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| author | Antony Polukhin <antoshkka@gmail.com> | 2019-09-09 11:12:44 +0000 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2019-09-09 12:12:44 +0100 |
| commit | d0e086ae4f9ac2138a5fa6c6405c61b1f7ae032d (patch) | |
| tree | b59733708c7b9a3b4caa6d4ecb5aad284d1b7d7b | |
| parent | 27dada7d06926cc7ef6293fbbf0629f523b49e48 (diff) | |
| download | gcc-d0e086ae4f9ac2138a5fa6c6405c61b1f7ae032d.zip gcc-d0e086ae4f9ac2138a5fa6c6405c61b1f7ae032d.tar.gz gcc-d0e086ae4f9ac2138a5fa6c6405c61b1f7ae032d.tar.bz2 | |
Minor std::to_chars optimisation for base 10
__to_chars_10_impl is quite fast. According to the IACA the main loop
takes only 6.0 cycles, the whole function with one iteration takes
10.0 cycles. Replacing the __first[pos] and __first[pos - 1] with
__first[0] and __first[1] drops the function time to 7.53 cycles.
2019-09-09 Antony Polukhin <antoshkka@gmail.com>
* include/bits/charconv.h (__detail::__to_chars_10_impl): Replace
final offsets with constants.
From-SVN: r275514
| -rw-r--r-- | libstdc++-v3/ChangeLog | 5 | ||||
| -rw-r--r-- | libstdc++-v3/include/bits/charconv.h | 6 |
2 files changed, 8 insertions, 3 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 0aff148..6cf1737 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,8 @@ +2019-09-09 Antony Polukhin <antoshkka@gmail.com> + + * include/bits/charconv.h (__detail::__to_chars_10_impl): Replace + final offsets with constants. + 2019-09-09 Jonathan Wakely <jwakely@redhat.com> * include/bits/range_access.h (__adl_to_address): Remove. diff --git a/libstdc++-v3/include/bits/charconv.h b/libstdc++-v3/include/bits/charconv.h index 0911660..a5b6be5 100644 --- a/libstdc++-v3/include/bits/charconv.h +++ b/libstdc++-v3/include/bits/charconv.h @@ -92,11 +92,11 @@ namespace __detail if (__val >= 10) { auto const __num = __val * 2; - __first[__pos] = __digits[__num + 1]; - __first[__pos - 1] = __digits[__num]; + __first[1] = __digits[__num + 1]; + __first[0] = __digits[__num]; } else - __first[__pos] = '0' + __val; + __first[0] = '0' + __val; } } // namespace __detail |