[gomp4] OpenACC wait directive

[Cesar Philippidis]

On 09/24/2014 12:18 AM, Ilmir Usmanov wrote:
> Hi Cesar!
> 
> Thank you for the patch!
> 
> On 24.09.2014 02:29, Cesar Philippidis wrote:
>> This patch adds support for the async clause in the wait directive in
>> fortran. It should be pretty straight forward. The fortran FE already
>> supports the wait directive, but the async clause was introduced to the
>> wait directive in OpenACC 2.0 and that was missing in gomp-4_0-branch.
> Yes, I've mostly focused on spec. ver. 1.0.
> 
>> Is this OK for gomp-4_0-branch?
> No, it isn't. According to the spec and this presentation:
> http://www.pgroup.com/lit/presentations/cea-3.pdf (See slide 1-35)
> it is possible to write construction like:
> !$acc wait(1) async(2)
> However, your patch doesn't support this. Also, don't forget to check
> whether a queue waits itself (for example, wait(1) async(1)).
> In addition, it breaks current support of the directive (for example,
> wait(1)).

Sorry for the delay. I encountered some problems with the runtime in our
internal branch, and that slowed things down a bit.

Anyway, you are correct, I broke the optional argument to wait in the
previous patch. This new patch addresses that and it also make the wait
construct conform with OpenACC 2.0. Specifically,

  !$acc wait (1, 2) async (3)

should behave as ex[ected.

If you look at gfc_trans_oacc_wait_directive, you'll note that a call to
GOACC_wait is emitted for the wait directive. Since I had to add a
runtime library stub for that builtin function, I decided to go ahead an
include the c front end bits.

Is this patch OK for gomp-4_0-branch? Julian is working on working on a
more complete implementation of the runtime. The runtime stub that I
included is only temporary.

Cesar

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