[llvm] r207212 - [LCG] Rather than doing a linear time SmallSetVector removal of each

[Chandler Carruth]

Author: chandlerc
Date: Fri Apr 25 04:08:05 2014
New Revision: 207212

URL: http://llvm.org/viewvc/llvm-project?rev=207212&view=rev
Log:
[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.

Modified:
    llvm/trunk/lib/Analysis/LazyCallGraph.cpp

Modified: llvm/trunk/lib/Analysis/LazyCallGraph.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/LazyCallGraph.cpp?rev=207212&r1=207211&r2=207212&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/LazyCallGraph.cpp (original)
+++ llvm/trunk/lib/Analysis/LazyCallGraph.cpp Fri Apr 25 04:08:05 2014
@@ -187,14 +187,13 @@ LazyCallGraph::SCC::removeInternalEdge(L
   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(L
 
   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(L
 
         // 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;