[libc++][format] Implements P3107R5 in <format>. (llvm#86713)

This adds the new std::enable_nonlocking_formatter_optimization trait in <format>. This trait will be used in std::print to implement the performance benefits. Implements parts of - P3107R5 - Permit an efficient implementation of ``std::print``
banach-space · Aug 7, 2024 · 61e313f · 61e313f
1 parent bf51086
commit 61e313f
Show file tree

Hide file tree

Showing 10 changed files with 337 additions and 10 deletions.
diff --git a/libcxx/include/__format/formatter.h b/libcxx/include/__format/formatter.h
@@ -39,6 +39,9 @@ struct _LIBCPP_TEMPLATE_VIS formatter {
 
 #  if _LIBCPP_STD_VER >= 23
 
+template <class _Tp>
+constexpr bool enable_nonlocking_formatter_optimization = false;
+
 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI constexpr void __set_debug_format(_Tp& __formatter) {
   if constexpr (requires { __formatter.set_debug_format(); })

diff --git a/libcxx/include/__format/formatter_bool.h b/libcxx/include/__format/formatter_bool.h
@@ -69,7 +69,11 @@ struct _LIBCPP_TEMPLATE_VIS formatter<bool, _CharT> {
   __format_spec::__parser<_CharT> __parser_;
 };
 
-#endif //_LIBCPP_STD_VER >= 20
+#  if _LIBCPP_STD_VER >= 23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<bool> = true;
+#  endif //_LIBCPP_STD_VER >= 23
+#endif   //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
 

diff --git a/libcxx/include/__format/formatter_char.h b/libcxx/include/__format/formatter_char.h
@@ -83,9 +83,17 @@ struct _LIBCPP_TEMPLATE_VIS formatter<char, wchar_t> : public __formatter_char<w
 
 template <>
 struct _LIBCPP_TEMPLATE_VIS formatter<wchar_t, wchar_t> : public __formatter_char<wchar_t> {};
-
 #  endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
 
+#  if _LIBCPP_STD_VER >= 23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<char> = true;
+#    ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<wchar_t> = true;
+#    endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#  endif   //_LIBCPP_STD_VER >= 23
+
 #endif //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD

diff --git a/libcxx/include/__format/formatter_floating_point.h b/libcxx/include/__format/formatter_floating_point.h
@@ -774,6 +774,14 @@ struct _LIBCPP_TEMPLATE_VIS formatter<double, _CharT> : public __formatter_float
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<long double, _CharT> : public __formatter_floating_point<_CharT> {};
 
+#  if _LIBCPP_STD_VER >= 23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<float> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<double> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<long double> = true;
+#  endif //_LIBCPP_STD_VER >= 23
 #endif //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD

diff --git a/libcxx/include/__format/formatter_integer.h b/libcxx/include/__format/formatter_integer.h
@@ -88,7 +88,38 @@ template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<__uint128_t, _CharT> : public __formatter_integer<_CharT> {};
 #  endif
 
-#endif //_LIBCPP_STD_VER >= 20
+#  if _LIBCPP_STD_VER >= 23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<signed char> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<short> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<int> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<long> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<long long> = true;
+#    ifndef _LIBCPP_HAS_NO_INT128
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<__int128_t> = true;
+#    endif
+
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<unsigned char> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<unsigned short> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<unsigned> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<unsigned long> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<unsigned long long> = true;
+#    ifndef _LIBCPP_HAS_NO_INT128
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<__uint128_t> = true;
+#    endif
+#  endif //_LIBCPP_STD_VER >= 23
+#endif   //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
 

diff --git a/libcxx/include/__format/formatter_pointer.h b/libcxx/include/__format/formatter_pointer.h
@@ -65,6 +65,14 @@ struct _LIBCPP_TEMPLATE_VIS formatter<void*, _CharT> : public __formatter_pointe
 template <__fmt_char_type _CharT>
 struct _LIBCPP_TEMPLATE_VIS formatter<const void*, _CharT> : public __formatter_pointer<_CharT> {};
 
+#  if _LIBCPP_STD_VER >= 23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<nullptr_t> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<void*> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<const void*> = true;
+#  endif //_LIBCPP_STD_VER >= 23
 #endif //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD

diff --git a/libcxx/include/__format/formatter_string.h b/libcxx/include/__format/formatter_string.h
@@ -143,7 +143,32 @@ struct _LIBCPP_TEMPLATE_VIS formatter<basic_string_view<_CharT, _Traits>, _CharT
   }
 };
 
-#endif //_LIBCPP_STD_VER >= 20
+#  if _LIBCPP_STD_VER >= 23
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<char*> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<const char*> = true;
+template <size_t _Size>
+inline constexpr bool enable_nonlocking_formatter_optimization<char[_Size]> = true;
+template <class _Traits, class _Allocator>
+inline constexpr bool enable_nonlocking_formatter_optimization<basic_string<char, _Traits, _Allocator>> = true;
+template <class _Traits>
+inline constexpr bool enable_nonlocking_formatter_optimization<basic_string_view<char, _Traits>> = true;
+
+#    ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<wchar_t*> = true;
+template <>
+inline constexpr bool enable_nonlocking_formatter_optimization<const wchar_t*> = true;
+template <size_t _Size>
+inline constexpr bool enable_nonlocking_formatter_optimization<wchar_t[_Size]> = true;
+template <class _Traits, class _Allocator>
+inline constexpr bool enable_nonlocking_formatter_optimization<basic_string<wchar_t, _Traits, _Allocator>> = true;
+template <class _Traits>
+inline constexpr bool enable_nonlocking_formatter_optimization<basic_string_view<wchar_t, _Traits>> = true;
+#    endif // _LIBCPP_HAS_NO_WIDE_CHARACTERS
+#  endif   //_LIBCPP_STD_VER >= 23
+#endif     //_LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
 

diff --git a/libcxx/include/format b/libcxx/include/format
@@ -126,14 +126,17 @@ namespace std {
   // [format.formatter], formatter
   template<class T, class charT = char> struct formatter;
 
+  template<class T>
+  constexpr bool enable_nonlocking_formatter_optimization = false;   // since C++23
+
   // [format.parse.ctx], class template basic_format_parse_context
   template<class charT> class basic_format_parse_context;
   using format_parse_context = basic_format_parse_context<char>;
   using wformat_parse_context = basic_format_parse_context<wchar_t>;
 
   // [format.range], formatting of ranges
   // [format.range.fmtkind], variable template format_kind
-  enum class range_format {                                     // since C++23
+  enum class range_format {                                          // since C++23
     disabled,
     map,
     set,
@@ -143,20 +146,20 @@ namespace std {
   };
 
   template<class R>
-    constexpr unspecified format_kind = unspecified;            // since C++23
+    constexpr unspecified format_kind = unspecified;                 // since C++23
 
   template<ranges::input_range R>
       requires same_as<R, remove_cvref_t<R>>
-    constexpr range_format format_kind<R> = see below;          // since C++23
+    constexpr range_format format_kind<R> = see below;               // since C++23
 
   // [format.range.formatter], class template range_formatter
   template<class T, class charT = char>
     requires same_as<remove_cvref_t<T>, T> && formattable<T, charT>
-  class range_formatter;                                        // since C++23
+  class range_formatter;                                             // since C++23
 
   // [format.range.fmtdef], class template range-default-formatter
   template<range_format K, ranges::input_range R, class charT>
-    struct range-default-formatter;                             // exposition only, since C++23
+    struct range-default-formatter;                                  // exposition only, since C++23
 
   // [format.range.fmtmap], [format.range.fmtset], [format.range.fmtstr],
   // specializations for maps, sets, and strings
@@ -173,7 +176,7 @@ namespace std {
     see below visit_format_arg(Visitor&& vis, basic_format_arg<Context> arg); // Deprecated in C++26
 
   // [format.arg.store], class template format-arg-store
-  template<class Context, class... Args> struct format-arg-store;      // exposition only
+  template<class Context, class... Args> struct format-arg-store;    // exposition only
 
   template<class Context = format_context, class... Args>
     format-arg-store<Context, Args...>

diff --git a/libcxx/modules/std/format.inc b/libcxx/modules/std/format.inc
@@ -46,6 +46,8 @@ export namespace std {
   using std::formatter;
 
 #if _LIBCPP_STD_VER >= 23
+  using std::enable_nonlocking_formatter_optimization;
+
   // [format.formattable], concept formattable
   using std::formattable;
 #endif