001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.nabla.forward.instructions;
018    
019    import org.apache.commons.nabla.DifferentiationException;
020    import org.apache.commons.nabla.forward.analysis.InstructionsTransformer;
021    import org.apache.commons.nabla.forward.analysis.MethodDifferentiator;
022    import org.objectweb.asm.Opcodes;
023    import org.objectweb.asm.tree.AbstractInsnNode;
024    import org.objectweb.asm.tree.InsnList;
025    import org.objectweb.asm.tree.InsnNode;
026    
027    /** Differentiation transformer for DUP2_X1 instructions.
028     * <p>DUP2_X1 instructions are replaced by DUP_X1 instructions
029     * as a reference to a {@link
030     * org.apache.commons.math3.analysis.differentiation.DerivativeStructure}
031     * instance uses only one stack slot instead of two.</p>
032     * @version $Id$
033     */
034    public class Dup2X1Transformer implements InstructionsTransformer {
035    
036        /** Simple constructor.
037         */
038        public Dup2X1Transformer() {
039        }
040    
041        /** {@inheritDoc} */
042        public InsnList getReplacement(final AbstractInsnNode insn,
043                                       final MethodDifferentiator methodDifferentiator)
044            throws DifferentiationException {
045    
046            final InsnList list = new InsnList();
047            list.add(new InsnNode(Opcodes.DUP_X1));
048            return list;
049    
050        }
051    
052    }