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
@@ -96,18 +96,9 @@
       /// A pointer to a C string instance.
       CStringKind,
 
-      /// A pointer to an std::string instance.
-      StdStringKind,
-
-      /// A pointer to a StringRef instance.
-      StringRefKind,
-
-      /// A pointer to a SmallString instance.
-      SmallStringKind,
-
-      /// A Pointer and Length representation. Used for std::string_view.
-      /// Can't use a StringRef here because they are not trivally
-      /// constructible.
+      /// A Pointer and Length representation. Used for std::string_view,
+      /// StringRef, SmallString and std::string.  Can't use a StringRef here
+      /// because they are not trivally constructible.
       PtrAndLengthKind,
 
       /// A pointer to a formatv_object_base instance.
@@ -149,9 +140,6 @@
         const char *ptr;
         size_t length;
       } ptrAndLength;
-      const std::string *stdString;
-      const StringRef *stringRef;
-      const SmallVectorImpl<char> *smallString;
       const formatv_object_base *formatvObject;
       char character;
       unsigned int decUI;
@@ -290,8 +278,9 @@
     /*implicit*/ Twine(std::nullptr_t) = delete;
 
     /// Construct from an std::string.
-    /*implicit*/ Twine(const std::string &Str) : LHSKind(StdStringKind) {
-      LHS.stdString = &Str;
+    /*implicit*/ Twine(const std::string &Str) : LHSKind(PtrAndLengthKind) {
+      LHS.ptrAndLength.ptr = Str.data();
+      LHS.ptrAndLength.length = Str.length();
       assert(isValid() && "Invalid twine!");
     }
 
@@ -309,15 +298,17 @@
 #endif
 
     /// Construct from a StringRef.
-    /*implicit*/ Twine(const StringRef &Str) : LHSKind(StringRefKind) {
-      LHS.stringRef = &Str;
+    /*implicit*/ Twine(const StringRef &Str) : LHSKind(PtrAndLengthKind) {
+      LHS.ptrAndLength.ptr = Str.data();
+      LHS.ptrAndLength.length = Str.size();
       assert(isValid() && "Invalid twine!");
     }
 
     /// Construct from a SmallString.
     /*implicit*/ Twine(const SmallVectorImpl<char> &Str)
-        : LHSKind(SmallStringKind) {
-      LHS.smallString = &Str;
+        : LHSKind(PtrAndLengthKind) {
+      LHS.ptrAndLength.ptr = Str.data();
+      LHS.ptrAndLength.length = Str.size();
       assert(isValid() && "Invalid twine!");
     }
 
@@ -380,16 +371,18 @@
 
     /// Construct as the concatenation of a C string and a StringRef.
     /*implicit*/ Twine(const char *LHS, const StringRef &RHS)
-        : LHSKind(CStringKind), RHSKind(StringRefKind) {
+        : LHSKind(CStringKind), RHSKind(PtrAndLengthKind) {
       this->LHS.cString = LHS;
-      this->RHS.stringRef = &RHS;
+      this->RHS.ptrAndLength.ptr = RHS.data();
+      this->RHS.ptrAndLength.length = RHS.size();
       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;
+        : LHSKind(PtrAndLengthKind), RHSKind(CStringKind) {
+      this->LHS.ptrAndLength.ptr = LHS.data();
+      this->LHS.ptrAndLength.length = LHS.size();
       this->RHS.cString = RHS;
       assert(isValid() && "Invalid twine!");
     }
@@ -434,9 +427,6 @@
       switch (getLHSKind()) {
       case EmptyKind:
       case CStringKind:
-      case StdStringKind:
-      case StringRefKind:
-      case SmallStringKind:
       case PtrAndLengthKind:
         return true;
       default:
@@ -470,12 +460,6 @@
         return StringRef();
       case CStringKind:
         return StringRef(LHS.cString);
-      case StdStringKind:
-        return StringRef(*LHS.stdString);
-      case StringRefKind:
-        return *LHS.stringRef;
-      case SmallStringKind:
-        return StringRef(LHS.smallString->data(), LHS.smallString->size());
       case PtrAndLengthKind:
         return StringRef(LHS.ptrAndLength.ptr, LHS.ptrAndLength.length);
       }
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
@@ -15,10 +15,6 @@
 using namespace llvm;
 
 std::string Twine::str() const {
-  // If we're storing only a std::string, just return it.
-  if (LHSKind == StdStringKind && RHSKind == EmptyKind)
-    return *LHS.stdString;
-
   // If we're storing a formatv_object, we can avoid an extra copy by formatting
   // it immediately and returning the result.
   if (LHSKind == FormatvObjectKind && RHSKind == EmptyKind)
@@ -35,18 +31,9 @@
 }
 
 StringRef Twine::toNullTerminatedStringRef(SmallVectorImpl<char> &Out) const {
-  if (isUnary()) {
-    switch (getLHSKind()) {
-    case CStringKind:
-      // Already null terminated, yay!
-      return StringRef(LHS.cString);
-    case StdStringKind: {
-      const std::string *str = LHS.stdString;
-      return StringRef(str->c_str(), str->size());
-    }
-    default:
-      break;
-    }
+  if (isUnary() && getLHSKind() == CStringKind) {
+    // Already null terminated, yay!
+    return StringRef(LHS.cString);
   }
   toVector(Out);
   Out.push_back(0);
@@ -68,15 +55,6 @@
   case Twine::PtrAndLengthKind:
     OS << StringRef(Ptr.ptrAndLength.ptr, Ptr.ptrAndLength.length);
     break;
-  case Twine::StdStringKind:
-    OS << *Ptr.stdString;
-    break;
-  case Twine::StringRefKind:
-    OS << *Ptr.stringRef;
-    break;
-  case Twine::SmallStringKind:
-    OS << *Ptr.smallString;
-    break;
   case Twine::FormatvObjectKind:
     OS << *Ptr.formatvObject;
     break;
@@ -126,17 +104,6 @@
     OS << "ptrAndLength:\""
        << StringRef(Ptr.ptrAndLength.ptr, Ptr.ptrAndLength.length) << "\"";
     break;
-  case Twine::StdStringKind:
-    OS << "std::string:\""
-       << Ptr.stdString << "\"";
-    break;
-  case Twine::StringRefKind:
-    OS << "stringref:\""
-       << Ptr.stringRef << "\"";
-    break;
-  case Twine::SmallStringKind:
-    OS << "smallstring:\"" << *Ptr.smallString << "\"";
-    break;
   case Twine::FormatvObjectKind:
     OS << "formatv:\"" << *Ptr.formatvObject << "\"";
     break;
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
@@ -68,13 +68,13 @@
             repr(Twine("hi").concat(Twine())));
   EXPECT_EQ("(Twine cstring:\"hi\" empty)", 
             repr(Twine().concat(Twine("hi"))));
-  EXPECT_EQ("(Twine smallstring:\"hi\" empty)", 
+  EXPECT_EQ("(Twine ptrAndLength:\"hi\" empty)",
             repr(Twine().concat(Twine(SmallString<5>("hi")))));
   EXPECT_EQ("(Twine formatv:\"howdy\" empty)",
             repr(Twine(formatv("howdy")).concat(Twine())));
   EXPECT_EQ("(Twine formatv:\"howdy\" empty)",
             repr(Twine().concat(Twine(formatv("howdy")))));
-  EXPECT_EQ("(Twine smallstring:\"hey\" cstring:\"there\")", 
+  EXPECT_EQ("(Twine ptrAndLength:\"hey\" cstring:\"there\")",
             repr(Twine(SmallString<7>("hey")).concat(Twine("there"))));
 #if __cplusplus > 201402L
   EXPECT_EQ("(Twine ptrAndLength:\"hey\" cstring:\"there\")",
@@ -90,8 +90,9 @@
             repr(Twine("a").concat(Twine("b")).concat(Twine("c"))));
   EXPECT_EQ("(Twine cstring:\"a\" rope:(Twine cstring:\"b\" cstring:\"c\"))",
             repr(Twine("a").concat(Twine("b").concat(Twine("c")))));
-  EXPECT_EQ("(Twine cstring:\"a\" rope:(Twine smallstring:\"b\" cstring:\"c\"))",
-            repr(Twine("a").concat(Twine(SmallString<3>("b")).concat(Twine("c")))));
+  EXPECT_EQ(
+      "(Twine cstring:\"a\" rope:(Twine Pt:\"b\" cstring:\"c\"))",
+      repr(Twine("a").concat(Twine(SmallString<3>("b")).concat(Twine("c")))));
 }
 
 TEST(TwineTest, toNullTerminatedStringRef) {