Index: lib/Basic/Targets/WebAssembly.h
===================================================================
--- lib/Basic/Targets/WebAssembly.h
+++ lib/Basic/Targets/WebAssembly.h
@@ -52,6 +52,7 @@
     SizeType = UnsignedLong;
     PtrDiffType = SignedLong;
     IntPtrType = SignedLong;
+    HasFloat16 = true;
   }
 
 protected:
Index: lib/Frontend/InitPreprocessor.cpp
===================================================================
--- lib/Frontend/InitPreprocessor.cpp
+++ lib/Frontend/InitPreprocessor.cpp
@@ -830,7 +830,8 @@
   DefineFmt("__UINTPTR", TI.getUIntPtrType(), TI, Builder);
   DefineTypeWidth("__UINTPTR_WIDTH__", TI.getUIntPtrType(), TI, Builder);
 
-  DefineFloatMacros(Builder, "FLT16", &TI.getHalfFormat(), "F16");
+  if (TI.hasFloat16Type())
+    DefineFloatMacros(Builder, "FLT16", &TI.getHalfFormat(), "F16");
   DefineFloatMacros(Builder, "FLT", &TI.getFloatFormat(), "F");
   DefineFloatMacros(Builder, "DBL", &TI.getDoubleFormat(), "");
   DefineFloatMacros(Builder, "LDBL", &TI.getLongDoubleFormat(), "L");
Index: test/Headers/float16.c
===================================================================
--- test/Headers/float16.c
+++ test/Headers/float16.c
@@ -1,7 +1,11 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c89 -ffreestanding %s
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c99 -ffreestanding %s
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c11 -ffreestanding %s
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -x c++ -ffreestanding %s
+// RUN: %clang_cc1 -triple=aarch64-none-none -fsyntax-only -verify -std=c89 \
+// RUN:   -ffreestanding %s
+// RUN: %clang_cc1 -triple=wasm64-unknown-unknown -fsyntax-only -verify \
+// RUN:   -std=c99 -ffreestanding %s
+// RUN: %clang_cc1 -triple=aarch64-none-none -fsyntax-only -verify -std=c11 \
+// RUN:   -ffreestanding %s
+// RUN: %clang_cc1 -triple=wasm64-unknown-unknown -fsyntax-only -verify \
+// RUN:   -std=c++11 -x c++ -ffreestanding %s
 // expected-no-diagnostics
 
 #define __STDC_WANT_IEC_60559_TYPES_EXT__