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Truffle SL is an example language implemented using the Truffle API.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
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 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
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 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
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 * minimum a reference to the UPL must be included in all copies or substantial
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package com.oracle.truffle.sl.nodes.expression;

import com.oracle.truffle.api.CallTarget;
import com.oracle.truffle.api.CompilerAsserts;
import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.nodes.NodeInfo;
import com.oracle.truffle.api.strings.TruffleString;
import com.oracle.truffle.sl.SLLanguage;
import com.oracle.truffle.sl.nodes.SLExpressionNode;
import com.oracle.truffle.sl.runtime.SLContext;
import com.oracle.truffle.sl.runtime.SLFunction;
import com.oracle.truffle.sl.runtime.SLFunctionRegistry;

/**
 * Constant literal for a {@link SLFunction function} value, created when a function name occurs as
 * a literal in SL source code. Note that function redefinition can change the {@link CallTarget
 * call target} that is executed when calling the function, but the {@link SLFunction} for a name
 * never changes. This is guaranteed by the {@link SLFunctionRegistry}.
 */
@NodeInfo(shortName = "func")
public final class SLFunctionLiteralNode extends SLExpressionNode {

    /** The name of the function. */
    private final TruffleString functionName;

    /**
     * The resolved function. During parsing (in the constructor of this node), we do not have the
     * {@link SLContext} available yet, so the lookup can only be done at {@link #executeGeneric
     * first execution}. The {@link CompilationFinal} annotation ensures that the function can still
     * be constant folded during compilation.
     */
    @CompilationFinal private SLFunction cachedFunction;

    public SLFunctionLiteralNode(TruffleString functionName) {
        this.functionName = functionName;
    }

    @Override
    public SLFunction executeGeneric(VirtualFrame frame) {
        SLLanguage l = SLLanguage.get(this);
        CompilerAsserts.partialEvaluationConstant(l);

        SLFunction function;
        if (l.isSingleContext()) {
            function = this.cachedFunction;
            if (function == null) {
                /* We are about to change a @CompilationFinal field. */
                CompilerDirectives.transferToInterpreterAndInvalidate();
                /* First execution of the node: lookup the function in the function registry. */
                this.cachedFunction = function = SLContext.get(this).getFunctionRegistry().lookup(functionName, true);
            }
        } else {
            /*
             * We need to rest the cached function otherwise it might cause a memory leak.
             */
            if (this.cachedFunction != null) {
                CompilerDirectives.transferToInterpreterAndInvalidate();
                this.cachedFunction = null;
            }
            // in the multi-context case we are not allowed to store
            // SLFunction objects in the AST. Instead we always perform the lookup in the hash map.
            function = SLContext.get(this).getFunctionRegistry().lookup(functionName, true);
        }
        return function;
    }

}