Re: [patch] invoke.texi: Update -fopenmp and -fopenmp-simd for omp::decl and loop semantic

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Sep 26, 2023 at 9:50 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Tue, Sep 26, 2023 at 09:34:15AM +0200, Richard Biener wrote:
> > On Mon, Sep 25, 2023 at 8:25 PM Tobias Burnus <tobias@codesourcery.com> wrote:
> > >
> > > I stumbled over this during the ARM64 talk at the cauldron as they
> > > consider using -fopenmp-simd by default.
> >
> > Ah, forgot to ask during the talk - isn't __attribute__((simd(..))) exactly to
> > avoid the need for -fopenmp-simd?
>
> Yes.  Though, -fopenmp-simd can do slightly more than that,
> #pragma GCC ivdep equivalent on various loops is the other important part
> (though for both simd attribute and ivdep pragma the OpenMP counterparts
> are significantly more flexible, in the declare simd case one can specify
> certain arguments should be linear (with various variants for
> references)/uniform, simd construct can specify not just everything is
> independent or not, but how many consecutive iterations must be independent,
> can specify reductions etc., preferred vectorization factors, ...).
> Though, I don't think it is a good idea to enable -fopenmp-simd by default.

Yeah, writing invalid OMP simd pragmas (syntactically or semantically) shouldn't
be causing problems when not using -fopenmp-simd but would if that's
the default.

Richard.

>
>         Jakub
>