/**
* Partition a congruence class.
*
* @param partition the class to partition
*/
private void partitionClass(OPT_GVCongruenceClass partition) {
// store a reference to the first node in c, which will serve
// as a representative for this class
Iterator i = partition.iterator();
OPT_ValueGraphVertex first = (OPT_ValueGraphVertex) i.next();
ArrayList newClasses = new ArrayList();
// now check each other node in c, to see if it matches the
// representative
ArrayList toRemove = new ArrayList();
for (; i.hasNext(); ) {
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) i.next();
if (!checkCongruence(first, v)) {
// NOT CONGRUENT!! split the partition. first check if
// v fits in any other newly created congruence classes
int index = findCongruenceMatch(newClasses, v);
if (index > -1) {
// MATCH FOUND!! place v in newClasses[index]
OPT_GVCongruenceClass match = (OPT_GVCongruenceClass) B.get(index);
match.addVertex(v);
v.setValueNumber(match.getValueNumber());
} else {
// NO MATCH FOUND!! create a new congruence class
// find the appropriate label for the new congruence class
// and create a new congruence class with this label
OPT_GVCongruenceClass c = createCongruenceClass(v);
newClasses.add(c);
c.addVertex(v);
v.setValueNumber(c.getValueNumber());
}
// mark v as to be removed from partition
// (Can't remove it yet while iterating over the set);
toRemove.add(v);
}
}
// remove necessary vertices
for (Iterator it = toRemove.iterator(); it.hasNext(); ) {
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) it.next();
partition.removeVertex(v);
}
// if needed place the original partition back on the work list
if ((newClasses.size() > 0) && (partition.size() > 1)) {
workList.push(partition);
}
// place any new congruence classes with size > 1 on the worklist
// also place any classes which might indirectly be affected
for (int j = 0; j < newClasses.size(); j++) {
OPT_GVCongruenceClass c = (OPT_GVCongruenceClass) newClasses.get(j);
if (c.size() > 1) workList.push(c);
addDependentClassesToWorklist(c);
}
}
/**
* Does vertex v belong to any congruence class in a vector? If so, returns the value number of
* the matching congruence class. If none found, returns -1.
*
* @param vector a vector of congruence classes
* @param v the vertex to search for
* @return the value number corresponding to the congruence class containing v. -1 iff no such
* class is found.
*/
private int findCongruenceMatch(ArrayList vector, OPT_ValueGraphVertex v) {
for (int i = 0; i < vector.size(); i++) {
OPT_GVCongruenceClass klass = (OPT_GVCongruenceClass) vector.get(i);
if (checkCongruence(v, klass)) {
return klass.getValueNumber();
}
}
return -1;
}
/**
* Initialize the congruence classes, assuming that all nodes with the same label are congruent.
*/
private void initialize() {
// store a map from label -> congruenceClass
HashMap labelMap = new HashMap(10);
for (Enumeration e = valueGraph.enumerateVertices(); e.hasMoreElements(); ) {
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) e.nextElement();
Object label = v.getLabel();
OPT_GVCongruenceClass c = findOrCreateCongruenceClass(label, labelMap);
// add this node to the congruence class
c.addVertex(v);
// set the value number for the node
v.setValueNumber(c.getValueNumber());
}
}