1 /*
   2  * Copyright (c) 2016, 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 org.graalvm.compiler.hotspot.meta;
  24 
  25 import org.graalvm.compiler.core.common.spi.JavaConstantFieldProvider;
  26 import org.graalvm.compiler.hotspot.GraalHotSpotVMConfig;
  27 
  28 import jdk.vm.ci.hotspot.HotSpotResolvedJavaField;
  29 import jdk.vm.ci.meta.MetaAccessProvider;
  30 import jdk.vm.ci.meta.ResolvedJavaField;
  31 import jdk.vm.ci.meta.ResolvedJavaType;
  32 
  33 /**
  34  * Implements the default constant folding semantics for Java fields in the HotSpot VM.
  35  */
  36 public class HotSpotConstantFieldProvider extends JavaConstantFieldProvider {
  37 
  38     private final GraalHotSpotVMConfig config;
  39 
  40     public HotSpotConstantFieldProvider(GraalHotSpotVMConfig config, MetaAccessProvider metaAccess) {
  41         super(metaAccess);
  42         this.config = config;
  43     }
  44 
  45     @Override
  46     protected boolean isStableField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
  47         if (!config.foldStableValues) {
  48             return false;
  49         }
  50         if (field.isStatic() && !isStaticFieldConstant(field)) {
  51             return false;
  52         }
  53 
  54         if (((HotSpotResolvedJavaField) field).isStable()) {
  55             return true;
  56         }
  57         return super.isStableField(field, tool);
  58     }
  59 
  60     @Override
  61     protected boolean isFinalField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
  62         if (field.isStatic() && !isStaticFieldConstant(field)) {
  63             return false;
  64         }
  65 
  66         return super.isFinalField(field, tool);
  67     }
  68 
  69     private static final String SystemClassName = "Ljava/lang/System;";
  70 
  71     protected boolean isStaticFieldConstant(ResolvedJavaField field) {
  72         ResolvedJavaType declaringClass = field.getDeclaringClass();
  73         return declaringClass.isInitialized() && !declaringClass.getName().equals(SystemClassName);
  74     }
  75 }