DirectedGraph: Add a constructor that takes a list of Nodes.

[jreiffers]

Summary

This makes it possible to efficiently build a graph without repeatedly iterating
over the list of nodes.

[bkramer]

Test case maybe?

llvm/include/llvm/ADT/DirectedGraph.h

186

Make it explicit

[jreiffers]

Add test.

[jreiffers]

Thanks, PTAL!

[jreiffers]

Fix test.

llvm/include/llvm/ADT/DirectedGraph.h

 
 /// Directed graph
 ///
 /// The graph is represented by a table of nodes.
 /// Each node contains a (possibly empty) list of outgoing edges.
 /// Each edge contains the target node it connects to.
 template <class NodeType, class EdgeType> class DirectedGraph {
 protected:
-  using NodeListTy = SmallVector<NodeType *, 10>;
   using EdgeListTy = SmallVector<EdgeType *, 10>;
 public:
+  using NodeListTy = SmallVector<NodeType *, 10>;
   using iterator = typename NodeListTy::iterator;
   using const_iterator = typename NodeListTy::const_iterator;
   using DGraphType = DirectedGraph<NodeType, EdgeType>;
 
   DirectedGraph() = default;
   explicit DirectedGraph(NodeType &N) : Nodes() { addNode(N); }
   DirectedGraph(const DGraphType &G) : Nodes(G.Nodes) {}
   DirectedGraph(DGraphType &&RHS) : Nodes(std::move(RHS.Nodes)) {}
+  explicit DirectedGraph(NodeListTy Nodes) : Nodes(std::move(Nodes)) {}
   DGraphType &operator=(const DGraphType &G) {
     Nodes = G.Nodes;
     return *this;
   }
   DGraphType &operator=(const DGraphType &&G) {
     Nodes = std::move(G.Nodes);
     return *this;
   }

llvm/unittests/ADT/DirectedGraphTest.cpp

 public:
   DGTestEdge() = delete;
   DGTestEdge(DGTestNode &N) : DGTestEdgeBase(N) {}
 };
 
 class DGTestGraph : public DGTestBase {
 public:
   DGTestGraph() = default;
+  using DGTestBase::DGTestBase;
   ~DGTestGraph(){};
 };
 
 using EdgeListTy = SmallVector<DGTestEdge *, 2>;
 
 //===--------------------------------------------------------------------===//
 // GraphTraits specializations for the DGTest
 //===--------------------------------------------------------------------===//
TEST(DirectedGraphTest, AddRemoveNode) {
   // Check that there are 2 nodes in the graph and only N2 is connected to N3.
   EXPECT_TRUE(DG.size() == 2);
   EXPECT_TRUE(N3.getEdges().empty());
   EdgeListTy EL;
   EXPECT_FALSE(DG.findIncomingEdgesToNode(N2, EL));
   EXPECT_TRUE(EL.empty());
 }
 
-TEST(DirectedGraphTest, SCC) {
+TEST(DirectedGraphTest, ConstructFromList) {
+  DGTestNode N1, N2;
+  DGTestGraph::NodeListTy nodes{&N1, &N2};
+  DGTestGraph graph(std::move(nodes));
+
+  EXPECT_FALSE(graph.addNode(N1));
+  EXPECT_FALSE(graph.addNode(N2));
+}
 
+TEST(DirectedGraphTest, SCC) {
   DGTestGraph DG;
   DGTestNode N1, N2, N3, N4;
   DGTestEdge E1(N1), E2(N2), E3(N3), E4(N4);
   DG.addNode(N1);
   DG.addNode(N2);
   DG.addNode(N3);
   DG.addNode(N4);
   DG.connect(N1, N2, E2);