diff --git a/clang/bindings/python/clang/cindex.py b/clang/bindings/python/clang/cindex.py
index 4d450eca1806..dac71916d314 100644
--- a/clang/bindings/python/clang/cindex.py
+++ b/clang/bindings/python/clang/cindex.py
@@ -1685,6 +1685,7 @@ TypeKind.DEPENDENT = TypeKind(26)
 TypeKind.OBJCID = TypeKind(27)
 TypeKind.OBJCCLASS = TypeKind(28)
 TypeKind.OBJCSEL = TypeKind(29)
+TypeKind.FLOAT128 = TypeKind(30)
 TypeKind.COMPLEX = TypeKind(100)
 TypeKind.POINTER = TypeKind(101)
 TypeKind.BLOCKPOINTER = TypeKind(102)
diff --git a/clang/include/clang-c/Index.h b/clang/include/clang-c/Index.h
index 9c9bc7a99843..e9f93364af06 100644
--- a/clang/include/clang-c/Index.h
+++ b/clang/include/clang-c/Index.h
@@ -2929,6 +2929,7 @@ enum CXTypeKind {
   CXType_ObjCId = 27,
   CXType_ObjCClass = 28,
   CXType_ObjCSel = 29,
+  CXType_Float128 = 30,
   CXType_FirstBuiltin = CXType_Void,
   CXType_LastBuiltin  = CXType_ObjCSel,
 
diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index e04d976441d9..4e4a98d801a3 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -893,9 +893,10 @@ public:
   CanQualType SignedCharTy, ShortTy, IntTy, LongTy, LongLongTy, Int128Ty;
   CanQualType UnsignedCharTy, UnsignedShortTy, UnsignedIntTy, UnsignedLongTy;
   CanQualType UnsignedLongLongTy, UnsignedInt128Ty;
-  CanQualType FloatTy, DoubleTy, LongDoubleTy;
+  CanQualType FloatTy, DoubleTy, LongDoubleTy, Float128Ty;
   CanQualType HalfTy; // [OpenCL 6.1.1.1], ARM NEON
   CanQualType FloatComplexTy, DoubleComplexTy, LongDoubleComplexTy;
+  CanQualType Float128ComplexTy;
   CanQualType VoidPtrTy, NullPtrTy;
   CanQualType DependentTy, OverloadTy, BoundMemberTy, UnknownAnyTy;
   CanQualType BuiltinFnTy;
@@ -968,9 +969,6 @@ public:
   /// \brief Retrieve the declaration for the 128-bit unsigned integer type.
   TypedefDecl *getUInt128Decl() const;
 
-  /// \brief Retrieve the declaration for a 128-bit float stub type.
-  TypeDecl *getFloat128StubType() const;
-
   //===--------------------------------------------------------------------===//
   //                           Type Constructors
   //===--------------------------------------------------------------------===//
diff --git a/clang/include/clang/AST/BuiltinTypes.def b/clang/include/clang/AST/BuiltinTypes.def
index dcca44df17a5..c0c6819280d2 100644
--- a/clang/include/clang/AST/BuiltinTypes.def
+++ b/clang/include/clang/AST/BuiltinTypes.def
@@ -133,6 +133,9 @@ FLOATING_TYPE(Double, DoubleTy)
 // 'long double'
 FLOATING_TYPE(LongDouble, LongDoubleTy)
 
+// '__float128'
+FLOATING_TYPE(Float128, Float128Ty)
+
 //===- Language-specific types --------------------------------------------===//
 
 // This is the type of C++0x 'nullptr'.
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index 1a968724ca44..3e4127fa48a0 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -2051,7 +2051,7 @@ public:
   }
 
   bool isFloatingPoint() const {
-    return getKind() >= Half && getKind() <= LongDouble;
+    return getKind() >= Half && getKind() <= Float128;
   }
 
   /// Determines whether the given kind corresponds to a placeholder type.
diff --git a/clang/include/clang/AST/TypeLoc.h b/clang/include/clang/AST/TypeLoc.h
index ba3f848958a2..67adf4a638bc 100644
--- a/clang/include/clang/AST/TypeLoc.h
+++ b/clang/include/clang/AST/TypeLoc.h
@@ -538,7 +538,7 @@ public:
   bool needsExtraLocalData() const {
     BuiltinType::Kind bk = getTypePtr()->getKind();
     return (bk >= BuiltinType::UShort && bk <= BuiltinType::UInt128)
-      || (bk >= BuiltinType::Short && bk <= BuiltinType::LongDouble)
+      || (bk >= BuiltinType::Short && bk <= BuiltinType::Float128)
       || bk == BuiltinType::UChar
       || bk == BuiltinType::SChar;
   }
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 822124f0dd9b..d5d6e874dd82 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5246,8 +5246,6 @@ def err_typecheck_pointer_arith_void_type : Error<
   "arithmetic on%select{ a|}0 pointer%select{|s}0 to void">;
 def err_typecheck_decl_incomplete_type : Error<
   "variable has incomplete type %0">;
-def err_typecheck_decl_incomplete_type___float128 : Error<
-  "support for type '__float128' is not yet implemented">;
 def ext_typecheck_decl_incomplete_type : ExtWarn<
   "tentative definition of variable with internal linkage has incomplete non-array type %0">,
   InGroup<DiagGroup<"tentative-definition-incomplete-type">>;
@@ -7601,8 +7599,8 @@ def err_c99_array_usage_cxx : Error<
   "feature, not permitted in C++">;
  def err_type_requires_extension : Error<
   "use of type %0 requires %1 extension to be enabled">;
-def err_int128_unsupported : Error<
-  "__int128 is not supported on this target">;
+def err_type_unsupported : Error<
+  "%0 is not supported on this target">;
 def err_nsconsumed_attribute_mismatch : Error<
   "overriding method has mismatched ns_consumed attribute on its"
   " parameter">;
diff --git a/clang/include/clang/Basic/Specifiers.h b/clang/include/clang/Basic/Specifiers.h
index 334719cd7d14..b2965782de90 100644
--- a/clang/include/clang/Basic/Specifiers.h
+++ b/clang/include/clang/Basic/Specifiers.h
@@ -54,6 +54,7 @@ namespace clang {
     TST_half,         // OpenCL half, ARM NEON __fp16
     TST_float,
     TST_double,
+    TST_float128,
     TST_bool,         // _Bool
     TST_decimal32,    // _Decimal32
     TST_decimal64,    // _Decimal64
diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index b98a5d6c4172..008723f4260a 100644
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -64,7 +64,7 @@ protected:
   unsigned char HalfWidth, HalfAlign;
   unsigned char FloatWidth, FloatAlign;
   unsigned char DoubleWidth, DoubleAlign;
-  unsigned char LongDoubleWidth, LongDoubleAlign;
+  unsigned char LongDoubleWidth, LongDoubleAlign, Float128Align;
   unsigned char LargeArrayMinWidth, LargeArrayAlign;
   unsigned char LongWidth, LongAlign;
   unsigned char LongLongWidth, LongLongAlign;
@@ -78,7 +78,7 @@ protected:
   std::unique_ptr<llvm::DataLayout> DataLayout;
   const char *MCountName;
   const llvm::fltSemantics *HalfFormat, *FloatFormat, *DoubleFormat,
-    *LongDoubleFormat;
+    *LongDoubleFormat, *Float128Format;
   unsigned char RegParmMax, SSERegParmMax;
   TargetCXXABI TheCXXABI;
   const LangAS::Map *AddrSpaceMap;
@@ -136,7 +136,8 @@ public:
     NoFloat = 255,
     Float = 0,
     Double,
-    LongDouble
+    LongDouble,
+    Float128
   };
 
   /// \brief The different kinds of __builtin_va_list types defined by
@@ -327,6 +328,11 @@ public:
     return getPointerWidth(0) >= 64;
   } // FIXME
 
+  /// \brief Determine whether the __float128 type is supported on this target.
+  virtual bool hasFloat128Type() const {
+    return false;
+  }
+
   /// \brief Return the alignment that is suitable for storing any
   /// object with a fundamental alignment requirement.
   unsigned getSuitableAlign() const { return SuitableAlign; }
@@ -379,6 +385,14 @@ public:
     return *LongDoubleFormat;
   }
 
+  /// getFloat128Width/Align/Format - Return the size/align/format of
+  /// '__float128'.
+  unsigned getFloat128Width() const { return 128; }
+  unsigned getFloat128Align() const { return Float128Align; }
+  const llvm::fltSemantics &getFloat128Format() const {
+    return *Float128Format;
+  }
+
   /// \brief Return true if the 'long double' type should be mangled like
   /// __float128.
   virtual bool useFloat128ManglingForLongDouble() const { return false; }
diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
index 3d0c65718f69..9d97a81773ee 100644
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -380,6 +380,7 @@ KEYWORD(__builtin_offsetof          , KEYALL)
 TYPE_TRAIT_2(__builtin_types_compatible_p, TypeCompatible, KEYNOCXX)
 KEYWORD(__builtin_va_arg            , KEYALL)
 KEYWORD(__extension__               , KEYALL)
+KEYWORD(__float128                  , KEYALL)
 KEYWORD(__imag                      , KEYALL)
 KEYWORD(__int128                    , KEYALL)
 KEYWORD(__label__                   , KEYALL)
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 1a8c7c606d19..21bfa3a2542e 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1495,6 +1495,10 @@ def minvariant_function_descriptors :
 def mno_invariant_function_descriptors :
   Flag<["-"], "mno-invariant-function-descriptors">,
   Group<m_ppc_Features_Group>;
+def mfloat128: Flag<["-"], "mfloat128">,
+    Group<m_ppc_Features_Group>;
+def mno_float128 : Flag<["-"], "mno-float128">,
+    Group<m_ppc_Features_Group>;
 
 def faltivec : Flag<["-"], "faltivec">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Enable AltiVec vector initializer syntax">;
diff --git a/clang/include/clang/Lex/LiteralSupport.h b/clang/include/clang/Lex/LiteralSupport.h
index 3a2e8d276e42..2bbcd262a748 100644
--- a/clang/include/clang/Lex/LiteralSupport.h
+++ b/clang/include/clang/Lex/LiteralSupport.h
@@ -64,6 +64,7 @@ public:
   bool isHalf : 1;          // 1.0h
   bool isFloat : 1;         // 1.0f
   bool isImaginary : 1;     // 1.0i
+  bool isFloat128 : 1;      // 1.0q
   uint8_t MicrosoftInteger; // Microsoft suffix extension i8, i16, i32, or i64.
 
   bool isIntegerLiteral() const {
diff --git a/clang/include/clang/Sema/DeclSpec.h b/clang/include/clang/Sema/DeclSpec.h
index b9e432b5ee14..d296e74b0747 100644
--- a/clang/include/clang/Sema/DeclSpec.h
+++ b/clang/include/clang/Sema/DeclSpec.h
@@ -280,6 +280,7 @@ public:
   static const TST TST_half = clang::TST_half;
   static const TST TST_float = clang::TST_float;
   static const TST TST_double = clang::TST_double;
+  static const TST TST_float128 = clang::TST_float128;
   static const TST TST_bool = clang::TST_bool;
   static const TST TST_decimal32 = clang::TST_decimal32;
   static const TST TST_decimal64 = clang::TST_decimal64;
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index 9a0f905c24f0..1f7ec43787ff 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -798,6 +798,8 @@ namespace clang {
       PREDEF_TYPE_RESERVE_ID_ID = 42,
       /// \brief The placeholder type for OpenMP array section.
       PREDEF_TYPE_OMP_ARRAY_SECTION = 43,
+      /// \brief The '__float128' type
+      PREDEF_TYPE_FLOAT128_ID = 44,
       /// \brief OpenCL image types with auto numeration
 #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
       PREDEF_TYPE_##Id##_ID,
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index fb4c80bd7fda..2b103308bb2e 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -58,7 +58,7 @@ unsigned ASTContext::NumImplicitDestructors;
 unsigned ASTContext::NumImplicitDestructorsDeclared;
 
 enum FloatingRank {
-  HalfRank, FloatRank, DoubleRank, LongDoubleRank
+  HalfRank, FloatRank, DoubleRank, LongDoubleRank, Float128Rank
 };
 
 RawComment *ASTContext::getRawCommentForDeclNoCache(const Decl *D) const {
@@ -967,14 +967,6 @@ TypedefDecl *ASTContext::getUInt128Decl() const {
   return UInt128Decl;
 }
 
-TypeDecl *ASTContext::getFloat128StubType() const {
-  assert(LangOpts.CPlusPlus && "should only be called for c++");
-  if (!Float128StubDecl)
-    Float128StubDecl = buildImplicitRecord("__float128");
-
-  return Float128StubDecl;
-}
-
 void ASTContext::InitBuiltinType(CanQualType &R, BuiltinType::Kind K) {
   BuiltinType *Ty = new (*this, TypeAlignment) BuiltinType(K);
   R = CanQualType::CreateUnsafe(QualType(Ty, 0));
@@ -1023,6 +1015,9 @@ void ASTContext::InitBuiltinTypes(const TargetInfo &Target,
   InitBuiltinType(DoubleTy,            BuiltinType::Double);
   InitBuiltinType(LongDoubleTy,        BuiltinType::LongDouble);
 
+  // GNU extension, __float128 for IEEE quadruple precision
+  InitBuiltinType(Float128Ty,          BuiltinType::Float128);
+
   // GNU extension, 128-bit integers.
   InitBuiltinType(Int128Ty,            BuiltinType::Int128);
   InitBuiltinType(UnsignedInt128Ty,    BuiltinType::UInt128);
@@ -1084,6 +1079,7 @@ void ASTContext::InitBuiltinTypes(const TargetInfo &Target,
   FloatComplexTy      = getComplexType(FloatTy);
   DoubleComplexTy     = getComplexType(DoubleTy);
   LongDoubleComplexTy = getComplexType(LongDoubleTy);
+  Float128ComplexTy   = getComplexType(Float128Ty);
 
   // Builtin types for 'id', 'Class', and 'SEL'.
   InitBuiltinType(ObjCBuiltinIdTy, BuiltinType::ObjCId);
@@ -1341,6 +1337,7 @@ const llvm::fltSemantics &ASTContext::getFloatTypeSemantics(QualType T) const {
   case BuiltinType::Float:      return Target->getFloatFormat();
   case BuiltinType::Double:     return Target->getDoubleFormat();
   case BuiltinType::LongDouble: return Target->getLongDoubleFormat();
+  case BuiltinType::Float128:   return Target->getFloat128Format();
   }
 }
 
@@ -1651,6 +1648,10 @@ TypeInfo ASTContext::getTypeInfoImpl(const Type *T) const {
       Width = Target->getLongDoubleWidth();
       Align = Target->getLongDoubleAlign();
       break;
+    case BuiltinType::Float128:
+      Width = Target->getFloat128Width();
+      Align = Target->getFloat128Align();
+      break;
     case BuiltinType::NullPtr:
       Width = Target->getPointerWidth(0); // C++ 3.9.1p11: sizeof(nullptr_t)
       Align = Target->getPointerAlign(0); //   == sizeof(void*)
@@ -4635,6 +4636,7 @@ static FloatingRank getFloatingRank(QualType T) {
   case BuiltinType::Float:      return FloatRank;
   case BuiltinType::Double:     return DoubleRank;
   case BuiltinType::LongDouble: return LongDoubleRank;
+  case BuiltinType::Float128:   return Float128Rank;
   }
 }
 
@@ -4651,6 +4653,7 @@ QualType ASTContext::getFloatingTypeOfSizeWithinDomain(QualType Size,
     case FloatRank:      return FloatComplexTy;
     case DoubleRank:     return DoubleComplexTy;
     case LongDoubleRank: return LongDoubleComplexTy;
+    case Float128Rank:   return Float128ComplexTy;
     }
   }
 
@@ -4660,6 +4663,7 @@ QualType ASTContext::getFloatingTypeOfSizeWithinDomain(QualType Size,
   case FloatRank:      return FloatTy;
   case DoubleRank:     return DoubleTy;
   case LongDoubleRank: return LongDoubleTy;
+  case Float128Rank:   return Float128Ty;
   }
   llvm_unreachable("getFloatingRank(): illegal value for rank");
 }
@@ -5489,6 +5493,7 @@ static char getObjCEncodingForPrimitiveKind(const ASTContext *C,
     case BuiltinType::LongDouble: return 'D';
     case BuiltinType::NullPtr:    return '*'; // like char*
 
+    case BuiltinType::Float128:
     case BuiltinType::Half:
       // FIXME: potentially need @encodes for these!
       return ' ';
@@ -8679,6 +8684,8 @@ QualType ASTContext::getRealTypeForBitwidth(unsigned DestWidth) const {
     return DoubleTy;
   case TargetInfo::LongDouble:
     return LongDoubleTy;
+  case TargetInfo::Float128:
+    return Float128Ty;
   case TargetInfo::NoFloat:
     return QualType();
   }
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 7ad464e1d912..67f5a57263a8 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -1992,7 +1992,7 @@ void CXXNameMangler::mangleType(const BuiltinType *T) {
   //                 ::= f  # float
   //                 ::= d  # double
   //                 ::= e  # long double, __float80
-  // UNSUPPORTED:    ::= g  # __float128
+  //                 ::= g  # __float128
   // UNSUPPORTED:    ::= Dd # IEEE 754r decimal floating point (64 bits)
   // UNSUPPORTED:    ::= De # IEEE 754r decimal floating point (128 bits)
   // UNSUPPORTED:    ::= Df # IEEE 754r decimal floating point (32 bits)
@@ -2073,6 +2073,12 @@ void CXXNameMangler::mangleType(const BuiltinType *T) {
                 ? 'g'
                 : 'e');
     break;
+  case BuiltinType::Float128:
+    if (getASTContext().getTargetInfo().useFloat128ManglingForLongDouble())
+      Out << "U10__float128"; // Match the GCC mangling
+    else
+      Out << 'g';
+    break;
   case BuiltinType::NullPtr:
     Out << "Dn";
     break;
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index b63b5e5651e1..c9caddbb6fc8 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1751,6 +1751,7 @@ void MicrosoftCXXNameMangler::mangleType(const BuiltinType *T, Qualifiers,
     Out << "$$T";
     break;
 
+  case BuiltinType::Float128:
   case BuiltinType::Half: {
     DiagnosticsEngine &Diags = Context.getDiags();
     unsigned DiagID = Diags.getCustomDiagID(
diff --git a/clang/lib/AST/NSAPI.cpp b/clang/lib/AST/NSAPI.cpp
index 4c49e4c9f6c1..ac2a8d354247 100644
--- a/clang/lib/AST/NSAPI.cpp
+++ b/clang/lib/AST/NSAPI.cpp
@@ -441,6 +441,7 @@ NSAPI::getNSNumberFactoryMethodKind(QualType T) const {
   case BuiltinType::Int128:
   case BuiltinType::LongDouble:
   case BuiltinType::UInt128:
+  case BuiltinType::Float128:
   case BuiltinType::NullPtr:
   case BuiltinType::ObjCClass:
   case BuiltinType::ObjCId:
diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
index cc3837409269..0b3f90879094 100644
--- a/clang/lib/AST/StmtPrinter.cpp
+++ b/clang/lib/AST/StmtPrinter.cpp
@@ -1310,6 +1310,7 @@ static void PrintFloatingLiteral(raw_ostream &OS, FloatingLiteral *Node,
   case BuiltinType::Double:     break; // no suffix.
   case BuiltinType::Float:      OS << 'F'; break;
   case BuiltinType::LongDouble: OS << 'L'; break;
+  case BuiltinType::Float128:   OS << 'Q'; break;
   }
 }
 
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 1c6ae2a2b9cf..0262f5ba4a3f 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -1777,7 +1777,7 @@ bool Type::hasUnsignedIntegerRepresentation() const {
 bool Type::isFloatingType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() >= BuiltinType::Half &&
-           BT->getKind() <= BuiltinType::LongDouble;
+           BT->getKind() <= BuiltinType::Float128;
   if (const ComplexType *CT = dyn_cast<ComplexType>(CanonicalType))
     return CT->getElementType()->isFloatingType();
   return false;
@@ -1799,7 +1799,7 @@ bool Type::isRealFloatingType() const {
 bool Type::isRealType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() >= BuiltinType::Bool &&
-           BT->getKind() <= BuiltinType::LongDouble;
+           BT->getKind() <= BuiltinType::Float128;
   if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
       return ET->getDecl()->isComplete() && !ET->getDecl()->isScoped();
   return false;
@@ -1808,7 +1808,7 @@ bool Type::isRealType() const {
 bool Type::isArithmeticType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() >= BuiltinType::Bool &&
-           BT->getKind() <= BuiltinType::LongDouble;
+           BT->getKind() <= BuiltinType::Float128;
   if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
     // GCC allows forward declaration of enum types (forbid by C99 6.7.2.3p2).
     // If a body isn't seen by the time we get here, return false.
@@ -2552,6 +2552,8 @@ StringRef BuiltinType::getName(const PrintingPolicy &Policy) const {
     return "double";
   case LongDouble:
     return "long double";
+  case Float128:
+    return "__float128";
   case WChar_S:
   case WChar_U:
     return Policy.MSWChar ? "__wchar_t" : "wchar_t";
diff --git a/clang/lib/AST/TypeLoc.cpp b/clang/lib/AST/TypeLoc.cpp
index 05e5a627b753..78947d18f953 100644
--- a/clang/lib/AST/TypeLoc.cpp
+++ b/clang/lib/AST/TypeLoc.cpp
@@ -320,6 +320,7 @@ TypeSpecifierType BuiltinTypeLoc::getWrittenTypeSpec() const {
   case BuiltinType::Float:
   case BuiltinType::Double:
   case BuiltinType::LongDouble:
+  case BuiltinType::Float128:
     llvm_unreachable("Builtin type needs extra local data!");
     // Fall through, if the impossible happens.
       
diff --git a/clang/lib/Analysis/PrintfFormatString.cpp b/clang/lib/Analysis/PrintfFormatString.cpp
index ff44a570de1d..ac6cef9d0842 100644
--- a/clang/lib/Analysis/PrintfFormatString.cpp
+++ b/clang/lib/Analysis/PrintfFormatString.cpp
@@ -616,6 +616,7 @@ bool PrintfSpecifier::fixType(QualType QT, const LangOptions &LangOpt,
   case BuiltinType::UInt128:
   case BuiltinType::Int128:
   case BuiltinType::Half:
+  case BuiltinType::Float128:
     // Various types which are non-trivial to correct.
     return false;
 
diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 40d6001e5325..c287073ead95 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -46,6 +46,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   DoubleAlign = 64;
   LongDoubleWidth = 64;
   LongDoubleAlign = 64;
+  Float128Align = 128;
   LargeArrayMinWidth = 0;
   LargeArrayAlign = 0;
   MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 0;
@@ -72,6 +73,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   FloatFormat = &llvm::APFloat::IEEEsingle;
   DoubleFormat = &llvm::APFloat::IEEEdouble;
   LongDoubleFormat = &llvm::APFloat::IEEEdouble;
+  Float128Format = &llvm::APFloat::IEEEquad;
   MCountName = "mcount";
   RegParmMax = 0;
   SSERegParmMax = 0;
@@ -223,6 +225,8 @@ TargetInfo::RealType TargetInfo::getRealTypeByWidth(unsigned BitWidth) const {
     if (&getLongDoubleFormat() == &llvm::APFloat::PPCDoubleDouble ||
         &getLongDoubleFormat() == &llvm::APFloat::IEEEquad)
       return LongDouble;
+    if (hasFloat128Type())
+      return Float128;
     break;
   }
 
diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 7639b04d25a2..4cce9cbd8a22 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -806,6 +806,7 @@ class PPCTargetInfo : public TargetInfo {
   bool HasHTM;
   bool HasBPERMD;
   bool HasExtDiv;
+  bool HasFloat128;
 
 protected:
   std::string ABI;
@@ -814,7 +815,7 @@ public:
   PPCTargetInfo(const llvm::Triple &Triple, const TargetOptions &)
     : TargetInfo(Triple), HasVSX(false), HasP8Vector(false),
       HasP8Crypto(false), HasDirectMove(false), HasQPX(false), HasHTM(false),
-      HasBPERMD(false), HasExtDiv(false) {
+      HasBPERMD(false), HasExtDiv(false), HasFloat128(false) {
     BigEndian = (Triple.getArch() != llvm::Triple::ppc64le);
     SimdDefaultAlign = 128;
     LongDoubleWidth = LongDoubleAlign = 128;
@@ -1058,6 +1059,9 @@ public:
            LongDoubleFormat == &llvm::APFloat::PPCDoubleDouble &&
            getTriple().isOSBinFormatELF();
   }
+  bool hasFloat128Type() const override {
+    return HasFloat128;
+  }
 };
 
 const Builtin::Info PPCTargetInfo::BuiltinInfo[] = {
@@ -1089,6 +1093,8 @@ bool PPCTargetInfo::handleTargetFeatures(std::vector<std::string> &Features,
       HasQPX = true;
     } else if (Feature == "+htm") {
       HasHTM = true;
+    } else if (Feature == "+float128") {
+      HasFloat128 = true;
     }
     // TODO: Finish this list and add an assert that we've handled them
     // all.
@@ -1246,6 +1252,8 @@ void PPCTargetInfo::getTargetDefines(const LangOptions &Opts,
     Builder.defineMacro("__CRYPTO__");
   if (HasHTM)
     Builder.defineMacro("__HTM__");
+  if (HasFloat128)
+    Builder.defineMacro("__FLOAT128__");
 
   Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_1");
   Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2");
@@ -1296,6 +1304,13 @@ static bool ppcUserFeaturesCheck(DiagnosticsEngine &Diags,
                                                      << "-mno-vsx";
       return false;
     }
+
+    if (std::find(FeaturesVec.begin(), FeaturesVec.end(), "+float128") !=
+        FeaturesVec.end()) {
+      Diags.Report(diag::err_opt_not_valid_with_opt) << "-mfloat128"
+                                                     << "-mno-vsx";
+      return false;
+    }
   }
 
   return true;
@@ -1364,6 +1379,7 @@ bool PPCTargetInfo::hasFeature(StringRef Feature) const {
     .Case("htm", HasHTM)
     .Case("bpermd", HasBPERMD)
     .Case("extdiv", HasExtDiv)
+    .Case("float128", HasFloat128)
     .Default(false);
 }
 
@@ -1373,19 +1389,19 @@ void PPCTargetInfo::setFeatureEnabled(llvm::StringMap<bool> &Features,
   // as well. Do the inverse if we're disabling vsx. We'll diagnose any user
   // incompatible options.
   if (Enabled) {
-    if (Name == "vsx") {
-     Features[Name] = true;
-    } else if (Name == "direct-move") {
+    if (Name == "direct-move") {
       Features[Name] = Features["vsx"] = true;
     } else if (Name == "power8-vector") {
       Features[Name] = Features["vsx"] = true;
+    } else if (Name == "float128") {
+      Features[Name] = Features["vsx"] = true;
     } else {
       Features[Name] = true;
     }
   } else {
     if (Name == "vsx") {
       Features[Name] = Features["direct-move"] = Features["power8-vector"] =
-          false;
+          Features["float128"] = false;
     } else {
       Features[Name] = false;
     }
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 13ee0fb1d993..4b7657bb3528 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -528,7 +528,13 @@ llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
   case BuiltinType::Half:
   case BuiltinType::Float:
   case BuiltinType::LongDouble:
+  case BuiltinType::Float128:
   case BuiltinType::Double:
+    // FIXME: For targets where long double and __float128 have the same size,
+    // they are currently indistinguishable in the debugger without some
+    // special treatment. However, there is currently no consensus on encoding
+    // and this should be updated once a DWARF encoding exists for distinct
+    // floating point types of the same size.
     Encoding = llvm::dwarf::DW_ATE_float;
     break;
   }
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 1fd79d0e0edc..8f122963a1f4 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -1796,15 +1796,19 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
       amt = llvm::ConstantFP::get(VMContext,
                                   llvm::APFloat(static_cast<double>(amount)));
     else {
-      // Remaining types are either Half or LongDouble.  Convert from float.
+      // Remaining types are Half, LongDouble or __float128. Convert from float.
       llvm::APFloat F(static_cast<float>(amount));
       bool ignored;
+      const llvm::fltSemantics *FS;
       // Don't use getFloatTypeSemantics because Half isn't
       // necessarily represented using the "half" LLVM type.
-      F.convert(value->getType()->isHalfTy()
-                    ? CGF.getTarget().getHalfFormat()
-                    : CGF.getTarget().getLongDoubleFormat(),
-                llvm::APFloat::rmTowardZero, &ignored);
+      if (value->getType()->isFP128Ty())
+        FS = &CGF.getTarget().getFloat128Format();
+      else if (value->getType()->isHalfTy())
+        FS = &CGF.getTarget().getHalfFormat();
+      else
+        FS = &CGF.getTarget().getLongDoubleFormat();
+      F.convert(*FS, llvm::APFloat::rmTowardZero, &ignored);
       amt = llvm::ConstantFP::get(VMContext, F);
     }
     value = Builder.CreateFAdd(value, amt, isInc ? "inc" : "dec");
diff --git a/clang/lib/CodeGen/CodeGenTypes.cpp b/clang/lib/CodeGen/CodeGenTypes.cpp
index 33e53a6cbe2a..ebe55c70d817 100644
--- a/clang/lib/CodeGen/CodeGenTypes.cpp
+++ b/clang/lib/CodeGen/CodeGenTypes.cpp
@@ -449,6 +449,7 @@ llvm::Type *CodeGenTypes::ConvertType(QualType T) {
     case BuiltinType::Float:
     case BuiltinType::Double:
     case BuiltinType::LongDouble:
+    case BuiltinType::Float128:
       ResultType = getTypeForFormat(getLLVMContext(),
                                     Context.getFloatTypeSemantics(T),
                                     /* UseNativeHalf = */ false);
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index b44e8405334d..52e519f30441 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2530,6 +2530,7 @@ static bool TypeInfoIsInStandardLibrary(const BuiltinType *Ty) {
     case BuiltinType::Float:
     case BuiltinType::Double:
     case BuiltinType::LongDouble:
+    case BuiltinType::Float128:
     case BuiltinType::Char16:
     case BuiltinType::Char32:
     case BuiltinType::Int128:
@@ -3349,8 +3350,8 @@ void ItaniumCXXABI::EmitFundamentalRTTIDescriptors() {
       getContext().UnsignedLongLongTy, getContext().Int128Ty,
       getContext().UnsignedInt128Ty,   getContext().HalfTy,
       getContext().FloatTy,            getContext().DoubleTy,
-      getContext().LongDoubleTy,       getContext().Char16Ty,
-      getContext().Char32Ty,
+      getContext().LongDoubleTy,       getContext().Float128Ty,
+      getContext().Char16Ty,           getContext().Char32Ty
   };
   for (const QualType &FundamentalType : FundamentalTypes)
     EmitFundamentalRTTIDescriptor(FundamentalType);
diff --git a/clang/lib/Format/FormatToken.cpp b/clang/lib/Format/FormatToken.cpp
index d6cd450d892e..2ae4ddcfd08a 100644
--- a/clang/lib/Format/FormatToken.cpp
+++ b/clang/lib/Format/FormatToken.cpp
@@ -53,6 +53,7 @@ bool FormatToken::isSimpleTypeSpecifier() const {
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_wchar_t:
   case tok::kw_bool:
   case tok::kw___underlying_type:
diff --git a/clang/lib/Index/USRGeneration.cpp b/clang/lib/Index/USRGeneration.cpp
index 65de75b5c4fb..40283dcd6863 100644
--- a/clang/lib/Index/USRGeneration.cpp
+++ b/clang/lib/Index/USRGeneration.cpp
@@ -618,6 +618,8 @@ void USRGenerator::VisitType(QualType T) {
           c = 'd'; break;
         case BuiltinType::LongDouble:
           c = 'D'; break;
+        case BuiltinType::Float128:
+          c = 'Q'; break;
         case BuiltinType::NullPtr:
           c = 'n'; break;
 #define BUILTIN_TYPE(Id, SingletonId)
diff --git a/clang/lib/Lex/LiteralSupport.cpp b/clang/lib/Lex/LiteralSupport.cpp
index 27c80b930158..e68b82fb499a 100644
--- a/clang/lib/Lex/LiteralSupport.cpp
+++ b/clang/lib/Lex/LiteralSupport.cpp
@@ -525,6 +525,7 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
   isHalf = false;
   isFloat = false;
   isImaginary = false;
+  isFloat128 = false;
   MicrosoftInteger = 0;
   hadError = false;
 
@@ -567,9 +568,17 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
     case 'f':      // FP Suffix for "float"
     case 'F':
       if (!isFPConstant) break;  // Error for integer constant.
-      if (isHalf || isFloat || isLong) break; // HF, FF, LF invalid.
+      if (isHalf || isFloat || isLong || isFloat128)
+        break; // HF, FF, LF, QF invalid.
       isFloat = true;
       continue;  // Success.
+    case 'q':    // FP Suffix for "__float128"
+    case 'Q':
+      if (!isFPConstant) break;  // Error for integer constant.
+      if (isHalf || isFloat || isLong || isFloat128)
+        break; // HQ, FQ, LQ, QQ invalid.
+      isFloat128 = true;
+      continue;  // Success.
     case 'u':
     case 'U':
       if (isFPConstant) break;  // Error for floating constant.
@@ -579,7 +588,7 @@ NumericLiteralParser::NumericLiteralParser(StringRef TokSpelling,
     case 'l':
     case 'L':
       if (isLong || isLongLong) break;  // Cannot be repeated.
-      if (isHalf || isFloat) break;     // LH, LF invalid.
+      if (isHalf || isFloat || isFloat128) break;     // LH, LF, LQ invalid.
 
       // Check for long long.  The L's need to be adjacent and the same case.
       if (s[1] == s[0]) {
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index b06eda9d23ca..ebe26cfb2dd7 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3306,6 +3306,10 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
       isInvalid = DS.SetTypeSpecType(DeclSpec::TST_double, Loc, PrevSpec,
                                      DiagID, Policy);
       break;
+    case tok::kw___float128:
+      isInvalid = DS.SetTypeSpecType(DeclSpec::TST_float128, Loc, PrevSpec,
+                                     DiagID, Policy);
+      break;
     case tok::kw_wchar_t:
       isInvalid = DS.SetTypeSpecType(DeclSpec::TST_wchar, Loc, PrevSpec,
                                      DiagID, Policy);
@@ -4300,6 +4304,7 @@ bool Parser::isKnownToBeTypeSpecifier(const Token &Tok) const {
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_bool:
   case tok::kw__Bool:
   case tok::kw__Decimal32:
@@ -4374,6 +4379,7 @@ bool Parser::isTypeSpecifierQualifier() {
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_bool:
   case tok::kw__Bool:
   case tok::kw__Decimal32:
@@ -4528,6 +4534,7 @@ bool Parser::isDeclarationSpecifier(bool DisambiguatingWithExpression) {
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_bool:
   case tok::kw__Bool:
   case tok::kw__Decimal32:
diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 2745c337765d..5b7c839454a9 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -1166,6 +1166,7 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_void:
   case tok::kw_typename:
   case tok::kw_typeof:
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index afed9b1ab463..b569e7aeba13 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -1928,6 +1928,9 @@ void Parser::ParseCXXSimpleTypeSpecifier(DeclSpec &DS) {
   case tok::kw_double:
     DS.SetTypeSpecType(DeclSpec::TST_double, Loc, PrevSpec, DiagID, Policy);
     break;
+  case tok::kw___float128:
+    DS.SetTypeSpecType(DeclSpec::TST_float128, Loc, PrevSpec, DiagID, Policy);
+    break;
   case tok::kw_wchar_t:
     DS.SetTypeSpecType(DeclSpec::TST_wchar, Loc, PrevSpec, DiagID, Policy);
     break;
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 747d0a982cf9..4d4bd806f3cc 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -946,6 +946,7 @@ Parser::isExpressionOrTypeSpecifierSimple(tok::TokenKind Kind) {
   case tok::kw_char:
   case tok::kw_const:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_enum:
   case tok::kw_half:
   case tok::kw_float:
@@ -1426,6 +1427,7 @@ Parser::isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_void:
   case tok::annot_decltype:
     if (NextToken().is(tok::l_paren))
@@ -1517,6 +1519,7 @@ bool Parser::isCXXDeclarationSpecifierAType() {
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_void:
   case tok::kw___unknown_anytype:
   case tok::kw___auto_type:
diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp
index 4bc1d3423b43..ddfe6257cf46 100644
--- a/clang/lib/Sema/DeclSpec.cpp
+++ b/clang/lib/Sema/DeclSpec.cpp
@@ -289,6 +289,7 @@ bool Declarator::isDeclarationOfFunction() const {
     case TST_decimal32:
     case TST_decimal64:
     case TST_double:
+    case TST_float128:
     case TST_enum:
     case TST_error:
     case TST_float:
@@ -457,6 +458,7 @@ const char *DeclSpec::getSpecifierName(DeclSpec::TST T,
   case DeclSpec::TST_half:        return "half";
   case DeclSpec::TST_float:       return "float";
   case DeclSpec::TST_double:      return "double";
+  case DeclSpec::TST_float128:    return "__float128";
   case DeclSpec::TST_bool:        return Policy.Bool ? "bool" : "_Bool";
   case DeclSpec::TST_decimal32:   return "_Decimal32";
   case DeclSpec::TST_decimal64:   return "_Decimal64";
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index b0e79f6f0e79..13002ba19a52 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -108,6 +108,7 @@ bool Sema::isSimpleTypeSpecifier(tok::TokenKind Kind) const {
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
+  case tok::kw___float128:
   case tok::kw_wchar_t:
   case tok::kw_bool:
   case tok::kw___underlying_type:
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index a4b1525d942f..fcc608fa1f51 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -1155,6 +1155,48 @@ static QualType handleFloatConversion(Sema &S, ExprResult &LHS,
                                     /*convertFloat=*/!IsCompAssign);
 }
 
+/// \brief Diagnose attempts to convert between __float128 and long double if
+/// there is no support for such conversion. Helper function of
+/// UsualArithmeticConversions().
+static bool unsupportedTypeConversion(const Sema &S, QualType LHSType,
+                                      QualType RHSType) {
+  /*  No issue converting if at least one of the types is not a floating point
+      type or the two types have the same rank.
+  */
+  if (!LHSType->isFloatingType() || !RHSType->isFloatingType() ||
+      S.Context.getFloatingTypeOrder(LHSType, RHSType) == 0)
+    return false;
+
+  assert(LHSType->isFloatingType() && RHSType->isFloatingType() &&
+         "The remaining types must be floating point types.");
+
+  auto *LHSComplex = LHSType->getAs<ComplexType>();
+  auto *RHSComplex = RHSType->getAs<ComplexType>();
+
+  QualType LHSElemType = LHSComplex ?
+    LHSComplex->getElementType() : LHSType;
+  QualType RHSElemType = RHSComplex ?
+    RHSComplex->getElementType() : RHSType;
+
+  // No issue if the two types have the same representation
+  if (&S.Context.getFloatTypeSemantics(LHSElemType) ==
+      &S.Context.getFloatTypeSemantics(RHSElemType))
+    return false;
+
+  bool Float128AndLongDouble = (LHSElemType == S.Context.Float128Ty &&
+                                RHSElemType == S.Context.LongDoubleTy);
+  Float128AndLongDouble |= (LHSElemType == S.Context.LongDoubleTy &&
+                            RHSElemType == S.Context.Float128Ty);
+
+  /* We've handled the situation where __float128 and long double have the same
+     representation. The only other allowable conversion is if long double is
+     really just double.
+  */
+  return Float128AndLongDouble &&
+    (&S.Context.getFloatTypeSemantics(S.Context.LongDoubleTy) !=
+     &llvm::APFloat::IEEEdouble);
+}
+
 typedef ExprResult PerformCastFn(Sema &S, Expr *operand, QualType toType);
 
 namespace {
@@ -1318,6 +1360,11 @@ QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
 
   // At this point, we have two different arithmetic types.
 
+  // Diagnose attempts to convert between __float128 and long double where
+  // such conversions currently can't be handled.
+  if (unsupportedTypeConversion(*this, LHSType, RHSType))
+    return QualType();
+
   // Handle complex types first (C99 6.3.1.8p1).
   if (LHSType->isComplexType() || RHSType->isComplexType())
     return handleComplexFloatConversion(*this, LHS, RHS, LHSType, RHSType,
@@ -3325,10 +3372,12 @@ ExprResult Sema::ActOnNumericConstant(const Token &Tok, Scope *UDLScope) {
       }
     } else if (Literal.isFloat)
       Ty = Context.FloatTy;
-    else if (!Literal.isLong)
-      Ty = Context.DoubleTy;
-    else
+    else if (Literal.isLong)
       Ty = Context.LongDoubleTy;
+    else if (Literal.isFloat128)
+      Ty = Context.Float128Ty;
+    else
+      Ty = Context.DoubleTy;
 
     Res = BuildFloatingLiteral(*this, Literal, Ty, Tok.getLocation());
 
@@ -6602,6 +6651,15 @@ QualType Sema::CheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
   QualType LHSTy = LHS.get()->getType();
   QualType RHSTy = RHS.get()->getType();
 
+  // Diagnose attempts to convert between __float128 and long double where
+  // such conversions currently can't be handled.
+  if (unsupportedTypeConversion(*this, LHSTy, RHSTy)) {
+    Diag(QuestionLoc,
+         diag::err_typecheck_cond_incompatible_operands) << LHSTy << RHSTy
+      << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
+    return QualType();
+  }
+
   // OpenCL v2.0 s6.12.5 - Blocks cannot be used as expressions of the ternary
   // selection operator (?:).
   if (getLangOpts().OpenCL &&
@@ -7335,6 +7393,11 @@ Sema::CheckAssignmentConstraints(QualType LHSType, ExprResult &RHS,
     return Incompatible;
   }
 
+  // Diagnose attempts to convert between __float128 and long double where
+  // such conversions currently can't be handled.
+  if (unsupportedTypeConversion(*this, LHSType, RHSType))
+    return Incompatible;
+
   // Arithmetic conversions.
   if (LHSType->isArithmeticType() && RHSType->isArithmeticType() &&
       !(getLangOpts().CPlusPlus && LHSType->isEnumeralType())) {
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 87c2ded7c8d0..4063464c45ee 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -5171,6 +5171,12 @@ QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
     QualType ResTy = UsualArithmeticConversions(LHS, RHS);
     if (LHS.isInvalid() || RHS.isInvalid())
       return QualType();
+    if (ResTy.isNull()) {
+      Diag(QuestionLoc,
+           diag::err_typecheck_cond_incompatible_operands) << LTy << RTy
+        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
+      return QualType();
+    }
 
     LHS = ImpCastExprToType(LHS.get(), ResTy, PrepareScalarCast(LHS, ResTy));
     RHS = ImpCastExprToType(RHS.get(), ResTy, PrepareScalarCast(RHS, ResTy));
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 08133d688994..fdf5346d92e4 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -681,13 +681,6 @@ static bool LookupBuiltin(Sema &S, LookupResult &R) {
       NameKind == Sema::LookupRedeclarationWithLinkage) {
     IdentifierInfo *II = R.getLookupName().getAsIdentifierInfo();
     if (II) {
-      if (S.getLangOpts().CPlusPlus11 && S.getLangOpts().GNUMode &&
-          II == S.getFloat128Identifier()) {
-        // libstdc++4.7's type_traits expects type __float128 to exist, so
-        // insert a dummy type to make that header build in gnu++11 mode.
-        R.addDecl(S.getASTContext().getFloat128StubType());
-        return true;
-      }
       if (S.getLangOpts().CPlusPlus && NameKind == Sema::LookupOrdinaryName &&
           II == S.getASTContext().getMakeIntegerSeqName()) {
         R.addDecl(S.getASTContext().getMakeIntegerSeqDecl());
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 034b090fdf31..e3a72c1e22d2 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1671,6 +1671,20 @@ static bool IsStandardConversion(Sema &S, Expr* From, QualType ToType,
     SCS.Second = ICK_Complex_Real;
     FromType = ToType.getUnqualifiedType();
   } else if (FromType->isRealFloatingType() && ToType->isRealFloatingType()) {
+    // FIXME: disable conversions between long double and __float128 if
+    // their representation is different until there is back end support
+    // We of course allow this conversion if long double is really double.
+    if (&S.Context.getFloatTypeSemantics(FromType) !=
+        &S.Context.getFloatTypeSemantics(ToType)) {
+      bool Float128AndLongDouble = ((FromType == S.Context.Float128Ty &&
+                                    ToType == S.Context.LongDoubleTy) ||
+                                   (FromType == S.Context.LongDoubleTy &&
+                                    ToType == S.Context.Float128Ty));
+      if (Float128AndLongDouble &&
+          (&S.Context.getFloatTypeSemantics(S.Context.LongDoubleTy) !=
+           &llvm::APFloat::IEEEdouble))
+        return false;
+    }
     // Floating point conversions (C++ 4.8).
     SCS.Second = ICK_Floating_Conversion;
     FromType = ToType.getUnqualifiedType();
@@ -1973,7 +1987,8 @@ bool Sema::IsFloatingPointPromotion(QualType FromType, QualType ToType) {
       if (!getLangOpts().CPlusPlus &&
           (FromBuiltin->getKind() == BuiltinType::Float ||
            FromBuiltin->getKind() == BuiltinType::Double) &&
-          (ToBuiltin->getKind() == BuiltinType::LongDouble))
+          (ToBuiltin->getKind() == BuiltinType::LongDouble ||
+           ToBuiltin->getKind() == BuiltinType::Float128))
         return true;
 
       // Half can be promoted to float.
@@ -7198,13 +7213,13 @@ class BuiltinOperatorOverloadBuilder {
   // provided via the getArithmeticType() method below.
   // The "promoted arithmetic types" are the arithmetic
   // types are that preserved by promotion (C++ [over.built]p2).
-  static const unsigned FirstIntegralType = 3;
-  static const unsigned LastIntegralType = 20;
-  static const unsigned FirstPromotedIntegralType = 3,
-                        LastPromotedIntegralType = 11;
+  static const unsigned FirstIntegralType = 4;
+  static const unsigned LastIntegralType = 21;
+  static const unsigned FirstPromotedIntegralType = 4,
+                        LastPromotedIntegralType = 12;
   static const unsigned FirstPromotedArithmeticType = 0,
-                        LastPromotedArithmeticType = 11;
-  static const unsigned NumArithmeticTypes = 20;
+                        LastPromotedArithmeticType = 12;
+  static const unsigned NumArithmeticTypes = 21;
 
   /// \brief Get the canonical type for a given arithmetic type index.
   CanQualType getArithmeticType(unsigned index) {
@@ -7215,6 +7230,7 @@ class BuiltinOperatorOverloadBuilder {
       &ASTContext::FloatTy,
       &ASTContext::DoubleTy,
       &ASTContext::LongDoubleTy,
+      &ASTContext::Float128Ty,
 
       // Start of integral types.
       &ASTContext::IntTy,
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index c23b5a2adc59..52a1ad545a5f 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -727,6 +727,7 @@ bool Sema::containsUnexpandedParameterPacks(Declarator &D) {
   case TST_half:
   case TST_float:
   case TST_double:
+  case TST_float128:
   case TST_bool:
   case TST_decimal32:
   case TST_decimal64:
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index cf47d867c8bf..4d68f4c1cfb5 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1355,7 +1355,8 @@ static QualType ConvertDeclSpecToType(TypeProcessingState &state) {
   }
   case DeclSpec::TST_int128:
     if (!S.Context.getTargetInfo().hasInt128Type())
-      S.Diag(DS.getTypeSpecTypeLoc(), diag::err_int128_unsupported);
+      S.Diag(DS.getTypeSpecTypeLoc(), diag::err_type_unsupported)
+        << "__int128";
     if (DS.getTypeSpecSign() == DeclSpec::TSS_unsigned)
       Result = Context.UnsignedInt128Ty;
     else
@@ -1377,6 +1378,12 @@ static QualType ConvertDeclSpecToType(TypeProcessingState &state) {
       declarator.setInvalidType(true);
     }
     break;
+  case DeclSpec::TST_float128:
+    if (!S.Context.getTargetInfo().hasFloat128Type())
+      S.Diag(DS.getTypeSpecTypeLoc(), diag::err_type_unsupported)
+        << "__float128";
+    Result = Context.Float128Ty;
+    break;
   case DeclSpec::TST_bool: Result = Context.BoolTy; break; // _Bool or bool
     break;
   case DeclSpec::TST_decimal32:    // _Decimal32
@@ -6959,13 +6966,6 @@ bool Sema::RequireCompleteTypeImpl(SourceLocation Loc, QualType T,
   if (!Diagnoser)
     return true;
 
-  // We have an incomplete type. Produce a diagnostic.
-  if (Ident___float128 &&
-      T == Context.getTypeDeclType(Context.getFloat128StubType())) {
-    Diag(Loc, diag::err_typecheck_decl_incomplete_type___float128);
-    return true;
-  }
-
   Diagnoser->diagnose(*this, Loc, T);
 
   // If the type was a forward declaration of a class/struct/union
diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
index 2382f8ea4bd0..792fac99e583 100644
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/lib/Serialization/ASTCommon.cpp
@@ -91,6 +91,9 @@ serialization::TypeIdxFromBuiltin(const BuiltinType *BT) {
   case BuiltinType::LongDouble:
     ID = PREDEF_TYPE_LONGDOUBLE_ID;
     break;
+  case BuiltinType::Float128:
+    ID = PREDEF_TYPE_FLOAT128_ID;
+    break;
   case BuiltinType::NullPtr:
     ID = PREDEF_TYPE_NULLPTR_ID;
     break;
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 0c2522311ac3..df1418649d61 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -6059,6 +6059,9 @@ QualType ASTReader::GetType(TypeID ID) {
     case PREDEF_TYPE_LONGDOUBLE_ID:
       T = Context.LongDoubleTy;
       break;
+    case PREDEF_TYPE_FLOAT128_ID:
+      T = Context.Float128Ty;
+      break;
     case PREDEF_TYPE_OVERLOAD_ID:
       T = Context.OverloadTy;
       break;
diff --git a/clang/test/CodeGenCXX/float128-declarations.cpp b/clang/test/CodeGenCXX/float128-declarations.cpp
new file mode 100644
index 000000000000..638f56fd0d63
--- /dev/null
+++ b/clang/test/CodeGenCXX/float128-declarations.cpp
@@ -0,0 +1,86 @@
+// RUN: %clang_cc1 -emit-llvm -triple powerpc64-unknown-unknown \
+// RUN:   -target-feature +float128 -std=c++11 %s -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -triple powerpc64le-unknown-unknown \
+// RUN:   -target-feature +float128 -std=c++11 %s -o - | FileCheck %s
+//
+/*  Various contexts where type __float128 can appear. */
+
+/*  Namespace */
+namespace {
+  __float128 f1n;
+  __float128 f2n = 33.q;
+  __float128 arr1n[10];
+  __float128 arr2n[] = { 1.2q, 3.0q, 3.e11q };
+  const volatile __float128 func1n(const __float128 &arg) {
+    return arg + f2n + arr1n[4] - arr2n[1];
+  }
+}
+
+/* File */
+__float128 f1f;
+__float128 f2f = 32.4q;
+static __float128 f3f = f2f;
+__float128 arr1f[10];
+__float128 arr2f[] = { -1.2q, -3.0q, -3.e11q };
+__float128 func1f(__float128 arg);
+
+/* Class */
+class C1 {
+  __float128 f1c;
+  static const __float128 f2c;
+  volatile __float128 f3c;
+public:
+  C1(__float128 arg) : f1c(arg), f3c(arg) { }
+  __float128 func1c(__float128 arg ) {
+    return f1c + arg;
+  }
+  static __float128 func2c(__float128 arg) {
+    return arg * C1::f2c;
+  }
+};
+
+/*  Template */
+template <class C> C func1t(C arg) { return arg * 2.q; }
+template <class C> struct S1 {
+  C mem1;
+};
+template <> struct S1<__float128> {
+  __float128 mem2;
+};
+
+/* Local */
+int main(void) {
+  __float128 f1l = 123e220q;
+  __float128 f2l = -0.q;
+  __float128 f3l = 1.189731495357231765085759326628007e4932q;
+  C1 c1(f1l);
+  S1<__float128> s1 = { 132.q };
+  __float128 f4l = func1n(f1l) + func1f(f2l) + c1.func1c(f3l) + c1.func2c(f1l) +
+    func1t(f1l) + s1.mem2 - f1n + f2n;
+#if (__cplusplus >= 201103L)
+  auto f5l = -1.q, *f6l = &f2l, f7l = func1t(f3l);
+#endif
+  __float128 f8l = f4l++;
+  __float128 arr1l[] = { -1.q, -0.q, -11.q };
+}
+// CHECK-DAG: @_ZN12_GLOBAL__N_13f1nE = internal global fp128 0xL00000000000000000000000000000000
+// CHECK-DAG: @_ZN12_GLOBAL__N_13f2nE = internal global fp128 0xL00000000000000004004080000000000
+// CHECK-DAG: @_ZN12_GLOBAL__N_15arr1nE = internal global [10 x fp128]
+// CHECK-DAG: @_ZN12_GLOBAL__N_15arr2nE = internal global [3 x fp128] [fp128 0xL33333333333333333FFF333333333333, fp128 0xL00000000000000004000800000000000, fp128 0xL00000000000000004025176592E00000]
+// CHECK-DAG: define internal fp128 @_ZN12_GLOBAL__N_16func1nERKU10__float128(fp128*
+// CHECK-DAG: @f1f = global fp128 0xL00000000000000000000000000000000
+// CHECK-DAG: @f2f = global fp128 0xL33333333333333334004033333333333
+// CHECK-DAG: @arr1f = global [10 x fp128]
+// CHECK-DAG: @arr2f = global [3 x fp128] [fp128 0xL3333333333333333BFFF333333333333, fp128 0xL0000000000000000C000800000000000, fp128 0xL0000000000000000C025176592E00000]
+// CHECK-DAG: declare fp128 @_Z6func1fU10__float128(fp128)
+// CHECK-DAG: define linkonce_odr void @_ZN2C1C2EU10__float128(%class.C1* %this, fp128 %arg)
+// CHECK-DAG: define linkonce_odr fp128 @_ZN2C16func2cEU10__float128(fp128 %arg)
+// CHECK-DAG: define linkonce_odr fp128 @_Z6func1tIU10__float128ET_S0_(fp128 %arg)
+// CHECK-DAG: @_ZZ4mainE2s1 = private unnamed_addr constant %struct.S1 { fp128 0xL00000000000000004006080000000000 }
+// CHECK-DAG: store fp128 0xLF0AFD0EBFF292DCE42E0B38CDD83F26F, fp128* %f1l, align 16
+// CHECK-DAG: store fp128 0xL00000000000000008000000000000000, fp128* %f2l, align 16
+// CHECK-DAG: store fp128 0xLFFFFFFFFFFFFFFFF7FFEFFFFFFFFFFFF, fp128* %f3l, align 16
+// CHECK-DAG: store fp128 0xL0000000000000000BFFF000000000000, fp128* %f5l, align 16
+// CHECK-DAG: [[F4L:%[a-z0-9]+]] = load fp128, fp128* %f4l
+// CHECK-DAG: [[INC:%[a-z0-9]+]] = fadd fp128 [[F4L]], 0xL00000000000000003FFF000000000000
+// CHECK-DAG: store fp128 [[INC]], fp128* %f4l
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
index dbd4de605e51..cc6eecc734eb 100644
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -5819,6 +5819,9 @@
 // PPCPOWER8:#define _ARCH_PWR7 1
 // PPCPOWER8:#define _ARCH_PWR8 1
 //
+// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-none-none -target-feature +float128 -target-cpu power8 -fno-signed-char < /dev/null | FileCheck -check-prefix PPC-FLOAT128 %s
+// PPC-FLOAT128:#define __FLOAT128__ 1
+//
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-unknown-linux-gnu -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-LINUX %s
 //
 // PPC64-LINUX:#define _ARCH_PPC 1
diff --git a/clang/test/Sema/128bitfloat.cpp b/clang/test/Sema/128bitfloat.cpp
index cb76dac96001..779c59dfd4a0 100644
--- a/clang/test/Sema/128bitfloat.cpp
+++ b/clang/test/Sema/128bitfloat.cpp
@@ -2,23 +2,23 @@
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
 
 #if !defined(__STRICT_ANSI__)
-__float128 f;  // expected-error {{support for type '__float128' is not yet implemented}}
+__float128 f;  // expected-error {{__float128 is not supported on this target}}
 // But this should work:
 template<typename> struct __is_floating_point_helper {};
-template<> struct __is_floating_point_helper<__float128> {};
+template<> struct __is_floating_point_helper<__float128> {};  // expected-error {{__float128 is not supported on this target}}
 
 // FIXME: This could have a better diag.
-void g(int x, __float128 *y) {
-  x + *y;  // expected-error {{invalid operands to binary expression ('int' and '__float128')}}
+int g(int x, __float128 *y) {  // expected-error {{__float128 is not supported on this target}}
+  return x + *y;
 }
 
 #else
-__float128 f;  // expected-error {{unknown type name '__float128'}}
+__float128 f;  // expected-error {{__float128 is not supported on this target}}
 template<typename> struct __is_floating_point_helper {};
-template<> struct __is_floating_point_helper<__float128> {};  // expected-error {{use of undeclared identifier '__float128'}}
+template<> struct __is_floating_point_helper<__float128> {};  // expected-error {{__float128 is not supported on this target}}
 
-void g(int x, __float128 *y) {  // expected-error {{unknown type name '__float128'}}
-  x + *y;
+int g(int x, __float128 *y) {  // expected-error {{__float128 is not supported on this target}}
+  return x + *y;
 }
 
 #endif
diff --git a/clang/test/Sema/float128-ld-incompatibility.cpp b/clang/test/Sema/float128-ld-incompatibility.cpp
new file mode 100644
index 000000000000..d993ed7b081c
--- /dev/null
+++ b/clang/test/Sema/float128-ld-incompatibility.cpp
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 \
+// RUN: -triple powerpc64le-unknown-linux-gnu -target-cpu pwr8 \
+// RUN: -target-feature +float128 %s
+
+__float128 qf();
+long double ldf();
+
+// FIXME: once operations between long double and __float128 are implemented for
+//        targets where the types are different, these next two will change
+long double ld{qf()}; // expected-error {{cannot initialize a variable of type 'long double' with an rvalue of type '__float128'}}
+__float128 q{ldf()};  // expected-error {{cannot initialize a variable of type '__float128' with an rvalue of type 'long double'}}
+
+auto test1(__float128 q, long double ld) -> decltype(q + ld) { // expected-error {{invalid operands to binary expression ('__float128' and 'long double')}}
+  return q + ld;      // expected-error {{invalid operands to binary expression ('__float128' and 'long double')}}
+}
+
+auto test2(long double a, __float128 b) -> decltype(a + b) { // expected-error {{invalid operands to binary expression ('long double' and '__float128')}}
+  return a + b;      // expected-error {{invalid operands to binary expression ('long double' and '__float128')}}
+}
+
+void test3(bool b) {
+  long double ld;
+  __float128 q;
+
+  ld + q; // expected-error {{invalid operands to binary expression ('long double' and '__float128')}}
+  q + ld; // expected-error {{invalid operands to binary expression ('__float128' and 'long double')}}
+  ld - q; // expected-error {{invalid operands to binary expression ('long double' and '__float128')}}
+  q - ld; // expected-error {{invalid operands to binary expression ('__float128' and 'long double')}}
+  ld * q; // expected-error {{invalid operands to binary expression ('long double' and '__float128')}}
+  q * ld; // expected-error {{invalid operands to binary expression ('__float128' and 'long double')}}
+  ld / q; // expected-error {{invalid operands to binary expression ('long double' and '__float128')}}
+  q / ld; // expected-error {{invalid operands to binary expression ('__float128' and 'long double')}}
+  ld = q; // expected-error {{assigning to 'long double' from incompatible type '__float128'}}
+  q = ld; // expected-error {{assigning to '__float128' from incompatible type 'long double'}}
+  q + b ? q : ld; // expected-error {{incompatible operand types ('__float128' and 'long double')}}
+}
diff --git a/clang/test/SemaCXX/deleted-operator.cpp b/clang/test/SemaCXX/deleted-operator.cpp
index df67978a36d6..f71e83aa2587 100644
--- a/clang/test/SemaCXX/deleted-operator.cpp
+++ b/clang/test/SemaCXX/deleted-operator.cpp
@@ -9,7 +9,7 @@ int PR10757f() {
   PR10757 a1;
   // FIXME: We get a ridiculous number of "built-in candidate" notes here...
   if(~a1) {} // expected-error {{overload resolution selected deleted operator}} expected-note 8 {{built-in candidate}}
-  if(a1==a1) {} // expected-error {{overload resolution selected deleted operator}} expected-note 121 {{built-in candidate}}
+  if(a1==a1) {} // expected-error {{overload resolution selected deleted operator}} expected-note 144 {{built-in candidate}}
 }
 
 struct DelOpDel {
diff --git a/clang/test/SemaCXX/overloaded-builtin-operators.cpp b/clang/test/SemaCXX/overloaded-builtin-operators.cpp
index 4c2953b0b3fe..7a99a898e209 100644
--- a/clang/test/SemaCXX/overloaded-builtin-operators.cpp
+++ b/clang/test/SemaCXX/overloaded-builtin-operators.cpp
@@ -183,7 +183,7 @@ void test_dr425(A a) {
   // FIXME: lots of candidates here!
   (void)(1.0f * a); // expected-error{{ambiguous}} \
                     // expected-note 4{{candidate}} \
-                    // expected-note {{remaining 117 candidates omitted; pass -fshow-overloads=all to show them}}
+                    // expected-note {{remaining 140 candidates omitted; pass -fshow-overloads=all to show them}}
 }
 
 // pr5432
diff --git a/clang/tools/libclang/CXType.cpp b/clang/tools/libclang/CXType.cpp
index 5cde23605529..ea955625aac6 100644
--- a/clang/tools/libclang/CXType.cpp
+++ b/clang/tools/libclang/CXType.cpp
@@ -51,6 +51,7 @@ static CXTypeKind GetBuiltinTypeKind(const BuiltinType *BT) {
     BTCASE(Float);
     BTCASE(Double);
     BTCASE(LongDouble);
+    BTCASE(Float128);
     BTCASE(NullPtr);
     BTCASE(Overload);
     BTCASE(Dependent);
@@ -466,6 +467,7 @@ CXString clang_getTypeKindSpelling(enum CXTypeKind K) {
     TKIND(Float);
     TKIND(Double);
     TKIND(LongDouble);
+    TKIND(Float128);
     TKIND(NullPtr);
     TKIND(Overload);
     TKIND(Dependent);