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.hotspot.HotSpotJVMCIRuntime.Option;
31 import jdk.vm.ci.meta.Constant;
32 import jdk.vm.ci.meta.ConstantReflectionProvider;
33 import jdk.vm.ci.meta.JavaConstant;
34 import jdk.vm.ci.meta.JavaKind;
35 import jdk.vm.ci.meta.JavaType;
36 import jdk.vm.ci.meta.MemoryAccessProvider;
37 import jdk.vm.ci.meta.MethodHandleAccessProvider;
38 import jdk.vm.ci.meta.ResolvedJavaField;
39 import jdk.vm.ci.meta.ResolvedJavaType;
40
41 /**
42 * HotSpot implementation of {@link ConstantReflectionProvider}.
43 */
44 public class HotSpotConstantReflectionProvider implements ConstantReflectionProvider, HotSpotProxified {
45
46 /**
47 * Determines whether to treat {@code final} fields with default values as constant.
48 */
49 private static final boolean TrustFinalDefaultFields = HotSpotJVMCIRuntime.getBooleanProperty(Option.TrustFinalDefaultFields, true);
50
51 protected final HotSpotJVMCIRuntimeProvider runtime;
52 protected final HotSpotMethodHandleAccessProvider methodHandleAccess;
53 protected final HotSpotMemoryAccessProviderImpl memoryAccess;
54
55 public HotSpotConstantReflectionProvider(HotSpotJVMCIRuntimeProvider runtime) {
56 this.runtime = runtime;
57 this.methodHandleAccess = new HotSpotMethodHandleAccessProvider(this);
58 this.memoryAccess = new HotSpotMemoryAccessProviderImpl(runtime);
59 }
60
61 public MethodHandleAccessProvider getMethodHandleAccess() {
62 return methodHandleAccess;
63 }
64
65 @Override
66 public MemoryAccessProvider getMemoryAccessProvider() {
67 return memoryAccess;
68 }
69
70 @Override
71 public Boolean constantEquals(Constant x, Constant y) {
72 if (x == y) {
73 return true;
74 } else if (x instanceof HotSpotObjectConstantImpl) {
75 return y instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) x).object() == ((HotSpotObjectConstantImpl) y).object();
76 } else {
77 return x.equals(y);
78 }
79 }
80
81 @Override
82 public Integer readArrayLength(JavaConstant array) {
83 if (array.getJavaKind() != JavaKind.Object || array.isNull()) {
84 return null;
85 }
86
87 Object arrayObject = ((HotSpotObjectConstantImpl) array).object();
88 if (!arrayObject.getClass().isArray()) {
89 return null;
90 }
91 return Array.getLength(arrayObject);
92 }
93
94 public JavaConstant readConstantArrayElement(JavaConstant array, int index) {
95 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) {
96 JavaConstant element = readArrayElement(array, index);
97 if (element != null && (((HotSpotObjectConstantImpl) array).isDefaultStable() || !element.isDefaultForKind())) {
98 return element;
99 }
100 }
101 return null;
102 }
103
104 /**
105 * Try to convert {@code offset} into an an index into {@code array}.
106 *
107 * @return the computed index or -1 if the offset isn't within the array
108 */
109 private int indexForOffset(JavaConstant array, long offset) {
110 if (array.getJavaKind() != JavaKind.Object || array.isNull()) {
111 return -1;
112 }
113 Class<?> componentType = ((HotSpotObjectConstantImpl) array).object().getClass().getComponentType();
114 JavaKind kind = runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType(componentType).getJavaKind();
115 int arraybase = getArrayBaseOffset(kind);
116 int scale = getArrayIndexScale(kind);
117 if (offset < arraybase) {
118 return -1;
119 }
120 long index = offset - arraybase;
121 if (index % scale != 0) {
122 return -1;
123 }
124 long result = index / scale;
125 if (result >= Integer.MAX_VALUE) {
126 return -1;
127 }
128 return (int) result;
129 }
130
131 public JavaConstant readConstantArrayElementForOffset(JavaConstant array, long offset) {
132 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) {
133 return readConstantArrayElement(array, indexForOffset(array, offset));
134 }
135 return null;
136 }
137
138 @Override
139 public JavaConstant readArrayElement(JavaConstant array, int index) {
140 if (array.getJavaKind() != JavaKind.Object || array.isNull()) {
141 return null;
142 }
143 Object a = ((HotSpotObjectConstantImpl) array).object();
144
145 if (index < 0 || index >= Array.getLength(a)) {
146 return null;
147 }
148
149 if (a instanceof Object[]) {
150 Object element = ((Object[]) a)[index];
151 if (((HotSpotObjectConstantImpl) array).getStableDimension() > 1) {
152 return HotSpotObjectConstantImpl.forStableArray(element, ((HotSpotObjectConstantImpl) array).getStableDimension() - 1, ((HotSpotObjectConstantImpl) array).isDefaultStable());
153 } else {
154 return HotSpotObjectConstantImpl.forObject(element);
155 }
156 } else {
157 return JavaConstant.forBoxedPrimitive(Array.get(a, index));
158 }
159 }
160
161 /**
162 * Check if the constant is a boxed value that is guaranteed to be cached by the platform.
163 * Otherwise the generated code might be the only reference to the boxed value and since object
164 * references from nmethods are weak this can cause GC problems.
165 *
166 * @param source
167 * @return true if the box is cached
168 */
169 private static boolean isBoxCached(JavaConstant source) {
170 switch (source.getJavaKind()) {
171 case Boolean:
172 return true;
173 case Char:
174 return source.asInt() <= 127;
175 case Byte:
176 case Short:
177 case Int:
178 return source.asInt() >= -128 && source.asInt() <= 127;
179 case Long:
180 return source.asLong() >= -128 && source.asLong() <= 127;
181 case Float:
182 case Double:
183 return false;
184 default:
185 throw new IllegalArgumentException("unexpected kind " + source.getJavaKind());
186 }
187 }
188
189 @Override
190 public JavaConstant boxPrimitive(JavaConstant source) {
191 if (!source.getJavaKind().isPrimitive() || !isBoxCached(source)) {
192 return null;
193 }
194 return HotSpotObjectConstantImpl.forObject(source.asBoxedPrimitive());
195 }
196
197 @Override
198 public JavaConstant unboxPrimitive(JavaConstant source) {
199 if (!source.getJavaKind().isObject()) {
200 return null;
201 }
202 if (source.isNull()) {
203 return null;
204 }
205 return JavaConstant.forBoxedPrimitive(((HotSpotObjectConstantImpl) source).object());
206 }
207
208 public JavaConstant forString(String value) {
209 return HotSpotObjectConstantImpl.forObject(value);
210 }
211
212 public JavaConstant forObject(Object value) {
213 return HotSpotObjectConstantImpl.forObject(value);
214 }
215
216 @Override
217 public ResolvedJavaType asJavaType(Constant constant) {
218 if (constant instanceof HotSpotObjectConstant) {
219 Object obj = ((HotSpotObjectConstantImpl) constant).object();
220 if (obj instanceof Class) {
221 return runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType((Class<?>) obj);
222 }
223 }
224 if (constant instanceof HotSpotMetaspaceConstant) {
225 MetaspaceWrapperObject obj = HotSpotMetaspaceConstantImpl.getMetaspaceObject(constant);
226 if (obj instanceof HotSpotResolvedObjectTypeImpl) {
227 return (ResolvedJavaType) obj;
228 }
229 }
230 return null;
231 }
232
233 private static final String SystemClassName = "Ljava/lang/System;";
234
235 /**
236 * Determines if a static field is constant for the purpose of
237 * {@link #readConstantFieldValue(ResolvedJavaField, JavaConstant)}.
238 */
239 protected boolean isStaticFieldConstant(HotSpotResolvedJavaField staticField) {
240 if (staticField.isFinal() || (staticField.isStable() && runtime.getConfig().foldStableValues)) {
241 ResolvedJavaType holder = staticField.getDeclaringClass();
242 if (holder.isInitialized() && !holder.getName().equals(SystemClassName)) {
243 return true;
244 }
245 }
246 return false;
247 }
248
249 /**
250 * Determines if a value read from a {@code final} instance field is considered constant. The
251 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is
252 * not the {@link JavaConstant#isDefaultForKind default value} for its kind or if
253 * {@link #TrustFinalDefaultFields} is true.
254 *
255 * @param value a value read from a {@code final} instance field
256 * @param receiverClass the {@link Object#getClass() class} of object from which the
257 * {@code value} was read
258 */
259 protected boolean isFinalInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) {
260 return !value.isDefaultForKind() || TrustFinalDefaultFields;
261 }
262
263 /**
264 * Determines if a value read from a {@link Stable} instance field is considered constant. The
265 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is
266 * not the {@link JavaConstant#isDefaultForKind default value} for its kind.
267 *
268 * @param value a value read from a {@link Stable} field
269 * @param receiverClass the {@link Object#getClass() class} of object from which the
270 * {@code value} was read
271 */
272 protected boolean isStableInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) {
273 return !value.isDefaultForKind();
274 }
275
276 public JavaConstant readConstantFieldValue(ResolvedJavaField field, JavaConstant receiver) {
277 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
278
279 if (hotspotField.isStatic()) {
280 if (isStaticFieldConstant(hotspotField)) {
281 JavaConstant value = readFieldValue(field, receiver);
282 if (hotspotField.isFinal() || !value.isDefaultForKind()) {
283 return value;
284 }
285 }
286 } else {
287 /*
288 * for non-static final fields, we must assume that they are only initialized if they
289 * have a non-default value.
290 */
291 Object object = receiver.isNull() ? null : ((HotSpotObjectConstantImpl) receiver).object();
292
293 // Canonicalization may attempt to process an unsafe read before
294 // processing a guard (e.g. a null check or a type check) for this read
295 // so we need to check the object being read
296 if (object != null) {
297 if (hotspotField.isFinal()) {
298 if (hotspotField.isInObject(object)) {
299 JavaConstant value = readFieldValue(field, receiver);
300 if (isFinalInstanceFieldValueConstant(value, object.getClass())) {
301 return value;
302 }
303 }
304 } else if (hotspotField.isStable() && runtime.getConfig().foldStableValues) {
305 if (hotspotField.isInObject(object)) {
306 JavaConstant value = readFieldValue(field, receiver);
307 if (isStableInstanceFieldValueConstant(value, object.getClass())) {
308 return value;
309 }
310 }
311 }
312 }
313 }
314 return null;
315 }
316
317 public JavaConstant readFieldValue(ResolvedJavaField field, JavaConstant receiver) {
318 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
319 if (!hotspotField.isStable()) {
320 return readNonStableFieldValue(field, receiver);
321 } else if (runtime.getConfig().foldStableValues) {
322 return readStableFieldValue(field, receiver, hotspotField.isDefaultStable());
323 } else {
324 return null;
325 }
326 }
327
328 private JavaConstant readNonStableFieldValue(ResolvedJavaField field, JavaConstant receiver) {
329 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
330 if (hotspotField.isStatic()) {
331 HotSpotResolvedJavaType holder = (HotSpotResolvedJavaType) hotspotField.getDeclaringClass();
332 if (holder.isInitialized()) {
333 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), HotSpotObjectConstantImpl.forObject(holder.mirror()), hotspotField.offset());
334 }
335 } else {
336 if (receiver.isNonNull() && hotspotField.isInObject(((HotSpotObjectConstantImpl) receiver).object())) {
337 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), receiver, hotspotField.offset());
338 }
339 }
340 return null;
341 }
342
343 public JavaConstant readStableFieldValue(ResolvedJavaField field, JavaConstant receiver, boolean isDefaultStable) {
344 JavaConstant fieldValue = readNonStableFieldValue(field, receiver);
345 if (fieldValue.isNonNull()) {
346 JavaType declaredType = field.getType();
347 if (declaredType.getComponentType() != null) {
348 int stableDimension = getArrayDimension(declaredType);
349 return HotSpotObjectConstantImpl.forStableArray(((HotSpotObjectConstantImpl) fieldValue).object(), stableDimension, isDefaultStable);
350 }
351 }
352 return fieldValue;
353 }
354
355 private static int getArrayDimension(JavaType type) {
356 int dimensions = 0;
357 JavaType componentType = type;
358 while ((componentType = componentType.getComponentType()) != null) {
359 dimensions++;
360 }
361 return dimensions;
362 }
363 }