[Bug target/105246] [amdgcn] Use library call for SQRT with -ffast-math + provide additional option to use single-precsion opcode

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105246

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
can one improve the precision by employing some additional NR step or so, using
v_sqrt only for the initial guess?  I agree that just v_sqrt isn't good for
-funsafe-math-optimizations.