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package org.openjdk.bench.vm.compiler;

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

import java.util.concurrent.TimeUnit;

/**
 * Tests transformation from "(x + x) << c" to "x << (c + 1)".
 * <p>
 * This benchmark needs to be run with {@code
 * JAVA_OPTIONS=-Djmh.blackhole.mode=COMPILER} to force using compiler
 * mode blackhole, which is enabled by default and thus not necessary
 * since JMH 1.34.
 */
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@State(Scope.Thread)
@Warmup(iterations = 20, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 20, time = 1, timeUnit = TimeUnit.SECONDS)
@Fork(value = 3)
public class LShiftIdeal_XPlusX_LShiftC {

    private int iFld = 4711;

    private long lFld = 4711 * 4711 * 4711;

    private final int SIZE = 10;

    @Benchmark
    public void baselineInt(Blackhole bh) {
        for (int i = 0; i < SIZE; i++) {
            bh.consume(iFld);
        }
    }

    @Benchmark
    public void baselineLong(Blackhole bh) {
        for (int i = 0; i < SIZE; i++) {
            bh.consume(lFld);
        }
    }

    // Convert "(x + x) << 10" into "x << 11" for int.
    // (x << 11) >>> 11 is then further converted into zero-extends.
    @Benchmark
    public void testInt(Blackhole bh) {
        for (int i = 0; i < SIZE; i++) {
            bh.consume(((iFld + iFld) << 10) >>> 11);
        }
    }

    // Convert "(x + x) << 40" into "x << 41" for long.
    // (x << 41) >>> 41 is then further converted into zero-extends.
    @Benchmark
    public void testLong(Blackhole bh) {
        for (int i = 0; i < SIZE; i++) {
            bh.consume(((lFld + lFld) << 40) >>> 41);
        }
    }
}