1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2014 Eric Lafortune (eric@graphics.cornell.edu)
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the Free
9 * Software Foundation; either version 2 of the License, or (at your option)
10 * any later version.
11 *
12 * This program is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 * more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21package proguard.optimize.peephole;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.*;
25import proguard.classfile.attribute.visitor.AttributeVisitor;
26import proguard.classfile.editor.CodeAttributeEditor;
27import proguard.classfile.instruction.visitor.InstructionVisitor;
28import proguard.classfile.util.SimplifiedVisitor;
29
30/**
31 * This AttributeVisitor sets up and applies the peephole optimizations of its
32 * instruction visitor. The instruction visitor should be using the same
33 * (optional) branch target finder and code attribute editor.
34 *
35 * @author Eric Lafortune
36 */
37public class PeepholeOptimizer
38extends      SimplifiedVisitor
39implements   AttributeVisitor
40{
41    private final BranchTargetFinder  branchTargetFinder;
42    private final CodeAttributeEditor codeAttributeEditor;
43    private final InstructionVisitor  instructionVisitor;
44
45
46    /**
47     * Creates a new PeepholeOptimizer.
48     * @param codeAttributeEditor the code attribute editor that will be reset
49     *                            and then executed.
50     * @param instructionVisitor  the instruction visitor that performs
51     *                            peephole optimizations using the above code
52     *                            attribute editor.
53     */
54    public PeepholeOptimizer(CodeAttributeEditor codeAttributeEditor,
55                             InstructionVisitor  instructionVisitor)
56    {
57        this(null, codeAttributeEditor, instructionVisitor);
58    }
59
60
61    /**
62     * Creates a new PeepholeOptimizer.
63     * @param branchTargetFinder  branch target finder that will be initialized
64     *                            to indicate branch targets in the visited code.
65     * @param codeAttributeEditor the code attribute editor that will be reset
66     *                            and then executed.
67     * @param instructionVisitor  the instruction visitor that performs
68     *                            peephole optimizations using the above code
69     *                            attribute editor.
70     */
71    public PeepholeOptimizer(BranchTargetFinder  branchTargetFinder,
72                             CodeAttributeEditor codeAttributeEditor,
73                             InstructionVisitor  instructionVisitor)
74    {
75        this.branchTargetFinder  = branchTargetFinder;
76        this.codeAttributeEditor = codeAttributeEditor;
77        this.instructionVisitor  = instructionVisitor;
78    }
79
80
81    // Implementations for AttributeVisitor.
82
83    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
84
85
86    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
87    {
88        if (branchTargetFinder != null)
89        {
90            // Set up the branch target finder.
91            branchTargetFinder.visitCodeAttribute(clazz, method, codeAttribute);
92        }
93
94        // Set up the code attribute editor.
95        codeAttributeEditor.reset(codeAttribute.u4codeLength);
96
97        // Find the peephole optimizations.
98        codeAttribute.instructionsAccept(clazz, method, instructionVisitor);
99
100        // Apply the peephole optimizations.
101        codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
102    }
103}
104