[Bug libstdc++/80826] Compilation Time for many of std::map insertions

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80826

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
For GCC 7 most time is spent in inlining.  I suspect C++14 helps with constexpr
evaluation doing some of the stuff in the frontend.

 integration             :  21.73 (39%) usr   0.33 (23%) sys  22.02 (39%) wall 
234388 kB (23%) ggc

C++14:

 integration             :   1.78 (14%) usr   0.16 (17%) sys   1.95 (14%) wall 
 99264 kB (17%) ggc

one likely reason is that early optimization is not good at reducing
abstraction with loops (not sure if std::map insertion involves loops that are
optimizable).

Maybe libstdc++ could still use features that make it faster with c++98 and
only restrict its interface?