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package ir_framework.examples;

import compiler.lib.ir_framework.*;
import java.lang.invoke.VarHandle;
import java.lang.invoke.MethodHandles;

/**
 * @test
 * @bug 8330153
 * @summary Example test that illustrates the use of the IR test framework for
 *          verification of late-expanded GC barriers.
 * @library /test/lib /
 * @requires vm.gc.Z
 * @run driver ir_framework.examples.GCBarrierIRExample
 */

public class GCBarrierIRExample {

    static class Outer {
        Object f;
    }

    static final VarHandle fVarHandle;
    static {
        MethodHandles.Lookup l = MethodHandles.lookup();
        try {
            fVarHandle = l.findVarHandle(Outer.class, "f", Object.class);
        } catch (Exception e) {
            throw new Error(e);
        }
    }
    static Outer o = new Outer();
    static Object oldVal = new Object();
    static Object newVal = new Object();

    public static void main(String[] args) {
        // These rules apply only to collectors that expand barriers at code
        // emission, such as ZGC. Because the collector selection flags are not
        // whitelisted (see IR framework's README.md file), the user (as opposed
        // to jtreg) needs to set these flags here.
        TestFramework.runWithFlags("-XX:+UseZGC");
    }

    @Test
    // IR rules can be used to verify collector-specific barrier info (in this
    // case, that a ZGC barrier corresponds to a strong OOP reference). Barrier
    // info can only be verified after matching, e.g. at the FINAL_CODE phase.
    @IR(counts = {IRNode.Z_COMPARE_AND_SWAP_P_WITH_BARRIER_FLAG, "strong", "1"},
        phase  = CompilePhase.FINAL_CODE)
    static boolean testBarrierOfCompareAndSwap() {
        return fVarHandle.compareAndSet(o, oldVal, newVal);
    }
}