[llvm-commits] PATCH: remove VICmp and VFCmp.

[David Greene]

On Tuesday 07 July 2009 15:16, Chris Lattner wrote:

> > Work has been one to support vector [fi]cmp in the IR, however no
> > work has been done to support it in CodeGen yet. Adding support in
> > CodeGen will require a variety of fairly straight-forward
> > changes, plus finding a solution for vectors of i1 in CodeGen.
>
> I don't see a need to fix the "vector of i1" issue right now.  In
> fact, I don't see an issue at all.
>
> There are two things we care about: making compare+sext turn into the
> current nice code that v*cmp produces, and eventually handling compare
> +select.  Both of these idioms are trivial enough that they could be
> handled by pre-legalize dag combine, forming (e.g.) ISD::VSETCC
> nodes.  Then legalize won't ever see vectors of i1 in code that we
> care about.

I haven't been tracking this, so can someone explain what the "vectors of
i1 problem" is?  Is it a problem of how to generate code on architectures
that don't have a mask concept?

compare+select is not enough for architectures like Larrabee.  We are very
soon going to want to support full vector predication, so it would seem like
solving the vectors of i1 problem is moderately important.

                                -Dave