jdk-24/test/hotspot/jtreg/gc/shenandoah/compiler/TestLoadBypassesNullCheck.java

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/**
 * @test
 * @bug 8342496
 * @summary C2/Shenandoah: SEGV in compiled code when running jcstress
 * @requires vm.flavor == "server"
 * @requires vm.gc.Shenandoah
 *
 * @run main/othervm -XX:-TieredCompilation -XX:-UseOnStackReplacement -XX:-BackgroundCompilation
 *                   -XX:+UseShenandoahGC -XX:LoopMaxUnroll=0
 *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressGCM -XX:+StressLCM -XX:StressSeed=270847015
 *                   TestLoadBypassesNullCheck
 * @run main/othervm -XX:-TieredCompilation -XX:-UseOnStackReplacement -XX:-BackgroundCompilation
 *                   -XX:+UseShenandoahGC -XX:LoopMaxUnroll=0
 *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressGCM -XX:+StressLCM
 *                   TestLoadBypassesNullCheck
 *
 */

public class TestLoadBypassesNullCheck {
    private static A fieldA = new A();
    private static Object fieldO = new Object();
    private static volatile int volatileField;

    public static void main(String[] args) {
        for (int i = 0; i < 20_000; i++) {
            test1();
        }
        fieldA = null;
        try {
            test1();
        } catch (NullPointerException npe) {
        }
    }

    private static boolean test1() {
        for (int i = 0; i < 1000; i++) {
            volatileField = 42;
            A a = fieldA;
            Object o = a.fieldO;
            if (o == fieldO) {
                return true;
            }
        }
        return false;
    }

    private static class A {
        public Object fieldO;
    }
}