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package com.oracle.truffle.api.dsl;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import com.oracle.truffle.api.TruffleLanguage.LanguageReference;
import com.oracle.truffle.api.nodes.Node;

Allows to access the current language instance in specializations or exported messages. The parameter type must be the exact type of the language access or a LanguageReference that provides it. The latter parameter allows to lookup the language lazily, e.g. in a conditional branch. Using this annotation always allows to generate uncached versions of the node.

This annotation can be used in two different ways:

  1. Direct language access:
  2. @GenerateUncached
    abstract static class ExampleNode extends Node {
        abstract Object execute(Object argument);
        @Specialization
        static int doInt(int value,
                        @CachedLanguage MyLanguage language) {
            // use context
            return value;
        }
    }
    
  3. Conditional language access:
  4. @GenerateUncached
    abstract class ExampleNode extends Node {
        abstract Object execute(Object argument);
        @Specialization
        static int doInt(int value,
                        @CachedLanguage LanguageReference ref) {
            if (value == 42) {
                // use context conditionally
                MyLanguage language = ref.get();
            }
            return value;
        }
    }
    

The generated code uses the Node.lookupLanguageReference(Class<TruffleLanguage>) method to implement this feature. This method may also be used manually.

See Also:
Since:19.0
/** * Allows to access the current language instance in specializations or exported messages. The * parameter type must be the exact type of the language access or a {@link LanguageReference} that * provides it. The latter parameter allows to lookup the language lazily, e.g. in a conditional * branch. Using this annotation always allows to generate {@link GenerateUncached uncached} * versions of the node. * <p> * This annotation can be used in two different ways: * <ol> * <li>Direct language access:</li> * * <pre> * &#64;GenerateUncached * abstract static class ExampleNode extends Node { * * abstract Object execute(Object argument); * * &#64;Specialization * static int doInt(int value, * &#64;CachedLanguage MyLanguage language) { * // use context * return value; * } * * } * </pre> * * <li>Conditional language access:</li> * * <pre> * &#64;GenerateUncached * abstract class ExampleNode extends Node { * * abstract Object execute(Object argument); * * &#64;Specialization * static int doInt(int value, * &#64;CachedLanguage LanguageReference<MyLanguage> ref) { * if (value == 42) { * // use context conditionally * MyLanguage language = ref.get(); * * } * return value; * } * } * </pre> * </ol> * <p> * The generated code uses the {@link Node#lookupLanguageReference(Class)} method to implement this * feature. This method may also be used manually. * * @see Cached @Cached for more information on using this annotation. * @see CachedContext @CachedContext to access the language instance. * @since 19.0 */
@Retention(RetentionPolicy.CLASS) @Target({ElementType.PARAMETER}) public @interface CachedLanguage { }