jasm.util
Class DeadCodeElimination

java.lang.Object
  jasm.util.DeadCodeElimination

public class DeadCodeElimination
extends java.lang.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

DeadCodeElimination()

Method Summary

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

buildLabelMap

protected java.util.HashMap<java.lang.String,java.lang.Integer> buildLabelMap(java.util.List<Bytecode> bytecodes)