[llvm] [Support] Use block numbers for DomTree construction (PR #101706)

[Alexis Engelke via llvm-commits]

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@@ -73,7 +73,11 @@ struct SemiNCAInfo {
   // Number to node mapping is 1-based. Initialize the mapping to start with
   // a dummy element.
   SmallVector<NodePtr, 64> NumToNode = {nullptr};
-  DenseMap<NodePtr, InfoRec> NodeToInfo;
+  // If blocks have numbers (e.g., BasicBlock, MachineBasicBlock), store node
+  // infos in a vector.
+  SmallVector<InfoRec, 64> NodeInfos;
+  // For blocks without numbers, store InfoRec in a map.
+  DenseMap<NodePtr, InfoRec> NodeInfoMap;
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aengelke wrote:

Good idea! I use conditional_t now to toggle the type of NodeInfos itself between a map and a vector.

https://github.com/llvm/llvm-project/pull/101706