/*
 * Copyright (c) 2012, 2014, 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.
 *
 * 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.sl.nodes.local;

import com.oracle.truffle.api.*;
import com.oracle.truffle.api.frame.*;
import com.oracle.truffle.api.utilities.*;
import com.oracle.truffle.sl.nodes.*;
import com.oracle.truffle.sl.parser.*;
import com.oracle.truffle.sl.runtime.*;

/**
 * Reads a function argument. Arguments are passed in as a {@link SLArguments} object, which
 * encapsulates an {@link SLArguments#getFromFrame Object[] array}. Language-defined subclasses of
 * {@link Arguments} are the standard Truffle way to pass values between function.
 * <p>
 * Arguments are not type-specialized. To ensure that repeated accesses within a method are
 * specialized and can, e.g., accessed without unboxing, all arguments are loaded into local
 * variables {@link SLNodeFactory#addFormalParameter in the method prologue}.
 */
public class SLReadArgumentNode extends SLExpressionNode {

    /** The argument number, i.e., the index into the array of arguments. */
    private final int index;

    /**
     * Profiling information, collected by the interpreter, capturing whether the function was
     * called with fewer actual arguments than formal arguments.
     */
    private final BranchProfile outOfBoundsTaken = new BranchProfile();

    public SLReadArgumentNode(int index) {
        this.index = index;
    }

    @Override
    public Object executeGeneric(VirtualFrame frame) {
        Object[] args = SLArguments.getFromFrame(frame);
        if (index < args.length) {
            return args[index];
        } else {
            /* In the interpreter, record profiling information that the branch was used. */
            outOfBoundsTaken.enter();
            /* Use the default null value. */
            return SLNull.SINGLETON;
        }
    }
}