[LCG] Rather than walking the directed graph structure to update graph

pointers in node objects, just walk the map from function to node.

It doesn't have stable ordering, but works just as well and is much
simpler. We don't need ordering when just updating internal pointers.

llvm-svn: 310163

llvm/lib/Analysis/LazyCallGraph.cpp

@@ -1684,20 +1684,10 @@ LazyCallGraph::Node &LazyCallGraph::insertInto(Function &F, Node *&MappedN) {
 }
 
 void LazyCallGraph::updateGraphPtrs() {
-  // Process all nodes updating the graph pointers.
-  {
-    SmallVector<Node *, 16> Worklist;
-    for (Edge &E : EntryEdges)
-      Worklist.push_back(&E.getNode());
-
-    while (!Worklist.empty()) {
-      Node &N = *Worklist.pop_back_val();
-      N.G = this;
-      if (N)
-        for (Edge &E : *N)
-          Worklist.push_back(&E.getNode());
-    }
-  }
+  // Walk the node map to update their graph pointers. While this iterates in
+  // an unstable order, the order has no effect so it remains correct.
+  for (auto &FunctionNodePair : NodeMap)
+    FunctionNodePair.second->G = this;
 
   for (auto *RC : PostOrderRefSCCs)
     RC->G = this;