diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -170,7 +170,8 @@ /// them) when they are deleted from the underlying DAG. It relies on /// stable indices of nodes within the worklist. DenseMap WorklistMap; - /// This records all nodes attempted to add to the worklist since we + + /// This records all nodes attempted to be added to the worklist since we /// considered a new worklist entry. As we keep do not add duplicate nodes /// in the worklist, this is different from the tail of the worklist. SmallSetVector PruningList; @@ -263,7 +264,7 @@ /// Add to the worklist making sure its instance is at the back (next to be /// processed.) - void AddToWorklist(SDNode *N) { + void AddToWorklist(SDNode *N, bool IsCandidateForPruning = true) { assert(N->getOpcode() != ISD::DELETED_NODE && "Deleted Node added to Worklist"); @@ -272,7 +273,8 @@ if (N->getOpcode() == ISD::HANDLENODE) return; - ConsiderForPruning(N); + if (IsCandidateForPruning) + ConsiderForPruning(N); if (WorklistMap.insert(std::make_pair(N, Worklist.size())).second) Worklist.push_back(N); @@ -1770,8 +1772,13 @@ WorklistInserter AddNodes(*this); // Add all the dag nodes to the worklist. + // + // Note: All nodes are not added to PruningList here, this is because the only + // nodes which can be deleted are those which have no uses and all other nodes + // which would otherwise be added to the worklist by the first call to + // getNextWorklistEntry are already present in it. for (SDNode &Node : DAG.allnodes()) - AddToWorklist(&Node); + AddToWorklist(&Node, /* IsCandidateForPruning */ Node.use_empty()); // Create a dummy node (which is not added to allnodes), that adds a reference // to the root node, preventing it from being deleted, and tracking any