| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| import java.util.Iterator; |
| |
| import org.apache.bcel.Repository; |
| import org.apache.bcel.classfile.JavaClass; |
| import org.apache.bcel.classfile.Method; |
| import org.apache.bcel.generic.ConstantPoolGen; |
| import org.apache.bcel.generic.InstructionHandle; |
| import org.apache.bcel.generic.InstructionList; |
| import org.apache.bcel.generic.InstructionTargeter; |
| import org.apache.bcel.generic.MethodGen; |
| import org.apache.bcel.generic.TargetLostException; |
| import org.apache.bcel.util.InstructionFinder; |
| |
| /** |
| * Remove NOPs from given class |
| * |
| * @version $Id$ |
| */ |
| public class Peephole { |
| |
| public static void main(String[] argv) { |
| try { |
| // Load the class from CLASSPATH. |
| JavaClass clazz = Repository.lookupClass(argv[0]); |
| Method[] methods = clazz.getMethods(); |
| ConstantPoolGen cp = new ConstantPoolGen(clazz.getConstantPool()); |
| |
| for (int i = 0; i < methods.length; i++) { |
| if (!(methods[i].isAbstract() || methods[i].isNative())) { |
| MethodGen mg = new MethodGen(methods[i], clazz.getClassName(), cp); |
| Method stripped = removeNOPs(mg); |
| |
| if (stripped != null) { |
| methods[i] = stripped; // Overwrite with stripped method |
| } |
| } |
| } |
| |
| // Dump the class to <class name>_.class |
| clazz.setConstantPool(cp.getFinalConstantPool()); |
| clazz.dump(clazz.getClassName() + "_.class"); |
| } catch (Exception e) { |
| e.printStackTrace(); |
| } |
| } |
| |
| private static Method removeNOPs(MethodGen mg) { |
| InstructionList il = mg.getInstructionList(); |
| InstructionFinder f = new InstructionFinder(il); |
| String pat = "NOP+"; // Find at least one NOP |
| InstructionHandle next = null; |
| int count = 0; |
| |
| for (Iterator<InstructionHandle[]> e = f.search(pat); e.hasNext(); ) { |
| InstructionHandle[] match = e.next(); |
| InstructionHandle first = match[0]; |
| InstructionHandle last = match[match.length - 1]; |
| |
| // Some nasty Java compilers may add NOP at end of method. |
| if ((next = last.getNext()) == null) { |
| break; |
| } |
| |
| count += match.length; |
| |
| // Delete NOPs and redirect any references to them to the following (non-nop) instruction. |
| try { |
| il.delete(first, last); |
| } catch (TargetLostException e2) { |
| for (InstructionHandle target : e2.getTargets()) { |
| for (InstructionTargeter targeter : target.getTargeters()) { |
| targeter.updateTarget(target, next); |
| } |
| } |
| } |
| } |
| |
| Method m = null; |
| |
| if (count > 0) { |
| System.out.println("Removed " + count + " NOP instructions from method " + mg.getName()); |
| m = mg.getMethod(); |
| } |
| |
| il.dispose(); // Reuse instruction handles |
| return m; |
| } |
| } |