import java.io.*;
import de.fub.bytecode.classfile.*;
import de.fub.bytecode.generic.*;
import de.fub.bytecode.Repository;
/**
* Remove NOPs from given class
*
* @version $Id: Peephole.java,v 1.3 2001/05/09 09:26:57 dahm Exp $
* @author M. Dahm
*/
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++) {
MethodGen mg = new MethodGen(methods[i],
clazz.getClassName(), cp);
Method stripped = removeNOPs(mg);
if(stripped != null) // Any NOPs stripped?
methods[i] = stripped; // Overwrite with stripped method
}
/* Dump the class to _.class
*/
clazz.setConstantPool(cp.getFinalConstantPool());
clazz.dump(clazz.getClassName() + "_.class");
} catch(Exception e) { e.printStackTrace(); }
}
private static final Method removeNOPs(MethodGen mg) {
InstructionList il = mg.getInstructionList();
FindPattern f = new FindPattern(il);
String pat = "(`NOP')+"; // Find at least one NOP
InstructionHandle next = null;
int count = 0;
for(InstructionHandle ih = f.search(pat); // Search with regular expression
ih != null;
ih = f.search(pat, next)) {
InstructionHandle[] match = f.getMatch();
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 e) {
InstructionHandle[] targets = e.getTargets();
for(int i=0; i < targets.length; i++) {
InstructionTargeter[] targeters = targets[i].getTargeters();
for(int j=0; j < targeters.length; j++)
targeters[j].updateTarget(targets[i], 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;
}
}