Thu, 14 Feb 2013 13:22:26 +0100
8008085: Integrate Dynalink source code into Nashorn codebase
Reviewed-by: jlaskey, lagergren, sundar
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
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10 *
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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).
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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.util.Iterator;
90 import java.util.LinkedList;
91 import java.util.concurrent.atomic.AtomicReference;
92 import jdk.internal.dynalink.linker.GuardedInvocation;
93 import jdk.internal.dynalink.support.AbstractRelinkableCallSite;
96 /**
97 * A relinkable call site that maintains a chain of linked method handles. In the default implementation, up to 8 method
98 * handles can be chained, cascading from one to the other through
99 * {@link MethodHandles#guardWithTest(MethodHandle, MethodHandle, MethodHandle)}. When this call site has to link a new
100 * method handle and the length of the chain is already at the maximum, it will throw away the oldest method handle.
101 * Switchpoint-invalidated handles in the chain are removed eagerly (on each linking request, and whenever a
102 * switchpoint-invalidated method handle is traversed during invocation). There is currently no profiling
103 * attached to the handles in the chain, so they are never reordered based on usage; the most recently linked method
104 * handle is always at the start of the chain.
105 */
106 public class ChainedCallSite extends AbstractRelinkableCallSite {
107 private final AtomicReference<LinkedList<GuardedInvocation>> invocations = new AtomicReference<>();
109 /**
110 * Creates a new chained call site.
111 * @param descriptor the descriptor for the call site.
112 */
113 public ChainedCallSite(CallSiteDescriptor descriptor) {
114 super(descriptor);
115 }
117 /**
118 * The maximum number of method handles in the chain. Defaults to 8. You can override it in a subclass if you need
119 * to change the value. If your override returns a value less than 1, the code will break.
120 * @return the maximum number of method handles in the chain.
121 */
122 @SuppressWarnings("static-method")
123 protected int getMaxChainLength() {
124 return 8;
125 }
127 @Override
128 public void relink(GuardedInvocation guardedInvocation, MethodHandle fallback) {
129 relinkInternal(guardedInvocation, fallback, false);
130 }
132 @Override
133 public void resetAndRelink(GuardedInvocation guardedInvocation, MethodHandle fallback) {
134 relinkInternal(guardedInvocation, fallback, true);
135 }
137 private MethodHandle relinkInternal(GuardedInvocation invocation, MethodHandle relink, boolean reset) {
138 final LinkedList<GuardedInvocation> currentInvocations = invocations.get();
139 @SuppressWarnings({ "unchecked", "rawtypes" })
140 final LinkedList<GuardedInvocation> newInvocations =
141 currentInvocations == null || reset ? new LinkedList<>() : (LinkedList)currentInvocations.clone();
143 // First, prune the chain of invalidated switchpoints.
144 for(Iterator<GuardedInvocation> it = newInvocations.iterator(); it.hasNext();) {
145 if(it.next().hasBeenInvalidated()) {
146 it.remove();
147 }
148 }
150 // prune() is allowed to invoke this method with invocation == null meaning we're just pruning the chain and not
151 // adding any new invocations to it.
152 if(invocation != null) {
153 // Remove oldest entry if we're at max length
154 if(newInvocations.size() == getMaxChainLength()) {
155 newInvocations.removeFirst();
156 }
157 newInvocations.addLast(invocation);
158 }
160 // prune-and-invoke is used as the fallback for invalidated switchpoints. If a switchpoint gets invalidated, we
161 // rebuild the chain and get rid of all invalidated switchpoints instead of letting them linger.
162 final MethodHandle pruneAndInvoke = makePruneAndInvokeMethod(relink);
164 // Fold the new chain
165 MethodHandle target = relink;
166 for(GuardedInvocation inv: newInvocations) {
167 target = inv.compose(pruneAndInvoke, target);
168 }
170 // If nobody else updated the call site while we were rebuilding the chain, set the target to our chain. In case
171 // we lost the race for multithreaded update, just do nothing. Either the other thread installed the same thing
172 // we wanted to install, or otherwise, we'll be asked to relink again.
173 if(invocations.compareAndSet(currentInvocations, newInvocations)) {
174 setTarget(target);
175 }
176 return target;
177 }
179 /**
180 * Creates a method that rebuilds our call chain, pruning it of any invalidated switchpoints, and then invokes that
181 * chain.
182 * @param relink the ultimate fallback for the chain (the {@code DynamicLinker}'s relink).
183 * @return a method handle for prune-and-invoke
184 */
185 private MethodHandle makePruneAndInvokeMethod(MethodHandle relink) {
186 // Bind prune to (this, relink)
187 final MethodHandle boundPrune = MethodHandles.insertArguments(PRUNE, 0, this, relink);
188 // Make it ignore all incoming arguments
189 final MethodHandle ignoreArgsPrune = MethodHandles.dropArguments(boundPrune, 0, type().parameterList());
190 // Invoke prune, then invoke the call site target with original arguments
191 return MethodHandles.foldArguments(MethodHandles.exactInvoker(type()), ignoreArgsPrune);
192 }
194 @SuppressWarnings("unused")
195 private MethodHandle prune(MethodHandle relink) {
196 return relinkInternal(null, relink, false);
197 }
199 private static final MethodHandle PRUNE;
200 static {
201 try {
202 PRUNE = MethodHandles.lookup().findSpecial(ChainedCallSite.class, "prune", MethodType.methodType(
203 MethodHandle.class, MethodHandle.class), ChainedCallSite.class);
204 // NOTE: using two catch blocks so we don't introduce a reference to 1.7 ReflectiveOperationException, allowing
205 // Dynalink to be used on 1.6 JVMs with Remi's backport library.
206 } catch(IllegalAccessException e) {
207 throw new AssertionError(e.getMessage(), e); // Can not happen
208 } catch(NoSuchMethodException e) {
209 throw new AssertionError(e.getMessage(), e); // Can not happen
210 }
211 }
212 }