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.internal.vm.annotation.Stable;
32 import jdk.vm.ci.common.JVMCIError;
33 import jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.Option;
34 import jdk.vm.ci.meta.Constant;
35 import jdk.vm.ci.meta.ConstantReflectionProvider;
36 import jdk.vm.ci.meta.JavaConstant;
37 import jdk.vm.ci.meta.JavaKind;
38 import jdk.vm.ci.meta.JavaType;
39 import jdk.vm.ci.meta.MemoryAccessProvider;
40 import jdk.vm.ci.meta.MethodHandleAccessProvider;
41 import jdk.vm.ci.meta.ResolvedJavaField;
42 import jdk.vm.ci.meta.ResolvedJavaType;
43
44 /**
45 * HotSpot implementation of {@link ConstantReflectionProvider}.
46 */
47 public class HotSpotConstantReflectionProvider implements ConstantReflectionProvider, HotSpotProxified {
48
49 protected final HotSpotJVMCIRuntimeProvider runtime;
50 protected final HotSpotMethodHandleAccessProvider methodHandleAccess;
51 protected final HotSpotMemoryAccessProviderImpl memoryAccess;
52
53 public HotSpotConstantReflectionProvider(HotSpotJVMCIRuntimeProvider runtime) {
54 this.runtime = runtime;
55 this.methodHandleAccess = new HotSpotMethodHandleAccessProvider(this);
56 this.memoryAccess = new HotSpotMemoryAccessProviderImpl(runtime);
57 }
58
59 public MethodHandleAccessProvider getMethodHandleAccess() {
60 return methodHandleAccess;
61 }
62
63 @Override
64 public MemoryAccessProvider getMemoryAccessProvider() {
65 return memoryAccess;
66 }
67
68 @Override
69 public Boolean constantEquals(Constant x, Constant y) {
70 if (x == y) {
71 return true;
72 } else if (x instanceof HotSpotObjectConstantImpl) {
73 return y instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) x).object() == ((HotSpotObjectConstantImpl) y).object();
74 } else {
75 return Objects.equals(x, y);
76 }
77 }
78
79 @Override
80 public Integer readArrayLength(JavaConstant array) {
81 if (array == null || array.getJavaKind() != JavaKind.Object || array.isNull()) {
82 return null;
83 }
84
85 Object arrayObject = ((HotSpotObjectConstantImpl) array).object();
86 if (!arrayObject.getClass().isArray()) {
87 return null;
88 }
89 return Array.getLength(arrayObject);
90 }
91
92 public JavaConstant readConstantArrayElement(JavaConstant array, int index) {
93 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) {
94 JavaConstant element = readArrayElement(array, index);
95 if (element != null && (((HotSpotObjectConstantImpl) array).isDefaultStable() || !element.isDefaultForKind())) {
96 return element;
97 }
98 }
99 return null;
100 }
101
102 /**
103 * Try to convert {@code offset} into an an index into {@code array}.
104 *
105 * @return the computed index or -1 if the offset isn't within the array
106 */
107 private int indexForOffset(JavaConstant array, long offset) {
108 if (array.getJavaKind() != JavaKind.Object || array.isNull()) {
109 return -1;
110 }
111 Class<?> componentType = ((HotSpotObjectConstantImpl) array).object().getClass().getComponentType();
112 JavaKind kind = runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType(componentType).getJavaKind();
113 int arraybase = getArrayBaseOffset(kind);
114 int scale = getArrayIndexScale(kind);
115 if (offset < arraybase) {
116 return -1;
117 }
118 long index = offset - arraybase;
119 if (index % scale != 0) {
120 return -1;
121 }
122 long result = index / scale;
123 if (result >= Integer.MAX_VALUE) {
124 return -1;
125 }
126 return (int) result;
127 }
128
129 public JavaConstant readConstantArrayElementForOffset(JavaConstant array, long offset) {
130 if (array instanceof HotSpotObjectConstantImpl && ((HotSpotObjectConstantImpl) array).getStableDimension() > 0) {
131 return readConstantArrayElement(array, indexForOffset(array, offset));
132 }
133 return null;
134 }
135
136 @Override
137 public JavaConstant readArrayElement(JavaConstant array, int index) {
138 if (array == null || array.getJavaKind() != JavaKind.Object || array.isNull()) {
139 return null;
140 }
141 Object a = ((HotSpotObjectConstantImpl) array).object();
142
143 if (!a.getClass().isArray() || index < 0 || index >= Array.getLength(a)) {
144 return null;
145 }
146
147 if (a instanceof Object[]) {
148 Object element = ((Object[]) a)[index];
149 if (((HotSpotObjectConstantImpl) array).getStableDimension() > 1) {
150 return HotSpotObjectConstantImpl.forStableArray(element, ((HotSpotObjectConstantImpl) array).getStableDimension() - 1, ((HotSpotObjectConstantImpl) array).isDefaultStable());
151 } else {
152 return HotSpotObjectConstantImpl.forObject(element);
153 }
154 } else {
155 return JavaConstant.forBoxedPrimitive(Array.get(a, index));
156 }
157 }
158
159 /**
160 * Check if the constant is a boxed value that is guaranteed to be cached by the platform.
161 * Otherwise the generated code might be the only reference to the boxed value and since object
162 * references from nmethods are weak this can cause GC problems.
163 *
164 * @param source
165 * @return true if the box is cached
166 */
167 private static boolean isBoxCached(JavaConstant source) {
168 switch (source.getJavaKind()) {
169 case Boolean:
170 return true;
171 case Char:
172 return source.asInt() <= 127;
173 case Byte:
174 case Short:
175 case Int:
176 return source.asInt() >= -128 && source.asInt() <= 127;
177 case Long:
178 return source.asLong() >= -128 && source.asLong() <= 127;
179 case Float:
180 case Double:
181 return false;
182 default:
183 throw new IllegalArgumentException("unexpected kind " + source.getJavaKind());
184 }
185 }
186
187 @Override
188 public JavaConstant boxPrimitive(JavaConstant source) {
189 if (source == null || !source.getJavaKind().isPrimitive() || !isBoxCached(source)) {
190 return null;
191 }
192 return HotSpotObjectConstantImpl.forObject(source.asBoxedPrimitive());
193 }
194
195 @Override
196 public JavaConstant unboxPrimitive(JavaConstant source) {
197 if (source == null || !source.getJavaKind().isObject()) {
198 return null;
199 }
200 if (source.isNull()) {
201 return null;
202 }
203 return JavaConstant.forBoxedPrimitive(((HotSpotObjectConstantImpl) source).object());
204 }
205
206 public JavaConstant forString(String value) {
207 return HotSpotObjectConstantImpl.forObject(value);
208 }
209
210 public JavaConstant forObject(Object value) {
211 return HotSpotObjectConstantImpl.forObject(value);
212 }
213
214 @Override
215 public ResolvedJavaType asJavaType(Constant constant) {
216 if (constant instanceof HotSpotObjectConstant) {
217 Object obj = ((HotSpotObjectConstantImpl) constant).object();
218 if (obj instanceof Class) {
219 return runtime.getHostJVMCIBackend().getMetaAccess().lookupJavaType((Class<?>) obj);
220 }
221 }
222 if (constant instanceof HotSpotMetaspaceConstant) {
223 MetaspaceWrapperObject obj = HotSpotMetaspaceConstantImpl.getMetaspaceObject(constant);
224 if (obj instanceof HotSpotResolvedObjectTypeImpl) {
225 return (ResolvedJavaType) obj;
226 }
227 }
228 return null;
229 }
230
231 private static final String SystemClassName = "Ljava/lang/System;";
232
233 /**
234 * Determines if a static field is constant for the purpose of
235 * {@link #readConstantFieldValue(ResolvedJavaField, JavaConstant)}.
236 */
237 protected boolean isStaticFieldConstant(HotSpotResolvedJavaField staticField) {
238 if (staticField.isFinal() || (staticField.isStable() && runtime.getConfig().foldStableValues)) {
239 ResolvedJavaType holder = staticField.getDeclaringClass();
240 if (holder.isInitialized() && !holder.getName().equals(SystemClassName)) {
241 return true;
242 }
243 }
244 return false;
245 }
246
247 /**
248 * Determines if a value read from a {@code final} instance field is considered constant. The
249 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is
250 * not the {@link JavaConstant#isDefaultForKind default value} for its kind or if
251 * {@link Option#TrustFinalDefaultFields} is true.
252 *
253 * @param value a value read from a {@code final} instance field
254 * @param receiverClass the {@link Object#getClass() class} of object from which the
255 * {@code value} was read
256 */
257 protected boolean isFinalInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) {
258 return !value.isDefaultForKind() || Option.TrustFinalDefaultFields.getBoolean();
259 }
260
261 /**
262 * Determines if a value read from a {@link Stable} instance field is considered constant. The
263 * implementation in {@link HotSpotConstantReflectionProvider} returns true if {@code value} is
264 * not the {@link JavaConstant#isDefaultForKind default value} for its kind.
265 *
266 * @param value a value read from a {@link Stable} field
267 * @param receiverClass the {@link Object#getClass() class} of object from which the
268 * {@code value} was read
269 */
270 protected boolean isStableInstanceFieldValueConstant(JavaConstant value, Class<?> receiverClass) {
271 return !value.isDefaultForKind();
272 }
273
274 public JavaConstant readConstantFieldValue(ResolvedJavaField field, JavaConstant receiver) {
275 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
276
277 if (hotspotField.isStatic()) {
278 if (isStaticFieldConstant(hotspotField)) {
279 JavaConstant value = readFieldValue(field, receiver);
280 if (hotspotField.isFinal() || !value.isDefaultForKind()) {
281 return value;
282 }
283 }
284 } else {
285 /*
286 * for non-static final fields, we must assume that they are only initialized if they
287 * have a non-default value.
288 */
289 Object object = receiver.isNull() ? null : ((HotSpotObjectConstantImpl) receiver).object();
290
291 // Canonicalization may attempt to process an unsafe read before
292 // processing a guard (e.g. a null check or a type check) for this read
293 // so we need to check the object being read
294 if (object != null) {
295 if (hotspotField.isFinal()) {
296 if (hotspotField.isInObject(object)) {
297 JavaConstant value = readFieldValue(field, receiver);
298 if (isFinalInstanceFieldValueConstant(value, object.getClass())) {
299 return value;
300 }
301 }
302 } else if (hotspotField.isStable() && runtime.getConfig().foldStableValues) {
303 if (hotspotField.isInObject(object)) {
304 JavaConstant value = readFieldValue(field, receiver);
305 if (isStableInstanceFieldValueConstant(value, object.getClass())) {
306 return value;
307 }
308 }
309 }
310 }
311 }
312 return null;
313 }
314
315 public JavaConstant readFieldValue(ResolvedJavaField field, JavaConstant receiver) {
316 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
317 if (!hotspotField.isStable()) {
318 return readNonStableFieldValue(field, receiver);
319 } else if (runtime.getConfig().foldStableValues) {
320 return readStableFieldValue(field, receiver, hotspotField.isDefaultStable());
321 } else {
322 return null;
323 }
324 }
325
326 private JavaConstant readNonStableFieldValue(ResolvedJavaField field, JavaConstant receiver) {
327 HotSpotResolvedJavaField hotspotField = (HotSpotResolvedJavaField) field;
328 if (hotspotField.isStatic()) {
329 HotSpotResolvedJavaType holder = (HotSpotResolvedJavaType) hotspotField.getDeclaringClass();
330 if (holder.isInitialized()) {
331 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), HotSpotObjectConstantImpl.forObject(holder.mirror()), hotspotField.offset());
332 }
333 } else {
334 if (receiver.isNonNull() && hotspotField.isInObject(((HotSpotObjectConstantImpl) receiver).object())) {
335 return memoryAccess.readUnsafeConstant(hotspotField.getJavaKind(), receiver, hotspotField.offset());
336 }
337 }
338 return null;
339 }
340
341 public JavaConstant readStableFieldValue(ResolvedJavaField field, JavaConstant receiver, boolean isDefaultStable) {
342 JavaConstant fieldValue = readNonStableFieldValue(field, receiver);
343 if (fieldValue != null && fieldValue.isNonNull()) {
344 JavaType declaredType = field.getType();
345 if (declaredType.getComponentType() != null) {
346 int stableDimension = getArrayDimension(declaredType);
347 return HotSpotObjectConstantImpl.forStableArray(((HotSpotObjectConstantImpl) fieldValue).object(), stableDimension, isDefaultStable);
348 }
349 }
350 return fieldValue;
351 }
352
353 private static int getArrayDimension(JavaType type) {
354 int dimensions = 0;
355 JavaType componentType = type;
356 while ((componentType = componentType.getComponentType()) != null) {
357 dimensions++;
358 }
359 return dimensions;
360 }
361
362 @Override
363 public JavaConstant asJavaClass(ResolvedJavaType type) {
364 return HotSpotObjectConstantImpl.forObject(((HotSpotResolvedJavaType) type).mirror());
365 }
366
367 @Override
368 public Constant asObjectHub(ResolvedJavaType type) {
369 if (type instanceof HotSpotResolvedObjectType) {
370 return ((HotSpotResolvedObjectType) type).klass();
371 } else {
372 throw JVMCIError.unimplemented();
373 }
374 }
375 }