Index: tools/llvm-exegesis/lib/Clustering.cpp
===================================================================
--- tools/llvm-exegesis/lib/Clustering.cpp
+++ tools/llvm-exegesis/lib/Clustering.cpp
@@ -8,7 +8,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "Clustering.h"
-#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include <string>
 
@@ -93,6 +92,8 @@
 
 void InstructionBenchmarkClustering::dbScan(const size_t MinPts) {
   std::vector<size_t> Neighbors; // Persistent buffer to avoid allocs.
+  std::deque<size_t> Workqueue(Points_.size());
+  std::vector<char> Set(Points_.size(), char(0));
   for (size_t P = 0, NumPoints = Points_.size(); P < NumPoints; ++P) {
     if (!ClusterIdForPoint_[P].isUndef())
       continue; // Previously processed in inner loop.
@@ -111,12 +112,14 @@
     CurrentCluster.PointIndices.push_back(P);
 
     // Process P's neighbors.
-    llvm::SetVector<size_t, std::deque<size_t>> ToProcess;
-    ToProcess.insert(Neighbors.begin(), Neighbors.end());
-    while (!ToProcess.empty()) {
+    Workqueue.assign(Neighbors.begin(), Neighbors.end());
+    for (size_t Neighbor : Neighbors)
+      Set[Neighbor] = 1;
+    while (!Workqueue.empty()) {
       // Retrieve a point from the set.
-      const size_t Q = *ToProcess.begin();
-      ToProcess.erase(ToProcess.begin());
+      const size_t Q = Workqueue.front();
+      Workqueue.pop_front();
+      Set[Q] = 0;
 
       if (ClusterIdForPoint_[Q].isNoise()) {
         // Change noise point to border point.
@@ -133,7 +136,12 @@
       // And extend to the neighbors of Q if the region is dense enough.
       rangeQuery(Q, Neighbors);
       if (Neighbors.size() + 1 >= MinPts) {
-        ToProcess.insert(Neighbors.begin(), Neighbors.end());
+        for (size_t Neighbor : Neighbors) {
+          if (Set[Neighbor])
+            continue;
+          Set[Neighbor] = 1;
+          Workqueue.push_back(Neighbor);
+        }
       }
     }
   }