/**
* Utility method used in the construction of {@link UnitGraph}s, to be called only after the
* unitToPreds and unitToSuccs maps have been built.
*
* <p><code>UnitGraph</code> provides an implementation of <code>buildHeadsAndTails()</code> which
* defines the graph's set of heads to include the first {@link Unit} in the graph's body,
* together with any other <tt>Unit</tt> which has no predecessors. It defines the graph's set of
* tails to include all <tt>Unit</tt>s with no successors. Subclasses of <code>UnitGraph</code>
* may override this method to change the criteria for classifying a node as a head or tail.
*/
protected void buildHeadsAndTails() {
List tailList = new ArrayList();
List headList = new ArrayList();
for (Iterator unitIt = unitChain.iterator(); unitIt.hasNext(); ) {
Unit s = (Unit) unitIt.next();
List succs = (List) unitToSuccs.get(s);
if (succs.size() == 0) {
tailList.add(s);
}
List preds = (List) unitToPreds.get(s);
if (preds.size() == 0) {
headList.add(s);
}
}
// Add the first Unit, even if it is the target of
// a branch.
Unit entryPoint = (Unit) unitChain.getFirst();
if (!headList.contains(entryPoint)) {
headList.add(entryPoint);
}
tails = Collections.unmodifiableList(tailList);
heads = Collections.unmodifiableList(headList);
}
/**
* Utility method that replaces the values of a {@link Map}, which must be instances of {@link
* List}, with unmodifiable equivalents.
*
* @param map The map whose values are to be made unmodifiable.
*/
protected static void makeMappedListsUnmodifiable(Map map) {
for (Iterator it = map.entrySet().iterator(); it.hasNext(); ) {
Map.Entry entry = (Map.Entry) it.next();
List value = (List) entry.getValue();
if (value.size() == 0) {
entry.setValue(Collections.EMPTY_LIST);
} else {
entry.setValue(Collections.unmodifiableList(value));
}
}
}
/**
* Computes the analysis given a UnitGraph computed from a method body. It is recommended that a
* ExceptionalUnitGraph (or similar) be provided for correct results in the case of exceptional
* control flow.
*
* @param g a graph on which to compute the analysis.
* @see ExceptionalUnitGraph
*/
public SimpleLiveLocals(UnitGraph graph) {
if (Options.v().time()) Timers.v().liveTimer.start();
if (Options.v().verbose())
G.v()
.out
.println(
"["
+ graph.getBody().getMethod().getName()
+ "] Constructing SimpleLiveLocals...");
SimpleLiveLocalsAnalysis analysis = new SimpleLiveLocalsAnalysis(graph);
if (Options.v().time()) Timers.v().livePostTimer.start();
// Build unitToLocals map
{
unitToLocalsAfter = new HashMap<Unit, List>(graph.size() * 2 + 1, 0.7f);
unitToLocalsBefore = new HashMap<Unit, List>(graph.size() * 2 + 1, 0.7f);
Iterator unitIt = graph.iterator();
while (unitIt.hasNext()) {
Unit s = (Unit) unitIt.next();
FlowSet set = (FlowSet) analysis.getFlowBefore(s);
unitToLocalsBefore.put(s, Collections.unmodifiableList(set.toList()));
set = (FlowSet) analysis.getFlowAfter(s);
unitToLocalsAfter.put(s, Collections.unmodifiableList(set.toList()));
}
}
if (Options.v().time()) Timers.v().livePostTimer.end();
if (Options.v().time()) Timers.v().liveTimer.end();
}
/**
* Utility method that produces a new map from the {@link Unit}s of this graph's body to the union
* of the values stored in the two argument {@link Map}s, used to combine the maps of exceptional
* and unexceptional predecessors and successors into maps of all predecessors and successors. The
* values stored in both argument maps must be {@link List}s of {@link Unit}s, which are assumed
* not to contain any duplicate <tt>Unit</tt>s.
*
* @param mapA The first map to be combined.
* @param mapB The second map to be combined.
*/
protected Map combineMapValues(Map mapA, Map mapB) {
// The duplicate screen
Map result = new HashMap(mapA.size() * 2 + 1, 0.7f);
for (Iterator chainIt = unitChain.iterator(); chainIt.hasNext(); ) {
Unit unit = (Unit) chainIt.next();
List listA = (List) mapA.get(unit);
if (listA == null) {
listA = Collections.EMPTY_LIST;
}
List listB = (List) mapB.get(unit);
if (listB == null) {
listB = Collections.EMPTY_LIST;
}
int resultSize = listA.size() + listB.size();
if (resultSize == 0) {
result.put(unit, Collections.EMPTY_LIST);
} else {
List resultList = new ArrayList(resultSize);
Iterator listIt = null;
// As a minor optimization of the duplicate screening,
// copy the longer list first.
if (listA.size() >= listB.size()) {
resultList.addAll(listA);
listIt = listB.iterator();
} else {
resultList.addAll(listB);
listIt = listA.iterator();
}
while (listIt.hasNext()) {
Object element = listIt.next();
// It is possible for there to be both an exceptional
// and an unexceptional edge connecting two Units
// (though probably not in a class generated by
// javac), so we need to screen for duplicates. On the
// other hand, we expect most of these lists to have
// only one or two elements, so it doesn't seem worth
// the cost to build a Set to do the screening.
if (!resultList.contains(element)) {
resultList.add(element);
}
}
result.put(unit, Collections.unmodifiableList(resultList));
}
}
return result;
}
