[Bug tree-optimization/55016] request for specific builtins for rcp and rsqrt

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55016

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> 2012-10-22 18:56:42 UTC ---
(In reply to comment #0)
> void v() {
>   for(int i=0; i!=1024; ++i)
>     v0[i] = rsqrtf(v1[i]);
> }

Doesn't writing
v0[i] = 1 / sqrtf(v1[i])
work with suitable fast-math flags? It still produces an extra iteration to
refine the result, do we want a -ffaster-math?