[Bug target/56843] PowerPC Newton-Raphson reciprocal estimates can be improved

[wschmidt at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56843

--- Comment #2 from Bill Schmidt <wschmidt at gcc dot gnu.org> 2013-04-04 16:12:31 UTC ---
Regarding the last point, I found this in the user manual:

"The double-precision square root estimate instructions are not generated by
default on low-precision machines, since they do not provide an estimate that
converges after three steps."

That seems to indicate someone decided the libcall is better than a four-step
iteration.  That doesn't necessarily seem obvious to me.