public double[] successorProbabilities() {
        double[] probabilities = new double[getSuccessorCount()];
        int index = 0;
        for (Node succ : successors()) {
            probabilities[index++] = probability((AbstractBeginNode) succ);
        }
        assert index == getSuccessorCount() : Assertions.errorMessage(index, getSuccessorCount());
        return probabilities;
    }

    /**
     * Primary successor of the control split. Data dependencies on the node have to be scheduled in
     * the primary successor. Returns null if data dependencies are not expected.
     *
     * @return the primary successor
     */
    public abstract AbstractBeginNode getPrimarySuccessor();

    /**
     * Returns the number of successors.
     */
    public abstract int getSuccessorCount();

    /**
     * Returns the source of this node's knowledge about its successor probabilities.
     */
    public abstract ProfileData getProfileData();
}