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 DADD instructions.
029     * <p>This transformer is used when only the second argument
030     * of DADD is an expanded differential pair. It implements the
031     * classical differentiation rules for addition.</p>
032     * @see DAddTransformer1
033     * @see DAddTransformer12
034     */
035    public class DAddTransformer2 implements InstructionsTransformer {
036    
037        // CHECKSTYLE: stop HideUtilityClassConstructor
038        /** Holder for the singleton instance.*/
039        private static class LazyHolder  {
040            /** The singleton instance. */
041            private static final InstructionsTransformer INSTANCE = new DAddTransformer2();
042        }
043        // CHECKSTYLE: resume HideUtilityClassConstructor
044    
045        /** Hidden constructor.
046         */
047        private DAddTransformer2() {
048        }
049    
050        /** Get the singleton instance.
051         * <p>We use here the Initialization on Demand Holder idiom.</p>
052         * @return the singleton instance
053         */
054        public static InstructionsTransformer getInstance() {
055            return LazyHolder.INSTANCE;
056        }
057    
058        /** {@inheritDoc} */
059        public InsnList getReplacement(final AbstractInsnNode insn,
060                                       final MethodDifferentiator methodDifferentiator)
061            throws DifferentiationException {
062    
063            final int tmp = methodDifferentiator.getTmp(1);
064            final InsnList list = new InsnList();
065    
066            // operand stack initial state: a, b0, b1
067            list.add(new VarInsnNode(Opcodes.DSTORE, tmp)); // => a, b0
068            list.add(new InsnNode(Opcodes.DADD));           // => a+b0
069            list.add(new VarInsnNode(Opcodes.DLOAD,  tmp)); // => a+b0, b1
070    
071            return list;
072    
073        }
074    
075    }