Thu, 31 Aug 2017 15:30:47 +0800
merge
1 /*
2 * Copyright (c) 2010, 2013, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
26 /*
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file, and Oracle licenses the original version of this file under the BSD
31 * license:
32 */
33 /*
34 Copyright 2009-2013 Attila Szegedi
36 Licensed under both the Apache License, Version 2.0 (the "Apache License")
37 and the BSD License (the "BSD License"), with licensee being free to
38 choose either of the two at their discretion.
40 You may not use this file except in compliance with either the Apache
41 License or the BSD License.
43 If you choose to use this file in compliance with the Apache License, the
44 following notice applies to you:
46 You may obtain a copy of the Apache License at
48 http://www.apache.org/licenses/LICENSE-2.0
50 Unless required by applicable law or agreed to in writing, software
51 distributed under the License is distributed on an "AS IS" BASIS,
52 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
53 implied. See the License for the specific language governing
54 permissions and limitations under the License.
56 If you choose to use this file in compliance with the BSD License, the
57 following notice applies to you:
59 Redistribution and use in source and binary forms, with or without
60 modification, are permitted provided that the following conditions are
61 met:
62 * Redistributions of source code must retain the above copyright
63 notice, this list of conditions and the following disclaimer.
64 * Redistributions in binary form must reproduce the above copyright
65 notice, this list of conditions and the following disclaimer in the
66 documentation and/or other materials provided with the distribution.
67 * Neither the name of the copyright holder nor the names of
68 contributors may be used to endorse or promote products derived from
69 this software without specific prior written permission.
71 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
72 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
73 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
74 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
75 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
76 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
77 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
78 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
79 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
80 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
81 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
82 */
84 package jdk.internal.dynalink;
86 import java.lang.invoke.MethodHandle;
87 import java.lang.invoke.MethodHandles;
88 import java.lang.invoke.MethodType;
89 import java.lang.invoke.MutableCallSite;
90 import java.util.List;
91 import jdk.internal.dynalink.linker.GuardedInvocation;
92 import jdk.internal.dynalink.linker.GuardingDynamicLinker;
93 import jdk.internal.dynalink.linker.LinkRequest;
94 import jdk.internal.dynalink.linker.LinkerServices;
95 import jdk.internal.dynalink.support.CallSiteDescriptorFactory;
96 import jdk.internal.dynalink.support.LinkRequestImpl;
97 import jdk.internal.dynalink.support.Lookup;
98 import jdk.internal.dynalink.support.RuntimeContextLinkRequestImpl;
100 /**
101 * The linker for {@link RelinkableCallSite} objects. Users of it (scripting frameworks and language runtimes) have to
102 * create a linker using the {@link DynamicLinkerFactory} and invoke its link method from the invokedynamic bootstrap
103 * methods to set the target of all the call sites in the code they generate. Usual usage would be to create one class
104 * per language runtime to contain one linker instance as:
105 *
106 * <pre>
107 * class MyLanguageRuntime {
108 * private static final GuardingDynamicLinker myLanguageLinker = new MyLanguageLinker();
109 * private static final DynamicLinker dynamicLinker = createDynamicLinker();
110 *
111 * private static DynamicLinker createDynamicLinker() {
112 * final DynamicLinkerFactory factory = new DynamicLinkerFactory();
113 * factory.setPrioritizedLinker(myLanguageLinker);
114 * return factory.createLinker();
115 * }
116 *
117 * public static CallSite bootstrap(MethodHandles.Lookup caller, String name, MethodType type) {
118 * return dynamicLinker.link(new MonomorphicCallSite(CallSiteDescriptorFactory.create(lookup, name, type)));
119 * }
120 * }
121 * </pre>
122 *
123 * Note how there are three components you will need to provide here:
124 * <ul>
125 * <li>You're expected to provide a {@link GuardingDynamicLinker} for your own language. If your runtime doesn't
126 * have its own language and/or object model (i.e. it's a generic scripting shell), you don't need to implement a
127 * dynamic linker; you would simply not invoke the {@code setPrioritizedLinker} method on the factory, or even better,
128 * simply use {@link DefaultBootstrapper}.</li>
129 * <li>The performance of the programs can depend on your choice of the class to represent call sites. The above
130 * example used {@link MonomorphicCallSite}, but you might want to use {@link ChainedCallSite} instead. You'll need to
131 * experiment and decide what fits your language runtime the best. You can subclass either of these or roll your own if
132 * you need to.</li>
133 * <li>You also need to provide {@link CallSiteDescriptor}s to your call sites. They are immutable objects that contain
134 * all the information about the call site: the class performing the lookups, the name of the method being invoked, and
135 * the method signature. The library has a default {@link CallSiteDescriptorFactory} for descriptors that you can use,
136 * or you can create your own descriptor classes, especially if you need to add further information (values passed in
137 * additional parameters to the bootstrap method) to them.</li>
138 * </ul>
139 *
140 * @author Attila Szegedi
141 */
142 public class DynamicLinker {
144 private static final String CLASS_NAME = DynamicLinker.class.getName();
145 private static final String RELINK_METHOD_NAME = "relink";
147 private static final String INITIAL_LINK_CLASS_NAME = "java.lang.invoke.MethodHandleNatives";
148 private static final String INITIAL_LINK_METHOD_NAME = "linkCallSite";
150 private final LinkerServices linkerServices;
151 private final int runtimeContextArgCount;
152 private final boolean syncOnRelink;
153 private final int unstableRelinkThreshold;
155 /**
156 * Creates a new dynamic linker.
157 *
158 * @param linkerServices the linkerServices used by the linker, created by the factory.
159 * @param runtimeContextArgCount see {@link DynamicLinkerFactory#setRuntimeContextArgCount(int)}
160 */
161 DynamicLinker(LinkerServices linkerServices, int runtimeContextArgCount, boolean syncOnRelink,
162 int unstableRelinkThreshold) {
163 if(runtimeContextArgCount < 0) {
164 throw new IllegalArgumentException("runtimeContextArgCount < 0");
165 }
166 if(unstableRelinkThreshold < 0) {
167 throw new IllegalArgumentException("unstableRelinkThreshold < 0");
168 }
169 this.runtimeContextArgCount = runtimeContextArgCount;
170 this.linkerServices = linkerServices;
171 this.syncOnRelink = syncOnRelink;
172 this.unstableRelinkThreshold = unstableRelinkThreshold;
173 }
175 /**
176 * Links an invokedynamic call site. It will install a method handle into the call site that invokes the relinking
177 * mechanism of this linker. Next time the call site is invoked, it will be linked for the actual arguments it was
178 * invoked with.
179 *
180 * @param callSite the call site to link.
181 * @return the callSite, for easy call chaining.
182 */
183 public <T extends RelinkableCallSite> T link(final T callSite) {
184 callSite.initialize(createRelinkAndInvokeMethod(callSite, 0));
185 return callSite;
186 }
188 /**
189 * Returns the object representing the lower level linker services of this class that are normally exposed to
190 * individual language-specific linkers. While as a user of this class you normally only care about the
191 * {@link #link(RelinkableCallSite)} method, in certain circumstances you might want to use the lower level services
192 * directly; either to lookup specific method handles, to access the type converters, and so on.
193 * @return the object representing the linker services of this class.
194 */
195 public LinkerServices getLinkerServices() {
196 return linkerServices;
197 }
199 private static final MethodHandle RELINK = Lookup.findOwnSpecial(MethodHandles.lookup(), RELINK_METHOD_NAME,
200 MethodHandle.class, RelinkableCallSite.class, int.class, Object[].class);
202 private MethodHandle createRelinkAndInvokeMethod(final RelinkableCallSite callSite, int relinkCount) {
203 // Make a bound MH of invoke() for this linker and call site
204 final MethodHandle boundRelinker = MethodHandles.insertArguments(RELINK, 0, this, callSite, Integer.valueOf(
205 relinkCount));
206 // Make a MH that gathers all arguments to the invocation into an Object[]
207 final MethodType type = callSite.getDescriptor().getMethodType();
208 final MethodHandle collectingRelinker = boundRelinker.asCollector(Object[].class, type.parameterCount());
209 return MethodHandles.foldArguments(MethodHandles.exactInvoker(type), collectingRelinker.asType(
210 type.changeReturnType(MethodHandle.class)));
211 }
213 /**
214 * Relinks a call site conforming to the invocation arguments.
215 *
216 * @param callSite the call site itself
217 * @param arguments arguments to the invocation
218 * @return return the method handle for the invocation
219 * @throws Exception rethrows any exception thrown by the linkers
220 */
221 @SuppressWarnings("unused")
222 private MethodHandle relink(RelinkableCallSite callSite, int relinkCount, Object... arguments) throws Exception {
223 final CallSiteDescriptor callSiteDescriptor = callSite.getDescriptor();
224 final boolean unstableDetectionEnabled = unstableRelinkThreshold > 0;
225 final boolean callSiteUnstable = unstableDetectionEnabled && relinkCount >= unstableRelinkThreshold;
226 final LinkRequest linkRequest =
227 runtimeContextArgCount == 0 ? new LinkRequestImpl(callSiteDescriptor, callSiteUnstable, arguments)
228 : new RuntimeContextLinkRequestImpl(callSiteDescriptor, callSiteUnstable, arguments,
229 runtimeContextArgCount);
231 // Find a suitable method handle with a guard
232 GuardedInvocation guardedInvocation = linkerServices.getGuardedInvocation(linkRequest);
234 // None found - throw an exception
235 if(guardedInvocation == null) {
236 throw new NoSuchDynamicMethodException(callSiteDescriptor.toString());
237 }
239 // If our call sites have a runtime context, and the linker produced a context-stripped invocation, adapt the
240 // produced invocation into contextual invocation (by dropping the context...)
241 if(runtimeContextArgCount > 0) {
242 final MethodType origType = callSiteDescriptor.getMethodType();
243 final MethodHandle invocation = guardedInvocation.getInvocation();
244 if(invocation.type().parameterCount() == origType.parameterCount() - runtimeContextArgCount) {
245 final List<Class<?>> prefix = origType.parameterList().subList(1, runtimeContextArgCount + 1);
246 final MethodHandle guard = guardedInvocation.getGuard();
247 guardedInvocation = guardedInvocation.dropArguments(1, prefix);
248 }
249 }
251 int newRelinkCount = relinkCount;
252 // Note that the short-circuited "&&" evaluation below ensures we'll increment the relinkCount until
253 // threshold + 1 but not beyond that. Threshold + 1 is treated as a special value to signal that resetAndRelink
254 // has already executed once for the unstable call site; we only want the call site to throw away its current
255 // linkage once, when it transitions to unstable.
256 if(unstableDetectionEnabled && newRelinkCount <= unstableRelinkThreshold && newRelinkCount++ == unstableRelinkThreshold) {
257 callSite.resetAndRelink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
258 } else {
259 callSite.relink(guardedInvocation, createRelinkAndInvokeMethod(callSite, newRelinkCount));
260 }
261 if(syncOnRelink) {
262 MutableCallSite.syncAll(new MutableCallSite[] { (MutableCallSite)callSite });
263 }
264 return guardedInvocation.getInvocation();
265 }
267 /**
268 * Returns a stack trace element describing the location of the call site currently being linked on the current
269 * thread. The operation internally creates a Throwable object and inspects its stack trace, so it's potentially
270 * expensive. The recommended usage for it is in writing diagnostics code.
271 * @return a stack trace element describing the location of the call site currently being linked, or null if it is
272 * not invoked while a call site is being linked.
273 */
274 public static StackTraceElement getLinkedCallSiteLocation() {
275 final StackTraceElement[] trace = new Throwable().getStackTrace();
276 for(int i = 0; i < trace.length - 1; ++i) {
277 final StackTraceElement frame = trace[i];
278 if(isRelinkFrame(frame) || isInitialLinkFrame(frame)) {
279 return trace[i + 1];
280 }
281 }
282 return null;
283 }
285 /**
286 * Deprecated because of not precise name.
287 * @deprecated Use {@link #getLinkedCallSiteLocation()} instead.
288 * @return see non-deprecated method
289 */
290 @Deprecated
291 public static StackTraceElement getRelinkedCallSiteLocation() {
292 return getLinkedCallSiteLocation();
293 }
295 /**
296 * Returns true if the frame represents {@code MethodHandleNatives.linkCallSite()}, the frame immediately on top of
297 * the call site frame when the call site is being linked for the first time.
298 * @param frame the frame
299 * @return true if this frame represents {@code MethodHandleNatives.linkCallSite()}
300 */
301 private static boolean isInitialLinkFrame(final StackTraceElement frame) {
302 return testFrame(frame, INITIAL_LINK_METHOD_NAME, INITIAL_LINK_CLASS_NAME);
303 }
305 /**
306 * Returns true if the frame represents {@code DynamicLinker.relink()}, the frame immediately on top of the call
307 * site frame when the call site is being relinked (linked for second and subsequent times).
308 * @param frame the frame
309 * @return true if this frame represents {@code DynamicLinker.relink()}
310 */
311 private static boolean isRelinkFrame(final StackTraceElement frame) {
312 return testFrame(frame, RELINK_METHOD_NAME, CLASS_NAME);
313 }
315 private static boolean testFrame(final StackTraceElement frame, final String methodName, final String className) {
316 return methodName.equals(frame.getMethodName()) && className.equals(frame.getClassName());
317 }
318 }