Re: Vector comparison

[Artem Shinkarov <artyom dot shinkaroff at gmail dot com>]

On Sun, Aug 15, 2010 at 6:30 PM, Andrew Pinski <pinskia@gmail.com> wrote:
> On Sun, Aug 15, 2010 at 10:09 AM, Artem Shinkarov
> <artyom.shinkaroff@gmail.com> wrote:
>> This patch implements vector comparison according to OpenCL standard.
>> The patch tries to dispatch vector comparison to hardware-specific
>> instructions. If case when it is impossible, vector comparison is
>> expanded piecewise.
>
> I had posted a patch which had implemented them using the standard
> tree codes and expansion and tree-lower-vect took care of the rest.
> This was for reduction of vector comparison into a single scalar.
> In fact we had agreed that they should implicitly turn a vector int
> into a scalar when used in the context of a bool.
> See http://gcc.gnu.org/ml/gcc-patches/2009-05/msg01912.html .

Yes, I looked over your patch. The thing is that OpenCL defines vector
comparison exactly in a way it is currently implemented. I can't see
any problem to reduce it with a max or min function over vector
elements for being able to use it inside if statement.

>
> Please consider using tree codes all the way through the gimple IR if
> the target supports expansion and doing the expansion only at expand
> time. ?Building a call expression is expensive and really you could
> use opcodes and not worry about a target hook. ?I think opcodes it is
> a much easier way allowing for targets to add support rather than
> adding more and more target hooks.

The hook approach was approved by Richard, so let's wait what he is
going to tell.


Thanks,
Artem.