/**
* Does the current state of the algorithm optimistically assume that two nodes are congruent?
* Note: this can return false even if the value numbers are currently the same.
*
* @param v1 first vertex
* @param v2 second vertex
*/
private boolean checkCongruence(OPT_ValueGraphVertex v1, OPT_ValueGraphVertex v2) {
if (v1 == v2) return true;
// make sure the two nodes have the same label
if (v1.getLabel() != v2.getLabel()) return false;
// make sure that the operands match
int arity = v1.getArity();
for (int i = 0; i < arity; i++) {
OPT_ValueGraphVertex target1 = v1.getTarget(i);
OPT_ValueGraphVertex target2 = v2.getTarget(i);
// if either target is null, then that particular control
// flow path is never realized, so assume TOP
if ((target1 == null) || (target2 == null)) continue;
if (target1.getValueNumber() != target2.getValueNumber()) return false;
}
return true;
}
/**
* 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());
}
}
