test/hotspot/jtreg/gc/shenandoah/compiler/LRBRightAfterMemBar.java

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/**
 * @test
 * @bug 8237007
 * @summary Shenandoah: assert(_base == Tuple) failure during C2 compilation
 * @key gc
 * @requires vm.flavor == "server"
 * @requires vm.gc.Shenandoah & !vm.graal.enabled
 *
 * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:-BackgroundCompilation -XX:+UseShenandoahGC LRBRightAfterMemBar
 *
 */

public class LRBRightAfterMemBar {
    private static Object field1;
    private static Object field2;
    static volatile int barrier;

    public static void main(String[] args) {
        for (int i = 0; i < 20_000; i++) {
            test(true, true, new Object());
            test(false, false, new Object());
        }
    }

    private static Object test(boolean flag, boolean flag2, Object o2) {
        for (int i = 0; i < 10; i++) {
            barrier = 0x42; // Membar
            if (o2 == null) { // hoisted out of loop
            }
            // The following line is converted to a CMove with an out
            // of loop control once the null check above is
            // hoisted. The CMove is pinned right after the membar and
            // assigned the membar as control.
            Object o = flag ? field1 : field2;
            if (flag2) {
                return o;
            }
        }

        return null;
    }
}