01: /***
02: * ASM Guide
03: * Copyright (c) 2007 Eric Bruneton
04: * All rights reserved.
05: *
06: * Redistribution and use in source and binary forms, with or without
07: * modification, are permitted provided that the following conditions
08: * are met:
09: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: * 2. Redistributions in binary form must reproduce the above copyright
12: * notice, this list of conditions and the following disclaimer in the
13: * documentation and/or other materials provided with the distribution.
14: * 3. Neither the name of the copyright holders nor the names of its
15: * contributors may be used to endorse or promote products derived from
16: * this software without specific prior written permission.
17: *
18: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19: * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21: * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
22: * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23: * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24: * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25: * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26: * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27: * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
28: * THE POSSIBILITY OF SUCH DAMAGE.
29: */package ch6.sec1;
30:
31: import static org.objectweb.asm.Opcodes.ALOAD;
32: import static org.objectweb.asm.Opcodes.ILOAD;
33: import static org.objectweb.asm.Opcodes.ISTORE;
34:
35: import java.util.Iterator;
36:
37: import org.objectweb.asm.tree.AbstractInsnNode;
38: import org.objectweb.asm.tree.InsnList;
39: import org.objectweb.asm.tree.LineNumberNode;
40: import org.objectweb.asm.tree.MethodNode;
41: import org.objectweb.asm.tree.VarInsnNode;
42:
43: /**
44: * ASM Guide example class.
45: *
46: * @author Eric Bruneton
47: */
48: public class RemoveLoadStoreTransformer extends MethodTransformer {
49:
50: public RemoveLoadStoreTransformer(MethodTransformer mt) {
51: super (mt);
52: }
53:
54: public void transform(MethodNode mn) {
55: InsnList insns = mn.instructions;
56: Iterator i = insns.iterator();
57: while (i.hasNext()) {
58: AbstractInsnNode i1 = (AbstractInsnNode) i.next();
59: if (i1 instanceof VarInsnNode) {
60: VarInsnNode v1 = (VarInsnNode) i1;
61: int op1 = v1.getOpcode();
62: if (op1 >= ILOAD && op1 <= ALOAD) {
63: AbstractInsnNode i2 = getNext(i);
64: if (i2 instanceof VarInsnNode) {
65: VarInsnNode v2 = (VarInsnNode) i2;
66: int op2 = v2.getOpcode();
67: if (op2 - ISTORE == op1 - ILOAD
68: && v2.var == v1.var) {
69: insns.remove(i1);
70: insns.remove(i2);
71: }
72: }
73: }
74: }
75: }
76: super .transform(mn);
77: }
78:
79: private static AbstractInsnNode getNext(Iterator i) {
80: while (i.hasNext()) {
81: AbstractInsnNode in = (AbstractInsnNode) i.next();
82: if (!(in instanceof LineNumberNode)) {
83: return in;
84: }
85: }
86: return null;
87: }
88: }
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