[WIP, OpenMP] OpenMP metadirectives support

[Kwok Cheung Yeung]

Hello

On 26/07/2021 8:56 pm, Jakub Jelinek wrote:
> On Mon, Jul 26, 2021 at 08:28:16PM +0100, Kwok Cheung Yeung wrote:
>> In Section 1.2.2 of the OpenMP TR10 spec, 'target variant' is defined as:
>>
>> A version of a device routine that can only be executed as part of a target region.
> 
> Yes, that is a target variant, but I'm pretty sure we've decided that
> the target construct added for declare target is actually not a dynamic
> property.  So basically mostly return to the 5.0 wording with clarifications
> for Fortran.  See
> https://github.com/OpenMP/spec/issues/2612#issuecomment-849742988
> for details.
> Making the target in construct dynamic would pretty much force all the
> scoring to be dynamic as well.

In that comment, Deepak says:

So, we decided to keep the target trait static, requiring that the declare 
target directive must be explicit and that the function version must be 
different from the version of the function that may be called outside of a 
target region (with the additional clarification that whether it differs or not 
will be implementation defined).

"the function version must be different from the version of the function that 
may be called outside of a target region": This is what we do not have in GCC at 
the moment - the function versions called within and outside target regions are 
the same on the host.

"whether it differs or not will be implementation defined": So whether a 
function with 'declare target' and a metadirective involving a 'target' 
construct behaves the same or not when called from both inside and outside of a 
target region is implementation defined?

I will leave the treatment of target constructs in the selector as it is then, 
with both calls going to the same function with the metadirective resolving to 
the 'target' variant. I will try to address your other concerns later.

Thanks

Kwok