/*
 * Copyright (c) 2012, 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 com.oracle.graal.snippets.nodes;

import com.oracle.graal.nodes.*;
import com.oracle.graal.nodes.spi.*;
import com.oracle.graal.nodes.type.*;
import com.oracle.graal.nodes.util.*;

/**
 * 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.
 */
public class BranchProbabilityNode extends FixedWithNextNode implements Simplifiable {

    private final double probability;

    public BranchProbabilityNode(double probability) {
        super(StampFactory.forVoid());
        assert probability >= 0 && probability <= 1;
        this.probability = probability;
    }

    @Override
    public void simplify(SimplifierTool tool) {
        FixedNode current = this;
        while (!(current instanceof BeginNode)) {
            current = (FixedNode) current.predecessor();
        }
        BeginNode begin = (BeginNode) current;
        assert begin.predecessor() instanceof IfNode : "explicit branch probability cannot follow a merge, only if nodes";
        IfNode ifNode = (IfNode) begin.predecessor();
        if (ifNode.trueSuccessor() == begin) {
            ifNode.setTakenProbability(probability);
        } else {
            ifNode.setTakenProbability(1 - probability);
        }

        FixedNode next = next();
        setNext(null);
        ((FixedWithNextNode) predecessor()).setNext(next);
        GraphUtil.killCFG(this);
    }

    @NodeIntrinsic
    public static native void probability(@ConstantNodeParameter
    double probability);

}