src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.api.replacements/src/org/graalvm/compiler/api/replacements/MethodSubstitution.java
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package org.graalvm.compiler.api.replacements;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Array;
import jdk.vm.ci.meta.Signature;
/**
* Denotes a method whose body is used by a compiler as the substitute (or intrinsification) of
* another method. The exact mechanism used to do the substitution is compiler dependent but every
* compiler should require substitute methods to be annotated with {@link MethodSubstitution}. In
* addition, a compiler is recommended to implement {@link MethodSubstitutionRegistry} to advertise
* the mechanism by which it supports registration of method substitutes.
*
* A compiler may support partial intrinsification where only a part of a method is implemented by
* the compiler. The unsupported path is expressed by a call to either the original or substitute
* method from within the substitute method. Such as call is a <i>partial intrinsic exit</i>.
*
* For example, here's a HotSpot specific intrinsic for {@link Array#newInstance(Class, int)} that
* only handles the case where the VM representation of the array class to be instantiated already
* exists:
*
* <pre>
* @MethodSubstitution
* public static Object newInstance(Class<?> componentType, int length) {
* if (componentType == null || loadKlassFromObject(componentType, arrayKlassOffset(INJECTED_VMCONFIG), CLASS_ARRAY_KLASS_LOCATION).isNull()) {
* // Array class not yet created - exit the intrinsic and call the original method
* return newInstance(componentType, length);
* }
* return DynamicNewArrayNode.newArray(GraalDirectives.guardingNonNull(componentType), length, JavaKind.Object);
* }
* </pre>
*
* Here's the same intrinsification where the exit is expressed as a call to the original method:
*
* <pre>
* @MethodSubstitution
* public static Object newInstance(Class<?> componentType, int length) {
* if (componentType == null || loadKlassFromObject(componentType, arrayKlassOffset(INJECTED_VMCONFIG), CLASS_ARRAY_KLASS_LOCATION).isNull()) {
* // Array class not yet created - exit the intrinsic and call the original method
* return java.lang.reflect.newInstance(componentType, length);
* }
* return DynamicNewArrayNode.newArray(GraalDirectives.guardingNonNull(componentType), length, JavaKind.Object);
* }
* </pre>
*
* A condition for a partial intrinsic exit is that it is uses the unmodified parameters of the
* substitute as arguments to the partial intrinsic exit call. There must also be no side effecting
* instruction between the start of the substitute method and the partial intrinsic exit.
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MethodSubstitution {
/**
* Gets the name of the original method.
* <p>
* If the default value is specified for this element, then the name of the original method is
* same as the substitute method.
*/
String value() default "";
/**
* Determines if the original method is static.
*/
boolean isStatic() default true;
/**
* Gets the {@linkplain Signature#toMethodDescriptor signature} of the original method.
* <p>
* If the default value is specified for this element, then the signature of the original method
* is the same as the substitute method.
*/
String signature() default "";
/**
* Determines if the substitution is for a method that may not be part of the runtime. For
* example, a method introduced in a later JDK version. Substitutions for such methods are
* omitted if the original method cannot be found.
*/
boolean optional() default false;
}