Re: [RFC 0/X] Implement GCC support for AArch64 libmvec

[Jakub Jelinek <jakub@redhat.com>]

On Fri, Apr 21, 2023 at 10:54:51AM +0100, Richard Sandiford wrote:
> > I'm guessing the keyword here is 'trait' which I'm guessing is different 
> > from a omp declare simd directive, which is why it's not required to 
> > have a simdlen clause in an omp declare simd (see Jakub's comment).
> 
> Sure.  The thread above is about whether we need extension("scalable")
> or should drop it.  And extension("scalable") is only used in omp
> declare variant.  This was in response to "I also do not see a need
> for the 'omp declare variant' scalable extension constructs".

I'm not sure extension("scalable") in context selectors is what you want
to handle declare variant.  While extension trait is allowed and it is
implementation defined what is accepted as its arguments (within the
boundaries of allowed syntax), in this case you really want to adjust
behavior of the simd trait, so it would be better to specify you want
scalable simdlen using a simd trait property.

There will be OpenMP F2F meeting next month, I think this should be
discussed there and agreed on how to do this, after all, seems ARM
won't be the only architecture that needs it, RISC-V might be another.

	Jakub