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