[Bug tree-optimization/102958] std::u8string suboptimal compared to std::string, triggers warnings

[jason at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102958

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
Let's focus on the missed-optimization issues in this PR, and address the
broader diagnostic issues in PR 103483.