1 /*
2 * Copyright (c) 2011, 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 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 import java.util.Objects;
30
31 import jdk.vm.ci.common.JVMCIError;
32 import jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.Option;
33 import jdk.vm.ci.meta.Constant;
34 import jdk.vm.ci.meta.ConstantReflectionProvider;
35 import jdk.vm.ci.meta.JavaConstant;
36 import jdk.vm.ci.meta.JavaKind;
37 import jdk.vm.ci.meta.JavaType;
38 import jdk.vm.ci.meta.MemoryAccessProvider;
39 import jdk.vm.ci.meta.MethodHandleAccessProvider;
40 import jdk.vm.ci.meta.ResolvedJavaField;
41 import jdk.vm.ci.meta.ResolvedJavaType;
42
43 /**
44 * HotSpot implementation of {@link ConstantReflectionProvider}.
45 */
46 public class HotSpotConstantReflectionProvider implements ConstantReflectionProvider, HotSpotProxified {
47
48 protected final HotSpotJVMCIRuntimeProvider runtime;
49 protected final HotSpotMethodHandleAccessProvider methodHandleAccess;
50 protected final HotSpotMemoryAccessProviderImpl memoryAccess;
51
52 public HotSpotConstantReflectionProvider(HotSpotJVMCIRuntimeProvider runtime) {
53 this.runtime = runtime;
54 this.methodHandleAccess = new HotSpotMethodHandleAccessProvider(this);
55 this.memoryAccess = new HotSpotMemoryAccessProviderImpl(runtime);
56 }
57
58 public MethodHandleAccessProvider getMethodHandleAccess() {
59 return methodHandleAccess;
60 }
61
62 @Override
63 public MemoryAccessProvider getMemoryAccessProvider() {
64 return memoryAccess;
65 }
66
67 @Override
68 public Boolean constantEquals(Constant x, Constant y) {
69 if (x == y) {
70 return true;
71 } else if (x instanceof HotSpotObjectConstantImpl) {
72 return y instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) x).object() == ((HotSpotObjectConstantImpl) y).object();
73 } else {
74 return Objects.equals(x, y);
75 }
76 }
77
78 @Override
79 public Integer readArrayLength(JavaConstant array) {
80 if (array == null || array.getJavaKind() != JavaKind.Object || array.isNull()) {
81 return null;
82 }
83
84 Object arrayObject = ((HotSpotObjectConstantImpl) array).object();
85 if (!arrayObject.getClass().isArray()) {
86 return null;
87 }
88 return Array.getLength(arrayObject);
89 }
90
91 public JavaConstant readConstantArrayElement(JavaConstant array, int index) {
92 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) {
93 JavaConstant element = readArrayElement(array, index);
94 if (element != null && (((HotSpotObjectConstantImpl) array).isDefaultStable() || !element.isDefaultForKind())) {
95 return element;
96 }
97 }
98 return null;
99 }
100
101 /**
102 * Try to convert {@code offset} into an an index into {@code array}.
103 *
104 * @return the computed index or -1 if the offset isn't within the array
105 */
106 private int indexForOffset(JavaConstant array, long offset) {
107 if (array.getJavaKind() != JavaKind.Object || array.isNull()) {
108 return -1;
109 }
110 Class<?> componentType = ((HotSpotObjectConstantImpl) array).object().getClass().getComponentType();
111 JavaKind kind = runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType(componentType).getJavaKind();
112 int arraybase = getArrayBaseOffset(kind);
113 int scale = getArrayIndexScale(kind);
114 if (offset < arraybase) {
115 return -1;
116 }
117 long index = offset - arraybase;
118 if (index % scale != 0) {
119 return -1;
120 }
121 long result = index / scale;
122 if (result >= Integer.MAX_VALUE) {
123 return -1;
124 }
125 return (int) result;
126 }
127
128 public JavaConstant readConstantArrayElementForOffset(JavaConstant array, long offset) {
129 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) {
130 return readConstantArrayElement(array, indexForOffset(array, offset));
131 }
132 return null;
133 }
134
135 @Override
136 public JavaConstant readArrayElement(JavaConstant array, int index) {
137 if (array == null || array.getJavaKind() != JavaKind.Object || array.isNull()) {
138 return null;
139 }
140 Object a = ((HotSpotObjectConstantImpl) array).object();
141
142 if (!a.getClass().isArray() || index < 0 || index >= Array.getLength(a)) {
143 return null;
144 }
145
146 if (a instanceof Object[]) {
147 Object element = ((Object[]) a)[index];
148 if (((HotSpotObjectConstantImpl) array).getStableDimension() > 1) {
149 return HotSpotObjectConstantImpl.forStableArray(element, ((HotSpotObjectConstantImpl) array).getStableDimension() - 1, ((HotSpotObjectConstantImpl) array).isDefaultStable());
150 } else {
151 return HotSpotObjectConstantImpl.forObject(element);
152 }
153 } else {
154 return JavaConstant.forBoxedPrimitive(Array.get(a, index));
155 }
156 }
157
158 /**
159 * Check if the constant is a boxed value that is guaranteed to be cached by the platform.
160 * Otherwise the generated code might be the only reference to the boxed value and since object
161 * references from nmethods are weak this can cause GC problems.
162 *
163 * @param source
164 * @return true if the box is cached
165 */
166 private static boolean isBoxCached(JavaConstant source) {
167 switch (source.getJavaKind()) {
168 case Boolean:
169 return true;
170 case Char:
171 return source.asInt() <= 127;
172 case Byte:
173 case Short:
174 case Int:
175 return source.asInt() >= -128 && source.asInt() <= 127;
176 case Long:
177 return source.asLong() >= -128 && source.asLong() <= 127;
178 case Float:
179 case Double:
180 return false;
181 default:
182 throw new IllegalArgumentException("unexpected kind " + source.getJavaKind());
183 }
184 }
185
186 @Override
187 public JavaConstant boxPrimitive(JavaConstant source) {
188 if (source == null || !source.getJavaKind().isPrimitive() || !isBoxCached(source)) {
189 return null;
190 }
191 return HotSpotObjectConstantImpl.forObject(source.asBoxedPrimitive());
192 }
193
194 @Override
195 public JavaConstant unboxPrimitive(JavaConstant source) {
196 if (source == null || !source.getJavaKind().isObject()) {
197 return null;
198 }
199 if (source.isNull()) {
200 return null;
201 }
202 return JavaConstant.forBoxedPrimitive(((HotSpotObjectConstantImpl) source).object());
203 }
204
205 public JavaConstant forString(String value) {
206 return HotSpotObjectConstantImpl.forObject(value);
207 }
208
209 public JavaConstant forObject(Object value) {
210 return HotSpotObjectConstantImpl.forObject(value);
211 }
212
213 @Override
214 public ResolvedJavaType asJavaType(Constant constant) {
215 if (constant instanceof HotSpotObjectConstant) {
216 Object obj = ((HotSpotObjectConstantImpl) constant).object();
217 if (obj instanceof Class) {
218 return runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType((Class<?>) obj);
219 }
220 }
221 if (constant instanceof HotSpotMetaspaceConstant) {
222 MetaspaceWrapperObject obj = HotSpotMetaspaceConstantImpl.getMetaspaceObject(constant);
223 if (obj instanceof HotSpotResolvedObjectTypeImpl) {
224 return (ResolvedJavaType) obj;
225 }
226 }
227 return null;
228 }
229
230 private static final String SystemClassName = "Ljava/lang/System;";
231
232 /**
233 * Determines if a static field is constant for the purpose of
234 * {@link #readConstantFieldValue(ResolvedJavaField, JavaConstant)}.
235 */
236 protected boolean isStaticFieldConstant(HotSpotResolvedJavaField staticField) {
237 if (staticField.isFinal() || (staticField.isStable() && runtime.getConfig().foldStableValues)) {
238 ResolvedJavaType holder = staticField.getDeclaringClass();
239 if (holder.isInitialized() && !holder.getName().equals(SystemClassName)) {
240 return true;
241 }
242 }
243 return false;
244 }
245
246 /**
247 * Determines if a value read from a {@code final} instance field is considered constant. The
248 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is
249 * not the {@link JavaConstant#isDefaultForKind default value} for its kind or if
250 * {@link Option#TrustFinalDefaultFields} is true.
251 *
252 * @param value a value read from a {@code final} instance field
253 * @param receiverClass the {@link Object#getClass() class} of object from which the
254 * {@code value} was read
255 */
256 protected boolean isFinalInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) {
257 return !value.isDefaultForKind() || Option.TrustFinalDefaultFields.getBoolean();
258 }
259
260 /**
261 * Determines if a value read from a {@link Stable} instance field is considered constant. The
262 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is
263 * not the {@link JavaConstant#isDefaultForKind default value} for its kind.
264 *
265 * @param value a value read from a {@link Stable} field
266 * @param receiverClass the {@link Object#getClass() class} of object from which the
267 * {@code value} was read
268 */
269 protected boolean isStableInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) {
270 return !value.isDefaultForKind();
271 }
272
273 public JavaConstant readConstantFieldValue(ResolvedJavaField field, JavaConstant receiver) {
274 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
275
276 if (hotspotField.isStatic()) {
277 if (isStaticFieldConstant(hotspotField)) {
278 JavaConstant value = readFieldValue(field, receiver);
279 if (hotspotField.isFinal() || !value.isDefaultForKind()) {
280 return value;
281 }
282 }
283 } else {
284 /*
285 * for non-static final fields, we must assume that they are only initialized if they
286 * have a non-default value.
287 */
288 Object object = receiver.isNull() ? null : ((HotSpotObjectConstantImpl) receiver).object();
289
290 // Canonicalization may attempt to process an unsafe read before
291 // processing a guard (e.g. a null check or a type check) for this read
292 // so we need to check the object being read
293 if (object != null) {
294 if (hotspotField.isFinal()) {
295 if (hotspotField.isInObject(object)) {
296 JavaConstant value = readFieldValue(field, receiver);
297 if (isFinalInstanceFieldValueConstant(value, object.getClass())) {
298 return value;
299 }
300 }
301 } else if (hotspotField.isStable() && runtime.getConfig().foldStableValues) {
302 if (hotspotField.isInObject(object)) {
303 JavaConstant value = readFieldValue(field, receiver);
304 if (isStableInstanceFieldValueConstant(value, object.getClass())) {
305 return value;
306 }
307 }
308 }
309 }
310 }
311 return null;
312 }
313
314 public JavaConstant readFieldValue(ResolvedJavaField field, JavaConstant receiver) {
315 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
316 if (!hotspotField.isStable()) {
317 return readNonStableFieldValue(field, receiver);
318 } else if (runtime.getConfig().foldStableValues) {
319 return readStableFieldValue(field, receiver, hotspotField.isDefaultStable());
320 } else {
321 return null;
322 }
323 }
324
325 private JavaConstant readNonStableFieldValue(ResolvedJavaField field, JavaConstant receiver) {
326 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
327 if (hotspotField.isStatic()) {
328 HotSpotResolvedJavaType holder = (HotSpotResolvedJavaType) hotspotField.getDeclaringClass();
329 if (holder.isInitialized()) {
330 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), HotSpotObjectConstantImpl.forObject(holder.mirror()), hotspotField.offset());
331 }
332 } else {
333 if (receiver.isNonNull() && hotspotField.isInObject(((HotSpotObjectConstantImpl) receiver).object())) {
334 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), receiver, hotspotField.offset());
335 }
336 }
337 return null;
338 }
339
340 public JavaConstant readStableFieldValue(ResolvedJavaField field, JavaConstant receiver, boolean isDefaultStable) {
341 JavaConstant fieldValue = readNonStableFieldValue(field, receiver);
342 if (fieldValue.isNonNull()) {
343 JavaType declaredType = field.getType();
344 if (declaredType.getComponentType() != null) {
345 int stableDimension = getArrayDimension(declaredType);
346 return HotSpotObjectConstantImpl.forStableArray(((HotSpotObjectConstantImpl) fieldValue).object(), stableDimension, isDefaultStable);
347 }
348 }
349 return fieldValue;
350 }
351
352 private static int getArrayDimension(JavaType type) {
353 int dimensions = 0;
354 JavaType componentType = type;
355 while ((componentType = componentType.getComponentType()) != null) {
356 dimensions++;
357 }
358 return dimensions;
359 }
360
361 @Override
362 public JavaConstant asJavaClass(ResolvedJavaType type) {
363 return HotSpotObjectConstantImpl.forObject(((HotSpotResolvedJavaType) type).mirror());
364 }
365
366 @Override
367 public Constant asObjectHub(ResolvedJavaType type) {
368 if (type instanceof HotSpotResolvedObjectType) {
369 return ((HotSpotResolvedObjectType) type).klass();
370 } else {
371 throw JVMCIError.unimplemented();
372 }
373 }
374 }