[PATCH] D151416: [NFC][DAGCombiner]: Only consider nodes with no uses for pruning when forming initial worklist

Dhruv Chawla via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Thu May 25 03:04:55 PDT 2023

0xdc03 updated this revision to Diff 525516.
0xdc03 added a comment.

- Removed unnecessary braces

  rG LLVM Github Monorepo




Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -170,9 +170,15 @@
     /// them) when they are deleted from the underlying DAG. It relies on
     /// stable indices of nodes within the worklist.
     DenseMap<SDNode *, unsigned> 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.
+    ///
+    /// Note: All nodes are not added here when the worklist is initially
+    /// formed, 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 are already present in it during the initial formation.
     SmallSetVector<SDNode *, 32> PruningList;
     /// Set of nodes which have been combined (at least once).
@@ -263,7 +269,7 @@
     /// 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 +278,8 @@
       if (N->getOpcode() == ISD::HANDLENODE)
-      ConsiderForPruning(N);
+      if (IsCandidateForPruning)
+        ConsiderForPruning(N);
       if (WorklistMap.insert(std::make_pair(N, Worklist.size())).second)
@@ -1771,7 +1778,7 @@
   // Add all the dag nodes to the worklist.
   for (SDNode &Node : DAG.allnodes())
-    AddToWorklist(&Node);
+    AddToWorklist(&Node, 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

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