* [committed] libstdc++: Add std::formatter specializations for extended float types
@ 2023-08-17 20:32 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2023-08-17 20:32 UTC (permalink / raw)
To: libstdc++, gcc-patches
Tested x86_64-linux. Pushed to trunk.
-- >8 --
This makes it possible to format _Float32, _Float64 etc. in C++20 mode.
Previously it was only possible to format them in C++23 when the
<stdfloat> typedefs and the std::to_chars overloads were defined.
Instead of relying on std::to_chars for those types, we can just reuse
the formatters for float, double and long double. This also avoids
template bloat by reusing the same specializations instead of
instantiating __formatter_fp for every different type.
libstdc++-v3/ChangeLog:
* include/std/format (formatter): Add partial specializations
for extended floating-point types.
* testsuite/std/format/functions/format.cc: Move test_float128()
to ...
* testsuite/std/format/formatter/ext_float.cc: New test.
---
libstdc++-v3/include/std/format | 146 +++++++++++++++++-
.../std/format/formatter/ext_float.cc | 92 +++++++++++
.../testsuite/std/format/functions/format.cc | 33 ----
3 files changed, 236 insertions(+), 35 deletions(-)
create mode 100644 libstdc++-v3/testsuite/std/format/formatter/ext_float.cc
diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 79f810acce3..13f700a10bf 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -2033,6 +2033,7 @@ namespace __format
};
#endif
+#if defined __cpp_lib_to_chars
/// Format a floating-point value.
template<__format::__formattable_float _Tp, __format::__char _CharT>
struct formatter<_Tp, _CharT>
@@ -2053,6 +2054,140 @@ namespace __format
__format::__formatter_fp<_CharT> _M_f;
};
+#if __LDBL_MANT_DIG__ == __DBL_MANT_DIG__
+ // Reuse __formatter_fp<C>::format<double, Out> for long double.
+ template<__format::__char _CharT>
+ struct formatter<long double, _CharT>
+ {
+ formatter() = default;
+
+ [[__gnu__::__always_inline__]]
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f.parse(__pc); }
+
+ template<typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(long double __u, basic_format_context<_Out, _CharT>& __fc) const
+ { return _M_f.format((double)__u, __fc); }
+
+ private:
+ __format::__formatter_fp<_CharT> _M_f;
+ };
+#endif
+
+#if defined(__FLT16_DIG__)
+ // Reuse __formatter_fp<C>::format<float, Out> for _Float16.
+ template<__format::__char _CharT>
+ struct formatter<_Float16, _CharT>
+ {
+ formatter() = default;
+
+ [[__gnu__::__always_inline__]]
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f.parse(__pc); }
+
+ template<typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(_Float16 __u, basic_format_context<_Out, _CharT>& __fc) const
+ { return _M_f.format((float)__u, __fc); }
+
+ private:
+ __format::__formatter_fp<_CharT> _M_f;
+ };
+#endif
+
+#if defined(__FLT32_DIG__)
+ // Reuse __formatter_fp<C>::format<float, Out> for _Float32.
+ template<__format::__char _CharT>
+ struct formatter<_Float32, _CharT>
+ {
+ formatter() = default;
+
+ [[__gnu__::__always_inline__]]
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f.parse(__pc); }
+
+ template<typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(_Float32 __u, basic_format_context<_Out, _CharT>& __fc) const
+ { return _M_f.format((float)__u, __fc); }
+
+ private:
+ __format::__formatter_fp<_CharT> _M_f;
+ };
+#endif
+
+#if defined(__FLT64_DIG__)
+ // Reuse __formatter_fp<C>::format<double, Out> for _Float64.
+ template<__format::__char _CharT>
+ struct formatter<_Float64, _CharT>
+ {
+ formatter() = default;
+
+ [[__gnu__::__always_inline__]]
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f.parse(__pc); }
+
+ template<typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(_Float64 __u, basic_format_context<_Out, _CharT>& __fc) const
+ { return _M_f.format((double)__u, __fc); }
+
+ private:
+ __format::__formatter_fp<_CharT> _M_f;
+ };
+#endif
+
+#if defined(__FLT128_DIG__) && _GLIBCXX_FORMAT_F128 == 1
+ // Reuse __formatter_fp<C>::format<__float128_t, Out> for _Float128.
+ template<__format::__char _CharT>
+ struct formatter<_Float128, _CharT>
+ {
+ formatter() = default;
+
+ [[__gnu__::__always_inline__]]
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f.parse(__pc); }
+
+ template<typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(_Float128 __u, basic_format_context<_Out, _CharT>& __fc) const
+ { return _M_f.format((__format::__float128_t)__u, __fc); }
+
+ private:
+ __format::__formatter_fp<_CharT> _M_f;
+ };
+#endif
+
+#if defined(__BFLT16_DIG__)
+ // Reuse __formatter_fp<C>::format<float, Out> for bfloat16_t.
+ template<__format::__char _CharT>
+ struct formatter<__gnu_cxx::__bfloat16_t, _CharT>
+ {
+ formatter() = default;
+
+ [[__gnu__::__always_inline__]]
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f.parse(__pc); }
+
+ template<typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(__gnu_cxx::__bfloat16_t __u,
+ basic_format_context<_Out, _CharT>& __fc) const
+ { return _M_f.format((float)__u, __fc); }
+
+ private:
+ __format::__formatter_fp<_CharT> _M_f;
+ };
+#endif
+#endif // __cpp_lib_to_chars
+
/** Format a pointer.
* @{
*/
@@ -2702,7 +2837,6 @@ namespace __format
__int128 _M_i128;
unsigned __int128 _M_u128;
#endif
- // TODO _Float16 etc.
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
__ieee128 _M_f128;
__ibm128 _M_ibm128;
@@ -2931,7 +3065,15 @@ namespace __format
return type_identity<__ieee128>();
#endif
- // TODO bfloat16 and float16
+#if defined(__FLT16_DIG__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
+ else if constexpr (is_same_v<_Td, _Float16>)
+ return type_identity<float>();
+#endif
+
+#if defined(__BFLT16_DIG__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32)
+ else if constexpr (is_same_v<_Td, decltype(0.0bf16)>)
+ return type_identity<float>();
+#endif
#ifdef __FLT32_DIG__
else if constexpr (is_same_v<_Td, _Float32>)
diff --git a/libstdc++-v3/testsuite/std/format/formatter/ext_float.cc b/libstdc++-v3/testsuite/std/format/formatter/ext_float.cc
new file mode 100644
index 00000000000..89810295b64
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/format/formatter/ext_float.cc
@@ -0,0 +1,92 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+
+#include <format>
+#include <testsuite_hooks.h>
+
+template<typename T>
+bool format_float()
+{
+ auto s = std::format("{:#} != {:<+7.3f}", (T)-0.0, (T)0.5);
+ return s == "-0. != +0.500 ";
+}
+
+#if __cplusplus > 202002L
+template<typename T>
+concept formattable = std::formattable<T, char>;
+#else
+template<typename T>
+concept formattable = std::semiregular<std::formatter<T, char>>;
+#endif
+
+void
+test_float16()
+{
+#if __FLT16_DIG__
+ if constexpr (formattable<_Float16>)
+ VERIFY( format_float<_Float16>() );
+ else
+ std::puts("Cannot format _Float16 on this target");
+#endif
+}
+
+void
+test_float32()
+{
+#if __FLT32_DIG__
+ if constexpr (formattable<_Float32>)
+ VERIFY( format_float<_Float32>() );
+ else
+ std::puts("Cannot format _Float32 on this target");
+#endif
+}
+
+void
+test_float64()
+{
+#if __FLT64_DIG__
+ if constexpr (formattable<_Float64>)
+ VERIFY( format_float<_Float64>() );
+ else
+ std::puts("Cannot format _Float64 on this target");
+#endif
+}
+
+void
+test_float128()
+{
+#ifdef __SIZEOF_FLOAT128__
+ if constexpr (formattable<__float128>)
+ VERIFY( format_float<__float128>() );
+ else
+ std::puts("Cannot format __float128 on this target");
+#endif
+#if __FLT128_DIG__
+ if constexpr (formattable<_Float128>)
+ VERIFY( format_float<_Float128>() );
+ else
+ std::puts("Cannot format _Float128 on this target");
+#endif
+}
+
+void
+test_bfloat16()
+{
+#if __BFLT16_DIG__
+ using bfloat16_t = decltype(0.0bf16);
+
+ if constexpr (formattable<bfloat16_t>)
+ VERIFY( format_float<bfloat16_t>() );
+ else
+ std::puts("Cannot format bfloat16_t on this target");
+#endif
+}
+
+int main()
+{
+ test_float16();
+ test_float32();
+ test_float64();
+ test_float128();
+ test_bfloat16();
+}
diff --git a/libstdc++-v3/testsuite/std/format/functions/format.cc b/libstdc++-v3/testsuite/std/format/functions/format.cc
index 59d327fccee..5141cbd11bf 100644
--- a/libstdc++-v3/testsuite/std/format/functions/format.cc
+++ b/libstdc++-v3/testsuite/std/format/functions/format.cc
@@ -347,38 +347,6 @@ test_p1652r1() // printf corner cases in std::format
VERIFY( s == "3.31" );
}
-template<typename T>
-bool format_float()
-{
- auto s = std::format("{:#} != {:<+7.3f}", (T)-0.0, (T)0.5);
- return s == "-0. != +0.500 ";
-}
-
-#if __cplusplus > 202002L
-template<typename T>
-concept formattable = std::formattable<T, char>;
-#else
-template<typename T>
-concept formattable = requires (T t, char* p) { std::to_chars(p, p, t); };
-#endif
-
-void
-test_float128()
-{
-#ifdef __SIZEOF_FLOAT128__
- if constexpr (formattable<__float128>)
- VERIFY( format_float<__float128>() );
- else
- std::puts("Cannot format __float128 on this target");
-#endif
-#if __FLT128_DIG__
- if constexpr (formattable<_Float128>)
- VERIFY( format_float<_Float128>() );
- else
- std::puts("Cannot format _Float128 on this target");
-#endif
-}
-
void
test_pointer()
{
@@ -429,6 +397,5 @@ int main()
test_wchar();
test_minmax();
test_p1652r1();
- test_float128();
test_pointer();
}
--
2.41.0
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