Index: include/llvm/ADT/DenseMap.h
===================================================================
--- include/llvm/ADT/DenseMap.h
+++ include/llvm/ADT/DenseMap.h
@@ -203,6 +203,24 @@
     return try_emplace(std::move(KV.first), std::move(KV.second));
   }
 
+  /// Inserts an element or assigns to the current element if the key already
+  /// exists. The return type is the same as try_emplace.
+  template <typename V>
+  std::pair<iterator, bool> insert_or_assign(KeyT &&Key, V &&Val) {
+    auto Ret = try_emplace(std::move(Key), std::forward<V>(Val));
+    if (!Ret.second)
+      Ret.first->second = std::forward<V>(Val);
+    return Ret;
+  }
+
+  template <typename V>
+  std::pair<iterator, bool> insert_or_assign(const KeyT &Key, V &&Val) {
+    auto Ret = try_emplace(Key, std::forward<V>(Val));
+    if (!Ret.second)
+      Ret.first->second = std::forward<V>(Val);
+    return Ret;
+  }
+
   // Inserts key,value pair into the map if the key isn't already in the map.
   // The value is constructed in-place if the key is not in the map, otherwise
   // it is not moved.
Index: unittests/ADT/DenseMapTest.cpp
===================================================================
--- unittests/ADT/DenseMapTest.cpp
+++ unittests/ADT/DenseMapTest.cpp
@@ -29,6 +29,11 @@
   return &dummy_arr1[i];
 }
 
+struct NotDefaultConstructible {
+  NotDefaultConstructible() = delete;
+  int v;
+};
+
 /// A test class that tries to check that construction and destruction
 /// occur correctly.
 class CtorTester {
@@ -191,6 +196,24 @@
   EXPECT_EQ(this->getValue(), this->Map[this->getKey()]);
 }
 
+TEST(DenseMapCustomTest, InsertOrAssignTest) {
+  DenseMap<int, NotDefaultConstructible> Map;
+  auto Try1 = Map.insert_or_assign(0, NotDefaultConstructible{1});
+  EXPECT_TRUE(Try1.second);
+  auto Try2 = Map.insert_or_assign(0, NotDefaultConstructible{2});
+  EXPECT_FALSE(Try2.second);
+  EXPECT_EQ(2, Try2.first->second.v);
+  EXPECT_EQ(Try1.first, Try2.first);
+
+  int Key = 1;
+  auto Try3 = Map.insert_or_assign(Key, NotDefaultConstructible{3});
+  EXPECT_TRUE(Try3.second);
+  auto Try4 = Map.insert_or_assign(Key, NotDefaultConstructible{4});
+  EXPECT_FALSE(Try4.second);
+  EXPECT_EQ(4, Try4.first->second.v);
+  EXPECT_EQ(Try3.first, Try4.first);
+}
+
 // Test copy constructor method
 TYPED_TEST(DenseMapTest, CopyConstructorTest) {
   this->Map[this->getKey()] = this->getValue();