[Bug c++/85747] suboptimal code without constexpr

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85747

--- Comment #5 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Antony Polukhin from comment #4)
> Does providing some kind of -Oon-the-fly switch solves the issue with JIT
> compile times while still allows more optimizations for the traditional non
> JIT  -O2 builds?

Not sure what you mean by -Oon-the-fly. If you want to JIT compile the code,
you more or less need to embed a compiler in the executable...

The closest I can think of is -fprofile-values. It is possible to collect the
values of constants during a training run and use them during a second
compilation. But then knowing more constants in one compilation than the other
may change the code in ways that the PGO framework will not like.