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

[mpeddie at gmail dot com]

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

--- Comment #2 from Matt Peddie <mpeddie at gmail dot com> ---
Thank you for your quick response.  The explanation makes sense, and I agree
this is not a bug.  I'd like to understand -- this seems to me to imply that
GCC will use MPFR to evaluate calls to libm functions even when optimizations
are disabled with -O0, since in the -O0 case I still get the MPFR result if I
don't use a separate function and call atanf() on a constant.  Is there a way
to disable this behavior?