1 /* 2 * Copyright (c) 2011, 2015, 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.HotSpotJVMCIRuntimeProvider.getArrayBaseOffset; 26 import static jdk.vm.ci.hotspot.HotSpotJVMCIRuntimeProvider.getArrayIndexScale; 27 28 import java.lang.reflect.Array; 29 30 import jdk.vm.ci.meta.Constant; 31 import jdk.vm.ci.meta.ConstantReflectionProvider; 32 import jdk.vm.ci.meta.JavaConstant; 33 import jdk.vm.ci.meta.JavaKind; 34 import jdk.vm.ci.meta.JavaType; 35 import jdk.vm.ci.meta.MemoryAccessProvider; 36 import jdk.vm.ci.meta.MethodHandleAccessProvider; 37 import jdk.vm.ci.meta.ResolvedJavaField; 38 import jdk.vm.ci.meta.ResolvedJavaType; 39 40 /** 41 * HotSpot implementation of {@link ConstantReflectionProvider}. 42 */ 43 public class HotSpotConstantReflectionProvider implements ConstantReflectionProvider, HotSpotProxified { 44 45 /** 46 * Determines whether to treat {@code final} fields with default values as constant. 47 */ 48 private static final boolean TrustFinalDefaultFields = HotSpotJVMCIRuntime.getBooleanProperty("TrustFinalDefaultFields", true); 49 50 protected final HotSpotJVMCIRuntimeProvider runtime; 51 protected final HotSpotMethodHandleAccessProvider methodHandleAccess; 52 protected final HotSpotMemoryAccessProviderImpl memoryAccess; 53 54 public HotSpotConstantReflectionProvider(HotSpotJVMCIRuntimeProvider runtime) { 55 this.runtime = runtime; 56 this.methodHandleAccess = new HotSpotMethodHandleAccessProvider(this); 57 this.memoryAccess = new HotSpotMemoryAccessProviderImpl(runtime); 58 } 59 60 public MethodHandleAccessProvider getMethodHandleAccess() { 61 return methodHandleAccess; 62 } 63 64 @Override 65 public MemoryAccessProvider getMemoryAccessProvider() { 66 return memoryAccess; 67 } 68 69 @Override 70 public Boolean constantEquals(Constant x, Constant y) { 71 if (x == y) { 72 return true; 73 } else if (x instanceof HotSpotObjectConstantImpl) { 74 return y instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) x).object() == ((HotSpotObjectConstantImpl) y).object(); 75 } else { 76 return x.equals(y); 77 } 78 } 79 80 @Override 81 public Integer readArrayLength(JavaConstant array) { 82 if (array.getJavaKind() != JavaKind.Object || array.isNull()) { 83 return null; 84 } 85 86 Object arrayObject = ((HotSpotObjectConstantImpl) array).object(); 87 if (!arrayObject.getClass().isArray()) { 88 return null; 89 } 90 return Array.getLength(arrayObject); 91 } 92 93 public JavaConstant readConstantArrayElement(JavaConstant array, int index) { 94 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) { 95 JavaConstant element = readArrayElement(array, index); 96 if (element != null && (((HotSpotObjectConstantImpl) array).isDefaultStable() || !element.isDefaultForKind())) { 97 return element; 98 } 99 } 100 return null; 101 } 102 103 /** 104 * Try to convert {@code offset} into an an index into {@code array}. 105 * 106 * @return the computed index or -1 if the offset isn't within the array 107 */ 108 private int indexForOffset(JavaConstant array, long offset) { 109 if (array.getJavaKind() != JavaKind.Object || array.isNull()) { 110 return -1; 111 } 112 Class<?> componentType = ((HotSpotObjectConstantImpl) array).object().getClass().getComponentType(); 113 JavaKind kind = runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType(componentType).getJavaKind(); 114 int arraybase = getArrayBaseOffset(kind); 115 int scale = getArrayIndexScale(kind); 116 if (offset < arraybase) { 117 return -1; 118 } 119 long index = offset - arraybase; 120 if (index % scale != 0) { 121 return -1; 122 } 123 long result = index / scale; 124 if (result >= Integer.MAX_VALUE) { 125 return -1; 126 } 127 return (int) result; 128 } 129 130 public JavaConstant readConstantArrayElementForOffset(JavaConstant array, long offset) { 131 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) { 132 return readConstantArrayElement(array, indexForOffset(array, offset)); 133 } 134 return null; 135 } 136 137 @Override 138 public JavaConstant readArrayElement(JavaConstant array, int index) { 139 if (array.getJavaKind() != JavaKind.Object || array.isNull()) { 140 return null; 141 } 142 Object a = ((HotSpotObjectConstantImpl) array).object(); 143 144 if (index < 0 || index >= Array.getLength(a)) { 145 return null; 146 } 147 148 if (a instanceof Object[]) { 149 Object element = ((Object[]) a)[index]; 150 if (((HotSpotObjectConstantImpl) array).getStableDimension() > 1) { 151 return HotSpotObjectConstantImpl.forStableArray(element, ((HotSpotObjectConstantImpl) array).getStableDimension() - 1, ((HotSpotObjectConstantImpl) array).isDefaultStable()); 152 } else { 153 return HotSpotObjectConstantImpl.forObject(element); 154 } 155 } else { 156 return JavaConstant.forBoxedPrimitive(Array.get(a, index)); 157 } 158 } 159 160 /** 161 * Check if the constant is a boxed value that is guaranteed to be cached by the platform. 162 * Otherwise the generated code might be the only reference to the boxed value and since object 163 * references from nmethods are weak this can cause GC problems. 164 * 165 * @param source 166 * @return true if the box is cached 167 */ 168 private static boolean isBoxCached(JavaConstant source) { 169 switch (source.getJavaKind()) { 170 case Boolean: 171 return true; 172 case Char: 173 return source.asInt() <= 127; 174 case Byte: 175 case Short: 176 case Int: 177 return source.asInt() >= -128 && source.asInt() <= 127; 178 case Long: 179 return source.asLong() >= -128 && source.asLong() <= 127; 180 case Float: 181 case Double: 182 return false; 183 default: 184 throw new IllegalArgumentException("unexpected kind " + source.getJavaKind()); 185 } 186 } 187 188 @Override 189 public JavaConstant boxPrimitive(JavaConstant source) { 190 if (!source.getJavaKind().isPrimitive() || !isBoxCached(source)) { 191 return null; 192 } 193 return HotSpotObjectConstantImpl.forObject(source.asBoxedPrimitive()); 194 } 195 196 @Override 197 public JavaConstant unboxPrimitive(JavaConstant source) { 198 if (!source.getJavaKind().isObject()) { 199 return null; 200 } 201 if (source.isNull()) { 202 return null; 203 } 204 return JavaConstant.forBoxedPrimitive(((HotSpotObjectConstantImpl) source).object()); 205 } 206 207 public JavaConstant forString(String value) { 208 return HotSpotObjectConstantImpl.forObject(value); 209 } 210 211 public JavaConstant forObject(Object value) { 212 return HotSpotObjectConstantImpl.forObject(value); 213 } 214 215 @Override 216 public ResolvedJavaType asJavaType(Constant constant) { 217 if (constant instanceof HotSpotObjectConstant) { 218 Object obj = ((HotSpotObjectConstantImpl) constant).object(); 219 if (obj instanceof Class) { 220 return runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType((Class<?>) obj); 221 } 222 } 223 if (constant instanceof HotSpotMetaspaceConstant) { 224 MetaspaceWrapperObject obj = HotSpotMetaspaceConstantImpl.getMetaspaceObject(constant); 225 if (obj instanceof HotSpotResolvedObjectTypeImpl) { 226 return (ResolvedJavaType) obj; 227 } 228 } 229 return null; 230 } 231 232 private static final String SystemClassName = "Ljava/lang/System;"; 233 234 /** 235 * Determines if a static field is constant for the purpose of 236 * {@link #readConstantFieldValue(ResolvedJavaField, JavaConstant)}. 237 */ 238 protected boolean isStaticFieldConstant(HotSpotResolvedJavaField staticField) { 239 if (staticField.isFinal() || (staticField.isStable() && runtime.getConfig().foldStableValues)) { 240 ResolvedJavaType holder = staticField.getDeclaringClass(); 241 if (holder.isInitialized() && !holder.getName().equals(SystemClassName)) { 242 return true; 243 } 244 } 245 return false; 246 } 247 248 /** 249 * Determines if a value read from a {@code final} instance field is considered constant. The 250 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is 251 * not the {@link JavaConstant#isDefaultForKind default value} for its kind or if 252 * {@link #TrustFinalDefaultFields} is true. 253 * 254 * @param value a value read from a {@code final} instance field 255 * @param receiverClass the {@link Object#getClass() class} of object from which the 256 * {@code value} was read 257 */ 258 protected boolean isFinalInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) { 259 return !value.isDefaultForKind() || TrustFinalDefaultFields; 260 } 261 262 /** 263 * Determines if a value read from a {@link Stable} instance field is considered constant. The 264 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is 265 * not the {@link JavaConstant#isDefaultForKind default value} for its kind. 266 * 267 * @param value a value read from a {@link Stable} field 268 * @param receiverClass the {@link Object#getClass() class} of object from which the 269 * {@code value} was read 270 */ 271 protected boolean isStableInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) { 272 return !value.isDefaultForKind(); 273 } 274 275 public JavaConstant readConstantFieldValue(ResolvedJavaField field, JavaConstant receiver) { 276 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field; 277 278 if (hotspotField.isStatic()) { 279 if (isStaticFieldConstant(hotspotField)) { 280 JavaConstant value = readFieldValue(field, receiver); 281 if (hotspotField.isFinal() || !value.isDefaultForKind()) { 282 return value; 283 } 284 } 285 } else { 286 /* 287 * for non-static final fields, we must assume that they are only initialized if they 288 * have a non-default value. 289 */ 290 Object object = receiver.isNull() ? null : ((HotSpotObjectConstantImpl) receiver).object(); 291 292 // Canonicalization may attempt to process an unsafe read before 293 // processing a guard (e.g. a null check or a type check) for this read 294 // so we need to check the object being read 295 if (object != null) { 296 if (hotspotField.isFinal()) { 297 if (hotspotField.isInObject(object)) { 298 JavaConstant value = readFieldValue(field, receiver); 299 if (isFinalInstanceFieldValueConstant(value, object.getClass())) { 300 return value; 301 } 302 } 303 } else if (hotspotField.isStable() && runtime.getConfig().foldStableValues) { 304 if (hotspotField.isInObject(object)) { 305 JavaConstant value = readFieldValue(field, receiver); 306 if (isStableInstanceFieldValueConstant(value, object.getClass())) { 307 return value; 308 } 309 } 310 } 311 } 312 } 313 return null; 314 } 315 316 public JavaConstant readFieldValue(ResolvedJavaField field, JavaConstant receiver) { 317 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field; 318 if (!hotspotField.isStable()) { 319 return readNonStableFieldValue(field, receiver); 320 } else if (runtime.getConfig().foldStableValues) { 321 return readStableFieldValue(field, receiver, hotspotField.isDefaultStable()); 322 } else { 323 return null; 324 } 325 } 326 327 private JavaConstant readNonStableFieldValue(ResolvedJavaField field, JavaConstant receiver) { 328 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field; 329 if (hotspotField.isStatic()) { 330 HotSpotResolvedJavaType holder = (HotSpotResolvedJavaType) hotspotField.getDeclaringClass(); 331 if (holder.isInitialized()) { 332 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), HotSpotObjectConstantImpl.forObject(holder.mirror()), hotspotField.offset()); 333 } 334 } else { 335 if (receiver.isNonNull() && hotspotField.isInObject(((HotSpotObjectConstantImpl) receiver).object())) { 336 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), receiver, hotspotField.offset()); 337 } 338 } 339 return null; 340 } 341 342 public JavaConstant readStableFieldValue(ResolvedJavaField field, JavaConstant receiver, boolean isDefaultStable) { 343 JavaConstant fieldValue = readNonStableFieldValue(field, receiver); 344 if (fieldValue.isNonNull()) { 345 JavaType declaredType = field.getType(); 346 if (declaredType.getComponentType() != null) { 347 int stableDimension = getArrayDimension(declaredType); 348 return HotSpotObjectConstantImpl.forStableArray(((HotSpotObjectConstantImpl) fieldValue).object(), stableDimension, isDefaultStable); 349 } 350 } 351 return fieldValue; 352 } 353 354 private static int getArrayDimension(JavaType type) { 355 int dimensions = 0; 356 JavaType componentType = type; 357 while ((componentType = componentType.getComponentType()) != null) { 358 dimensions++; 359 } 360 return dimensions; 361 } 362 }