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.algorithmic.forward.arithmetic;
018    
019    import org.apache.commons.nabla.algorithmic.forward.analysis.InstructionsTransformer;
020    import org.apache.commons.nabla.algorithmic.forward.analysis.MethodDifferentiator;
021    import org.apache.commons.nabla.core.DifferentiationException;
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    import org.objectweb.asm.tree.VarInsnNode;
027    
028    /** Differentiation transformer for DNEG instructions.
029     */
030    public class DNegTransformer implements InstructionsTransformer {
031    
032        // CHECKSTYLE: stop HideUtilityClassConstructor
033        /** Holder for the singleton instance.*/
034        private static class LazyHolder  {
035            /** The singleton instance. */
036            private static final InstructionsTransformer INSTANCE = new DNegTransformer();
037        }
038        // CHECKSTYLE: resume HideUtilityClassConstructor
039    
040        /** Hidden constructor.
041         */
042        private DNegTransformer() {
043        }
044    
045        /** Get the singleton instance.
046         * <p>We use here the Initialization on Demand Holder idiom.</p>
047         * @return the singleton instance
048         */
049        public static InstructionsTransformer getInstance() {
050            return LazyHolder.INSTANCE;
051        }
052    
053        /** {@inheritDoc} */
054        public InsnList getReplacement(final AbstractInsnNode insn,
055                                       final MethodDifferentiator methodDifferentiator)
056            throws DifferentiationException {
057    
058            final int tmp = methodDifferentiator.getTmp(1);
059            final InsnList list = new InsnList();
060    
061            list.add(new VarInsnNode(Opcodes.DSTORE, tmp));
062            list.add(new InsnNode(Opcodes.DNEG));
063            list.add(new VarInsnNode(Opcodes.DLOAD, tmp));
064            list.add(new InsnNode(Opcodes.DNEG));
065    
066            return list;
067    
068        }
069    
070    }