[Bug middle-end/122913] [16 Regression?] pr12392.cpp -Ofast compile time went up 66% when switching to -std=c++20

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122913

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note `-O0 -g` compile time seems faster too:
https://lnt.opensuse.org/db_default/v4/CPP/graph?plot.0=468.585.8

Which makes me wonder what IR changes caused both a decrease in compile time at
-O0 (and -O2) but an increase at -Ofast.