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| author | Cassio Neri <cassio.neri@gmail.com> | 2023-11-11 22:59:50 +0000 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2023-11-14 22:32:08 +0000 |
| commit | 86a0df1a6c7fe4a835620b868e76ea78d42d6620 (patch) | |
| tree | aa03c7925bbe6429e24ed974d5b6e949ef3c4d1e /libcpp | |
| parent | b011535456396a6846ff24fb5b1baea8fe0a33b1 (diff) | |
| download | gcc-86a0df1a6c7fe4a835620b868e76ea78d42d6620.zip gcc-86a0df1a6c7fe4a835620b868e76ea78d42d6620.tar.gz gcc-86a0df1a6c7fe4a835620b868e76ea78d42d6620.tar.bz2 | |
libstdc++: Simplify year::is_leap()
The current implementation returns
(_M_y & (__is_multiple_of_100 ? 15 : 3)) == 0;
where __is_multiple_of_100 is calculated using an obfuscated algorithm which
saves one ror instruction when compared to _M_y % 100 == 0 [1].
In leap years calculation, it's correct to replace the divisibility check by
100 with the one by 25. It turns out that _M_y % 25 == 0 also saves the ror
instruction [2]. Therefore, the obfuscation is not required.
[1] https://godbolt.org/z/5PaEv6a6b
[2] https://godbolt.org/z/55G8rn77e
libstdc++-v3/ChangeLog:
* include/std/chrono (year::is_leap): Clear code.
Diffstat (limited to 'libcpp')
0 files changed, 0 insertions, 0 deletions