/*
 * Copyright (c) 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.  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 com.oracle.truffle.api.utilities;

import com.oracle.truffle.api.nodes.NodeCloneable;

/**
 * Utility class to speculate on certain properties of values.
 *
 * Example usage:
 *
 * <pre>
 * private final ValueProfile classProfile = ValueProfile.createClassProfile();
 *
 * return classProfile.profile(value);
 * </pre>
 *
 * All instances of {@code ValueProfile} (and subclasses) must be held in {@code final} fields for
 * compiler optimizations to take effect.
 *
 * @see #createPrimitiveProfile()
 * @see #createIdentityProfile()
 * @see #createClassProfile()
 */
public abstract class ValueProfile extends NodeCloneable {

    public abstract <T> T profile(T value);

    /**
     * Returns a {@link PrimitiveValueProfile} that speculates on the primitive equality or object
     * identity of a value.
     */
    public static PrimitiveValueProfile createPrimitiveProfile() {
        return new PrimitiveValueProfile();
    }

    /**
     * Returns a {@link ValueProfile} that speculates on the exact class of a value. It will check
     * the class of the profiled value and provide additional information to the compiler if only
     * non-null values of exactly one concrete Java class are passed as a parameter to the
     * {@link ValueProfile#profile} method. This can be beneficial if subsequent code can take
     * advantage of knowing the concrete class of the value. The profile will degrade to the generic
     * case if a null value or if at least two instances of two different Java classes are
     * registered.
     */
    public static ValueProfile createClassProfile() {
        return new ExactClassValueProfile();
    }

    /**
     * Returns a {@link ValueProfile} that speculates on the object identity of a value.
     */
    public static ValueProfile createIdentityProfile() {
        return new IdentityValueProfile();
    }

}