Re: [PATCH 2/6, OpenACC, libgomp] Async re-work, oacc-* parts

[Thomas Schwinge <thomas@codesourcery.com>]

Hi Chung-Lin!

On Fri, 14 Dec 2018 22:52:44 +0800, Chung-Lin Tang <chunglin_tang@mentor.com> wrote:
> On 2018/12/14 10:17 PM, Thomas Schwinge wrote:
> > On Tue, 25 Sep 2018 21:10:47 +0800, Chung-Lin Tang <chunglin_tang@mentor.com> wrote:
> >> --- a/libgomp/oacc-async.c
> >> +++ b/libgomp/oacc-async.c
> > 
> >> +attribute_hidden struct goacc_asyncqueue *
> >> +lookup_goacc_asyncqueue (struct goacc_thread *thr, bool create, int async)
> >> +{
> >> +  /* The special value acc_async_noval (-1) maps to the thread-specific
> >> +     default async stream.  */
> >> +  if (async == acc_async_noval)
> >> +    async = thr->default_async;
> >> +
> >> +  if (async == acc_async_sync)
> >> +    return NULL;
> >> +
> >> +  if (async < 0)
> >> +    gomp_fatal ("bad async %d", async);
> > 
> > To make this "resolve" part more obvious, that is, the translation from
> > the "async" argument to an "asyncqueue" array index:
> > 
> >> +  if (!create
> >> +      && (async >= dev->openacc.async.nasyncqueue
> >> +	  || !dev->openacc.async.asyncqueue[async]))
> >> +    return NULL;
> >> +[...]
> > 
> > ..., I propose adding a "async2id" function for that, and then rename all
> > "asyncqueue[async]" to "asyncqueue[id]".
> 
> I don't think this is needed. This is the only place in the entire runtime that
> does asyncqueue indexing, adding more conceptual layers of re-directed indexing
> seems unneeded.

It makes the code better understandable?  Or, curious, why do you think
that the translation from an OpenACC async-argument to an internal
asyncqueue ID should not be a separate function?


> I do think the more descriptive comments are nice though.


> > And, this also restores the current trunk behavior, so that
> > "acc_async_noval" gets its own, separate "asyncqueue".
> 
> Is there a reason we need to restore that behavior right now?

Because otherwise that's a functional change ("regression") from the
current GCC trunk behavior, which I wouldn't expect in a re-work.


Grüße
 Thomas