1 /*

     2  * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.

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

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

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

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

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

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

    13  * accompanied this code).

    14  *

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

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 package jdk.vm.ci.hotspot;

    24 

    25 import static jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime;

    26 

    27 import jdk.vm.ci.meta.JavaConstant;

    28 

    29 final class IndirectHotSpotObjectConstantImpl extends HotSpotObjectConstantImpl {

    30     /**

    31      * An object handle in {@code JVMCI::_jvmci_handles}.

    32      */

    33     final long objectHandle;

    34     private int hashCode;

    35 

    36     final IndirectHotSpotObjectConstantImpl base;

    37 

    38     @VMEntryPoint

    39     private IndirectHotSpotObjectConstantImpl(long objectHandle, boolean compressed, boolean skipRegister) {

    40         super(compressed);

    41         assert objectHandle != 0 && UnsafeAccess.UNSAFE.getLong(objectHandle) != 0;

    42         this.objectHandle = objectHandle;

    43         this.base = null;

    44         if (!skipRegister) {

    45             HandleCleaner.create(this, objectHandle);

    46         }

    47     }

    48 

    49     private IndirectHotSpotObjectConstantImpl(IndirectHotSpotObjectConstantImpl base, boolean compressed) {

    50         super(compressed);

    51         // This is a variant of an original object that only varies in compress vs uncompressed.

    52         // Instead of creating a new handle, reference that object and objectHandle.

    53         this.objectHandle = base.objectHandle;

    54         // There should only be on level of indirection to the base object.

    55         assert base.base == null || base.base.base == null;

    56         this.base = base.base != null ? base.base : base;

    57     }

    58 

    59     @Override

    60     public JavaConstant compress() {

    61         assert !compressed;

    62         return new IndirectHotSpotObjectConstantImpl(this, true);

    63     }

    64 

    65     @Override

    66     public JavaConstant uncompress() {

    67         assert compressed;

    68         return new IndirectHotSpotObjectConstantImpl(this, false);

    69     }

    70 

    71     @Override

    72     public int getIdentityHashCode() {

    73         int hash = hashCode;

    74         if (hash == 0) {

    75             hash = runtime().compilerToVm.getIdentityHashCode(this);

    76             if (hash == 0) {

    77                 hash = 31;

    78             }

    79             hashCode = hash;

    80         }

    81         return hash;

    82     }

    83 }