diff --git a/llvm/include/llvm/ADT/Twine.h b/llvm/include/llvm/ADT/Twine.h
--- a/llvm/include/llvm/ADT/Twine.h
+++ b/llvm/include/llvm/ADT/Twine.h
@@ -99,14 +99,9 @@
       /// A pointer to an std::string instance.
       StdStringKind,
 
-      /// A pointer to a StringRef instance.
+      /// A StringRef instance.
       StringRefKind,
 
-#if __cplusplus > 201402L
-      // A pointer to a std::string_view instance.
-      StdStringViewKind,
-#endif
-
       /// A pointer to a SmallString instance.
       SmallStringKind,
 
@@ -146,10 +141,7 @@
       const Twine *twine;
       const char *cString;
       const std::string *stdString;
-      const StringRef *stringRef;
-#if __cplusplus > 201402L
-      const std::string_view *stdStringView;
-#endif
+      StringRef stringRef;
       const SmallVectorImpl<char> *smallString;
       const formatv_object_base *formatvObject;
       char character;
@@ -160,6 +152,7 @@
       const unsigned long long *decULL;
       const long long *decLL;
       const uint64_t *uHex;
+      Child() : stringRef(){};
     };
 
     /// LHS - The prefix in the concatenation, which may be uninitialized for
@@ -295,17 +288,19 @@
     }
 
 #if __cplusplus > 201402L
-    /// Construct from an std::string_view.
-    /*implicit*/ Twine(const std::string_view &Str)
-        : LHSKind(StdStringViewKind) {
-      LHS.stdStringView = &Str;
+    /// Construct from an std::string_view by converting it to a StringRef.
+    /// This handles string_views on a pure API basis, and avoids storing one
+    /// (or a pointer to one) inside a Twine, which avoids problems when mixing
+    /// code compiled under various C++ standards.
+    /*implicit*/ Twine(const std::string_view &Str) : LHSKind(StringRefKind) {
+      LHS.stringRef = Str;
       assert(isValid() && "Invalid twine!");
     }
 #endif
 
     /// Construct from a StringRef.
     /*implicit*/ Twine(const StringRef &Str) : LHSKind(StringRefKind) {
-      LHS.stringRef = &Str;
+      LHS.stringRef = Str;
       assert(isValid() && "Invalid twine!");
     }
 
@@ -377,14 +372,14 @@
     /*implicit*/ Twine(const char *LHS, const StringRef &RHS)
         : LHSKind(CStringKind), RHSKind(StringRefKind) {
       this->LHS.cString = LHS;
-      this->RHS.stringRef = &RHS;
+      this->RHS.stringRef = RHS;
       assert(isValid() && "Invalid twine!");
     }
 
     /// Construct as the concatenation of a StringRef and a C string.
     /*implicit*/ Twine(const StringRef &LHS, const char *RHS)
         : LHSKind(StringRefKind), RHSKind(CStringKind) {
-      this->LHS.stringRef = &LHS;
+      this->LHS.stringRef = LHS;
       this->RHS.cString = RHS;
       assert(isValid() && "Invalid twine!");
     }
@@ -430,9 +425,6 @@
       case EmptyKind:
       case CStringKind:
       case StdStringKind:
-#if __cplusplus > 201402L
-      case StdStringViewKind:
-#endif
       case StringRefKind:
       case SmallStringKind:
         return true;
@@ -469,12 +461,8 @@
         return StringRef(LHS.cString);
       case StdStringKind:
         return StringRef(*LHS.stdString);
-#if __cplusplus > 201402L
-      case StdStringViewKind:
-        return StringRef(*LHS.stdStringView);
-#endif
       case StringRefKind:
-        return *LHS.stringRef;
+        return LHS.stringRef;
       case SmallStringKind:
         return StringRef(LHS.smallString->data(), LHS.smallString->size());
       }
diff --git a/llvm/lib/Support/Twine.cpp b/llvm/lib/Support/Twine.cpp
--- a/llvm/lib/Support/Twine.cpp
+++ b/llvm/lib/Support/Twine.cpp
@@ -68,13 +68,8 @@
   case Twine::StdStringKind:
     OS << *Ptr.stdString;
     break;
-#if __cplusplus > 201402L
-  case StdStringViewKind:
-    OS << StringRef(*Ptr.stdStringView);
-    break;
-#endif
   case Twine::StringRefKind:
-    OS << *Ptr.stringRef;
+    OS << Ptr.stringRef;
     break;
   case Twine::SmallStringKind:
     OS << *Ptr.smallString;
@@ -128,11 +123,6 @@
     OS << "std::string:\""
        << Ptr.stdString << "\"";
     break;
-#if __cplusplus > 201402L
-  case Twine::StdStringViewKind:
-    OS << "std::string_view:\"" << StringRef(*Ptr.stdStringView) << "\"";
-    break;
-#endif
   case Twine::StringRefKind:
     OS << "stringref:\""
        << Ptr.stringRef << "\"";
diff --git a/llvm/unittests/ADT/TwineTest.cpp b/llvm/unittests/ADT/TwineTest.cpp
--- a/llvm/unittests/ADT/TwineTest.cpp
+++ b/llvm/unittests/ADT/TwineTest.cpp
@@ -77,7 +77,9 @@
   EXPECT_EQ("(Twine smallstring:\"hey\" cstring:\"there\")", 
             repr(Twine(SmallString<7>("hey")).concat(Twine("there"))));
 #if __cplusplus > 201402L
-  EXPECT_EQ("(Twine std::string_view:\"hey\" cstring:\"there\")",
+  // string_views are immediately converted to stringrefs to avoid
+  // C++ standard dependencies.
+  EXPECT_EQ("(Twine stringref:\"hey\" cstring:\"there\")",
             repr(Twine(std::string_view("hey")).concat(Twine("there"))));
 #endif