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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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
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 *
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package org.openjdk.bench.vm.compiler;

import org.openjdk.jmh.annotations.*;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.ThreadLocalRandom;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(value = 3)
@Warmup(iterations = 10, time = 1)
@Measurement(iterations = 5, time = 1)
@State(Scope.Thread)
public class CountLeadingZeros {
    private long[] longArray = new long[1000];

    @Setup
    public void setup() {
        for (int i = 0; i < longArray.length; i++) {
            longArray[i] = ThreadLocalRandom.current().nextLong();
        }
    }

    @Benchmark
    public int benchNumberOfNibbles() {
        int sum = 0;
        for (long l : longArray) {
            sum += numberOfNibbles((int) l);
        }
        return sum;
    }

    public static int numberOfNibbles(int i) {
        int mag = Integer.SIZE - Integer.numberOfLeadingZeros(i);
        return Math.max((mag + 3) / 4, 1);
    }

    @Benchmark
    public int benchClzLongConstrained() {
        int sum = 0;
        for (long l : longArray) {
            sum += clzLongConstrained(l);
        }
        return sum;
    }

    public static int clzLongConstrained(long param) {
        long constrainedParam = Math.min(175, Math.max(param, 160));
        return Long.numberOfLeadingZeros(constrainedParam);
    }
}