[LCG] Add the really, *really* boring edge insertion case: adding an

edge entirely within an existing SCC. Shockingly, making the connected
component more connected is ... a total snooze fest. =]

Anyways, its wired up, and I even added a test case to make sure it
pretty much sorta works. =D

llvm-svn: 207631

llvm/include/llvm/Analysis/LazyCallGraph.h

@@ -186,6 +186,9 @@ public:
     /// \brief Internal helper to insert a callee.
     void insertEdgeInternal(Function &Callee);
 
+    /// \brief Internal helper to insert a callee.
+    void insertEdgeInternal(Node &CalleeN);
+
     /// \brief Internal helper to remove a callee from this node.
     void removeEdgeInternal(Function &Callee);
 
@@ -249,6 +252,12 @@ public:
     /// Note that these methods sometimes have complex runtimes, so be careful
     /// how you call them.
 
+    /// \brief Insert an edge from one node in this SCC to another in this SCC.
+    ///
+    /// By the definition of an SCC, this does not change the nature or make-up
+    /// of any SCCs.
+    void insertIntraSCCEdge(Node &CallerN, Node &CalleeN);
+
     /// \brief Remove an edge whose source is in this SCC and target is *not*.
     ///
     /// This removes an inter-SCC edge. All inter-SCC edges originating from

llvm/lib/Analysis/LazyCallGraph.cpp

@@ -76,11 +76,16 @@ LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F)
 }
 
 void LazyCallGraph::Node::insertEdgeInternal(Function &Callee) {
-  CalleeIndexMap.insert(std::make_pair(&Callee, Callees.size()));
   if (Node *N = G->lookup(Callee))
-    Callees.push_back(N);
-  else
-    Callees.push_back(&Callee);
+    return insertEdgeInternal(*N);
+
+  CalleeIndexMap.insert(std::make_pair(&Callee, Callees.size()));
+  Callees.push_back(&Callee);
+}
+
+void LazyCallGraph::Node::insertEdgeInternal(Node &CalleeN) {
+  CalleeIndexMap.insert(std::make_pair(&CalleeN.getFunction(), Callees.size()));
+  Callees.push_back(&CalleeN);
 }
 
 void LazyCallGraph::Node::removeEdgeInternal(Function &Callee) {
@@ -157,6 +162,16 @@ void LazyCallGraph::SCC::insert(Node &N) {
   G->SCCMap[&N] = this;
 }
 
+void LazyCallGraph::SCC::insertIntraSCCEdge(Node &CallerN, Node &CalleeN) {
+  // First insert it into the caller.
+  CallerN.insertEdgeInternal(CalleeN);
+
+  assert(G->SCCMap.lookup(&CallerN) == this && "Caller must be in this SCC.");
+  assert(G->SCCMap.lookup(&CalleeN) == this && "Callee must be in this SCC.");
+
+  // Nothing changes about this SCC or any other.
+}
+
 void LazyCallGraph::SCC::removeInterSCCEdge(Node &CallerN, Node &CalleeN) {
   // First remove it from the node.
   CallerN.removeEdgeInternal(CalleeN.getFunction());

llvm/unittests/Analysis/LazyCallGraphTest.cpp

@@ -386,6 +386,52 @@ TEST(LazyCallGraphTest, InterSCCEdgeRemoval) {
   EXPECT_EQ(BC.parent_end(), BC.parent_begin());
 }
 
+TEST(LazyCallGraphTest, IntraSCCEdgeInsertion) {
+  std::unique_ptr<Module> M1 = parseAssembly(
+      "define void @a() {\n"
+      "entry:\n"
+      "  call void @b()\n"
+      "  ret void\n"
+      "}\n"
+      "define void @b() {\n"
+      "entry:\n"
+      "  call void @c()\n"
+      "  ret void\n"
+      "}\n"
+      "define void @c() {\n"
+      "entry:\n"
+      "  call void @a()\n"
+      "  ret void\n"
+      "}\n");
+  LazyCallGraph CG1(*M1);
+
+  // Force the graph to be fully expanded.
+  auto SCCI = CG1.postorder_scc_begin();
+  LazyCallGraph::SCC &SCC = *SCCI++;
+  EXPECT_EQ(CG1.postorder_scc_end(), SCCI);
+
+  LazyCallGraph::Node &A = *CG1.lookup(lookupFunction(*M1, "a"));
+  LazyCallGraph::Node &B = *CG1.lookup(lookupFunction(*M1, "b"));
+  LazyCallGraph::Node &C = *CG1.lookup(lookupFunction(*M1, "c"));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(A));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(B));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(C));
+
+  // Insert an edge from 'a' to 'c'. Nothing changes about the SCCs.
+  SCC.insertIntraSCCEdge(A, C);
+  EXPECT_EQ(2, std::distance(A.begin(), A.end()));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(A));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(B));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(C));
+
+  // Insert a self edge from 'a' back to 'a'.
+  SCC.insertIntraSCCEdge(A, A);
+  EXPECT_EQ(3, std::distance(A.begin(), A.end()));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(A));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(B));
+  EXPECT_EQ(&SCC, CG1.lookupSCC(C));
+}
+
 TEST(LazyCallGraphTest, IntraSCCEdgeRemoval) {
   // A nice fully connected (including self-edges) SCC.
   std::unique_ptr<Module> M1 = parseAssembly(