Add stdfloat header

Fixes #1260

Author: jart

third_party/libcxx/BUILD.mk

@@ -1040,6 +1040,7 @@ third_party/libcxx/ryu/d2s_intrinsics.h \
 third_party/libcxx/ryu/digit_table.h \
 third_party/libcxx/ryu/f2s.h \
 third_party/libcxx/ryu/ryu.h \
+third_party/libcxx/stdfloat \
 
 THIRD_PARTY_LIBCXX_A_SRCS = \
 third_party/libcxx/algorithm.cpp \

third_party/libcxx/stdfloat

@@ -0,0 +1,25 @@
+// -*- C++ -*-
+
+export namespace std {
+
+#if defined(__STDCPP_FLOAT16_T__)
+  using float16_t = _Float16;
+#endif
+
+#if defined(__STDCPP_FLOAT32_T__)
+  using float32_t = float;
+#endif
+
+#if defined(__STDCPP_FLOAT64_T__)
+  using float64_t = double;
+#endif
+
+#if defined(__STDCPP_FLOAT128_T__)
+  using float128_t = long double;
+#endif
+
+#if defined(__STDCPP_BFLOAT16_T__)
+  using bfloat16_t = __bf16;
+#endif
+
+} // namespace std