add debug info to dep_graph

src/librustc/dep_graph/thread.rs

@@ -28,6 +28,7 @@ use super::DepGraphQuery;
 use super::DepNode;
 use super::edges::DepGraphEdges;
 
+#[derive(Debug)]
 pub enum DepMessage {
     Read(DepNode<DefId>),
     Write(DepNode<DefId>),
@@ -117,6 +118,8 @@ impl DepGraphThreadData {
     /// the buffer is full, this may swap.)
     #[inline]
     pub fn enqueue(&self, message: DepMessage) {
+        debug!("enqueue: {:?} tasks_pushed={}", message, self.tasks_pushed.get());
+
         // Regardless of whether dep graph construction is enabled, we
         // still want to check that we always have a valid task on the
         // stack when a read/write/etc event occurs.

src/librustc/dep_graph/visit.rs

@@ -42,7 +42,8 @@ pub fn visit_all_items_in_krate<'a, 'tcx, V, F>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             let _task = self.tcx.dep_graph.in_task(task_id);
             debug!("Started task {:?}", task_id);
             self.tcx.dep_graph.read(DepNode::Hir(item_def_id));
-            self.visitor.visit_item(i)
+            self.visitor.visit_item(i);
+            debug!("Ended task {:?}", task_id);
         }
     }