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 }