[Bug libstdc++/110060] [14 Regression] Adding optimizer hints to std::vector causes a new -Wstringop-overread false positive

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110060

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:b7b255e77a271974479c34d1db3daafc04b920bc

commit r14-1470-gb7b255e77a271974479c34d1db3daafc04b920bc
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jun 1 10:26:10 2023 +0100

    libstdc++: Fix code size regressions in std::vector [PR110060]

    My r14-1452-gfb409a15d9babc change to add optimization hints to
    std::vector causes regressions because it makes std::vector::size() and
    std::vector::capacity() too big to inline. That's the opposite of what
    I wanted, so revert the changes to those functions.

    To achieve the original aim of optimizing vec.assign(vec.size(), x) we
    can add a local optimization hint to _M_fill_assign, so that it doesn't
    affect all other uses of size() and capacity().

    Additionally, add the same hint to the _M_assign_aux overload for
    forward iterators and add that to the testcase.

    It would be nice to similarly optimize:
      if (vec1.size() == vec2.size()) vec1 = vec2;
    but adding hints to operator=(const vector&) doesn't help. Presumably
    the relationships between the two sizes and two capacities are too
    complex to track effectively.

    libstdc++-v3/ChangeLog:

            PR libstdc++/110060
            * include/bits/stl_vector.h (_Vector_base::_M_invariant):
            Remove.
            (vector::size, vector::capacity): Remove calls to _M_invariant.
            * include/bits/vector.tcc (vector::_M_fill_assign): Add
            optimization hint to reallocating path.
            (vector::_M_assign_aux(FwdIter, FwdIter, forward_iterator_tag)):
            Likewise.
            * testsuite/23_containers/vector/capacity/invariant.cc: Moved
            to...
            * testsuite/23_containers/vector/modifiers/assign/no_realloc.cc:
            ...here. Check assign(FwdIter, FwdIter) too.
            * testsuite/23_containers/vector/types/1.cc: Revert addition
            of -Wno-stringop-overread option.