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| author | Will Hawkins <whh8b@obs.cr> | 2022-08-24 02:16:48 -0400 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2022-08-24 15:22:44 +0100 |
| commit | 0b7c9254998b3fb2c39f6b86b5b196f415530205 (patch) | |
| tree | 3c5842373e17a003ff7159b0ba506af72f971152 | |
| parent | 02de9d26b1820e4af35ebdd271c3a788e3c99035 (diff) | |
| download | gcc-0b7c9254998b3fb2c39f6b86b5b196f415530205.zip gcc-0b7c9254998b3fb2c39f6b86b5b196f415530205.tar.gz gcc-0b7c9254998b3fb2c39f6b86b5b196f415530205.tar.bz2 | |
libstdc++: Optimize operator+(string/char*, char*/string) equally
Until now operator+(char*, const string&) and operator+(const string&,
char*) had different performance characteristics. The former required a
single memory allocation and the latter required two. This patch makes
the performance equal.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (operator+(const string&, const char*)):
Remove naive implementation.
* include/bits/basic_string.tcc (operator+(const string&, const char*)):
Add single-allocation implementation.
Signed-off-by: Will Hawkins <whh8b@obs.cr>
| -rw-r--r-- | libstdc++-v3/include/bits/basic_string.h | 9 | ||||
| -rw-r--r-- | libstdc++-v3/include/bits/basic_string.tcc | 21 |
2 files changed, 23 insertions, 7 deletions
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index b04fba9..fa67389 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -3521,14 +3521,9 @@ _GLIBCXX_END_NAMESPACE_CXX11 */ template<typename _CharT, typename _Traits, typename _Alloc> _GLIBCXX20_CONSTEXPR - inline basic_string<_CharT, _Traits, _Alloc> + basic_string<_CharT, _Traits, _Alloc> operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, - const _CharT* __rhs) - { - basic_string<_CharT, _Traits, _Alloc> __str(__lhs); - __str.append(__rhs); - return __str; - } + const _CharT* __rhs); /** * @brief Concatenate string and character. diff --git a/libstdc++-v3/include/bits/basic_string.tcc b/libstdc++-v3/include/bits/basic_string.tcc index 4563c61..95ba8e5 100644 --- a/libstdc++-v3/include/bits/basic_string.tcc +++ b/libstdc++-v3/include/bits/basic_string.tcc @@ -641,6 +641,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } template<typename _CharT, typename _Traits, typename _Alloc> + _GLIBCXX20_CONSTEXPR + basic_string<_CharT, _Traits, _Alloc> + operator+(const basic_string<_CharT, _Traits, _Alloc>& __lhs, + const _CharT* __rhs) + { + __glibcxx_requires_string(__rhs); + typedef basic_string<_CharT, _Traits, _Alloc> __string_type; + typedef typename __string_type::size_type __size_type; + typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template + rebind<_CharT>::other _Char_alloc_type; + typedef __gnu_cxx::__alloc_traits<_Char_alloc_type> _Alloc_traits; + const __size_type __len = _Traits::length(__rhs); + __string_type __str(_Alloc_traits::_S_select_on_copy( + __lhs.get_allocator())); + __str.reserve(__len + __lhs.size()); + __str.append(__lhs); + __str.append(__rhs, __len); + return __str; + } + + template<typename _CharT, typename _Traits, typename _Alloc> _GLIBCXX_STRING_CONSTEXPR typename basic_string<_CharT, _Traits, _Alloc>::size_type basic_string<_CharT, _Traits, _Alloc>:: |