Tested x86_64-linux. Pushed to trunk.
-- >8 --
This makes to_string approximately twice as fast at any optimization
level. Instead of iterating through every bit, jump straight to the next
bit that is set, by using _Find_first and _Find_next.
libstdc++-v3/ChangeLog:
* include/std/bitset (bitset::_M_copy_to_string): Find set bits
instead of iterating over individual bits.
---
libstdc++-v3/include/std/bitset | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/libstdc++-v3/include/std/bitset b/libstdc++-v3/include/std/bitset
index 0c84f15fda0..83c6416b770 100644
--- a/libstdc++-v3/include/std/bitset
+++ b/libstdc++-v3/include/std/bitset
@@ -1495,9 +1495,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_CharT __zero, _CharT __one) const
{
__s.assign(_Nb, __zero);
- for (size_t __i = _Nb; __i > 0; --__i)
- if (_Unchecked_test(__i - 1))
- _Traits::assign(__s[_Nb - __i], __one);
+ size_t __n = this->_Find_first();
+ while (__n < _Nb)
+ {
+ __s[_Nb - __n - 1] = __one;
+ __n = _Find_next(__n);
+ }
}
#endif // HOSTED
--
2.37.3
