Index: include/llvm/ADT/DenseSet.h
===================================================================
--- include/llvm/ADT/DenseSet.h
+++ include/llvm/ADT/DenseSet.h
@@ -16,6 +16,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/type_traits.h"
 #include <algorithm>
 #include <cstddef>
@@ -67,7 +68,7 @@
   explicit DenseSetImpl(unsigned InitialReserve = 0) : TheMap(InitialReserve) {}
 
   DenseSetImpl(std::initializer_list<ValueT> Elems)
-      : DenseSetImpl(Elems.size()) {
+      : DenseSetImpl(PowerOf2Ceil(Elems.size())) {
     insert(Elems.begin(), Elems.end());
   }
 
Index: unittests/ADT/DenseSetTest.cpp
===================================================================
--- unittests/ADT/DenseSetTest.cpp
+++ unittests/ADT/DenseSetTest.cpp
@@ -80,6 +80,14 @@
   EXPECT_EQ(0u, set.count(3));
 }
 
+TYPED_TEST(DenseSetTest, InitializerListWithNonPowerOfTwoLength) {
+  TypeParam set({1, 2, 3});
+  EXPECT_EQ(3u, set.size());
+  EXPECT_EQ(1u, set.count(1));
+  EXPECT_EQ(1u, set.count(2));
+  EXPECT_EQ(1u, set.count(3));
+}
+
 TYPED_TEST(DenseSetTest, ConstIteratorComparison) {
   TypeParam set({1});
   const TypeParam &cset = set;