/// instruciton selection graph.
class VISIBILITY_HIDDEN ISelUpdater : public SelectionDAG::DAGUpdateListener {
SelectionDAG::allnodes_iterator &ISelPosition;
- bool HadDelete; // Indicate if any deletions were done.
public:
explicit ISelUpdater(SelectionDAG::allnodes_iterator &isp)
: ISelPosition(isp) {}
- /// NodeDeleted - remove node from the selection queue.
+ /// NodeDeleted - Handle nodes deleted from the graph. If the
+ /// node being deleted is the current ISelPosition node, update
+ /// ISelPosition.
+ ///
virtual void NodeDeleted(SDNode *N, SDNode *E) {
if (ISelPosition == SelectionDAG::allnodes_iterator(N))
++ISelPosition;
HandleSDNode Dummy(CurDAG->getRoot());
ISelPosition = next(SelectionDAG::allnodes_iterator(CurDAG->getRoot().getNode()));
- // Select pending nodes from the instruction selection queue
- // until no more nodes are left for selection.
+ // The AllNodes list is now topological-sorted. Visit the
+ // nodes by starting at the end of the list (the root of the
+ // graph) and preceding back toward the beginning (the entry
+ // node).
while (ISelPosition != CurDAG->allnodes_begin()) {
SDNode *Node = --ISelPosition;
+ // Skip dead nodes. DAGCombiner is expected to eliminate all dead nodes,
+ // but there are currently some corner cases that it misses. Also, this
+ // makes it theoretically possible to disable the DAGCombiner.
+ if (Node->use_empty())
+ continue;
#if 0
DAG.setSubgraphColor(Node, "red");
#endif