Index: tools/llvm-exegesis/lib/BitVectorVector.h
===================================================================
--- tools/llvm-exegesis/lib/BitVectorVector.h
+++ tools/llvm-exegesis/lib/BitVectorVector.h
@@ -57,6 +57,14 @@
   /// Get a const_iterator to the beginning of the BitVectorVector.
   const_iterator begin() const { return vector_.begin(); }
 
+  /// Assign a range of elements, replacing the existing content.
+  template <typename It> void assign(It Start, It End) {
+    clear();
+    vector_.assign(Start, End);
+    for (const value_type Value : llvm::make_range(Start, End))
+      bitvector_.set(Value);
+  }
+
   /// Insert a range of elements into the BitVectorVector.
   template <typename It> void insert(It Start, It End) {
     for (; Start != End; ++Start) {
Index: tools/llvm-exegesis/lib/Clustering.cpp
===================================================================
--- tools/llvm-exegesis/lib/Clustering.cpp
+++ tools/llvm-exegesis/lib/Clustering.cpp
@@ -112,8 +112,7 @@
     CurrentCluster.PointIndices.push_back(P);
 
     // Process P's neighbors.
-    ToProcess.clear();
-    ToProcess.insert(Neighbors.begin(), Neighbors.end());
+    ToProcess.assign(Neighbors.begin(), Neighbors.end());
     while (!ToProcess.empty()) {
       // Retrieve a point from the set.
       const size_t Q = *ToProcess.begin();