Index: lib/Frontend/InitPreprocessor.cpp
===================================================================
--- lib/Frontend/InitPreprocessor.cpp
+++ lib/Frontend/InitPreprocessor.cpp
@@ -109,9 +109,11 @@
 /// PickFP - This is used to pick a value based on the FP semantics of the
 /// specified FP model.
 template <typename T>
-static T PickFP(const llvm::fltSemantics *Sem, T IEEESingleVal,
+static T PickFP(const llvm::fltSemantics *Sem, T IEEEHalfVal, T IEEESingleVal,
                 T IEEEDoubleVal, T X87DoubleExtendedVal, T PPCDoubleDoubleVal,
                 T IEEEQuadVal) {
+  if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::IEEEhalf())
+    return IEEEHalfVal;
   if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::IEEEsingle())
     return IEEESingleVal;
   if (Sem == (const llvm::fltSemantics*)&llvm::APFloat::IEEEdouble())
@@ -127,26 +129,26 @@
 static void DefineFloatMacros(MacroBuilder &Builder, StringRef Prefix,
                               const llvm::fltSemantics *Sem, StringRef Ext) {
   const char *DenormMin, *Epsilon, *Max, *Min;
-  DenormMin = PickFP(Sem, "1.40129846e-45", "4.9406564584124654e-324",
-                     "3.64519953188247460253e-4951",
+  DenormMin = PickFP(Sem, "5.9604644775390625e-8", "1.40129846e-45",
+                     "4.9406564584124654e-324", "3.64519953188247460253e-4951",
                      "4.94065645841246544176568792868221e-324",
                      "6.47517511943802511092443895822764655e-4966");
-  int Digits = PickFP(Sem, 6, 15, 18, 31, 33);
-  int DecimalDigits = PickFP(Sem, 9, 17, 21, 33, 36);
-  Epsilon = PickFP(Sem, "1.19209290e-7", "2.2204460492503131e-16",
-                   "1.08420217248550443401e-19",
+  int Digits = PickFP(Sem, 3, 6, 15, 18, 31, 33);
+  int DecimalDigits = PickFP(Sem, 5, 9, 17, 21, 33, 36);
+  Epsilon = PickFP(Sem, "9.765625e-4", "1.19209290e-7", 
+                   "2.2204460492503131e-16", "1.08420217248550443401e-19",
                    "4.94065645841246544176568792868221e-324",
                    "1.92592994438723585305597794258492732e-34");
-  int MantissaDigits = PickFP(Sem, 24, 53, 64, 106, 113);
-  int Min10Exp = PickFP(Sem, -37, -307, -4931, -291, -4931);
-  int Max10Exp = PickFP(Sem, 38, 308, 4932, 308, 4932);
-  int MinExp = PickFP(Sem, -125, -1021, -16381, -968, -16381);
-  int MaxExp = PickFP(Sem, 128, 1024, 16384, 1024, 16384);
-  Min = PickFP(Sem, "1.17549435e-38", "2.2250738585072014e-308",
+  int MantissaDigits = PickFP(Sem, 11, 24, 53, 64, 106, 113);
+  int Min10Exp = PickFP(Sem, -13, -37, -307, -4931, -291, -4931);
+  int Max10Exp = PickFP(Sem, 4, 38, 308, 4932, 308, 4932);
+  int MinExp = PickFP(Sem, -14, -125, -1021, -16381, -968, -16381);
+  int MaxExp = PickFP(Sem, 15, 128, 1024, 16384, 1024, 16384);
+  Min = PickFP(Sem, "6.103515625e-5", "1.17549435e-38", "2.2250738585072014e-308",
                "3.36210314311209350626e-4932",
                "2.00416836000897277799610805135016e-292",
                "3.36210314311209350626267781732175260e-4932");
-  Max = PickFP(Sem, "3.40282347e+38", "1.7976931348623157e+308",
+  Max = PickFP(Sem, "6.5504e+4", "3.40282347e+38", "1.7976931348623157e+308",
                "1.18973149535723176502e+4932",
                "1.79769313486231580793728971405301e+308",
                "1.18973149535723176508575932662800702e+4932");
@@ -783,6 +785,7 @@
   DefineFmt("__UINTPTR", TI.getUIntPtrType(), TI, Builder);
   DefineTypeWidth("__UINTPTR_WIDTH__", TI.getUIntPtrType(), TI, Builder);
 
+  DefineFloatMacros(Builder, "FLT16", &TI.getHalfFormat(), "F16");
   DefineFloatMacros(Builder, "FLT", &TI.getFloatFormat(), "F");
   DefineFloatMacros(Builder, "DBL", &TI.getDoubleFormat(), "");
   DefineFloatMacros(Builder, "LDBL", &TI.getLongDoubleFormat(), "L");
Index: lib/Headers/float.h
===================================================================
--- lib/Headers/float.h
+++ lib/Headers/float.h
@@ -134,4 +134,18 @@
 #  define LDBL_DECIMAL_DIG __LDBL_DECIMAL_DIG__
 #endif
 
+#ifdef __STDC_WANT_IEC_60559_TYPES_EXT__
+#  define FLT16_MANT_DIG  __FLT16_MANT_DIG__
+#  define FLT16_DECIMAL_DIG __LT16_DECIMAL_DIG__
+#  define FLT16_DIG  __LT16_DIG__
+#  define FLT16_MIN_EXP  __LT16_MIN_EXP__
+#  define FLT16_MIN_10_EXP __FLT16_MIN_10_EXP__
+#  define FLT16_MAX_EXP __FLT16_MAX_EXP__
+#  define FLT16_MAX_10_EXP __FLT16_MAX_10_EXP__
+#  define FLT16_MAX __FLT16_MAX__
+#  define FLT16_EPSILON __FLT16_EPSILON__
+#  define FLT16_MIN __FLT16_MIN__
+#  define FLT_TRUE_MIN __FLT_TRUE_MIN__
+#endif /* __STDC_WANT_IEC_60559_TYPES_EXT__ */
+
 #endif /* __FLOAT_H */
Index: test/Preprocessor/init.c
===================================================================
--- test/Preprocessor/init.c
+++ test/Preprocessor/init.c
@@ -285,6 +285,20 @@
 // AARCH64:#define __DBL_MIN_EXP__ (-1021)
 // AARCH64:#define __DBL_MIN__ 2.2250738585072014e-308
 // AARCH64:#define __DECIMAL_DIG__ __LDBL_DECIMAL_DIG__
+// AARCH64:#define __FLT16_DECIMAL_DIG__ 5
+// AARCH64:#define __FLT16_DENORM_MIN__ 5.9604644775390625e-8F16
+// AARCH64:#define __FLT16_DIG__ 3
+// AARCH64:#define __FLT16_EPSILON__ 9.765625e-4F16
+// AARCH64:#define __FLT16_HAS_DENORM__ 1
+// AARCH64:#define __FLT16_HAS_INFINITY__ 1
+// AARCH64:#define __FLT16_HAS_QUIET_NAN__ 1
+// AARCH64:#define __FLT16_MANT_DIG__ 11
+// AARCH64:#define __FLT16_MAX_10_EXP__ 4
+// AARCH64:#define __FLT16_MAX_EXP__ 15
+// AARCH64:#define __FLT16_MAX__ 6.5504e+4F16
+// AARCH64:#define __FLT16_MIN_10_EXP__ (-13)
+// AARCH64:#define __FLT16_MIN_EXP__ (-14)
+// AARCH64:#define __FLT16_MIN__ 6.103515625e-5F16
 // AARCH64:#define __FLT_DENORM_MIN__ 1.40129846e-45F
 // AARCH64:#define __FLT_DIG__ 6
 // AARCH64:#define __FLT_EPSILON__ 1.19209290e-7F
@@ -8884,7 +8898,7 @@
 // WEBASSEMBLY32-NEXT:#define __DECIMAL_DIG__ __LDBL_DECIMAL_DIG__
 // WEBASSEMBLY32-NOT:#define __ELF__
 // WEBASSEMBLY32-NEXT:#define __FINITE_MATH_ONLY__ 0
-// WEBASSEMBLY32-NEXT:#define __FLT_DECIMAL_DIG__ 9
+// WEBASSEMBLY32:#define __FLT_DECIMAL_DIG__ 9
 // WEBASSEMBLY32-NEXT:#define __FLT_DENORM_MIN__ 1.40129846e-45F
 // WEBASSEMBLY32-NEXT:#define __FLT_DIG__ 6
 // WEBASSEMBLY32-NEXT:#define __FLT_EPSILON__ 1.19209290e-7F
@@ -9210,7 +9224,7 @@
 // WEBASSEMBLY64-NEXT:#define __DECIMAL_DIG__ __LDBL_DECIMAL_DIG__
 // WEBASSEMBLY64-NOT:#define __ELF__
 // WEBASSEMBLY64-NEXT:#define __FINITE_MATH_ONLY__ 0
-// WEBASSEMBLY64-NEXT:#define __FLT_DECIMAL_DIG__ 9
+// WEBASSEMBLY64:#define __FLT_DECIMAL_DIG__ 9
 // WEBASSEMBLY64-NEXT:#define __FLT_DENORM_MIN__ 1.40129846e-45F
 // WEBASSEMBLY64-NEXT:#define __FLT_DIG__ 6
 // WEBASSEMBLY64-NEXT:#define __FLT_EPSILON__ 1.19209290e-7F