[llvm] [MachineOutliner] Leaf Descendants (PR #90275)

[Xuan Zhang via llvm-commits]

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@@ -105,6 +112,70 @@ void SuffixTree::setSuffixIndices() {
   }
 }
 
+void SuffixTree::setLeafNodes() {
+  // A stack that keeps track of nodes to visit for post-order DFS traversal.
+  SmallVector<SuffixTreeNode *> ToVisit;
+  ToVisit.push_back(Root);
+
+  // This keeps track of the index of the next leaf node to be added to
+  // the LeafNodes vector of the suffix tree.
+  unsigned LeafCounter = 0;
+
+  // This keeps track of nodes whose children have been added to the stack.
+  // The value is a pair, representing a node's first and last children.
+  DenseMap<SuffixTreeInternalNode *,
+           std::pair<SuffixTreeNode *, SuffixTreeNode *>>
+      ChildrenMap;
+
+  // Traverse the tree in post-order.
+  while (!ToVisit.empty()) {
+    SuffixTreeNode *CurrNode = ToVisit.pop_back_val();
+    if (auto *CurrInternalNode = dyn_cast<SuffixTreeInternalNode>(CurrNode)) {
+      // The current node is an internal node.
+      auto I = ChildrenMap.find(CurrInternalNode);
+      if (I == ChildrenMap.end()) {
+        // This is the first time we visit this node.
+        // Its children have not been added to the stack yet.
+        // We add current node back, and add its children to the stack.
+        // We keep track of the first and last children of the current node.
+        auto it = CurrInternalNode->Children.begin();
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xuanzh-meta wrote:

aha, was googling how to do this and failed to find any good suggestion. This is nice :)

https://github.com/llvm/llvm-project/pull/90275