/*
 * 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
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 */
package com.oracle.truffle.sl.nodes.local;

import com.oracle.truffle.api.dsl.*;
import com.oracle.truffle.api.frame.*;
import com.oracle.truffle.api.source.*;
import com.oracle.truffle.sl.nodes.*;

/**
 * Node to read a local variable from a function's {@link VirtualFrame frame}. The Truffle frame API
 * allows to store primitive values of all Java primitive types, and Object values. This means that
 * all SL types that are objects are handled by the {@link #readObject} method. When a local
 * variable changes its type, the frame access method throws an {@link FrameSlotTypeException},
 * which causes not rewriting. The rewriting code is generated by the Truffle DSL.
 */
@NodeField(name = "slot", type = FrameSlot.class)
public abstract class SLReadLocalVariableNode extends SLExpressionNode {

    public SLReadLocalVariableNode(SourceSection src) {
        super(src);
    }

    /**
     * Returns the descriptor of the accessed local variable. The implementation of this method is
     * created by the Truffle DSL based on the {@link NodeField} annotation on the class.
     */
    protected abstract FrameSlot getSlot();

    @Specialization(rewriteOn = FrameSlotTypeException.class)
    protected long readLong(VirtualFrame frame) throws FrameSlotTypeException {
        return frame.getLong(getSlot());
    }

    @Specialization(rewriteOn = FrameSlotTypeException.class)
    protected boolean readBoolean(VirtualFrame frame) throws FrameSlotTypeException {
        return frame.getBoolean(getSlot());
    }

    @Specialization(order = 1, rewriteOn = FrameSlotTypeException.class)
    protected Object readObject(VirtualFrame frame) throws FrameSlotTypeException {
        return frame.getObject(getSlot());
    }

    /**
     * This is the generic case that always succeeds. Since we already have another specialization
     * with the same signature above, we need to order them explicitly with the order attribute.
     */
    @Specialization(order = 2)
    protected Object read(VirtualFrame frame) {
        return frame.getValue(getSlot());
    }
}