1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.nabla.forward.instructions;
18
19 import org.apache.commons.nabla.DifferentiationException;
20 import org.apache.commons.nabla.forward.analysis.InstructionsTransformer;
21 import org.apache.commons.nabla.forward.analysis.MethodDifferentiator;
22 import org.objectweb.asm.Opcodes;
23 import org.objectweb.asm.tree.AbstractInsnNode;
24 import org.objectweb.asm.tree.InsnList;
25 import org.objectweb.asm.tree.InsnNode;
26
27 /** Differentiation transformer for DRETURN instructions.
28 * <p>DRETURN instructions are replaced by ARETURN instructions
29 * as a reference to a {@link
30 * org.apache.commons.math3.analysis.differentiation.DerivativeStructure}
31 * instance uses only one stack slot instead of two.</p>
32 * @version $Id$
33 */
34 public class DReturnTransformer implements InstructionsTransformer {
35
36 /** Indicator for top stack element conversion. */
37 private final boolean stack0Converted;
38
39 /** Simple constructor.
40 * @param stack0Converted if true, the top level stack element has already been converted
41 */
42 public DReturnTransformer(final boolean stack0Converted) {
43 this.stack0Converted = stack0Converted;
44 }
45
46 /** {@inheritDoc} */
47 public InsnList getReplacement(final AbstractInsnNode insn,
48 final MethodDifferentiator methodDifferentiator)
49 throws DifferentiationException {
50
51 final InsnList list = new InsnList();
52
53 if (!stack0Converted) {
54 // add conversion for top level stack element
55 list.add(methodDifferentiator.doubleToDerivativeStructureConversion());
56 }
57
58 // add the return instruction for a reference type
59 list.add(new InsnNode(Opcodes.ARETURN));
60
61 return list;
62
63 }
64
65 }