[Bug ipa/113478] -Os does not inline single instruction function

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113478

--- Comment #4 from Jan Hubicka <hubicka at ucw dot cz> ---
> Possibly, at least when we know it doesn't expand to a libatomic call?  OTOH
> even then a function just wrapping such call should probably be inlined,
> so the question is whether the problem that
> is estimated as too big compared to the call calling the function
> (OTOH a1.test () has no arguments while __atomic_load_1 has two).

If we really want to optimize for size, calling function with one
parameter is shorter then calling function with two parameters.  The
code size model takes into account when the offline copy of the function
will disappear and it also has some biass towards understanding that a
lot of comdat functions are not really shared across units.

The testcase calls function 15 times and I guess wrapper function on
most architectures is shorter than 15 load zero instructions...

We now have -Os and -Oz and two-level optimize_size predicates. We may
make this less restrictive with lower size optimization level. But when
optimizing for size and if __atomic_load was ordinary function call, I
think the decision is correct.