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.Type;
024    import org.objectweb.asm.tree.AbstractInsnNode;
025    import org.objectweb.asm.tree.InsnList;
026    import org.objectweb.asm.tree.InsnNode;
027    import org.objectweb.asm.tree.MethodInsnNode;
028    
029    /** Differentiation transformer for narrowing a derivative structure on the stack
030     * to a double.
031     * @version $Id$
032     */
033    public class NarrowingTransformer implements InstructionsTransformer {
034    
035        /** Simple constructor.
036         */
037        public NarrowingTransformer() {
038        }
039    
040        /** {@inheritDoc} */
041        public InsnList getReplacement(final AbstractInsnNode insn,
042                                       final MethodDifferentiator methodDifferentiator)
043            throws DifferentiationException {
044    
045            final InsnList list = new InsnList();
046    
047            list.add(new MethodInsnNode(Opcodes.INVOKEVIRTUAL, DS_TYPE.getInternalName(),
048                                        "getValue",
049                                        Type.getMethodDescriptor(Type.DOUBLE_TYPE)));
050    
051            // copy the instruction consuming the double (D2I, D2L or D2F)
052            list.add(new InsnNode(insn.getOpcode()));
053    
054            return list;
055    
056        }
057    
058    }