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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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 *

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 */

/**

 * @test

 * @bug 8150804

 * @summary Tests elimination of Phi nodes without losing type information.

 * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement TestPhiElimination

 */

public class TestPhiElimination {

    /*

       A::get() is inlined into test(obj) producing the following graph:

               Parm (obj)

            TestPhiElimination

                   |

                 CastPP

        TestPhiElimination:NotNull

                   |

              CheckCastPP

               A:NotNull

               /       \

       CheckCastPP     |

        A:NotNull      |

                \     /

                  Phi

                   A

                   |

               Safepoint

       PhiNode::ideal() then replaces the Phi by a CheckCastPP:

               Parm (obj)

            TestPhiElimination

                   |

              CheckCastPP

                   A

                   |

               Safepoint

       losing the :NotNull information. Therefore, we cannot prove that obj != null

       when accessing a field and add an uncommon trap. Since obj is used as monitor, we

       set it to TOP in the uncommon trap branch and later fail in Process_OopMap_Node

       because the monitor object is TOP.

    */

    public Object test(TestPhiElimination obj) {

        if (obj instanceof A) {

            return ((A) obj).get();

        }

        return null;

    }

    static public void main(String[] args) {

        TestPhiElimination t = new TestPhiElimination();

        // Warmup

        B b = new B();

        for (int i = 0; i < 1_000; ++i) {

            t.test(b);

        }

        // Compile

        A a = new A();

        for (int i = 0; i < 20_000; ++i) {

            if (i % 2 == 0) {

                a.f = null;

            }

            t.test(a);

        }

    }

}

class A extends TestPhiElimination {

    public Object f;

    public A create() {

        return new A();

    }

    public synchronized Object get() {

        if (f == null) {

            f = create();

        }

        return f;

    }

}

class B extends A {

}