Index: include/llvm/ADT/DenseMap.h
===================================================================
--- include/llvm/ADT/DenseMap.h
+++ include/llvm/ADT/DenseMap.h
@@ -40,7 +40,23 @@
 template <typename KeyT, typename ValueT>
 struct DenseMapPair : public std::pair<KeyT, ValueT> {
 
-  using std::pair<KeyT, ValueT>::pair;
+  // FIXME: Switch to inheriting constructors when we drop support for older
+  //        clang versions.
+  // NOTE: This default constructor is declared with '{}' rather than
+  //       '= default' to work around a bug in clang-800.
+  DenseMapPair() {}
+
+  template <typename AltKeyT, typename AltValueT>
+  DenseMapPair(AltKeyT &&AltKey, AltValueT &&AltValue,
+               typename std::enable_if<std::is_convertible<AltKeyT, KeyT>::value &&
+                              std::is_convertible<AltValueT, ValueT>::value>::type* = 0)
+    : std::pair<KeyT, ValueT>(std::forward<AltKeyT>(AltKey),
+                              std::forward<AltValueT>(AltValue)) {}
+
+  template <typename AltPairT>
+  DenseMapPair(AltPairT &&AltPair,
+               typename std::enable_if<std::is_convertible<AltPairT, std::pair<KeyT, ValueT>>::value>::type* = 0)
+    : std::pair<KeyT, ValueT>(std::forward<AltPairT>(AltPair)) {}
 
   KeyT &getFirst() { return std::pair<KeyT, ValueT>::first; }
   const KeyT &getFirst() const { return std::pair<KeyT, ValueT>::first; }