[libc++][NFC] Rename _LIBCPP_NODISCARD_ATTRIBUTE to _LIBCPP_NODISCARD

Differential Revision: https://reviews.llvm.org/D108940

Author: ldionne

libcxx/include/__config

@@ -1052,30 +1052,28 @@ typedef unsigned int   char32_t;
 #  define _LIBCPP_CONSTEXPR_AFTER_CXX17
 #endif
 
-// The _LIBCPP_NODISCARD_ATTRIBUTE should only be used to define other
-// NODISCARD macros to the correct attribute.
 #if __has_cpp_attribute(nodiscard) || defined(_LIBCPP_COMPILER_MSVC)
-#  define _LIBCPP_NODISCARD_ATTRIBUTE [[nodiscard]]
+#  define _LIBCPP_NODISCARD [[nodiscard]]
 #elif defined(_LIBCPP_COMPILER_CLANG_BASED) && !defined(_LIBCPP_CXX03_LANG)
-#  define _LIBCPP_NODISCARD_ATTRIBUTE [[clang::warn_unused_result]]
+#  define _LIBCPP_NODISCARD [[clang::warn_unused_result]]
 #else
 // We can't use GCC's [[gnu::warn_unused_result]] and
 // __attribute__((warn_unused_result)), because GCC does not silence them via
 // (void) cast.
-#  define _LIBCPP_NODISCARD_ATTRIBUTE
+#  define _LIBCPP_NODISCARD
 #endif
 
 // _LIBCPP_NODISCARD_EXT may be used to apply [[nodiscard]] to entities not
 // specified as such as an extension.
 #if defined(_LIBCPP_ENABLE_NODISCARD) && !defined(_LIBCPP_DISABLE_NODISCARD_EXT)
-#  define _LIBCPP_NODISCARD_EXT _LIBCPP_NODISCARD_ATTRIBUTE
+#  define _LIBCPP_NODISCARD_EXT _LIBCPP_NODISCARD
 #else
 #  define _LIBCPP_NODISCARD_EXT
 #endif
 
 #if !defined(_LIBCPP_DISABLE_NODISCARD_AFTER_CXX17) && \
     (_LIBCPP_STD_VER > 17 || defined(_LIBCPP_ENABLE_NODISCARD))
-#  define _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_NODISCARD_ATTRIBUTE
+#  define _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_NODISCARD
 #else
 #  define _LIBCPP_NODISCARD_AFTER_CXX17
 #endif

libcxx/include/type_traits

@@ -2340,7 +2340,7 @@ template <class _Tp> using make_unsigned_t = typename make_unsigned<_Tp>::type;
 
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Tp>
-_LIBCPP_NODISCARD_ATTRIBUTE _LIBCPP_INLINE_VISIBILITY constexpr
+_LIBCPP_HIDE_FROM_ABI constexpr
 typename make_unsigned<_Tp>::type __to_unsigned_like(_Tp __x) noexcept {
     return static_cast<typename make_unsigned<_Tp>::type>(__x);
 }