Re: [PATCH, PR82428] Add __builtin_goacc_{gang,worker,vector}_{id,size}

[Tom de Vries <Tom_deVries at mentor dot com>]

On 01/15/2018 11:44 AM, Jakub Jelinek wrote:
> On Mon, Jan 15, 2018 at 11:39:28AM +0100, Tom de Vries wrote:
> > > Does OpenACC have some term for the 3 dimensions/kinds of parallelism?
> >
> > openacc spec: "OpenACC exposes these three levels of parallelism via gang,
> > worker and vector parallelism."
> >
> > So, maybe we abbreviate to: 'parlevel' or 'par_level'?
> >
> > > Is there some enum describing those 3 already?
> >
> > There's no enum type in openacc.h or gomp-constants.h.
> >
> > There's an enumeration of int constants from gomp-constants.h:
> > ...
> > #define GOMP_DIM_GANG   0
> > #define GOMP_DIM_WORKER 1
> > #define GOMP_DIM_VECTOR 2
> > ...
> > which I'm currently using as argument.
> >
> > Given the amount of trouble that having an enum type as argument for
> > acc_on_device has given us, I'm not sure that we want an enum type as
> > argument for these builtins. [ See the comments and kludge related to c++ in
> > the https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01529.html patch for
> > PR82391 Fold acc_on_device with const arg. ]
>
> Sure, the argument to the builtin should be just int.

Right.

>  I'm talking about
> what would users use and what would be documented in extend.texi.

And that is precisely my concern. Say that we define:
...
enum goacc_parlevel_t { gang = 0, worker = 1, vector = 2 };
...
and define as interface:
...
int __builtin_goacc_parlevel_id (enum goacc_parlevel_t);
...
but define the builtin with int argument.

Then we run into the same trouble as for acc_on_device: in c++ the 
__builtin_goacc_parlevel_id (enum goacc_parlevel_t) does not map onto 
the __builtin_goacc_parlevel_id (int), and we need to employ a kludge to 
make it so (the current kludge for acc_on_device is the inline function 
in openacc.h. The patch mentioned above replaces that kludge with 
another one: testing for name and signature of the function).

> It can be just number of course.  parlevel is fine for me.

So, in summary, I propose as interface:
- int __builtin_goacc_parlevel_id (int);
- int __builtin_goacc_parlevel_size (int);
with arguments 0, 1, and 2 meaning gang, worker and vector.

Thanks,
- Tom