/**
* Due to PI nodes and Moves, the initial label for a register may be another register. Fix up the
* value graph for cases where the initial register label was not removed.
*/
private void computeClosure() {
for (Enumeration<GraphNode> e = enumerateVertices(); e.hasMoreElements(); ) {
ValueGraphVertex v = (ValueGraphVertex) e.nextElement();
if (v.getName() instanceof Register) {
if (v.getLabel() instanceof Register) {
if (v.getName() != v.getLabel()) {
ValueGraphVertex v2 = getVertex(v.getLabel());
if (VM.VerifyAssertions) {
if (v2.getName() instanceof Register
&& v2.getLabel() instanceof Register
&& v2.getLabel() != v2.getName()) {
VM._assert(VM.NOT_REACHED);
}
}
v.copyVertex(v2);
}
}
}
}
}
/**
* Initialize the congruence classes, assuming that all nodes with the same label are congruent.
*/
private void initialize() {
// store a map from label -> congruenceClass
HashMap<Object, GVCongruenceClass> labelMap = new HashMap<Object, GVCongruenceClass>(10);
for (Enumeration<GraphNode> e = valueGraph.enumerateVertices(); e.hasMoreElements(); ) {
ValueGraphVertex v = (ValueGraphVertex) e.nextElement();
Object label = v.getLabel();
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());
}
}
/**
* 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
* @return whether the notes are assumed to be congruent
*/
private boolean checkCongruence(ValueGraphVertex v1, 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++) {
ValueGraphVertex target1 = v1.getTarget(i);
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;
}
