procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Optimize truncating a basic_string

Browse source 
* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
	(basic_string::erase(size_type, size_type)): Add fast path for
	truncating the string, by calling _M_set_length directly.
	(basic_string::erase(__const_iterator, __const_iterator)): Likewise.
	* include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
	(basic_string::resize(size_type, _CharT)): Likewise.

From-SVN: r240446
This commit is contained in:
Jonathan Wakely 2016-09-23 18:25:23 +01:00 • committed by Jonathan Wakely
parent b862552dff
commit a922c5ff6f
3 changed files with 19 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
libstdc++-v3/ChangeLog
View file

@ -1,3 +1,12 @@
2016-09-23 Jonathan Wakely <jwakely@redhat.com>
* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
(basic_string::erase(size_type, size_type)): Add fast path for
truncating the string, by calling _M_set_length directly.
(basic_string::erase(__const_iterator, __const_iterator)): Likewise.
* include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
(basic_string::resize(size_type, _CharT)): Likewise.
2016-09-22 Jason Merrill <jason@redhat.com>
* configure.ac: Define HAVE_MEMALIGN for newlib.

12
libstdc++-v3/include/bits/basic_string.h
View file

@ -1709,8 +1709,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
basic_string&
erase(size_type __pos = 0, size_type __n = npos)
{
this->_M_erase(_M_check(__pos, "basic_string::erase"),
_M_limit(__pos, __n));
_M_check(__pos, "basic_string::erase");
if (__n == npos)
this->_M_set_length(__pos);
else if (__n != 0)
this->_M_erase(__pos, _M_limit(__pos, __n));
return *this;
}
@ -1747,7 +1750,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_GLIBCXX_DEBUG_PEDASSERT(__first >= begin() && __first <= __last
&& __last <= end());
const size_type __pos = __first - begin();
this->_M_erase(__pos, __last - __first);
if (__last == end())
this->_M_set_length(__pos);
else
this->_M_erase(__pos, __last - __first);
return iterator(this->_M_data() + __pos);
}

2
libstdc++-v3/include/bits/basic_string.tcc
View file

@ -351,7 +351,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
if (__size < __n)
this->append(__n - __size, __c);
else if (__n < __size)
this->_M_erase(__n, __size - __n);
this->_M_set_length(__n);
}
template<typename _CharT, typename _Traits, typename _Alloc>