Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
BytecodeTrimmer |
|
| 3.0;3 |
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.trimming; | |
18 | ||
19 | import org.objectweb.asm.tree.AbstractInsnNode; | |
20 | import org.objectweb.asm.tree.InsnList; | |
21 | ||
22 | /** Base class for code trimmers. | |
23 | * @version $Id$ | |
24 | */ | |
25 | public abstract class BytecodeTrimmer { | |
26 | ||
27 | /** Current instructions window. */ | |
28 | private AbstractInsnNode[] currentWindow; | |
29 | ||
30 | /** Simple constructor. | |
31 | * @param lookahead number of lookahead instructions | |
32 | */ | |
33 | 198 | protected BytecodeTrimmer(final int lookahead) { |
34 | 198 | currentWindow = new AbstractInsnNode[lookahead]; |
35 | 198 | } |
36 | ||
37 | /** Trim a list of instructions. | |
38 | * @param instructions list of instructions to optimize | |
39 | */ | |
40 | public void trim(final InsnList instructions) { | |
41 | ||
42 | // set up lookahead instructions | |
43 | 198 | currentWindow[0] = instructions.get(0); |
44 | 660 | for (int i = 1; (i < currentWindow.length) && (currentWindow[i - 1] != null); ++i) { |
45 | 462 | currentWindow[i] = currentWindow[i - 1].getNext(); |
46 | } | |
47 | ||
48 | // trim the whole instructions set using a sliding window | |
49 | 981 | while (currentWindow[currentWindow.length - 1] != null) { |
50 | ||
51 | // trim current window | |
52 | 783 | final boolean updated = trimWindow(instructions, currentWindow); |
53 | ||
54 | 783 | if (!updated) { |
55 | // slide the window ourselves one instruction forward | |
56 | 2434 | for (int i = 1; i < currentWindow.length; ++i) { |
57 | 1651 | currentWindow[i - 1] = currentWindow[i]; |
58 | } | |
59 | 783 | if (currentWindow[currentWindow.length - 1] != null) { |
60 | 783 | currentWindow[currentWindow.length - 1] = currentWindow[currentWindow.length - 1].getNext(); |
61 | } | |
62 | } | |
63 | ||
64 | 783 | } |
65 | ||
66 | 198 | } |
67 | ||
68 | /** Trim the current window of lookahead instructions. | |
69 | * @param instructions complete instructions list of instructions to trim | |
70 | * @param window current instructions window (belongs to the list) | |
71 | * @return true if instructions and window have been updated and are ready | |
72 | * for next iteration | |
73 | */ | |
74 | protected abstract boolean trimWindow(InsnList instructions, | |
75 | AbstractInsnNode[] window); | |
76 | ||
77 | } |