Index: libcxx/include/type_traits
===================================================================
--- libcxx/include/type_traits
+++ libcxx/include/type_traits
@@ -741,7 +741,7 @@
 #ifdef __clang__
 template <>          struct __libcpp_is_floating_point<__fp16>      : public true_type {};
 #endif
-#ifdef __FLT16_MANT_DIG__
+#if defined(__clang__) && defined(__FLT16_MANT_DIG__)
 template <>          struct __libcpp_is_floating_point<_Float16>    : public true_type {};
 #endif
 template <>          struct __libcpp_is_floating_point<float>       : public true_type {};