[LCG] Rather than doing a linear time SmallSetVector removal of each

child from the worklist, wait until we actually need to pop another
element off of the worklist and skip over any that were already visited
by the DFS. This also enables swapping the nodes of the SCC into the
worklist. No functionality changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207212 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/LazyCallGraph.cpp b/lib/Analysis/LazyCallGraph.cpp
index 871787154b41b11eb7cb3202ffe97c3e7771b669..bcefd4f24d5dae54b3c0e8e4d27f18e6b2b6de58 100644 (file)
--- a/lib/Analysis/LazyCallGraph.cpp
+++ b/lib/Analysis/LazyCallGraph.cpp
@@ -187,14 +187,13 @@ LazyCallGraph::SCC::removeInternalEdge(LazyCallGraph &G, Node &Caller,
   SmallVector<std::pair<Node *, Node::iterator>, 4> DFSStack;
   SmallVector<Node *, 4> PendingSCCStack;
 
-  // The worklist is every node in the original SCC. FIXME: switch the SCC to
-  // use a SmallSetVector and swap here.
-  SmallSetVector<Node *, 1> Worklist;
-  for (Node *N : Nodes) {
+  // The worklist is every node in the original SCC.
+  SmallVector<Node *, 1> Worklist;
+  Worklist.swap(Nodes);
+  for (Node *N : Worklist) {
     // Clear these to 0 while we re-run Tarjan's over the SCC.
     N->DFSNumber = 0;
     N->LowLink = 0;
-    Worklist.insert(N);
   }
 
   // The callee can already reach every node in this SCC (by definition). It is
@@ -208,6 +207,9 @@ LazyCallGraph::SCC::removeInternalEdge(LazyCallGraph &G, Node &Caller,
 
   for (;;) {
     if (DFSStack.empty()) {
+      // Clear off any nodes which have already been visited in the DFS.
+      while (!Worklist.empty() && Worklist.back()->DFSNumber != 0)
+        Worklist.pop_back();
       if (Worklist.empty())
         break;
       Node *N = Worklist.pop_back_val();
@@ -253,7 +255,6 @@ LazyCallGraph::SCC::removeInternalEdge(LazyCallGraph &G, Node &Caller,
 
         // Recurse onto this node via a tail call.
         ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
-        Worklist.remove(&ChildN);
         DFSStack.push_back(std::make_pair(&ChildN, ChildN.begin()));
         Recurse = true;
         break;