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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package org.openjdk.bench.java.lang.invoke;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;

import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;

/**
 * A benchmark testing lazy static var handle vs regular static var handle,
 * to ensure the lazy static var handle doesn't have too much post-initialization
 * invocation penalties.
 */
@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@State(Scope.Thread)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(3)
public class VarHandleLazyStaticInvocation {

    static final VarHandle initialized;
    static final VarHandle lazy;
    static long longField;

    static {
        try {
            lazy = MethodHandles.lookup().findStaticVarHandle(Data.class, "longField", long.class);
            initialized = MethodHandles.lookup().findStaticVarHandle(VarHandleLazyStaticInvocation.class, "longField", long.class);
        } catch (ReflectiveOperationException e) {
            throw new RuntimeException(e);
        }
    }


    static class Data {
        static long longField;
    }

    @Benchmark
    public long lazyInvocation() {
        lazy.set((long) ThreadLocalRandom.current().nextLong());
        return (long) lazy.get();
    }

    @Benchmark
    public long initializedInvocation() {
        initialized.set((long) ThreadLocalRandom.current().nextLong());
        return (long) initialized.get();
    }
}
