[llvm] 7ea0ee3 - [DomTree] Avoid creating an empty GD to reduce compile time.

[Alina Sbirlea via llvm-commits]

Author: Alina Sbirlea
Date: 2020-08-21T13:45:00-07:00
New Revision: 7ea0ee30588ebda7c5cd69e2472d2a8e46f62035

URL: https://github.com/llvm/llvm-project/commit/7ea0ee30588ebda7c5cd69e2472d2a8e46f62035
DIFF: https://github.com/llvm/llvm-project/commit/7ea0ee30588ebda7c5cd69e2472d2a8e46f62035.diff

LOG: [DomTree] Avoid creating an empty GD to reduce compile time.

Added: 
    

Modified: 
    llvm/include/llvm/Support/GenericDomTreeConstruction.h

Removed: 
    


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diff  --git a/llvm/include/llvm/Support/GenericDomTreeConstruction.h b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
index 984ddfbf4f4c..ff4b32193715 100644
--- a/llvm/include/llvm/Support/GenericDomTreeConstruction.h
+++ b/llvm/include/llvm/Support/GenericDomTreeConstruction.h
@@ -107,8 +107,19 @@ struct SemiNCAInfo {
   static SmallVector<NodePtr, 8> getChildren(NodePtr N, BatchUpdatePtr BUI) {
     if (BUI)
       return BUI->PreViewCFG.template getChildren<Inversed>(N);
-    GraphDiffT GD;
-    return GD.template getChildren<Inversed>(N);
+    return getChildren<Inversed>(N);
+  }
+
+  template <bool Inversed>
+  static SmallVector<NodePtr, 8> getChildren(NodePtr N) {
+    using DirectedNodeT =
+        std::conditional_t<Inversed, Inverse<NodePtr>, NodePtr>;
+    auto R = children<DirectedNodeT>(N);
+    SmallVector<NodePtr, 8> Res(detail::reverse_if<!Inversed>(R));
+
+    // Remove nullptr children for clang.
+    llvm::erase_value(Res, nullptr);
+    return Res;
   }
 
   NodePtr getIDom(NodePtr BB) const {