/*
* Copyright (c) 2010, 2015, 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 jdk.nashorn.internal.objects.annotations;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.invoke.MethodHandle;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.linker.LinkRequest;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.UnwarrantedOptimismException;
/**
* The SpecializedFunction annotation is used to flag more type specific
* functions than the standard one in the native objects.
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface SpecializedFunction {
/**
* Functionality for testing if we are allowed to link a specialized
* function the first time we encounter it. Then the guard will handle the
* rest of the invocations.
*
* This is the same for all callsites in Nashorn; the first time a callsite is
* linked, we have to manually check that the linkage is OK. Even if we add
* a guard and it fails upon the first try, this is not good enough.
* (Symmetrical to how it works everywhere else in the Nashorn runtime.)
*
* Here we abstract out a few of the most common link guard checks.
*/
public static abstract class LinkLogic {
/**
* Empty link logic instance - this is the default.
* "no special linking or runtime guard behavior"
*/
public static final LinkLogic EMPTY_INSTANCE = new Empty();
/** Empty link logic class - allow all linking, no guards. */
private static final class Empty extends LinkLogic {
@Override
public boolean canLink(final Object self, final CallSiteDescriptor desc, final LinkRequest request) {
return true;
}
@Override
public boolean isEmpty() {
return true;
}
}
/**
* Get the class representing the empty link logic.
*
* @return class representing empty link logic
*/
public static Class<? extends LinkLogic> getEmptyLinkLogicClass() {
return Empty.class;
}
/**
* Should this callsite relink when an exception is thrown?
*
* @return the relink exception, or {@code null} if none
*/
public Class<? extends Throwable> getRelinkException() {
return null;
}
/**
* Is this link logic class empty - i.e., no special linking logic
* supplied?
*
* @param clazz class to check
*
* @return {@code true} if this link logic is empty
*/
public static boolean isEmpty(final Class<? extends LinkLogic> clazz) {
return clazz == Empty.class;
}
/**
* Is this link logic instance empty - i.e., no special linking logic
* supplied?
*
* @return {@code true} if this link logic instance is empty
*/
public boolean isEmpty() {
return false;
}
/**
* Given a callsite, can we link this method based on the receiver and
* parameters?
*
* @param self receiver
* @param desc callsite descriptor
* @param request link request
*
* @return {@code true} if we can link this callsite at this time
*/
public abstract boolean canLink(final Object self, final CallSiteDescriptor desc, final LinkRequest request);
/**
* Given a callsite, do we require an extra guard for specialization to
* go through?
*
* @param self receiver
*
* @return {@code true} if a guard is to be woven into the callsite
*/
public boolean needsGuard(final Object self) {
return true;
}
/**
* Given a callsite, and optional arguments, do we need an extra guard
* for specialization to go through? This guard can be a function of
* the arguments too.
*
* @param self receiver
* @param args arguments
*
* @return {@code true} if a guard is to be woven into the callsite
*/
public boolean needsGuard(final Object self, final Object... args) {
return true;
}
/**
* Given a callsite, and optional arguments, return any extra guard we
* might need for specialization as a method handle.
*
* @return methodhandle for guard, or null if no guard is needed
*/
public MethodHandle getGuard() {
return null;
}
/**
* Check, given a link request and a receiver, if this specialization
* fits This is used by the linker in {@link ScriptFunction} to figure
* out if an optimistic builtin can be linked when first discovered
*
* @param self receiver
* @param desc callsite descriptor
* @param request link request
*
* @return {@code true} if we can link, {@code false} otherwise - that
* means we have to pick a non specialized target
*/
public boolean checkLinkable(final Object self, final CallSiteDescriptor desc, final LinkRequest request) {
// check the link guard, if it says we can link, go ahead
return canLink(self, desc, request);
}
}
/**
* Name override for return value polymorphism, for example we can't have
* pop(V)I and pop(V)D in the same Java class, so they need to be named,
* e.g., popInt(V)I and popDouble(V)D for disambiguation, however, their
* names still need to resolve to "pop" to JavaScript so we can still
* specialize on return values and so that the linker can find them.
*
* @return name, "" means no override, use the Java function name, e.g.
* "push"
*/
String name() default "";
/**
* Return the guard for this specialized function. The default is no guard.
*
* @return guard
*/
Class<?> linkLogic() default LinkLogic.Empty.class;
/**
* @return whether this is a specialized constructor.
*/
boolean isConstructor() default false;
/**
* Can this function throw {@link UnwarrantedOptimismException}s? This works
* just like the normal functions, but we need the function to be
* immutable/non-state modifying, as we can't generate continuations for
* native code. Luckily a lot of the methods we want to specialize have this
* property.
*
* @return whether this function can throw {@link UnwarrantedOptimismException}.
*/
boolean isOptimistic() default false;
/**
* Is it safe to convert non-numeric arguments to numbers for this function's primitive numeric parameters?
* This is true for many built-in functions which expect numeric arguments, but not for those that
* expect generic arguments and just have specializations with numeric params to avoid boxing overhead.
* The default value is {@code true} because that is by far the most common case.
*
* @return true if it is safe to convert arguments to numbers
*/
boolean convertsNumericArgs() default true;
}