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.algorithmic.forward.instructions;
18
19 import org.apache.commons.nabla.algorithmic.forward.analysis.InstructionsTransformer;
20 import org.apache.commons.nabla.algorithmic.forward.analysis.MethodDifferentiator;
21 import org.apache.commons.nabla.core.DifferentiationException;
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.VarInsnNode;
26
27 /** Differentiation transformer for DSTORE instructions.
28 * <p>Each DSTORE instruction for double variable <i>k</i>
29 * is replaced by two DSTORE instructions for double variables
30 * <i>k+2</i> and <i>k</i> representing an expanded differential pair.
31 */
32 public class DStoreTransformer implements InstructionsTransformer {
33
34 // CHECKSTYLE: stop HideUtilityClassConstructor
35 /** Holder for the singleton instance.*/
36 private static class LazyHolder {
37 /** The singleton instance. */
38 private static final InstructionsTransformer INSTANCE = new DStoreTransformer();
39 }
40 // CHECKSTYLE: resume HideUtilityClassConstructor
41
42 /** Hidden constructor.
43 */
44 private DStoreTransformer() {
45 }
46
47 /** Get the singleton instance.
48 * <p>We use here the Initialization on Demand Holder idiom.</p>
49 * @return the singleton instance
50 */
51 public static InstructionsTransformer getInstance() {
52 return LazyHolder.INSTANCE;
53 }
54
55 /** {@inheritDoc} */
56 public InsnList getReplacement(final AbstractInsnNode insn,
57 final MethodDifferentiator methodDifferentiator)
58 throws DifferentiationException {
59 final int var = ((VarInsnNode) insn).var;
60 final InsnList list = new InsnList();
61 list.add(new VarInsnNode(Opcodes.DSTORE, var + 2));
62 list.add(new VarInsnNode(Opcodes.DSTORE, var));
63 return list;
64 }
65
66 }