1 /*
   2  * Copyright (c) 2013, 2018, 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
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 
  25 package org.graalvm.compiler.api.replacements;
  26 
  27 import java.lang.annotation.ElementType;
  28 import java.lang.annotation.Retention;
  29 import java.lang.annotation.RetentionPolicy;
  30 import java.lang.annotation.Target;
  31 import java.lang.reflect.Array;
  32 
  33 import jdk.vm.ci.meta.Signature;
  34 
  35 /**
  36  * Denotes a method whose body is used by a compiler as the substitute (or intrinsification) of
  37  * another method. The exact mechanism used to do the substitution is compiler dependent but every
  38  * compiler should require substitute methods to be annotated with {@link MethodSubstitution}. In
  39  * addition, a compiler is recommended to implement {@link MethodSubstitutionRegistry} to advertise
  40  * the mechanism by which it supports registration of method substitutes.
  41  *
  42  * A compiler may support partial intrinsification where only a part of a method is implemented by
  43  * the compiler. The unsupported path is expressed by a call to either the original or substitute
  44  * method from within the substitute method. Such as call is a <i>partial intrinsic exit</i>.
  45  *
  46  * For example, here's a HotSpot specific intrinsic for {@link Array#newInstance(Class, int)} that
  47  * only handles the case where the VM representation of the array class to be instantiated already
  48  * exists:
  49  *
  50  * <pre>
  51  * @MethodSubstitution
  52  * public static Object newInstance(Class<?> componentType, int length) {
  53  *     if (componentType == null || loadKlassFromObject(componentType, arrayKlassOffset(INJECTED_VMCONFIG), CLASS_ARRAY_KLASS_LOCATION).isNull()) {
  54  *         // Array class not yet created - exit the intrinsic and call the original method
  55  *         return newInstance(componentType, length);
  56  *     }
  57  *     return DynamicNewArrayNode.newArray(GraalDirectives.guardingNonNull(componentType), length, JavaKind.Object);
  58  * }
  59  * </pre>
  60  *
  61  * Here's the same intrinsification where the exit is expressed as a call to the original method:
  62  *
  63  * <pre>
  64  * @MethodSubstitution
  65  * public static Object newInstance(Class<?> componentType, int length) {
  66  *     if (componentType == null || loadKlassFromObject(componentType, arrayKlassOffset(INJECTED_VMCONFIG), CLASS_ARRAY_KLASS_LOCATION).isNull()) {
  67  *         // Array class not yet created - exit the intrinsic and call the original method
  68  *         return java.lang.reflect.newInstance(componentType, length);
  69  *     }
  70  *     return DynamicNewArrayNode.newArray(GraalDirectives.guardingNonNull(componentType), length, JavaKind.Object);
  71  * }
  72  * </pre>
  73  *
  74  * A condition for a partial intrinsic exit is that it is uses the unmodified parameters of the
  75  * substitute as arguments to the partial intrinsic exit call. There must also be no side effecting
  76  * instruction between the start of the substitute method and the partial intrinsic exit.
  77  */
  78 @Retention(RetentionPolicy.RUNTIME)
  79 @Target(ElementType.METHOD)
  80 public @interface MethodSubstitution {
  81 
  82     /**
  83      * Gets the name of the original method.
  84      * <p>
  85      * If the default value is specified for this element, then the name of the original method is
  86      * same as the substitute method.
  87      */
  88     String value() default "";
  89 
  90     /**
  91      * Determines if the original method is static.
  92      */
  93     boolean isStatic() default true;
  94 
  95     /**
  96      * Gets the {@linkplain Signature#toMethodDescriptor signature} of the original method.
  97      * <p>
  98      * If the default value is specified for this element, then the signature of the original method
  99      * is the same as the substitute method.
 100      */
 101     String signature() default "";
 102 
 103     /**
 104      * Determines if the substitution is for a method that may not be part of the runtime. For
 105      * example, a method introduced in a later JDK version. Substitutions for such methods are
 106      * omitted if the original method cannot be found.
 107      */
 108     boolean optional() default false;
 109 }