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 }