TestUnsafeLoadControl.java

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 * 2 along with this work; if not, write to the Free Software Foundation,
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/*
 * @test
 * @bug 8077504
 * @summary Unsafe load can loose control dependency and cause crash
 * @modules java.base/jdk.internal.misc:+open
 *
 * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement
 *                   compiler.unsafe.TestUnsafeLoadControl
 */

package compiler.unsafe;

import jdk.internal.misc.Unsafe;

import java.lang.reflect.Field;

public class TestUnsafeLoadControl {

    private static final Unsafe UNSAFE;

    static {
        try {
            Field unsafeField = Unsafe.class.getDeclaredField("theUnsafe");
            unsafeField.setAccessible(true);
            UNSAFE = (Unsafe) unsafeField.get(null);
        } catch(Exception e) {
            throw new RuntimeException(e);
        }
    }

    static int val;
    static void test1(int[] a, boolean[] flags, boolean flag, long j) {
        for (int i = 0; i < 10; i++) {
            if (flags[i]) {
                if (flag) {
                    long address = (j << 2) + UNSAFE.ARRAY_INT_BASE_OFFSET;
                    int v = UNSAFE.getInt(a, address);
                    val = v;
                }
            }
        }
    }

    static int test2(int[] a, boolean[] flags, boolean flag, long j) {
        int sum = 0;
        for (int i = 0; i < 10; i++) {
            if (flags[i]) {
                if (flag) {
                    long address = (j << 2) + UNSAFE.ARRAY_INT_BASE_OFFSET;
                    int v = UNSAFE.getInt(a, address);
                    if (v == 0) {
                        sum++;
                    }
                }
            }
        }
        return sum;
    }

    static public void main(String[] args) {
        boolean[] flags = new boolean[10];
        for (int i = 0; i < flags.length; i++) {
            flags[i] = true;
        }
        int[] array = new int[10];
        for (int i = 0; i < 20000; i++) {
            test1(array, flags, true, 0);
        }
        for (int i = 0; i < flags.length; i++) {
            flags[i] = false;
        }
        test1(array, flags, true, Long.MAX_VALUE/4);

        for (int i = 0; i < flags.length; i++) {
            flags[i] = true;
        }
        for (int i = 0; i < 20000; i++) {
            test2(array, flags, true, 0);
        }
        for (int i = 0; i < flags.length; i++) {
            flags[i] = false;
        }
        test2(array, flags, true, Long.MAX_VALUE/4);
    }
}