A JMH microbenchmark to determine if a JVM is optimizing divisions by two.

ArithmeticBenchmark.java

package benchmark;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;

@State(Scope.Thread)
public class ArithmeticBenchmark {

    @Benchmark
    public long testDivide() {
    	long value = Long.MAX_VALUE;
    	while (value > 0) {
    		value /= 2;
    	}
    	return value;
    }

    @Benchmark
    public long testShift() {
    	long value = Long.MAX_VALUE;
    	while (value > 0) {
    		value = value >>> 1;
    	}
    	return value;
    }

    public static void main(String... args) throws Exception {
		Options opts = new OptionsBuilder()
			.include(ArithmeticBenchmark.class.getSimpleName())
			.mode(Mode.Throughput)
			.warmupIterations(10)
			.measurementIterations(10)
			.jvmArgs("-server")
			.forks(1)
			.build();
		new Runner(opts).run();
	}
}

results.txt

Benchmark                        Mode  Samples        Score        Error  Units
b.ArithmeticBenchmark.testDivide    thrpt       10  3695399.946 ±  87327.372  ops/s
b.ArithmeticBenchmark.testShift     thrpt       10  8091063.504 ± 114824.341  ops/s