[RFC PATCH]: Reciprocal sqrt (rsqrt) conversion pass

[Richard Guenther]

On Wed, 13 Jun 2007, Paolo Bonzini wrote:

> 
> > I don't think a target-independent builtin makes much sense, this is more
> > like supporting special instructions as opposed to widely available sincos
> > library implementations.
> 
> ... but widely available special instructions.

But also really special, as usually only available for floats and not
generally applicable due to precision issues.  Also (as you mentioned)
it raises the question if it is the canonical representation (how do
you handle rcp (1/x) in this context?).

Richard.