Mercurial > hg > graal-compiler
diff graal/com.oracle.truffle.api.dsl/src/com/oracle/truffle/api/dsl/Cached.java @ 19288:3a37116ef37f
Truffle-DSL: added @Cached annotation, added limit property and updated @Specialization javadoc.
author | Christian Humer <christian.humer@gmail.com> |
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date | Mon, 29 Dec 2014 18:32:03 +0100 |
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children | 67ab244ab689 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/graal/com.oracle.truffle.api.dsl/src/com/oracle/truffle/api/dsl/Cached.java Mon Dec 29 18:32:03 2014 +0100 @@ -0,0 +1,235 @@ +/* + * Copyright (c) 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 com.oracle.truffle.api.dsl; + +import java.lang.annotation.*; + +import com.oracle.truffle.api.*; +import com.oracle.truffle.api.nodes.*; +import com.oracle.truffle.api.utilities.*; + +/** + * <p> + * A parameter annotated with {@link Cached} in a {@link Specialization} refers to a <b>cached</b> + * value of a specialization instance. A cached parameter value is initialized once using the + * initializer expression at specialization instantiation. For each call of the specialization + * method the cached value is provided by using the annotated parameter from the method body. Cache + * initializers are potentially executed before guard expressions declared in + * {@link Specialization#guards()}. + * </p> + * <p> + * A typical specialization may define multiple dynamic and multiple cached parameters. Dynamic + * parameter values are typically provided by executing child nodes of the operation. Cached + * parameters are initialized and stored once per specialization instantiation. Cached parameters + * are always constant at compile time. You may verify this by invoking + * {@link CompilerAsserts#compilationConstant(Object)} on any cached parameter. For consistency + * between specialization declarations cached parameters must be declared last in a specialization + * method. + * </p> + * <p> + * The initializer expression of a cached parameter is defined using a subset of Java. This subset + * includes field/parameter accesses, function calls, type exact infix comparisons (==, !=, <, <=, + * >, >=) and integer literals. The return type of the initializer expression must be assignable to + * the parameter type. If the annotated parameter type is derived from {@link Node} then the + * {@link Node} instance is allowed to use the {@link Node#replace(Node)} method to replace itself. + * Bound elements without receivers are resolved using the following order: + * <ol> + * <li>Dynamic and cached parameters of the enclosing specialization.</li> + * <li>Fields defined using {@link NodeField} for the enclosing node.</li> + * <li>Public constructors of the type of the annotated parameter using the <code>new</code> keyword + * as method name.</li> + * <li>Public and static methods or fields of the type of the annotated parameter.</li> + * <li>Non-private, static or virtual methods or fields of enclosing node.</li> + * <li>Non-private, static or virtual methods or fields of super types of the enclosing node.</li> + * <li>Public and static methods or fields imported using {@link ImportStatic}.</li> + * </ol> + * + * The following examples explain the intended use of the {@link Cached} annotation. All of the + * examples have to be enclosed in the following node declaration: + * </p> + * + * <pre> + * @NodeChild("operand") + * abstract TestNode extends Node { + * abstract void execute(Object operandValue); + * // ... example here ... + * } + * </pre> + * + * <ol> + * <li> + * This example defines one dynamic and one cached parameter. The operand parameter is representing + * the dynamic value of the operand while the cachedOperand is initialized once at first execution + * of the specialization (specialization instantiation time). + * + * <pre> + * @Specialization + * void doCached(int operand, @Local("operand") int cachedOperand) { + * CompilerAsserts.compilationConstant(cachedOperand); + * ... + * } + * + * Example executions: + * execute(1) => doCached(1, 1) // new instantiation, localOperand is bound to 1 + * execute(0) => doCached(0, 1) + * execute(2) => doCached(2, 1) + * + * </pre> + * + * </li> + * <li> + * We extend the previous example by a guard for the cachedOperand value to be equal to the dynamic + * operand value. This specifies that the specialization is instantiated for each individual operand + * value that is provided. There are a lot of individual <code>int</code> values and for each + * individual <code>int</code> value a new specialization would get instantiated. The + * {@link Specialization#limit()} property defines a limit for the number of specializations that + * can get instantiated. If the specialization instantiation limit is reached then no further + * specializations are instantiated. Like for other specializations if there are no more + * specializations defined an {@link UnsupportedSpecializationException} is thrown. The default + * specialization instantiation limit is <code>3</code>. + * + * <pre> + * @Specialization(guards = "==(operand, cachedOperand)") + * void doCached(int operand, @Cached("operand") int cachedOperand) { + * CompilerAsserts.compilationConstant(cachedOperand); + * ... + * } + * + * Example executions: + * execute(0) => doCached(0, 0) // new instantiation, cachedOperand is bound to 0 + * execute(1) => doCached(1, 1) // new instantiation, cachedOperand is bound to 1 + * execute(1) => doCached(1, 1) + * execute(2) => doCached(2, 2) // new instantiation, cachedOperand is bound to 2 + * execute(3) => throws UnsupportedSpecializationException // instantiation limit overflows + * + * </pre> + * + * </li> + * <li> + * To handle the limit overflow we extend our example by an additional specialization named + * <code>doNormal</code>. This specialization has the same type restrictions but does not have local + * state nor the operand identity guard. It is also declared after <code>doCached</code> therefore + * it is only instantiated if the limit of the <code>doCached</code> specialization has been + * reached. In other words <code>doNormal</code> is more generic than <code>doCached</code> . The + * <code>doNormal</code> specialization uses <code>contains="doCached"</code> to specify + * that all instantiations of <code>doCached</code> get removed if <code>doNormal</code> is + * instantiated. Alternatively if the <code>contains</code> relation is omitted then all + * <code>doCached</code> instances remain but no new instances are created. + * + * <pre> + * @Specialization(guards = "==(operand, cachedOperand)") + * void doCached(int operand, @Cached("operand") int cachedOperand) { + * CompilerAsserts.compilationConstant(cachedOperand); + * ... + * } + * + * @Specialization(contains = "doCached") + * void doNormal(int operand) {...} + * + * Example executions with contains = "doCached": + * execute(0) => doCached(0, 0) // new instantiation, cachedOperand is bound to 0 + * execute(1) => doCached(1, 1) // new instantiation, cachedOperand is bound to 1 + * execute(1) => doCached(1, 1) + * execute(2) => doCached(2, 2) // new instantiation, cachedOperand is bound to 2 + * execute(3) => doNormal(3) // new instantiation of doNormal due to limit overflow; doCached gets removed. + * execute(1) => doNormal(1) + * + * Example executions without contains = "doCached": + * execute(0) => doCached(0, 0) // new instantiation, cachedOperand is bound to 0 + * execute(1) => doCached(1, 1) // new instantiation, cachedOperand is bound to 1 + * execute(1) => doCached(1, 1) + * execute(2) => doCached(2, 2) // new instantiation, cachedOperand is bound to 2 + * execute(3) => doNormal(3) // new instantiation of doNormal due to limit overflow + * execute(1) => doCached(1, 1) + * + * </pre> + * + * </li> + * <li> + * This next example shows how methods from the enclosing node can be used to initialize cached + * parameters. Please note that the visibility of transformLocal must not be <code>private</code>. + * + * <pre> + * @Specialization + * void s(int operand, @Cached("transformLocal(operand)") int cachedOperand) { + * } + * + * int transformLocal(int operand) { + * return operand & 0x42; + * } + * + * </li> + * </pre> + * <li> + * The <code>new</code> keyword can be used to initialize a cached parameter using a constructor of + * the parameter type. + * + * <pre> + * @Specialization + * void s(Object operand, @Cached("new()") OtherNode someNode) { + * someNode.execute(operand); + * } + * + * static class OtherNode extends Node { + * + * public String execute(Object value) { + * throw new UnsupportedOperationException(); + * } + * } + * + * </pre> + * + * </li> + * <li> + * Java types without public constructor but with a static factory methods can be initialized by + * just referencing its static factory method and its parameters. In this case + * {@link BranchProfile#create()} is used to instantiate the {@link BranchProfile} instance. + * + * <pre> + * @Specialization + * void s(int operand, @Local("create()") BranchProfile profile) { + * } + * </pre> + * + * </li> + * </ol> + * + * @see Specialization#guards() + * @see Specialization#contains() + * @see Specialization#limit() + * @see ImportStatic + */ +@Retention(RetentionPolicy.RUNTIME) +@Target({ElementType.PARAMETER}) +public @interface Cached { + + /** + * Defines the initializer expression of the cached parameter value. + * + * @see Cached + */ + String value(); + +}