Add unextractable to reachability analysis

dag_in_context/src/greedy_dag_extractor.rs

@@ -193,13 +193,17 @@ pub fn extract(
     let mut frontier: VecDeque<NodeId> = root_nodes(&egraph.nodes).collect();
     let mut reachable = HashSet::new();
     while let Some(nid) = frontier.pop_front() {
+        let node = egraph.nodes.get(&nid).unwrap();
+        // Don't add unextractable nodes to the reachable set
+        if unextractables.contains(&node.op) {
+            continue;
+        }
         // Try to add the node to the reachable set
         if !reachable.insert(nid.clone()) {
             // If we already reached the node, we're in a cycle
             continue;
         }
         // Add the non-ignored children to the frontier
-        let node = egraph.nodes.get(&nid).unwrap();
         let ignored_children = cm.ignored_children(&node.op);
         for (i, child) in node.children.iter().enumerate() {
             if !ignored_children.contains(&i) {
@@ -230,9 +234,8 @@ pub fn extract(
         let class_id = n2c(&node_id);
         let node = &egraph[&node_id];
 
-        if unextractables.contains(&node.op) || !reachable.contains(&node_id) {
-            continue;
-        }
+        assert!(reachable.contains(&node_id));
+        assert!(!unextractables.contains(&node.op));
 
         let ignored_children = cm.ignored_children(&node.op);
         let all_non_ignored_children_have_costs = node
@@ -254,7 +257,12 @@ pub fn extract(
                 costs.insert(class_id.clone(), cost_set);
             }
 
-            worklist.extend(parents[class_id].iter().cloned());
+            worklist.extend(
+                parents[class_id]
+                    .iter()
+                    .filter(|nid| reachable.contains(nid))
+                    .cloned(),
+            );
         }
     }