Index: include/llvm/ADT/Optional.h
===================================================================
--- include/llvm/ADT/Optional.h
+++ include/llvm/ADT/Optional.h
@@ -20,6 +20,7 @@
 #include "llvm/Support/AlignOf.h"
 #include "llvm/Support/Compiler.h"
 #include <cassert>
+#include <new>
 #include <utility>
 
 namespace llvm {
@@ -69,6 +70,61 @@
     return *this;
   }
 
+#if LLVM_HAS_VARIADIC_TEMPLATES
+
+  /// Create a new object by constructing it in place with the given arguments.
+  template<typename ...ArgTypes>
+  void emplace(ArgTypes &&...Args) {
+    reset();
+    hasVal = true;
+    new (storage.buffer) T(std::forward<ArgTypes>(Args)...);
+  }
+
+#else
+  
+  /// Create a new object by default-constructing it in place.
+  void emplace() {
+    reset();
+    hasVal = true;
+    new (storage.buffer) T();
+  }
+  
+  /// Create a new object by constructing it in place with the given arguments.
+  template<typename T1>
+  void emplace(T1 &&A1) {
+    reset();
+    hasVal = true;
+    new (storage.buffer) T(std::forward<T1>(A1));
+  }
+  
+  /// Create a new object by constructing it in place with the given arguments.
+  template<typename T1, typename T2>
+  void emplace(T1 &&A1, T2 &&A2) {
+    reset();
+    hasVal = true;
+    new (storage.buffer) T(std::forward<T1>(A1), std::forward<T2>(A2));
+  }
+  
+  /// Create a new object by constructing it in place with the given arguments.
+  template<typename T1, typename T2, typename T3>
+  void emplace(T1 &&A1, T2 &&A2, T3 &&A3) {
+    reset();
+    hasVal = true;
+    new (storage.buffer) T(std::forward<T1>(A1), std::forward<T2>(A2),
+        std::forward<T3>(A3));
+  }
+  
+  /// Create a new object by constructing it in place with the given arguments.
+  template<typename T1, typename T2, typename T3, typename T4>
+  void emplace(T1 &&A1, T2 &&A2, T3 &&A3, T4 &&A4) {
+    reset();
+    hasVal = true;
+    new (storage.buffer) T(std::forward<T1>(A1), std::forward<T2>(A2),
+        std::forward<T3>(A3), std::forward<T4>(A4));
+  }
+
+#endif // LLVM_HAS_VARIADIC_TEMPLATES
+
   static inline Optional create(const T* y) {
     return y ? Optional(*y) : Optional();
   }
Index: unittests/ADT/OptionalTest.cpp
===================================================================
--- unittests/ADT/OptionalTest.cpp
+++ unittests/ADT/OptionalTest.cpp
@@ -177,6 +177,19 @@
   EXPECT_EQ(5, A.getValueOr(42));
 }
 
+struct MultiArgConstructor {
+  int x, y;
+  MultiArgConstructor(int x, int y) : x(x), y(y) {}
+};
+
+TEST_F(OptionalTest, Emplace) {
+  Optional<MultiArgConstructor> A;
+  A.emplace(1, 2);
+  EXPECT_TRUE(A.hasValue());
+  EXPECT_EQ(1, A->x);
+  EXPECT_EQ(2, A->y);
+}
+
 struct MoveOnly {
   static unsigned MoveConstructions;
   static unsigned Destructions;
@@ -286,6 +299,17 @@
   EXPECT_EQ(1u, MoveOnly::Destructions);
 }
 
+TEST_F(OptionalTest, MoveOnlyEmplace) {
+  Optional<MoveOnly> A;
+  MoveOnly::ResetCounts();
+  A.emplace(4);
+  EXPECT_TRUE((bool)A);
+  EXPECT_EQ(4, A->val);
+  EXPECT_EQ(0u, MoveOnly::MoveConstructions);
+  EXPECT_EQ(0u, MoveOnly::MoveAssignments);
+  EXPECT_EQ(0u, MoveOnly::Destructions);
+}
+
 #if LLVM_HAS_RVALUE_REFERENCE_THIS
 
 TEST_F(OptionalTest, MoveGetValueOr) {