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| author | Cassio Neri <cassio.neri@gmail.com> | 2023-11-14 00:27:39 +0000 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2023-11-14 22:32:09 +0000 |
| commit | f71352c71d78ac977ea0e71a6900699a8cf09219 (patch) | |
| tree | 717f7ee03699fb6ad845634e4503edbf1f358cc0 /libcpp | |
| parent | f6ce081d0ffb5f25d71eb2f30fcfdff7f20dba22 (diff) | |
| download | gcc-f71352c71d78ac977ea0e71a6900699a8cf09219.zip gcc-f71352c71d78ac977ea0e71a6900699a8cf09219.tar.gz gcc-f71352c71d78ac977ea0e71a6900699a8cf09219.tar.bz2 | |
libstdc++: Improve operator-(weekday x, weekday y)
The current implementation calls __detail::__modulo which is relatively
expensive.
A better implementation is possible if we assume that x.ok() && y.ok() == true,
so that n = x.c_encoding() - y.c_encoding() is in [-6, 6]. In this case, it
suffices to return n >= 0 ? n : n + 7.
The above is allowed by [time.cal.wd.nonmembers]/5: the returned value is
unspecified when x.ok() || y.ok() == false.
The assembly emitted for x86-64 and ARM can be seen in:
https://godbolt.org/z/nMdc5vv9n.
libstdc++-v3/ChangeLog:
* include/std/chrono (operator-(const weekday&, const weekday&)):
Optimize.
Diffstat (limited to 'libcpp')
0 files changed, 0 insertions, 0 deletions