/**
* Tries to find an original value of the given node by traversing through proxies and unambiguous
* phis. Note that this method will perform an exhaustive search through phis. It is intended to
* be used during graph building, when phi nodes aren't yet canonicalized.
*
* @param proxy The node whose original value should be determined.
*/
public static ValueNode originalValue(ValueNode proxy) {
ValueNode v = proxy;
do {
if (v instanceof ValueProxy) {
v = ((ValueProxy) v).getOriginalValue();
} else if (v instanceof PhiNode) {
v = ((PhiNode) v).singleValue();
} else {
break;
}
} while (v != null);
// if the simple check fails (this can happen for complicated phi/proxy/phi constructs), we
// do an exhaustive search
if (v == null) {
NodeWorkList worklist = proxy.graph().createNodeWorkList();
worklist.add(proxy);
for (Node node : worklist) {
if (node instanceof ValueProxy) {
worklist.add(((ValueProxy) node).getOriginalValue());
} else if (node instanceof PhiNode) {
worklist.addAll(((PhiNode) node).values());
} else {
if (v == null) {
v = (ValueNode) node;
} else {
return null;
}
}
}
}
return v;
}
public OriginalValueSearch(ValueNode proxy) {
NodeWorkList worklist = proxy.graph().createNodeWorkList();
worklist.add(proxy);
for (Node node : worklist) {
if (node instanceof LimitedValueProxy) {
ValueNode originalValue = ((LimitedValueProxy) node).getOriginalNode();
if (!process(originalValue, worklist)) {
return;
}
} else if (node instanceof PhiNode) {
for (Node value : ((PhiNode) node).values()) {
if (!process((ValueNode) value, worklist)) {
return;
}
}
} else {
if (!process((ValueNode) node, null)) {
return;
}
}
}
}
/**
* Process a node as part of this search.
*
* @param node the next node encountered in the search
* @param worklist if non-null, {@code node} will be added to this list. Otherwise, {@code node}
* is treated as a candidate result.
* @return true if the search should continue, false if a definitive {@link #result} has been
* found
*/
private boolean process(ValueNode node, NodeWorkList worklist) {
if (node.isAlive()) {
if (worklist == null) {
if (result == null) {
// Initial candidate result: continue search
result = node;
} else if (result != node) {
// Conflicts with existing candidate: stop search with null result
result = null;
return false;
}
} else {
worklist.add(node);
}
}
return true;
}