When _Duration uses integer seconds precision (period::den == 1,
not floating-point), time_point formatting has no sub-second
digits and therefore no locale-dependent components. Add an
overload of __detail::__chrono_write that conditionally skips
the locale argument, eliminating the format_to_n locale overload
and the basic_format_context locale member initialization.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h
(__detail::__chrono_write): New overload skipping locale
for integer-second durations.
(operator<< for hh_mm_ss, sys_time, utc_time, tai_time,
gps_time, file_time, local_time, zoned_time): Use it.
Suggested-by: Tomasz Kamiński <[email protected]>
Signed-off-by: Anlai Lu <[email protected]>
---
Performance data (Xeon, -O2, core pinned, turbo off, 50M iters):
den==1 types instructions branches
--------------- ------------ --------
sys_time_s -4.2% -9.6%
utc_time_s -3.8% -8.7%
tai_time_s -4.2% -9.6%
gps_time_s -4.2% -9.6%
file_time_s -4.2% -9.6%
local_time_s -4.2% -9.6%
zoned_time_s -2.4% -4.6%
hh_mm_ss_s -6.0% -13.6%
den!=1 (control):
sys_time_ms +1.0% +1.1%
utc_time_ms +1.0% +1.1%
local_time_ms +1.0% +1.1%
hh_mm_ss_ms +1.3% +1.4%
The den==1 improvement comes from compile-time removal of the
format_to_n locale overload and basic_format_context locale
member. The den!=1 +1.0% is a known measurement artifact from
mixing 12 time_point instantiations in one translation unit;
isolated single-type tests show zero difference.
libstdc++-v3/include/bits/chrono_io.h | 35 +++++++++++++++++++--------
1 file changed, 25 insertions(+), 10 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono_io.h
b/libstdc++-v3/include/bits/chrono_io.h
index c5170368f..fa40290a8 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -3635,6 +3635,21 @@ namespace __detail
return std::__ostream_insert(__os, __s.data(), __s.size());
}
+ // Overload of __chrono_write that conditionally skips locale for
+ // integer-second time_points, hh_mm_ss, and zoned_time.
+ template<size_t _BufSize, typename _Duration, typename _CharT,
+ typename _Traits, typename _Tp>
+ inline basic_ostream<_CharT, _Traits>&
+ __chrono_write(basic_ostream<_CharT, _Traits>& __os,
+ const _Tp& __val)
+ {
+ if constexpr (!treat_as_floating_point_v<typename _Duration::rep>
+ && _Duration::period::den == 1)
+ return __chrono_write<_BufSize>(__os, __val);
+ else
+ return __chrono_write<_BufSize>(__os, __val, __os.getloc());
+ }
+
} // namespace __detail
/// @endcond
@@ -3740,7 +3755,7 @@ namespace __detail
operator<<(basic_ostream<_CharT, _Traits>& __os,
const weekday_last& __wdl)
{ return __detail::__chrono_write<128>(__os, __wdl, __os.getloc()); }
-
+
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os, const month_day& __md)
@@ -3846,7 +3861,7 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const hh_mm_ss<_Duration>& __hms)
- { return __detail::__chrono_write<64>(__os, __hms, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __hms); }
#if _GLIBCXX_USE_CXX11_ABI || ! _GLIBCXX_USE_DUAL_ABI
/// Writes a sys_info object to an ostream in an unspecified format.
@@ -3866,7 +3881,7 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const zoned_time<_Duration, _TimeZonePtr>& __t)
- { return __detail::__chrono_write<128>(__os, __t, __os.getloc()); }
+ { return __detail::__chrono_write<128, _Duration>(__os, __t); }
#endif
template<typename _CharT, typename _Traits, typename _Duration>
@@ -3875,12 +3890,12 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const sys_time<_Duration>& __tp)
- { return __detail::__chrono_write<64>(__os, __tp, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __tp); }
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os, const sys_days& __dp)
- { return __detail::__chrono_write<32>(__os, __dp); };
+ { return __detail::__chrono_write<32>(__os, __dp); }
template<typename _CharT, typename _Traits, typename _Duration,
typename _Alloc = allocator<_CharT>>
@@ -3914,7 +3929,7 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const utc_time<_Duration>& __t)
- { return __detail::__chrono_write<64>(__os, __t, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __t); }
template<typename _CharT, typename _Traits, typename _Duration,
typename _Alloc = allocator<_CharT>>
@@ -3946,7 +3961,7 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const tai_time<_Duration>& __t)
- { return __detail::__chrono_write<64>(__os, __t, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __t); }
template<typename _CharT, typename _Traits, typename _Duration,
typename _Alloc = allocator<_CharT>>
@@ -3982,7 +3997,7 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const gps_time<_Duration>& __t)
- { return __detail::__chrono_write<64>(__os, __t, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __t); }
template<typename _CharT, typename _Traits, typename _Duration,
typename _Alloc = allocator<_CharT>>
@@ -4017,7 +4032,7 @@ namespace __detail
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os,
const file_time<_Duration>& __t)
- { return __detail::__chrono_write<64>(__os, __t, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __t); }
template<typename _CharT, typename _Traits, typename _Duration,
typename _Alloc = allocator<_CharT>>
@@ -4040,7 +4055,7 @@ namespace __detail
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 4257. Stream insertion for chrono::local_time should be constrained
requires requires(const sys_time<_Duration>& __st) { __os << __st; }
- { return __detail::__chrono_write<64>(__os, __lt, __os.getloc()); }
+ { return __detail::__chrono_write<64, _Duration>(__os, __lt); }
template<typename _CharT, typename _Traits, typename _Duration,
typename _Alloc = allocator<_CharT>>
--
2.34.1
