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_X2 instructions.
028     * @version $Id$
029     */
030    public class Dup2X2Transformer implements InstructionsTransformer {
031    
032        /** Indicator for top stack element conversion. */
033        private final boolean stack0Converted;
034    
035        /** Indicator for next to top stack element conversion. */
036        private final boolean stack1Converted;
037    
038        /** Simple constructor.
039         * @param stack0Converted if true, the top level stack element has already been converted
040         * @param stack1Converted if true, the next to top level stack element has already been converted
041         */
042        public Dup2X2Transformer(final boolean stack0Converted, final boolean stack1Converted) {
043            this.stack0Converted = stack0Converted;
044            this.stack1Converted = stack1Converted;
045        }
046    
047        /** {@inheritDoc} */
048        public InsnList getReplacement(final AbstractInsnNode insn,
049                                       final MethodDifferentiator methodDifferentiator)
050            throws DifferentiationException {
051    
052            final InsnList list = new InsnList();
053    
054            if (stack1Converted) {
055                if (stack0Converted) {
056                    list.add(new InsnNode(Opcodes.DUP_X1));
057                } else {
058                    list.add(new InsnNode(Opcodes.DUP2_X1));
059                }
060            } else {
061                list.add(new InsnNode(Opcodes.DUP_X2));
062            }
063    
064            return list;
065    
066        }
067    
068    }