attila@90: /*
attila@90:  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
attila@90:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
attila@90:  *
attila@90:  * This code is free software; you can redistribute it and/or modify it
attila@90:  * under the terms of the GNU General Public License version 2 only, as
attila@90:  * published by the Free Software Foundation.  Oracle designates this
attila@90:  * particular file as subject to the "Classpath" exception as provided
attila@90:  * by Oracle in the LICENSE file that accompanied this code.
attila@90:  *
attila@90:  * This code is distributed in the hope that it will be useful, but WITHOUT
attila@90:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
attila@90:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
attila@90:  * version 2 for more details (a copy is included in the LICENSE file that
attila@90:  * accompanied this code).
attila@90:  *
attila@90:  * You should have received a copy of the GNU General Public License version
attila@90:  * 2 along with this work; if not, write to the Free Software Foundation,
attila@90:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
attila@90:  *
attila@90:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
attila@90:  * or visit www.oracle.com if you need additional information or have any
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attila@90:  */
attila@90: 
attila@90: /*
attila@90:  * This file is available under and governed by the GNU General Public
attila@90:  * License version 2 only, as published by the Free Software Foundation.
attila@90:  * However, the following notice accompanied the original version of this
attila@90:  * file, and Oracle licenses the original version of this file under the BSD
attila@90:  * license:
attila@90:  */
attila@90: /*
attila@90:    Copyright 2009-2013 Attila Szegedi
attila@90: 
attila@90:    Licensed under both the Apache License, Version 2.0 (the "Apache License")
attila@90:    and the BSD License (the "BSD License"), with licensee being free to
attila@90:    choose either of the two at their discretion.
attila@90: 
attila@90:    You may not use this file except in compliance with either the Apache
attila@90:    License or the BSD License.
attila@90: 
attila@90:    If you choose to use this file in compliance with the Apache License, the
attila@90:    following notice applies to you:
attila@90: 
attila@90:        You may obtain a copy of the Apache License at
attila@90: 
attila@90:            http://www.apache.org/licenses/LICENSE-2.0
attila@90: 
attila@90:        Unless required by applicable law or agreed to in writing, software
attila@90:        distributed under the License is distributed on an "AS IS" BASIS,
attila@90:        WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
attila@90:        implied. See the License for the specific language governing
attila@90:        permissions and limitations under the License.
attila@90: 
attila@90:    If you choose to use this file in compliance with the BSD License, the
attila@90:    following notice applies to you:
attila@90: 
attila@90:        Redistribution and use in source and binary forms, with or without
attila@90:        modification, are permitted provided that the following conditions are
attila@90:        met:
attila@90:        * Redistributions of source code must retain the above copyright
attila@90:          notice, this list of conditions and the following disclaimer.
attila@90:        * Redistributions in binary form must reproduce the above copyright
attila@90:          notice, this list of conditions and the following disclaimer in the
attila@90:          documentation and/or other materials provided with the distribution.
attila@90:        * Neither the name of the copyright holder nor the names of
attila@90:          contributors may be used to endorse or promote products derived from
attila@90:          this software without specific prior written permission.
attila@90: 
attila@90:        THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
attila@90:        IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
attila@90:        TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
attila@90:        PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
attila@90:        BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
attila@90:        CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
attila@90:        SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
attila@90:        BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
attila@90:        WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
attila@90:        OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
attila@90:        ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
attila@90: */
attila@90: 
attila@90: package jdk.internal.dynalink;
attila@90: 
attila@90: import java.lang.invoke.MethodHandle;
attila@90: import java.lang.invoke.MethodHandles;
attila@90: import java.util.Iterator;
attila@90: import java.util.LinkedList;
attila@90: import java.util.concurrent.atomic.AtomicReference;
attila@90: import jdk.internal.dynalink.linker.GuardedInvocation;
attila@90: import jdk.internal.dynalink.support.AbstractRelinkableCallSite;
attila@488: import jdk.internal.dynalink.support.Lookup;
attila@90: 
attila@90: /**
attila@90:  * A relinkable call site that maintains a chain of linked method handles. In the default implementation, up to 8 method
attila@90:  * handles can be chained, cascading from one to the other through
attila@90:  * {@link MethodHandles#guardWithTest(MethodHandle, MethodHandle, MethodHandle)}. When this call site has to link a new
attila@90:  * method handle and the length of the chain is already at the maximum, it will throw away the oldest method handle.
attila@90:  * Switchpoint-invalidated handles in the chain are removed eagerly (on each linking request, and whenever a
attila@90:  * switchpoint-invalidated method handle is traversed during invocation). There is currently no profiling
attila@90:  * attached to the handles in the chain, so they are never reordered based on usage; the most recently linked method
attila@90:  * handle is always at the start of the chain.
attila@90:  */
attila@90: public class ChainedCallSite extends AbstractRelinkableCallSite {
attila@963:     private static final MethodHandle PRUNE_CATCHES =
attila@963:             MethodHandles.insertArguments(
attila@963:                     Lookup.findOwnSpecial(
attila@963:                             MethodHandles.lookup(),
attila@963:                             "prune",
attila@963:                             MethodHandle.class,
attila@963:                             MethodHandle.class,
attila@963:                             boolean.class),
attila@963:                     2,
attila@963:                     true);
attila@963: 
attila@963:     private static final MethodHandle PRUNE_SWITCHPOINTS =
attila@963:             MethodHandles.insertArguments(
attila@963:                     Lookup.findOwnSpecial(
attila@963:                             MethodHandles.lookup(),
attila@963:                             "prune",
attila@963:                             MethodHandle.class,
attila@963:                             MethodHandle.class,
attila@963:                             boolean.class),
attila@963:                     2,
attila@963:                     false);
attila@488: 
attila@90:     private final AtomicReference<LinkedList<GuardedInvocation>> invocations = new AtomicReference<>();
attila@90: 
attila@90:     /**
attila@90:      * Creates a new chained call site.
attila@90:      * @param descriptor the descriptor for the call site.
attila@90:      */
attila@962:     public ChainedCallSite(final CallSiteDescriptor descriptor) {
attila@90:         super(descriptor);
attila@90:     }
attila@90: 
attila@90:     /**
attila@90:      * The maximum number of method handles in the chain. Defaults to 8. You can override it in a subclass if you need
attila@90:      * to change the value. If your override returns a value less than 1, the code will break.
attila@90:      * @return the maximum number of method handles in the chain.
attila@90:      */
attila@90:     protected int getMaxChainLength() {
attila@90:         return 8;
attila@90:     }
attila@90: 
attila@90:     @Override
attila@962:     public void relink(final GuardedInvocation guardedInvocation, final MethodHandle fallback) {
attila@963:         relinkInternal(guardedInvocation, fallback, false, false);
attila@90:     }
attila@90: 
attila@90:     @Override
attila@962:     public void resetAndRelink(final GuardedInvocation guardedInvocation, final MethodHandle fallback) {
attila@963:         relinkInternal(guardedInvocation, fallback, true, false);
attila@90:     }
attila@90: 
attila@963:     private MethodHandle relinkInternal(final GuardedInvocation invocation, final MethodHandle relink, final boolean reset, final boolean removeCatches) {
attila@90:         final LinkedList<GuardedInvocation> currentInvocations = invocations.get();
attila@90:         @SuppressWarnings({ "unchecked", "rawtypes" })
attila@90:         final LinkedList<GuardedInvocation> newInvocations =
attila@90:             currentInvocations == null || reset ? new LinkedList<>() : (LinkedList)currentInvocations.clone();
attila@90: 
attila@963:         // First, prune the chain of invalidated switchpoints, we always do this
attila@963:         // We also remove any catches if the remove catches flag is set
attila@962:         for(final Iterator<GuardedInvocation> it = newInvocations.iterator(); it.hasNext();) {
attila@963:             final GuardedInvocation inv = it.next();
attila@963:             if(inv.hasBeenInvalidated() || (removeCatches && inv.getException() != null)) {
attila@90:                 it.remove();
attila@90:             }
attila@90:         }
attila@90: 
attila@90:         // prune() is allowed to invoke this method with invocation == null meaning we're just pruning the chain and not
attila@90:         // adding any new invocations to it.
attila@90:         if(invocation != null) {
attila@90:             // Remove oldest entry if we're at max length
attila@90:             if(newInvocations.size() == getMaxChainLength()) {
attila@90:                 newInvocations.removeFirst();
attila@90:             }
attila@90:             newInvocations.addLast(invocation);
attila@90:         }
attila@90: 
attila@90:         // prune-and-invoke is used as the fallback for invalidated switchpoints. If a switchpoint gets invalidated, we
attila@90:         // rebuild the chain and get rid of all invalidated switchpoints instead of letting them linger.
attila@963:         final MethodHandle pruneAndInvokeSwitchPoints = makePruneAndInvokeMethod(relink, getPruneSwitchpoints());
attila@963:         final MethodHandle pruneAndInvokeCatches      = makePruneAndInvokeMethod(relink, getPruneCatches());
attila@90: 
attila@90:         // Fold the new chain
attila@90:         MethodHandle target = relink;
attila@962:         for(final GuardedInvocation inv: newInvocations) {
attila@963:             target = inv.compose(target, pruneAndInvokeSwitchPoints, pruneAndInvokeCatches);
attila@90:         }
attila@90: 
attila@90:         // If nobody else updated the call site while we were rebuilding the chain, set the target to our chain. In case
attila@90:         // we lost the race for multithreaded update, just do nothing. Either the other thread installed the same thing
attila@90:         // we wanted to install, or otherwise, we'll be asked to relink again.
attila@90:         if(invocations.compareAndSet(currentInvocations, newInvocations)) {
attila@90:             setTarget(target);
attila@90:         }
attila@90:         return target;
attila@90:     }
attila@90: 
attila@90:     /**
attila@963:      * Get the switchpoint pruning function for a chained call site
attila@963:      * @return function that removes invalidated switchpoints tied to callsite guard chain and relinks
attila@963:      */
attila@963:     protected MethodHandle getPruneSwitchpoints() {
attila@963:         return PRUNE_SWITCHPOINTS;
attila@963:     }
attila@963: 
attila@963:     /**
attila@963:      * Get the catch pruning function for a chained call site
attila@963:      * @return function that removes all catches tied to callsite guard chain and relinks
attila@963:      */
attila@963:     protected MethodHandle getPruneCatches() {
attila@963:         return PRUNE_CATCHES;
attila@963:     }
attila@963: 
attila@963:     /**
attila@90:      * Creates a method that rebuilds our call chain, pruning it of any invalidated switchpoints, and then invokes that
attila@90:      * chain.
attila@90:      * @param relink the ultimate fallback for the chain (the {@code DynamicLinker}'s relink).
attila@90:      * @return a method handle for prune-and-invoke
attila@90:      */
attila@963:     private MethodHandle makePruneAndInvokeMethod(final MethodHandle relink, final MethodHandle prune) {
attila@90:         // Bind prune to (this, relink)
attila@963:         final MethodHandle boundPrune = MethodHandles.insertArguments(prune, 0, this, relink);
attila@90:         // Make it ignore all incoming arguments
attila@90:         final MethodHandle ignoreArgsPrune = MethodHandles.dropArguments(boundPrune, 0, type().parameterList());
attila@90:         // Invoke prune, then invoke the call site target with original arguments
attila@90:         return MethodHandles.foldArguments(MethodHandles.exactInvoker(type()), ignoreArgsPrune);
attila@90:     }
attila@90: 
attila@90:     @SuppressWarnings("unused")
attila@963:     private MethodHandle prune(final MethodHandle relink, final boolean catches) {
attila@963:         return relinkInternal(null, relink, false, catches);
attila@90:     }
attila@101: }