From: Cassio Neri <cassio.neri@gmail.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: [PATCH] libstdc++: More efficient std::chrono::year::leap.
Date: Fri, 21 May 2021 18:46:40 +0100 [thread overview]
Message-ID: <CAOfgUPgc+4fZ65GtcprdiM+ObP6o-avP85frLzY0A1uqZHOoUg@mail.gmail.com> (raw)
Simple change to std::chrono::year::is_leap. If a year is multiple of 100,
then it's divisible by 400 if and only if it's divisible by 16. The latter
allows for better code generation.
Tested on x86_64-pc-linux-gnu.
libstdc++-v3/ChangeLog:
* include/std/chrono:
diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index 4631a727d73..6221d02c1b3 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -1612,7 +1612,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr uint32_t __offset = __max_dividend / 2 / 100 * 100;
const bool __is_multiple_of_100
= __multiplier * (_M_y + __offset) < __bound;
- return (!__is_multiple_of_100 || _M_y % 400 == 0) && _M_y % 4 == 0;
+ return (!__is_multiple_of_100 || _M_y % 16 == 0) && _M_y % 4 == 0;
}
explicit constexpr
next reply other threads:[~2021-05-21 17:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 17:46 Cassio Neri [this message]
2021-05-21 18:05 ` Koning, Paul
2021-05-21 18:44 ` Cassio Neri
2021-06-23 11:45 ` Jonathan Wakely
2021-06-23 13:16 ` Jonathan Wakely
2021-06-23 17:51 ` Jonathan Wakely
2021-06-23 17:52 ` Jonathan Wakely
2021-06-24 11:42 ` Cassio Neri
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