polyglot.visit
Class CodeCleaner

java.lang.Object
  polyglot.visit.NodeVisitor
      polyglot.visit.CodeCleaner

public class CodeCleaner
extends NodeVisitor

The CodeCleaner runs over the AST and performs some trivial dead code elimination, while flattening blocks wherever possible.

Field Summary

protected AlphaRenamer	alphaRen
protected NodeFactory	nf

Constructor Summary

CodeCleaner(NodeFactory nf)
Creates a visitor for cleaning code.

Method Summary

protected java.util.List	clean(java.util.List l) Performs some trivial dead code elimination on a list of statements.
protected java.util.List	flattenBlock(Block b) Turns a Block into a list of Stmts.
protected java.util.Set	labelRefs(Block b) Traverses a Block and determines the set of label references.
Node	leave(Node old, Node n, NodeVisitor v) This method is called after all of the children of n have been visited.

Methods inherited from class polyglot.visit.NodeVisitor

begin, enter, enter, finish, finish, leave, override, override, toString, visitEdge

Methods inherited from class java.lang.Object

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

Field Detail

nf

protected NodeFactory nf

alphaRen

protected AlphaRenamer alphaRen

Constructor Detail

CodeCleaner

public CodeCleaner(NodeFactory nf)

Creates a visitor for cleaning code.

Parameters:

nf - The node factory to be used when generating new nodes.

Method Detail

leave

public Node leave(Node old,
                  Node n,
                  NodeVisitor v)

Description copied from class: NodeVisitor

This method is called after all of the children of n have been visited. In this case, these children were visited by the visitor v. This is the last chance for the visitor to modify the tree rooted at n. This method will be called exactly the same number of times as entry is called. That is, for each node that is not overriden, enter and leave are each called exactly once.

Note that if old == n then the vistior should make a copy of n before modifying it. It should then return the modified copy.

This method is typically called by the method leave(parent, old, n v). If a subclass overrides the method leave(parent, old, n v) then this method may not be called.

Overrides:

leave in class NodeVisitor

Parameters:

old - The original state of root of the current subtree.

n - The current state of the root of the current subtree.

v - The NodeVisitor object used to visit the children.

Returns:

The final result of the traversal of the tree rooted at n.

flattenBlock

protected java.util.List flattenBlock(Block b)

Turns a Block into a list of Stmts.

clean

protected java.util.List clean(java.util.List l)

Performs some trivial dead code elimination on a list of statements.

labelRefs

protected java.util.Set labelRefs(Block b)

Traverses a Block and determines the set of label references.