https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105329
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Here is an untested patch for the cold part of the function:
--- libstdc++-v3/include/bits/basic_string.h.jj 2022-01-21 22:48:42.220261654
+0100
+++ libstdc++-v3/include/bits/basic_string.h 2022-05-02 15:51:42.381923962
+0200
@@ -2504,6 +2504,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
_CharT __c);
+ __attribute__((__noinline__, __noclone__, __cold__)) void
+ _M_replace_cold(pointer __p, size_type __len1, const _CharT* __s,
+ const size_type __len2, const size_type __how_much);
+
_GLIBCXX20_CONSTEXPR
basic_string&
_M_replace(size_type __pos, size_type __len1, const _CharT* __s,
--- libstdc++-v3/include/bits/basic_string.tcc.jj 2022-01-11
22:31:41.482757256 +0100
+++ libstdc++-v3/include/bits/basic_string.tcc 2022-05-02 15:51:38.630975348
+0200
@@ -471,6 +471,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
template<typename _CharT, typename _Traits, typename _Alloc>
+ __attribute__((__noinline__, __noclone__, __cold__)) void
+ basic_string<_CharT, _Traits, _Alloc>::
+ _M_replace_cold(pointer __p, size_type __len1, const _CharT* __s,
+ const size_type __len2, const size_type __how_much)
+ {
+ // Work in-place.
+ if (__len2 && __len2 <= __len1)
+ this->_S_move(__p, __s, __len2);
+ if (__how_much && __len1 != __len2)
+ this->_S_move(__p + __len2, __p + __len1, __how_much);
+ if (__len2 > __len1)
+ {
+ if (__s + __len2 <= __p + __len1)
+ this->_S_move(__p, __s, __len2);
+ else if (__s >= __p + __len1)
+ {
+ // Hint to middle end that __p and __s overlap
+ // (PR 98465).
+ const size_type __poff = (__s - __p) + (__len2 - __len1);
+ this->_S_copy(__p, __p + __poff, __len2);
+ }
+ else
+ {
+ const size_type __nleft = (__p + __len1) - __s;
+ this->_S_move(__p, __s, __nleft);
+ this->_S_copy(__p + __nleft, __p + __len2, __len2 - __nleft);
+ }
+ }
+ }
+
+ template<typename _CharT, typename _Traits, typename _Alloc>
_GLIBCXX20_CONSTEXPR
basic_string<_CharT, _Traits, _Alloc>&
basic_string<_CharT, _Traits, _Alloc>::
@@ -500,7 +531,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
else
#endif
- if (_M_disjunct(__s))
+ if (__builtin_expect(_M_disjunct(__s),true))
{
if (__how_much && __len1 != __len2)
this->_S_move(__p + __len2, __p + __len1, __how_much);
@@ -508,32 +539,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
this->_S_copy(__p, __s, __len2);
}
else
- {
- // Work in-place.
- if (__len2 && __len2 <= __len1)
- this->_S_move(__p, __s, __len2);
- if (__how_much && __len1 != __len2)
- this->_S_move(__p + __len2, __p + __len1, __how_much);
- if (__len2 > __len1)
- {
- if (__s + __len2 <= __p + __len1)
- this->_S_move(__p, __s, __len2);
- else if (__s >= __p + __len1)
- {
- // Hint to middle end that __p and __s overlap
- // (PR 98465).
- const size_type __poff = (__s - __p) + (__len2 - __len1);
- this->_S_copy(__p, __p + __poff, __len2);
- }
- else
- {
- const size_type __nleft = (__p + __len1) - __s;
- this->_S_move(__p, __s, __nleft);
- this->_S_copy(__p + __nleft, __p + __len2,
- __len2 - __nleft);
- }
- }
- }
+ _M_replace_cold(__p, __len1, __s, __len2, __how_much);
}
else
this->_M_mutate(__pos, __len1, __s, __len2);
Note, on the #c0 testcase alone it actually results in larger generated code
(unless we arrange for it to be exported from libstdc++, for which it is quite
late for 12.1 right now), but say on:
#include <string>
void f (std::string& s)
{
s = "5";
}
void g (std::string& s)
{
s = "56";
}
void h (std::string& s)
{
s = "6";
}
it is already smaller (note, obviously it doesn't need to be in the same TU).
