/** Merge the congruence classes containing vertices v1 and v2.; */
public void mergeClasses(OPT_ValueGraphVertex v1, OPT_ValueGraphVertex v2) {
if (DEBUG) {
System.out.println("@@@@ mergeClasses called with v1 = " + v1 + " ; v2 = " + v2);
}
int val1 = v1.getValueNumber();
int val2 = v2.getValueNumber();
if (val1 == val2) return;
OPT_GVCongruenceClass class1 = (OPT_GVCongruenceClass) B.get(val1);
while (true) {
OPT_GVCongruenceClass class2 = (OPT_GVCongruenceClass) B.get(val2);
Iterator i = class2.iterator();
if (!i.hasNext()) break;
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) i.next();
if (DEBUG)
System.out.println("@@@@ moving vertex " + v + " from class " + val2 + " to class " + val1);
class1.addVertex(v);
class2.removeVertex(v);
v.setValueNumber(val1);
}
// Null out entry for val2
B.set(val2, null);
}
/** Print the value numbers for each node in the value graph. */
public void printValueNumbers() {
for (Enumeration e = valueGraph.enumerateVertices(); e.hasMoreElements(); ) {
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) e.nextElement();
int valueNumber = v.getValueNumber();
OPT_GVCongruenceClass c = (OPT_GVCongruenceClass) B.get(valueNumber);
System.out.println(v.name + " " + valueNumber + " " + c.getLabel());
}
}
/**
* 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());
}
}
/**
* Initialize the work list. A congruence class gets put on the work list if any two nodes in the
* class point to corresponding targets in separate partitions.
*/
private void initializeWorkList() {
for (Iterator it = B.iterator(); it.hasNext(); ) {
OPT_GVCongruenceClass c = (OPT_GVCongruenceClass) it.next();
if (c.size() == 1) continue;
// store a reference to the first node in c
Iterator i = c.iterator();
OPT_ValueGraphVertex first = (OPT_ValueGraphVertex) i.next();
// now check that each other target matches the first element
// if not, add this class to the work list
congruenceClass:
for (; i.hasNext(); ) {
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) i.next();
if (!checkCongruence(first, v)) {
workList.push(c);
break congruenceClass;
}
}
}
}
/**
* Assuming congruence class c has changed: find all other classes that might be affected, and add
* them to the worklist
*
* @param c the congruence class that has changed
*/
private void addDependentClassesToWorklist(OPT_GVCongruenceClass c) {
// for each element of this congruence class:
for (Iterator elements = c.iterator(); elements.hasNext(); ) {
OPT_ValueGraphVertex v = (OPT_ValueGraphVertex) elements.next();
// for each vertex which points to v in the value graph
for (Enumeration e = v.inNodes(); e.hasMoreElements(); ) {
OPT_ValueGraphVertex in = (OPT_ValueGraphVertex) e.nextElement();
int vn = in.getValueNumber();
OPT_GVCongruenceClass x = (OPT_GVCongruenceClass) B.get(vn);
workList.push(x);
}
}
}
/**
* Definitely-different relation for two value numbers. Returns true for the following cases:
*
* <ul>
* <li>v1 and v2 are both constants, but don't match
* <li>v1 and v2 both result from NEW statements, but don't match
* <li>one of v1 and v2 is a parameter, and the other results from a new statement
* </ul>
*
* <p>TODO: add more smarts
*
* @param v1 first value number
* @param v2 second value number
* @return true iff the value numbers for two variables are definitely different
*/
public boolean DD(int v1, int v2) {
if ((v1 == -1) || (v2 == -1)) return false;
OPT_GVCongruenceClass class1 = (OPT_GVCongruenceClass) B.get(v1);
OPT_GVCongruenceClass class2 = (OPT_GVCongruenceClass) B.get(v2);
Object label1 = class1.getLabel();
Object label2 = class2.getLabel();
// if one is a constant, they must both be ...
if (isConstant(label1) && !isConstant(label2)) return false;
if (!isConstant(label1) && isConstant(label2)) return false;
if (isConstant(label1)) return (v1 != v2);
// handle DD for allocations
if (isBornAtAllocation(label1)) {
if (isBornAtAllocation(label2)) {
// both are NEW. Are they dd?
return (v1 != v2);
} else if (class2.containsParameter()) {
// one is NEW, other is parameter. They are DD.
return true;
}
} else {
if (isBornAtAllocation(label2)) {
if (class1.containsParameter()) {
// one is NEW, other is parameter. They are DD.
return true;
}
}
}
// assume parameters are not aliased?
if (NO_PARAM_ALIAS) {
if (v1 != v2) {
if (class1.containsParameter()) {
if (class2.containsParameter()) {
return true;
}
}
}
}
// if we haven't figured out they're DD, return false;
return false;
}
/**
* Does the current state of the algorithm optimistically assume that a vertex v is congruent to
* the vertices in a congruence class? Note: this can return true even if if the value numbers
* don't currently match.
*
* @param v the vertex in question
* @param c the congurence class to check
* @return true or false
*/
private boolean checkCongruence(OPT_ValueGraphVertex v, OPT_GVCongruenceClass c) {
OPT_ValueGraphVertex r = c.getRepresentative();
boolean result = checkCongruence(r, v);
return result;
}
/**
* 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);
}
}