Provide floating point overloads for std::signbit

Author: robincaloudis

libcxx/include/__math/traits.h

@@ -38,6 +38,48 @@ _LIBCPP_NODISCARD inline
   return __builtin_signbit(__x);
 }
 
+_LIBCPP_NODISCARD inline
+// TODO(LLVM 22): Remove `__has_constexpr_builtin` conditional once support for Clang 19 is dropped.
+#if __has_constexpr_builtin(__builtin_signbit)
+    _LIBCPP_CONSTEXPR_SINCE_CXX23
+#endif
+_LIBCPP_HIDE_FROM_ABI
+#ifdef _LIBCPP_PREFERRED_OVERLOAD
+_LIBCPP_PREFERRED_OVERLOAD
+#endif
+    bool
+    signbit(float __x) _NOEXCEPT {
+  return __builtin_signbit(__x);
+}
+
+_LIBCPP_NODISCARD inline
+// TODO(LLVM 22): Remove `__has_constexpr_builtin` conditional once support for Clang 19 is dropped.
+#if __has_constexpr_builtin(__builtin_signbit)
+    _LIBCPP_CONSTEXPR_SINCE_CXX23
+#endif
+_LIBCPP_HIDE_FROM_ABI
+#ifdef _LIBCPP_PREFERRED_OVERLOAD
+_LIBCPP_PREFERRED_OVERLOAD
+#endif
+    bool
+    signbit(double __x) _NOEXCEPT {
+  return __builtin_signbit(__x);
+}
+
+_LIBCPP_NODISCARD inline
+// TODO(LLVM 22): Remove `__has_constexpr_builtin` conditional once support for Clang 19 is dropped.
+#if __has_constexpr_builtin(__builtin_signbit)
+    _LIBCPP_CONSTEXPR_SINCE_CXX23
+#endif
+_LIBCPP_HIDE_FROM_ABI
+#ifdef _LIBCPP_PREFERRED_OVERLOAD
+_LIBCPP_PREFERRED_OVERLOAD
+#endif
+    bool
+    signbit(long double __x) _NOEXCEPT {
+  return __builtin_signbit(__x);
+}
+
 template <class _A1, __enable_if_t<is_integral<_A1>::value && is_signed<_A1>::value, int> = 0>
 _LIBCPP_NODISCARD inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool signbit(_A1 __x) _NOEXCEPT {
   return __x < 0;