Re: libmvec in gcc to have vector math in fortran

[Richard Biener <richard dot guenther at gmail dot com>]

On Fri, Jun 15, 2018 at 11:08 AM Florian Weimer <fw@deneb.enyo.de> wrote:
>
> * Richard Biener:
>
> > That said, good to see some glibc folks jump in on this thread.
> > I'd like to see glibc provide a fortran intrinsic header advertising
> > the libmvec routines it has.  We probably do need some gfortran
> > adjustments here but I think that glibc advertising is better than
> > hard-coding lists into GCC (like we do for some targets with
> > their -mveclibabi= option).
>
> The advantage of putting into GCC is that it will work irrespective of
> the installed glibc header version, so if we get this going:
>
>   <https://sourceware.org/ml/libc-alpha/2018-05/msg00501.html>
>
> you could use libmvec along with really old glibcs (probably as far
> back as 2.12, maybe even older).

Well, ok - I obviously meant bundling the header with libmvec, not with
glibc (which currently is the same).

Putting it into GCC means that you have mismatches in both directions.

I was also considering to somehow auto-generate a header based
on what the C headers advertise at GCC install time.
[or put a C parser into the fortran frontend, eh...]

> But then we might into a different direction altogether.
>
> Another question is wheter the Fortran header can be generated by
> something like -fdump-ada-spec, so that we don't have to maintain it
> separately from the C header.

Sure, see above - I think that's possible and it doesn't have to be as
complicated as -fdump-ada-spec.  Instead a simple script in your
favorite language will do the job.

First and foremost we need a syntax that actually works for the
Fortran frontend and a way to automatically include this special
header / module.

Richard.