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6964498: JSR 292 invokedynamic sites need local bootstrap methods

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Add JVM_CONSTANT_InvokeDynamic records to constant pool to determine per-instruction BSMs; add MethodHandleProvider.

Reviewed-by: twisti
This commit is contained in:
John R Rose 2010-09-08 18:40:11 -07:00
parent ae1cce3a74
commit c7b608b1ed
12 changed files with 507 additions and 148 deletions
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82
jdk/src/share/classes/java/dyn/BootstrapMethod.java Normal file
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@ -0,0 +1,82 @@
/*
* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.dyn;
import java.lang.annotation.*;
/**
* Annotation on InvokeDynamic method calls which requests the JVM to use a specific
* <a href="package-summary.html#bsm">bootstrap method</a>
* to link the call. This annotation is not retained as such in the class file,
* but is transformed into a constant-pool entry for the invokedynamic instruction which
* specifies the desired bootstrap method.
* <p>
* If only the <code>value</code> is given, it must name a subclass of {@link CallSite}
* with a constructor which accepts a class, string, and method type.
* If the <code>value</code> and <code>name</code> are both given, there must be
* a static method in the given class of the given name which accepts a class, string,
* and method type, and returns a reference coercible to {@link CallSite}.
* <p>
* This annotation can be placed either on the return type of a single {@link InvokeDynamic}
* call (see examples) or else it can be placed on an enclosing class or method, where it
* determines a default bootstrap method for any {@link InvokeDynamic} calls which are not
* specifically annotated with a bootstrap method.
* Every {@link InvokeDynamic} call must be given a bootstrap method.
* <p>
* Examples:
<blockquote><pre>
&#064;BootstrapMethod(value=MyLanguageRuntime.class, name="bootstrapDynamic")
String x = (String) InvokeDynamic.greet();
//BSM => MyLanguageRuntime.bootstrapDynamic(Here.class, "greet", methodType(String.class))
&#064;BootstrapMethod(MyCallSite.class)
void example() throws Throwable {
InvokeDynamic.greet();
//BSM => new MyCallSite(Here.class, "greet", methodType(void.class))
}
</pre></blockquote>
* <p>
*/
@Target({ElementType.TYPE_USE,
// For defaulting every indy site within a class or method; cf. @SuppressWarnings:
ElementType.TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR
})
@Retention(RetentionPolicy.SOURCE)
public @interface BootstrapMethod {
/** The class containing the bootstrap method. */
Class<?> value();
/** The name of the bootstrap method.
* If this is the empty string, an instance of the bootstrap class is created,
* and a constructor is invoked.
* Otherwise, there must be a static method of the required name.
*/
String name() default ""; // empty string denotes a constructor with 'new'
/** The argument types of the bootstrap method, as passed out by the JVM.
* There is usually no reason to override the default.
*/
Class<?>[] arguments() default {Class.class, String.class, MethodType.class};
}

116
jdk/src/share/classes/java/dyn/CallSite.java
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@ -25,56 +25,26 @@
package java.dyn;
import sun.dyn.Access;
import sun.dyn.MemberName;
import sun.dyn.CallSiteImpl;
import sun.dyn.*;
import java.util.Collection;
/**
* A {@code CallSite} reifies an {@code invokedynamic} instruction from bytecode,
* and controls its linkage.
* Every linked {@code CallSite} object corresponds to a distinct instance
* of the {@code invokedynamic} instruction, and vice versa.
* A {@code CallSite} is a holder for a variable {@link MethodHandle},
* which is called its {@code target}.
* Every call to a {@code CallSite} is delegated to the site's current target.
* <p>
* Every linked {@code CallSite} object has one state variable,
* a {@link MethodHandle} reference called the {@code target}.
* This reference is never null. Though it can change its value
* successive values must always have exactly the {@link MethodType method type}
* called for by the bytecodes of the associated {@code invokedynamic} instruction
* A call site is initially created in an <em>unlinked</em> state,
* which is distinguished by a null target variable.
* Before the call site may be invoked (and before certain other
* operations are attempted), the call site must be linked to
* a non-null target.
* <p>
* It is the responsibility of each class's
* {@link Linkage#registerBootstrapMethod(Class, MethodHandle) bootstrap method}
* to produce call sites which have been pre-linked to an initial target method.
* The required {@link MethodType type} for the target method is a parameter
* to each bootstrap method call.
* <p>
* The bootstrap method may elect to produce call sites of a
* language-specific subclass of {@code CallSite}. In such a case,
* the subclass may claim responsibility for initializing its target to
* a non-null value, by overriding {@link #initialTarget}.
* <p>
* An {@code invokedynamic} instruction which has not yet been executed
* is said to be <em>unlinked</em>. When an unlinked call site is executed,
* the containing class's bootstrap method is called to manufacture a call site,
* for the instruction. If the bootstrap method does not assign a non-null
* value to the new call site's target variable, the method {@link #initialTarget}
* is called to produce the new call site's first target method.
* <p>
* A freshly-created {@code CallSite} object is not yet in a linked state.
* An unlinked {@code CallSite} object reports null for its {@code callerClass}.
* When the JVM receives a {@code CallSite} object from a bootstrap method,
* it first ensures that its target is non-null and of the correct type.
* The JVM then links the {@code CallSite} object to the call site instruction,
* enabling the {@code callerClass} to return the class in which the instruction occurs.
* <p>
* Next, the JVM links the instruction to the {@code CallSite}, at which point
* any further execution of the {@code invokedynamic} instruction implicitly
* invokes the current target of the {@code CallSite} object.
* After this two-way linkage, both the instruction and the {@code CallSite}
* object are said to be linked.
* <p>
* This state of linkage continues until the method containing the
* dynamic call site is garbage collected, or the dynamic call site
* is invalidated by an explicit request.
* A call site may be <em>relinked</em> by changing its target.
* The new target must be non-null and must have the same
* {@linkplain MethodHandle#type() type}
* as the previous target.
* Thus, though a call site can be relinked to a series of
* successive targets, it cannot change its type.
* <p>
* Linkage happens once in the lifetime of any given {@code CallSite} object.
* Because of call site invalidation, this linkage can be repeated for
@ -87,6 +57,10 @@ import sun.dyn.CallSiteImpl;
* Here is a sample use of call sites and bootstrap methods which links every
* dynamic call site to print its arguments:
<blockquote><pre><!-- see indy-demo/src/PrintArgsDemo.java -->
&#064;BootstrapMethod(value=PrintArgsDemo.class, name="bootstrapDynamic")
static void test() throws Throwable {
InvokeDynamic.baz("baz arg", 2, 3.14);
}
private static void printArgs(Object... args) {
System.out.println(java.util.Arrays.deepToString(args));
}
@ -96,17 +70,16 @@ static {
Class thisClass = lookup.lookupClass(); // (who am I?)
printArgs = lookup.findStatic(thisClass,
"printArgs", MethodType.methodType(void.class, Object[].class));
Linkage.registerBootstrapMethod("bootstrapDynamic");
}
private static CallSite bootstrapDynamic(Class caller, String name, MethodType type) {
// ignore caller and name, but match the type:
return new CallSite(MethodHandles.collectArguments(printArgs, type));
}
</pre></blockquote>
* @see Linkage#registerBootstrapMethod(java.lang.Class, java.dyn.MethodHandle)
* @author John Rose, JSR 292 EG
*/
public class CallSite
implements MethodHandleProvider
{
private static final Access IMPL_TOKEN = Access.getToken();
@ -209,6 +182,7 @@ public class CallSite
* {@code InvokeDynamicBootstrapError}, which in turn causes the
* linkage of the {@code invokedynamic} instruction to terminate
* abnormally.
* @deprecated transitional form defined in EDR but removed in PFD
*/
protected MethodHandle initialTarget(Class<?> callerClass, String name, MethodType type) {
throw new InvokeDynamicBootstrapError("target must be initialized before call site is linked: "+name+type);
@ -278,16 +252,40 @@ public class CallSite
*/
@Override
public String toString() {
StringBuilder buf = new StringBuilder("CallSite#");
buf.append(hashCode());
if (!isLinked())
buf.append("[unlinked]");
else
buf.append("[")
.append("from ").append(vmmethod.getDeclaringClass().getName())
.append(" : ").append(getTarget().type())
.append(" => ").append(getTarget())
.append("]");
return buf.toString();
return "CallSite"+(target == null ? "" : target.type());
}
/**
* <em>PROVISIONAL API, WORK IN PROGRESS:</em>
* Produce a method handle equivalent to an invokedynamic instruction
* which has been linked to this call site.
* <p>If this call site is a {@link ConstantCallSite}, this method
* simply returns the call site's target, since that will not change.
* <p>Otherwise, this method is equivalent to the following code:
* <p><blockquote><pre>
* MethodHandle getTarget, invoker, result;
* getTarget = MethodHandles.lookup().bind(this, "getTarget", MethodType.methodType(MethodHandle.class));
* invoker = MethodHandles.exactInvoker(this.type());
* result = MethodHandles.foldArguments(invoker, getTarget)
* </pre></blockquote>
* @return a method handle which always invokes this call site's current target
*/
public final MethodHandle dynamicInvoker() {
if (this instanceof ConstantCallSite)
return getTarget(); // will not change dynamically
MethodHandle getCSTarget = GET_TARGET;
if (getCSTarget == null)
GET_TARGET = getCSTarget = MethodHandles.Lookup.IMPL_LOOKUP.
findVirtual(CallSite.class, "getTarget", MethodType.methodType(MethodHandle.class));
MethodHandle getTarget = MethodHandleImpl.bindReceiver(IMPL_TOKEN, getCSTarget, this);
MethodHandle invoker = MethodHandles.exactInvoker(this.type());
return MethodHandles.foldArguments(invoker, getTarget);
}
private static MethodHandle GET_TARGET = null; // link this lazily, not eagerly
/** Implementation of {@link MethodHandleProvider} which returns {@code this.dynamicInvoker()}. */
public final MethodHandle asMethodHandle() { return dynamicInvoker(); }
/** Implementation of {@link MethodHandleProvider}, which returns {@code this.dynamicInvoker().asType(type)}. */
public final MethodHandle asMethodHandle(MethodType type) { return dynamicInvoker().asType(type); }
}

43
jdk/src/share/classes/java/dyn/ConstantCallSite.java Normal file
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@ -0,0 +1,43 @@
/*
* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.dyn;
/**
* A {@code ConstantCallSite} is a {@link CallSite} whose target is permanent, and can never be changed.
* The only way to relink an {@code invokedynamic} instruction bound to a {@code ConstantCallSite} is
* to invalidate the instruction as a whole.
* @author John Rose, JSR 292 EG
*/
public class ConstantCallSite extends CallSite {
/** Create a call site with a permanent target. */
public ConstantCallSite(MethodHandle target) {
super(target);
}
/** Throw an {@link IllegalArgumentException}, because this kind of call site cannot change its target. */
@Override public final void setTarget(MethodHandle ignore) {
throw new IllegalArgumentException("ConstantCallSite");
}
}

31
jdk/src/share/classes/java/dyn/InvokeDynamic.java
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@ -35,7 +35,7 @@ package java.dyn;
* The target method is a property of the reified {@linkplain CallSite call site object}
* which is linked to each active {@code invokedynamic} instruction.
* The call site object is initially produced by a
* {@linkplain java.dyn.Linkage#registerBootstrapMethod(Class, MethodHandle) bootstrap method}
* {@linkplain BootstrapMethod bootstrap method}
* associated with the class whose bytecodes include the dynamic call site.
* <p>
* The type {@code InvokeDynamic} has no particular meaning as a
@ -45,22 +45,31 @@ package java.dyn;
* It may be imported for ease of use.
* <p>
* Here are some examples:
* <p><blockquote><pre>
* Object x; String s; int i;
* x = InvokeDynamic.greet("world"); // greet(Ljava/lang/String;)Ljava/lang/Object;
* s = InvokeDynamic.&lt;String&gt;hail(x); // hail(Ljava/lang/Object;)Ljava/lang/String;
* InvokeDynamic.&lt;void&gt;cogito(); // cogito()V
* i = InvokeDynamic.&lt;int&gt;#"op:+"(2, 3); // "op:+"(II)I
* </pre></blockquote>
<blockquote><pre><!-- see indy-demo/src/JavaDocExamples.java -->
&#064;BootstrapMethod(value=Here.class, name="bootstrapDynamic")
static void example() throws Throwable {
Object x; String s; int i;
x = InvokeDynamic.greet("world"); // greet(Ljava/lang/String;)Ljava/lang/Object;
s = (String) InvokeDynamic.hail(x); // hail(Ljava/lang/Object;)Ljava/lang/String;
InvokeDynamic.cogito(); // cogito()V
i = (int) InvokeDynamic.#"op:+"(2, 3); // "op:+"(II)I
}
static MethodHandle bootstrapDynamic(Class caller, String name, MethodType type) { ... }
</pre></blockquote>
* Each of the above calls generates a single invokedynamic instruction
* with the name-and-type descriptors indicated in the comments.
* <p>
* The argument types are taken directly from the actual arguments,
* while the return type is taken from the type parameter.
* (This type parameter may be a primtive, and it defaults to {@code Object}.)
* while the return type corresponds to the target of the assignment.
* (Currently, the return type must be given as a false type parameter.
* This type parameter is an irregular use of the generic type syntax,
* and is likely to change in favor of a convention based on target typing.)
* <p>
* The final example uses a special syntax for uttering non-Java names.
* Any name legal to the JVM may be given between the double quotes.
* <p>
* None of these calls is complete without a bootstrap method,
* which must be registered by the static initializer of the enclosing class.
* which must be declared for the enclosing class or method.
* @author John Rose, JSR 292 EG
*/
@MethodHandle.PolymorphicSignature

6
jdk/src/share/classes/java/dyn/InvokeDynamicBootstrapError.java
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@ -28,15 +28,11 @@ package java.dyn;
/**
* Thrown to indicate that an {@code invokedynamic} instruction has
* failed to find its
* {@linkplain Linkage#registerBootstrapMethod(Class, MethodHandle) bootstrap method},
* {@linkplain BootstrapMethod bootstrap method},
* or the bootstrap method has
* failed to provide a
* {@linkplain CallSite} call site with a non-null {@linkplain MethodHandle target}
* of the correct {@linkplain MethodType method type}.
* <p>
* The bootstrap method must have been declared during a class's initialization
* by a call to one of the overloadings of
* {@link Linkage#registerBootstrapMethod registerBootstrapMethod}.
*
* @author John Rose, JSR 292 EG
*/

30
jdk/src/share/classes/java/dyn/Linkage.java
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@ -25,7 +25,6 @@
package java.dyn;
import java.lang.annotation.Annotation;
import java.dyn.MethodHandles.Lookup;
import java.util.WeakHashMap;
import sun.dyn.Access;
@ -56,11 +55,7 @@ public class Linkage {
* <li>the class containing the {@code invokedynamic} instruction, for which the bootstrap method was registered
* <li>the name of the method being invoked (a {@link String})
* <li>the type of the method being invoked (a {@link MethodType})
* <li><em>TBD</em> optionally, an unordered array of {@link Annotation}s attached to the call site
* <em>(Until this feature is implemented, this will always receive an empty array.)</em>
* </ul>
* <em>(TBD: The final argument type may be missing from the method handle's type.
* Additional arguments may be added in the future.)</em>
* The bootstrap method acts as a factory method which accepts the given arguments
* and returns a {@code CallSite} object (possibly of a subclass of {@code CallSite}).
* <p>
@ -86,6 +81,7 @@ public class Linkage {
* or is already running in another thread
* @exception SecurityException if there is a security manager installed,
* and a {@link LinkagePermission} check fails for "registerBootstrapMethod"
* @deprecated Use @{@link BootstrapMethod} annotations instead
*/
public static
void registerBootstrapMethod(Class callerClass, MethodHandle bootstrapMethod) {
@ -97,14 +93,9 @@ public class Linkage {
static private void checkBSM(MethodHandle mh) {
if (mh == null) throw newIllegalArgumentException("null bootstrap method");
if (mh.type() == BOOTSTRAP_METHOD_TYPE_2)
// For now, always pass an empty array for the Annotations argument
mh = MethodHandles.insertArguments(mh, BOOTSTRAP_METHOD_TYPE_2.parameterCount()-1,
(Object)NO_ANNOTATIONS);
if (mh.type() == BOOTSTRAP_METHOD_TYPE) return;
throw new WrongMethodTypeException(mh.toString());
}
static private final Annotation[] NO_ANNOTATIONS = { };
/**
* <em>PROVISIONAL API, WORK IN PROGRESS:</em>
@ -115,6 +106,7 @@ public class Linkage {
* @throws NoSuchMethodException if there is no such method
* @throws IllegalStateException if the caller class's static initializer
* has already run, or is already running in another thread
* @deprecated Use @{@link BootstrapMethod} annotations instead
*/
public static
void registerBootstrapMethod(Class<?> runtime, String name) {
@ -131,6 +123,7 @@ public class Linkage {
* @throws IllegalArgumentException if there is no such method
* @throws IllegalStateException if the caller class's static initializer
* has already run, or is already running in another thread
* @deprecated Use @{@link BootstrapMethod} annotations instead
*/
public static
void registerBootstrapMethod(String name) {
@ -142,18 +135,10 @@ public class Linkage {
void registerBootstrapMethodLookup(Class<?> callerClass, Class<?> runtime, String name) {
Lookup lookup = new Lookup(IMPL_TOKEN, callerClass);
MethodHandle bootstrapMethod;
// Try both types. TBD
try {
bootstrapMethod = lookup.findStatic(runtime, name, BOOTSTRAP_METHOD_TYPE_2);
bootstrapMethod = lookup.findStatic(runtime, name, BOOTSTRAP_METHOD_TYPE);
} catch (NoAccessException ex) {
bootstrapMethod = null;
}
if (bootstrapMethod == null) {
try {
bootstrapMethod = lookup.findStatic(runtime, name, BOOTSTRAP_METHOD_TYPE);
} catch (NoAccessException ex) {
throw new IllegalArgumentException("no such bootstrap method in "+runtime+": "+name, ex);
}
throw new IllegalArgumentException("no such bootstrap method in "+runtime+": "+name, ex);
}
checkBSM(bootstrapMethod);
MethodHandleImpl.registerBootstrap(IMPL_TOKEN, callerClass, bootstrapMethod);
@ -172,6 +157,7 @@ public class Linkage {
* and the immediate caller of this method is not in the same
* package as the caller class
* and a {@link LinkagePermission} check fails for "getBootstrapMethod"
* @deprecated
*/
public static
MethodHandle getBootstrapMethod(Class callerClass) {
@ -188,10 +174,6 @@ public class Linkage {
public static final MethodType BOOTSTRAP_METHOD_TYPE
= MethodType.methodType(CallSite.class,
Class.class, String.class, MethodType.class);
static final MethodType BOOTSTRAP_METHOD_TYPE_2
= MethodType.methodType(CallSite.class,
Class.class, String.class, MethodType.class,
Annotation[].class);
/**
* <em>PROVISIONAL API, WORK IN PROGRESS:</em>

15
jdk/src/share/classes/java/dyn/LinkagePermission.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -31,6 +31,7 @@ import java.util.Hashtable;
import java.util.StringTokenizer;
/**
* <em>PROVISIONAL API, WORK IN PROGRESS:</em>
* This class is for managing runtime permission checking for
* operations performed by methods in the {@link Linkage} class.
* Like a {@link RuntimePermission}, on which it is modeled,
@ -52,13 +53,6 @@ import java.util.StringTokenizer;
* </tr>
*
* <tr>
* <td>registerBootstrapMethod.{class name}</td>
* <td>Specifying a bootstrap method for {@code invokedynamic} instructions within a class of the given name</td>
* <td>An attacker could attempt to attach a bootstrap method to a class which
* has just been loaded, thus gaining control of its {@code invokedynamic} calls.</td>
* </tr>
*
* <tr>
* <td>invalidateAll</td>
* <td>Force the relinking of invokedynamic call sites everywhere.</td>
* <td>This could allow an attacker to slow down the system,
@ -73,8 +67,9 @@ import java.util.StringTokenizer;
* <td>See {@code invalidateAll}.</td>
* </tr>
* </table>
* <p>ISSUE: Is this still needed?
*
* @see java.security.RuntimePermission
* @see java.lang.RuntimePermission
* @see java.lang.SecurityManager
*
* @author John Rose, JSR 292 EG
@ -84,7 +79,7 @@ public final class LinkagePermission extends BasicPermission {
/**
* Create a new LinkagePermission with the given name.
* The name is the symbolic name of the LinkagePermission, such as
* "registerBootstrapMethod", "invalidateCallerClass.*", etc. An asterisk
* "invalidateCallerClass.*", etc. An asterisk
* may appear at the end of the name, following a ".", or by itself, to
* signify a wildcard match.
*

32
jdk/src/share/classes/java/dyn/MethodHandle.java
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2008, 2009, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -36,11 +36,13 @@ import static sun.dyn.MemberName.newIllegalArgumentException; // utility
/**
* A method handle is a typed, directly executable reference to a method,
* constructor, field, or similar low-level operation, with optional
* conversion or substitution of arguments or return values.
* transformations of arguments or return values.
* (These transformations include conversion, insertion, deletion,
* substitution. See the methods of this class and of {@link MethodHandles}.)
* <p>
* Method handles are strongly typed according to signature.
* They are not distinguished by method name or enclosing class.
* A method handle must be invoked under a signature which exactly matches
* A method handle must be invoked under a signature which matches
* the method handle's own {@link MethodType method type}.
* <p>
* Every method handle confesses its type via the {@code type} accessor.
@ -174,9 +176,10 @@ assert(i == 3);
* merely a documentation convention. These type parameters do
* not play a role in type-checking method handle invocations.
* <p>
* Note: Like classes and strings, method handles that correspond directly
* to fields and methods can be represented directly as constants to be
* loaded by {@code ldc} bytecodes.
* Like classes and strings, method handles that correspond to accessible
* fields, methods, and constructors can be represented directly
* in a class file's constant pool as constants to be loaded by {@code ldc} bytecodes.
* Loading such a constant causes the component classes of its type to be loaded as necessary.
*
* @see MethodType
* @see MethodHandles
@ -186,6 +189,7 @@ public abstract class MethodHandle
// Note: This is an implementation inheritance hack, and will be removed
// with a JVM change which moves the required hidden state onto this class.
extends MethodHandleImpl
implements MethodHandleProvider
{
private static Access IMPL_TOKEN = Access.getToken();
@ -197,7 +201,7 @@ public abstract class MethodHandle
* those methods which are signature polymorphic.
*/
@java.lang.annotation.Target({java.lang.annotation.ElementType.METHOD,java.lang.annotation.ElementType.TYPE})
@java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.CLASS)
@java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.RUNTIME)
@interface PolymorphicSignature { }
private MethodType type;
@ -274,10 +278,14 @@ public abstract class MethodHandle
* and performing simple conversions for arguments and return types.
* The signature at the call site of {@code invokeGeneric} must
* have the same arity as this method handle's {@code type}.
* The same conversions are allowed on arguments or return values as are supported by
* by {@link MethodHandles#convertArguments}.
* <p>
* If the call site signature exactly matches this method handle's {@code type},
* the call proceeds as if by {@link #invokeExact}.
* <p>
* Otherwise, the call proceeds as if this method handle were first
* adjusted by calling {@link #asType} to adjust this method handle
* to the required type, and then the call proceeds as if by
* {@link #invokeExact} on the adjusted method handle.
*/
public final native @PolymorphicSignature <R,A> R invokeGeneric(A... args) throws Throwable;
@ -538,4 +546,10 @@ public abstract class MethodHandle
public final MethodHandle bindTo(Object x) {
return MethodHandles.insertArguments(this, 0, x);
}
/** Implementation of {@link MethodHandleProvider}, which returns {@code this}. */
public final MethodHandle asMethodHandle() { return this; }
/** Implementation of {@link MethodHandleProvider}, which returns {@code this.asType(type)}. */
public final MethodHandle asMethodHandle(MethodType type) { return this.asType(type); }
}

80
jdk/src/share/classes/java/dyn/MethodHandleProvider.java Normal file
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@ -0,0 +1,80 @@
/*
* Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.dyn;
/**
* An interface for an object to provide a target {@linkplain MethodHandle method handle} to a {@code invokedynamic} instruction.
* There are many function-like objects in various Java APIs.
* This interface provides a standard way for such function-like objects to be bound
* to a dynamic call site, by providing a view of their behavior in the form of a low-level method handle.
* <p>
* The type {@link MethodHandle} is a concrete class whose implementation
* hierarchy (if any) may be tightly coupled to the underlying JVM implementation.
* It cannot also serve as a base type for user-defined functional APIs.
* For this reason, {@code MethodHandle} cannot be subclassed to add new
* behavior to method handles. But this interface can be used to provide
* a link between a user-defined function and the {@code invokedynamic}
* instruction and the method handle API.
*/
public interface MethodHandleProvider {
/** Produce a method handle which will serve as a behavioral proxy for the current object.
* The type and invocation behavior of the proxy method handle are user-defined,
* and should have some relation to the intended meaning of the original object itself.
* <p>
* The current object may have a changeable behavior.
* For example, {@link CallSite} has a {@code setTarget} method which changes its invocation.
* In such a case, it is <em>incorrect</em> for {@code asMethodHandle} to return
* a method handle whose behavior may diverge from that of the current object.
* Rather, the returned method handle must stably and permanently access
* the behavior of the current object, even if that behavior is changeable.
* <p>
* The reference identity of the proxy method handle is not guaranteed to
* have any particular relation to the reference identity of the object.
* In particular, several objects with the same intended meaning could
* share a common method handle, or the same object could return different
* method handles at different times. In the latter case, the different
* method handles should have the same type and invocation behavior,
* and be usable from any thread at any time.
* In particular, if a MethodHandleProvider is bound to an <code>invokedynamic</code>
* call site, the proxy method handle extracted at the time of binding
* will be used for an unlimited time, until the call site is rebound.
* <p>
* The type {@link MethodHandle} itself implements {@code MethodHandleProvider}, and
* for this method simply returns {@code this}.
*/
public MethodHandle asMethodHandle();
/** Produce a method handle of a given type which will serve as a behavioral proxy for the current object.
* As for the no-argument version {@link #asMethodHandle()}, the invocation behavior of the
* proxy method handle is user-defined. But the type must be the given type,
* or else a {@link WrongMethodTypeException} must be thrown.
* <p>
* If the current object somehow represents a variadic or overloaded behavior,
* the method handle returned for a given type might represent only a subset of
* the current object's repertoire of behaviors, which correspond to that type.
*/
public MethodHandle asMethodHandle(MethodType type) throws WrongMethodTypeException;
}

192
jdk/src/share/classes/java/dyn/package-info.java
View File

@ -40,20 +40,18 @@
* The JVM links any such call (regardless of signature) to a dynamically
* typed method handle invocation. In the case of {@code invokeGeneric},
* argument and return value conversions are applied.
* </li>
*
* <li>In source code, the class {@link java.dyn.InvokeDynamic} appears to accept
* <li>In source code, the class {@link java.dyn.InvokeDynamic InvokeDynamic} appears to accept
* any static method invocation, of any name and any signature.
* But instead of emitting
* an {@code invokestatic} instruction for such a call, the Java compiler emits
* an {@code invokedynamic} instruction with the given name and signature.
*
* <li>When the JVM links an {@code invokedynamic} instruction, it calls the
* {@linkplain java.dyn.Linkage#registerBootstrapMethod(Class, MethodHandle) bootstrap method}
* of the containing class to obtain a {@linkplain java.dyn.CallSite call site} object through which
* the call site will link its target {@linkplain java.dyn.MethodHandle method handle}.
* </li>
*
* <li>The JVM bytecode format supports immediate constants of
* the classes {@link java.dyn.MethodHandle} and {@link java.dyn.MethodType}.
* the classes {@link java.dyn.MethodHandle MethodHandle} and {@link java.dyn.MethodType MethodType}.
* </li>
* </ul>
*
* <h2><a name="jvm_mods"></a>Corresponding JVM bytecode format changes</h2>
@ -65,18 +63,50 @@
* The first byte is the opcode 186 (hexadecimal {@code BA}).
* The next two bytes are a constant pool index (in the same format as for the other {@code invoke} instructions).
* The final two bytes are reserved for future use and required to be zero.
* The constant pool reference is to a entry with tag {@code CONSTANT_NameAndType}
* (decimal 12). It is thus not a method reference of any sort, but merely
* the method name, argument types, and return type of the dynamic call site.
* <em>(TBD: The EG is discussing the possibility of a special constant pool entry type,
* so that other information may be added, such as a per-instruction bootstrap
* method and/or annotations.)</em>
* The constant pool reference of an {@code invokedynamic} instruction is to a entry
* with tag {@code CONSTANT_InvokeDynamic} (decimal 17). See below for its format.
* The entry specifies the bootstrap method (a {@link java.dyn.MethodHandle MethodHandle} constant),
* the dynamic invocation name, and the argument types and return type of the call.
* <p>
* Each instance of an {@code invokedynamic} instruction is called a <em>dynamic call site</em>.
* Multiple instances of an {@code invokedynamic} instruction can share a single
* {@code CONSTANT_InvokeDynamic} entry.
* In any case, distinct call sites always have distinct linkage state.
* <p>
* Moreover, for the purpose of distinguishing dynamic call sites,
* the JVM is allowed (but not required) to make internal copies
* of {@code invokedynamic} instructions, each one
* constituting a separate dynamic call site with its own linkage state.
* Such copying, if it occurs, cannot be observed except indirectly via
* execution of bootstrap methods and target methods.
* <p>
* A dynamic call site is originally in an unlinked state. In this state, there is
* no target method for the call site to invoke.
* A dynamic call site is linked by means of a bootstrap method,
* as <a href="#bsm">described below</a>.
* <p>
* <em>(Historic Note: Some older JVMs may allow the index of a {@code CONSTANT_NameAndType}
* instead of a {@code CONSTANT_InvokeDynamic}. In earlier, obsolete versions of this API, the
* bootstrap method was specified dynamically, in a per-class basis, during class initialization.)</em>
*
* <h3>constant pool entries for {@code invokedynamic} instructions</h3>
* If a constant pool entry has the tag {@code CONSTANT_InvokeDynamic} (decimal 17),
* it must contain exactly four more bytes.
* The first two bytes after the tag must be an index to a {@code CONSTANT_MethodHandle}
* entry, and the second two bytes must be an index to a {@code CONSTANT_NameAndType}.
* The first index specifies a bootstrap method used by the associated dynamic call sites.
* The second index specifies the method name, argument types, and return type of the dynamic call site.
* The structure of such an entry is therefore analogous to a {@code CONSTANT_Methodref},
* except that the {@code CONSTANT_Class} reference in a {@code CONSTANT_Methodref} entry
* is replaced by a bootstrap method reference.
*
* <h3>constant pool entries for {@code MethodType}s</h3>
* If a constant pool entry has the tag {@code CONSTANT_MethodType} (decimal 16),
* it must contain exactly two more bytes, which are an index to a {@code CONSTANT_Utf8}
* entry which represents a method type signature. The JVM will ensure that on first
* execution of an {@code ldc} instruction for this entry, a {@link java.dyn.MethodType}
* it must contain exactly two more bytes, which must be an index to a {@code CONSTANT_Utf8}
* entry which represents a method type signature.
* <p>
* The JVM will ensure that on first
* execution of an {@code ldc} instruction for this entry, a {@link java.dyn.MethodType MethodType}
* will be created which represents the signature.
* Any classes mentioned in the {@code MethodType} will be loaded if necessary,
* but not initialized.
@ -86,12 +116,15 @@
* <h3>constant pool entries for {@code MethodHandle}s</h3>
* If a constant pool entry has the tag {@code CONSTANT_MethodHandle} (decimal 15),
* it must contain exactly three more bytes. The first byte after the tag is a subtag
* value in the range 1 through 9, and the last two are an index to a
* value which must be in the range 1 through 9, and the last two must be an index to a
* {@code CONSTANT_Fieldref}, {@code CONSTANT_Methodref}, or
* {@code CONSTANT_InterfaceMethodref} entry which represents a field or method
* for which a method handle is to be created.
* Furthermore, the subtag value and the type of the constant index value
* must agree according to the table below.
* <p>
* The JVM will ensure that on first execution of an {@code ldc} instruction
* for this entry, a {@link java.dyn.MethodHandle} will be created which represents
* for this entry, a {@link java.dyn.MethodHandle MethodHandle} will be created which represents
* the field or method reference, according to the specific mode implied by the subtag.
* <p>
* As with {@code CONSTANT_Class} and {@code CONSTANT_MethodType} constants,
@ -126,6 +159,129 @@
* Method handles for subtags {@code REF_getStatic}, {@code REF_putStatic}, and {@code REF_invokeStatic}
* may force class initialization on their first invocation, just like the corresponding bytecodes.
*
* <h2><a name="bsm"></a>Bootstrap Methods</h2>
* Before the JVM can execute a dynamic call site (an {@code invokedynamic} instruction),
* the call site must first be <em>linked</em>.
* Linking is accomplished by calling a <em>bootstrap method</em>
* which is given the static information content of the call site,
* and which must produce a {@link java.dyn.MethodHandle method handle}
* that gives the behavior of the call site.
* <p>
* Each {@code invokedynamic} instruction statically specifies its own
* bootstrap method as a constant pool reference.
* The constant pool reference also specifies the call site's name and type signature,
* just like {@code invokevirtual} and the other invoke instructions.
* <p>
* Linking starts with resolving the constant pool entry for the
* bootstrap method, and resolving a {@link java.dyn.MethodType MethodType} object for
* the type signature of the dynamic call site.
* This resolution process may trigger class loading.
* It may therefore throw an error if a class fails to load.
* This error becomes the abnormal termination of the dynamic
* call site execution.
* Linkage does not trigger class initialization.
* <p>
* Next, the bootstrap method call is started, with four values being stacked:
* <ul>
* <li>a {@code MethodHandle}, the resolved bootstrap method itself </li>
* <li>a {@code Class}, the <em>caller class</em> in which dynamic call site occurs </li>
* <li>a {@code String}, the method name mentioned in the call site </li>
* <li>a {@code MethodType}, the resolved type signature of the call </li>
* </ul>
* The method handle is then applied to the other values as if by
* {@linkplain java.dyn.MethodHandle#invokeGeneric the <code>invokeGeneric</code> method}.
* The returned result must be a {@link java.dyn.CallSite CallSite}, a {@link java.dyn.MethodHandle MethodHandle},
* or another {@link java.dyn.MethodHandleProvider MethodHandleProvider} value.
* The method {@linkplain java.dyn.MethodHandleProvider#asMethodHandle asMethodHandle}
* is then called on the returned value. The result of that second
* call is the {@code MethodHandle} which becomes the
* permanent binding for the dynamic call site.
* That method handle's type must be exactly equal to the type
* derived from the dynamic call site signature and passed to
* the bootstrap method.
* <p>
* After resolution, the linkage process may fail in a variety of ways.
* All failures are reported by an {@link java.dyn.InvokeDynamicBootstrapError InvokeDynamicBootstrapError},
* which is thrown as the abnormal termination of the dynamic call
* site execution.
* The following circumstances will cause this:
* <ul>
* <li>the bootstrap method invocation completes abnormally </li>
* <li>the result from the bootstrap invocation is not a reference to
* an object of type {@link java.dyn.MethodHandleProvider MethodHandleProvider} </li>
* <li>the call to {@code asMethodHandle} completes abnormally </li>
* <li>the call to {@code asMethodHandle} fails to return a reference to
* an object of type {@link java.dyn.MethodHandle MethodHandle} </li>
* <li>the method handle produced by {@code asMethodHandle} does not have
* the expected {@code MethodType} </li>
* </ul>
* <h3>timing of linkage</h3>
* A dynamic call site is linked just before its first execution.
* The bootstrap method call implementing the linkage occurs within
* a thread that is attempting a first execution.
* <p>
* If there are several such threads, the JVM picks one thread
* and runs the bootstrap method while the others wait for the
* invocation to terminate normally or abnormally.
* <p>
* After a bootstrap method is called and a method handle target
* successfully extracted, the JVM attempts to link the instruction
* being executed to the target method handle.
* This may fail if there has been intervening linkage
* or invalidation event for the same instruction.
* If such a failure occurs, the dynamic call site must be
* re-executed from the beginning, either re-linking it
* (if it has been invalidated) or invoking the target
* (if it the instruction has been linked by some other means).
* <p>
* If the instruction is linked successfully, the target method
* handle is invoked to complete the instruction execution.
* The state of linkage continues until the method containing the
* dynamic call site is garbage collected, or the dynamic call site
* is invalidated by an explicit request,
* such as {@link java.dyn.Linkage#invalidateCallerClass Linkage.invalidateCallerClass}.
* <p>
* In an application which requires dynamic call sites with individually
* mutable behaviors, their bootstrap methods should produce distinct
* {@link java.dyn.CallSite CallSite} objects, one for each linkage request.
* <p>
* If a class containing {@code invokedynamic} instructions
* is {@linkplain java.dyn.Linkage#invalidateCallerClass(Class) invalidated},
* subsequent execution of those {@code invokedynamic} instructions
* will require linking.
* It is as if they had never been executed in the first place.
* (However, invalidation does not cause constant pool entries to be
* resolved a second time.)
* <p>
* Invalidation events and bootstrap method calls for a particular
* dynamic call site are globally ordered relative to each other.
* When an invokedynamic instruction is invalidated, if there is
* simultaneously a bootstrap method invocation in process
* (in the same thread or a different thread), the result
* eventually returned must not be used to link the call site.
* Put another way, when a call site is invalidated, its
* subsequent linkage (if any) must be performed by a bootstrap method
* call initiated after the invalidation occurred.
* <p>
* If several threads simultaneously execute a bootstrap method for a single dynamic
* call site, the JVM must choose one target object and installs it visibly to
* all threads. Any other bootstrap method calls are allowed to complete, but their
* results are ignored, and their dynamic call site invocations proceed with the originally
* chosen target object.
* <p>
* The JVM is free to duplicate dynamic call sites.
* This means that, even if a class contains just one {@code invokedynamic}
* instruction, its bootstrap method may be executed several times,
* once for each duplicate. Thus, bootstrap method code should not
* assume an exclusive one-to-one correspondence between particular occurrences
* of {@code invokedynamic} bytecodes in class files and linkage events.
* <p>
* In principle, each individual execution of an {@code invokedynamic}
* instruction could be deemed (by a conforming implementation) to be a separate
* duplicate, requiring its own execution of the bootstrap method.
* However, implementations are expected to perform code duplication
* (if at all) in order to improve performance, not make it worse.
*
* @author John Rose, JSR 292 EG
*/

25
jdk/src/share/classes/sun/dyn/CallSiteImpl.java
View File

@ -49,18 +49,21 @@ public class CallSiteImpl {
}
CallSite site;
try {
if (bootstrapMethod.type().parameterCount() == 3)
site = bootstrapMethod.<CallSite>invokeExact(caller, name, type);
else if (bootstrapMethod.type().parameterCount() == 4)
site = bootstrapMethod.<CallSite>invokeExact(caller, name, type,
!(info instanceof java.lang.annotation.Annotation[]) ? null
: (java.lang.annotation.Annotation[]) info);
Object binding;
if (false) // switch when invokeGeneric works
binding = bootstrapMethod.invokeGeneric(caller, name, type);
else
throw new InternalError("bad BSM: "+bootstrapMethod);
if (!(site instanceof CallSite))
throw new InvokeDynamicBootstrapError("class bootstrap method failed to create a call site: "+caller);
PRIVATE_INITIALIZE_CALL_SITE.<void>invokeExact(site,
name, type,
binding = bootstrapMethod.invokeVarargs(new Object[]{ caller, name, type });
//System.out.println("BSM for "+name+type+" => "+binding);
if (binding instanceof CallSite) {
site = (CallSite) binding;
} else if (binding instanceof MethodHandleProvider) {
MethodHandle target = ((MethodHandleProvider) binding).asMethodHandle();
site = new ConstantCallSite(target);
} else {
throw new ClassCastException("bootstrap method failed to produce a MethodHandle or CallSite");
}
PRIVATE_INITIALIZE_CALL_SITE.<void>invokeExact(site, name, type,
callerMethod, callerBCI);
assert(site.getTarget() != null);
assert(site.getTarget().type().equals(type));

3
jdk/test/java/dyn/MethodHandlesTest.java
View File

@ -1327,7 +1327,8 @@ public class MethodHandlesTest {
MethodHandle result = MethodHandles.spreadArguments(target2, newType);
Object[] returnValue;
if (pos == 0) {
returnValue = (Object[]) result.invokeExact(args);
Object rawRetVal = result.invokeExact(args);
returnValue = (Object[]) rawRetVal;
} else {
Object[] args1 = Arrays.copyOfRange(args, 0, pos+1);
args1[pos] = Arrays.copyOfRange(args, pos, args.length);