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package com.oracle.truffle.api.benchmark;

import com.oracle.truffle.api.memory.ByteArraySupport;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;

import java.util.Random;

This benchmarks compares different ways to access a sequence of integers with bounds checks. Half
of the accesses are out of bounds.
 In interpreter mode (without Truffle compilation), bytesArrayCondition and intsArrayCondition are ~1.2x faster than bytesArrayException and intsArrayException respectively. This is the reason for exposing ByteArraySupport.inBounds. /**
 * This benchmarks compares different ways to access a sequence of integers with bounds checks. Half
 * of the accesses are out of bounds.
 * <p>
 * In interpreter mode (without Truffle compilation), {@link #bytesArrayCondition} and
 * {@link #intsArrayCondition} are ~1.2x faster than {@link #bytesArrayException} and
 * {@link #intsArrayException} respectively. This is the reason for exposing
 * {@link ByteArraySupport#inBounds}.
 */
@State(Scope.Benchmark)
public class ByteArrayAccessOutOfBoundsBenchmark extends TruffleBenchmark {
    static final int N = 100000;
    final byte[] bytes = new byte[N * 4];
    final int[] ints = new int[N];
    final int[] indices = new int[N];

    @Setup(Level.Trial)
    public void setup() {
        Random r = new Random();
        r.setSeed(0);
        for (int i = 0; i < N; ++i) {
            final int value = r.nextInt();
            ByteArraySupport.bigEndian().putInt(bytes, i * 4, value);
            ints[i] = value;
        }

        for (int i = 0; i < N; ++i) {
            indices[i] = r.nextInt(N * 2);
        }
    }

    @Benchmark
    public long intsArrayException() {
        long sum = 0;
        for (int i = 0; i < N; i++) {
            try {
                sum += ints[indices[i]];
            } catch (ArrayIndexOutOfBoundsException e) {
                sum += 1;
            }
        }
        return sum;
    }

    @Benchmark
    public long intsArrayCondition() {
        long sum = 0;
        for (int i = 0; i < N; i++) {
            final int index = indices[i];
            if (Integer.compareUnsigned(index, ints.length) < 0) {
                sum += ints[index];
            } else {
                sum += 1;
            }
        }
        return sum;
    }

    @Benchmark
    public long bytesArrayException() {
        long sum = 0;
        for (int i = 0; i < N; i++) {
            try {
                sum += ByteArraySupport.bigEndian().getInt(bytes, indices[i] * 4);
            } catch (IndexOutOfBoundsException e) {
                sum += 1;
            }
        }
        return sum;
    }

    @Benchmark
    public long bytesArrayCondition() {
        long sum = 0;
        for (int i = 0; i < N; i++) {
            final int index = indices[i] * 4;
            if (ByteArraySupport.bigEndian().inBounds(bytes, index, Integer.BYTES)) {
                sum += ByteArraySupport.bigEndian().getInt(bytes, index);
            } else {
                sum += 1;
            }
        }
        return sum;
    }
}