jasm.util

Class DeadCodeElimination

java.lang.Object

jasm.util.DeadCodeElimination

public class DeadCodeElimination
extends Object

The purpose of this pass is to eliminate any statically determinable dead-code. This is required to generate correct java bytecode. For example, consider the following Java code:

 void f(...) {
  if(...) {
   return ...;
  else {
   return ...;
  }
 }
 

Then, the front-end will produce the following (pseudo) bytecode:

 void f(...) {
  if(...) goto iftrue0;
  return ...;
  goto ifexit0;
 iftrue0:
   return ...;
 ifexit0:
 }
 

Here, we can see quite clearly that the code after the first return statement, as well as the ifexit label, is dead.

Author:

David J. Pearce

Constructor Summary

Constructors

Constructor and Description
DeadCodeElimination()

Method Summary

Modifier and Type	Method and Description
void	apply(ClassFile.Method method)
void	apply(ClassFile cf)
void	apply(Code code)
protected HashMap<String,Integer>	buildLabelMap(List<Bytecode> bytecodes)
protected void	visit(int index, HashSet<Integer> visited, HashMap<String,Integer> labels, List<Bytecode> bytecodes)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DeadCodeElimination

public DeadCodeElimination()

Method Detail

apply

public void apply(ClassFile cf)

apply

public void apply(ClassFile.Method method)

apply

public void apply(Code code)

visit

protected void visit(int index,
                     HashSet<Integer> visited,
                     HashMap<String,Integer> labels,
                     List<Bytecode> bytecodes)

buildLabelMap

protected HashMap<String,Integer> buildLabelMap(List<Bytecode> bytecodes)