[Bug middle-end/78879] -fprofile-generate causes undefined reference to `____ilog2_NaN'

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78879

--- Comment #3 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Yuan Pengfei from comment #2)
> (In reply to Markus Trippelsdorf from comment #1)
> > See discussion in PR72785.
> 
> I am using GCC 6.2.1. Is it the same problem?

Yes, I think so. The compiler is under no obligation to optimize the
____ilog2_NaN call away. It looks like a kernel bug.