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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libstdc++/103755] {has,use}_facet() and iostream constructor
 performance
Date: Fri, 21 Apr 2023 15:01:29 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103755

--- Comment #17 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:8caf5805ad76125b84430b8653003f4776489d46

commit r12-9462-g8caf5805ad76125b84430b8653003f4776489d46
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Apr 20 21:02:22 2023 +0100

    libstdc++: Optimize std::try_facet and std::use_facet [PR103755]

    The std::try_facet and std::use_facet functions were optimized in
    r13-3888-gb3ac43a3c05744 to avoid redundant checking for all facets that
    are required to always be present in every locale.

    This performs a simpler version of the optimization that only applies to
    std::ctype<char>, std::num_get<char>, std::num_put<char>, and the
    wchar_t specializations of those facets. Those are the facets that are
    cached by std::basic_ios, which means they're used on construction for
    every iostream object. This smaller change is suitable for the gcc-12
    branch, and mitigates the performance loss for powerpc64le-linux on the
    gcc-12 branch caused by r12-9454-g24cf9f4c6f45f7 for PR 103387. It also
    greatly improves the performance of constructing iostreams objects, for
    all targets.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103755
            * include/bits/locale_classes.tcc (try_facet, use_facet): Do not
            check array index or dynamic type when accessing required
            specializations of std::ctype, std::num_get, or std::num_put.
            * testsuite/22_locale/ctype/is/string/89728_neg.cc: Adjust
            expected errors.=