[Bug c++/86590] Codegen is poor when passing std::string by value with _GLIBCXX_EXTERN_TEMPLATE undefined

[s_gccbugzilla at nedprod dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86590

Niall Douglas <s_gccbugzilla at nedprod dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Codegen regression when     |Codegen is poor when
                   |passing std::string by      |passing std::string by
                   |value in C++ 17 and C++ 20  |value with
                   |                            |_GLIBCXX_EXTERN_TEMPLATE
                   |                            |undefined

--- Comment #4 from Niall Douglas <s_gccbugzilla at nedprod dot com> ---
Title made more accurate as per Jonathan's request