[RFC] Split -mrecip

[Uros Bizjak]

On Wed, Aug 31, 2011 at 6:16 PM, Michael Matz <matz@suse.de> wrote:

> I'd like to have tighter control over the individual situations that
> -mrecip handles, and I think the user might appreciate this too.  Hence
> I've introduced four new target options -mrecip-div, -mrecip-sqrt,
> -mrecip-vec-div and -mrecip-vec-sqrt.  I've redefined -mrecip to be
> equivalent to using those four options together.  In addition one can
> selectively disable some part via -mrecip -mno-recip-vec for instance.
>
> I was split mind about the approach, I could also have done like rs6000
> (-mrecip=<csv list>) with the disadvantage of having to write an own
> parser as our opt framework can't deal with comma separated lists of
> masks.  With the approach I chose our opt framework gets most of the work
> done.
>
> I've decided to not use four new bits from target_flags, and instead
> created a new mask (recip_mask).  Four bits would have fit in target bits
> right now,  but in the future we might want to add more specialization,
> like modes for which the reciprocals are active.
>
> What do you think?

These new flags looks like a nice addition, but I wonder, why we need
separate options to handle vector recip. A vector rsqrt or rdiv is
generated automatically in the same way as scalar rsqrt or rdiv is
generated, so IMO, -mrecip-sqrt and -mrecip-div should be enough.

For the future - could rs6000 and x86 use the same compile options to
handle reciprocals?

Uros.