https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88971
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hubicka at gcc dot gnu.org
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #3)
> (In reply to Richard Biener from comment #1)
> > This is because it still needs to generate the std::string objects at the
> > caller
> > site (outside of the if (print)). This involves quite some code to get
> > rid of, and even at -O3 we do not inline basic_string::basic_string it seems
> > (ISTR that is out-of-line in the library):
> >
> > __asm__ __volatile__("mfence" : : : "memory");
> > _6 = MEM[(const int *)&data + 4B];
> > if (_6 > 0)
> > goto <bb 3>; [41.48%]
> > else
> > goto <bb 11>; [58.52%]
> >
> > <bb 3> [local count: 445388109]:
> > std::basic_string<char>::basic_string (&D.39204, "<", &D.39205);
> > _7 = MEM[(char * *)&D.39204];
> > _8 = _7 + 18446744073709551592;
> > if (_8 != &_S_empty_rep_storage)
> > goto <bb 5>; [10.00%]
> > else
> > goto <bb 4>; [90.00%]
>
> Looks like you're using -D_GLIBCXX_USE_CXX11_ABI=0 but the OP is not.
Indeed. It's still missed inlining that makes elding of the argument
construction difficult. Looks like
std::__cxx11::basic_string<char>::_M_construct<const char*>
is not marked inline (so needs -finline-functions to get IPA inlining
processing). Indeed I see
// For forward_iterators up to random_access_iterators, used for
// string::iterator, _CharT*, etc.
template<typename _FwdIterator>
void
_M_construct(_FwdIterator __beg, _FwdIterator __end,
std::forward_iterator_tag);
and others.
