[turbofan] Handle dead diamonds in scheduling and add a test.

src/compiler/graph-visualizer.cc

Index: src/compiler/graph-visualizer.cc
diff --git a/src/compiler/graph-visualizer.cc b/src/compiler/graph-visualizer.cc
index 6a9e620d0bc8d2a71a58e5a040f735d9b04d0dcb..6493093dae6365a2ad02b0cc125cec9cce6046fb 100644
--- a/src/compiler/graph-visualizer.cc
+++ b/src/compiler/graph-visualizer.cc
@@ -612,6 +612,7 @@ std::ostream& operator<<(std::ostream& os, const AsRPO& ar) {
   Zone local_zone;
   ZoneVector<byte> state(ar.graph.NodeCount(), kUnvisited, &local_zone);
   ZoneStack<Node*> stack(&local_zone);
+  ZoneVector<Node*> all(&local_zone);
 
   stack.push(ar.graph.end());
   state[ar.graph.end()->id()] = kOnStack;
@@ -627,6 +628,7 @@ std::ostream& operator<<(std::ostream& os, const AsRPO& ar) {
       }
     }
     if (pop) {
+      all.push_back(n);
       state[n->id()] = kVisited;
       stack.pop();
       os << "#" << n->id() << ":" << *n->op() << "(";
@@ -638,6 +640,29 @@ std::ostream& operator<<(std::ostream& os, const AsRPO& ar) {
       os << ")" << std::endl;
     }
   }
+
+  bool first = true;
+
+  for (size_t i = 0; i < all.size(); i++) {
+    Node* l = all[i];
+    for (Node* n : l->uses()) {
+      if (state[n->id()] == kUnvisited) {
+        state[n->id()] = kVisited;
+        all.push_back(n);
+        if (first) {
+          os << "Gray nodes:" << std::endl;
+          first = false;
+        }
+        os << "#" << n->id() << ":" << *n->op() << "(";
+        int j = 0;
+        for (Node* const i : n->inputs()) {
+          if (j++ > 0) os << ", ";
+          os << "#" << SafeId(i) << ":" << SafeMnemonic(i);
+        }
+        os << ")" << std::endl;
+      }
+    }
+  }
   return os;
 }
 }  // namespace compiler