private void removeRedundantCopies(
Program program, List<MutableGraphNode> interferenceGraph, DisjointSet congruenceClasses) {
for (int i = 0; i < program.basicBlockCount(); ++i) {
BasicBlock block = program.basicBlockAt(i);
for (int j = 0; j < block.getInstructions().size(); ++j) {
Instruction insn = block.getInstructions().get(j);
if (!(insn instanceof AssignInstruction)) {
continue;
}
AssignInstruction assignment = (AssignInstruction) insn;
boolean interfere = false;
int copyClass = congruenceClasses.find(assignment.getReceiver().getIndex());
int origClass = congruenceClasses.find(assignment.getAssignee().getIndex());
for (MutableGraphEdge edge : interferenceGraph.get(origClass).getEdges()) {
if (edge.getFirst() == edge.getSecond()) {
continue;
}
int neighbour = congruenceClasses.find(edge.getSecond().getTag());
if (neighbour == copyClass || neighbour == origClass) {
interfere = true;
break;
}
}
if (!interfere) {
int newClass = congruenceClasses.union(copyClass, origClass);
block.getInstructions().set(j, new EmptyInstruction());
if (newClass == interferenceGraph.size()) {
MutableGraphNode newNode = new MutableGraphNode(interferenceGraph.size());
interferenceGraph.add(newNode);
}
for (MutableGraphEdge edge :
interferenceGraph.get(origClass).getEdges().toArray(new MutableGraphEdge[0])) {
if (edge.getFirst() == interferenceGraph.get(origClass)) {
edge.setFirst(interferenceGraph.get(newClass));
}
if (edge.getSecond() == interferenceGraph.get(origClass)) {
edge.setSecond(interferenceGraph.get(newClass));
}
}
for (MutableGraphEdge edge :
interferenceGraph.get(copyClass).getEdges().toArray(new MutableGraphEdge[0])) {
if (edge.getFirst() == interferenceGraph.get(copyClass)) {
edge.setFirst(interferenceGraph.get(newClass));
}
if (edge.getSecond() == interferenceGraph.get(copyClass)) {
edge.setSecond(interferenceGraph.get(newClass));
}
}
interferenceGraph.set(copyClass, interferenceGraph.get(newClass));
interferenceGraph.set(origClass, interferenceGraph.get(newClass));
}
}
}
}
private static void joinClassNodes(List<MutableGraphNode> graph, DisjointSet classes) {
int sz = graph.size();
for (int i = 0; i < sz; ++i) {
int cls = classes.find(i);
while (cls >= graph.size()) {
graph.add(new MutableGraphNode(graph.size()));
}
if (cls != i) {
for (MutableGraphEdge edge : graph.get(i).getEdges().toArray(new MutableGraphEdge[0])) {
if (edge.getFirst() == graph.get(i)) {
edge.setFirst(graph.get(cls));
}
if (edge.getSecond() == graph.get(i)) {
edge.setSecond(graph.get(cls));
}
}
graph.set(i, graph.get(cls));
}
}
}