[Bug libstdc++/110801] std::format code runs slower than equivalent {fmt} code

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110801

--- Comment #3 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:41a5ea4cab2c59f9911325281f7df1d3ae846d48

commit r14-5587-g41a5ea4cab2c59f9911325281f7df1d3ae846d48
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Aug 15 22:43:41 2023 +0100

    libstdc++: Add fast path for std::format("{}", x) [PR110801]

    This optimizes the simple case of formatting a single string, integer
    or bool, with no format-specifier (so no padding, alignment, alternate
    form etc.)

    libstdc++-v3/ChangeLog:

            PR libstdc++/110801
            * include/std/format (_Sink_iter::_M_reserve): New member
            function.
            (_Sink::_Reservation): New nested class.
            (_Sink::_M_reserve, _Sink::_M_bump): New virtual functions.
            (_Seq_sink::_M_reserve, _Seq_sink::_M_bump): New virtual
            overrides.
            (_Iter_sink<O, ContigIter>::_M_reserve): Likewise.
            (__do_vformat_to): Use new functions to optimize "{}" case.