[Bug tree-optimization/103989] [12 regression] std::optional and bogus -Wmaybe-unitialized at -Og since r12-1992-g6feb628a706e86eb

["hubicka at kam dot mff.cuni.cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103989

--- Comment #10 from hubicka at kam dot mff.cuni.cz ---
> And I'm intentionally not doing this because -Og should still remove
> abstraction during early inlining (for functions marked 'inline'), we
> just don't want to spend the extra compile time doing IPA inlining
> or cleaning up after IPA inlining.

Indeed it seemed bit too extreme to disable inlining completely at -Og :)
So you want early inliner to behave normally according to flags
while IPA inliner to skip all calls where either caller or
callee is -Og and callee is not always_inline?
This can be done in can_inline_edge_p. I will make patch for that.

It may be nice to also avoid re-analyzing functions completely to save
some compile time, but that may be bit tricky if we decide to do things
like cross-module always_inline.  I will look into that too, but perhaps
that can wait for next stage1.
> 
> but of course IPA inline size estimates are a bit off since we are not
> going to do any optimization on the inlined body.

We still do late ccp and other things, but indeed inline estimates
anticipate FRE to happen which it doesn't.

Looking into what passes are in the pipeline I also noticed that
we could also probably skip late modref from -Og optimization pipeline.
(I think David added it htere originally since we do pure-const).
I am thinking about retiring pure-const from pure-const discovery next
stage1 since modref should be monotonosly stronger doing that (and
if we add a stripped down mode of modref it should not be more expensive
than pure-const)