[Bug middle-end/85992] Invalid optimization with atanf

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85992

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Matt Peddie from comment #2)
> Is there a way to disable this behavior?

-fno-builtin (or a more specific -fno-builtin-atanf) tells gcc to handle atanf
as a regular function call, not as a standard function, so it should avoid
constant folding (I didn't check).