Re: [Fortran][PATCH][gomp4]: Transform OpenACC loop directive

[Tobias Burnus <burnus at net-b dot de>]

Hi Illmir,

Ilmir Usmanov:
> This patch implements transformation of OpenACC loop directive from 
> Fortran AST to GENERIC.

If I followed correctly, with this patch the Fortran FE implementation 
of OpenACC is complete, except for:

* !$acc cache() - parsing supported, but then aborting with a 
not-implemented error
* OpenACC 2.0a additions.

Am I right?

> Successfully bootstrapped and tested with no new regressions on 
> x86_64-unknown-linux-gnu.
> OK for gomp4 branch?

I leave the review of gcc/tree-pretty-print.c part (looks good to me) to 
Thomas, who might have also a comment to the Fortran part.

For a DO loop, the code looks okay.


For DO CONCURRENT, it is not. I think we should really consider to 
reject DO CONCURRENT with a "not permitted"; it is currently not 
explicitly supported by OpenACC; I think we can still worry about it, 
when it will be explicitly added to OpenACC. Otherwise, see 
gfc_trans_do_concurrent for how to handle the do concurrent loops.

Issues with DO CONCURRENT:

* You use "code->ext.iterator->var" - that's fine with DO but not with 
DO CONCURRENT, which uses a "code->ext.forall_iterator"

* Do concurrent also handles multiple variables in a single statement, 
such as:

integer :: i, j, b(3,5)
DO CONCURRENT(i=1:3, j=1:5:2)
  b(i, j) = -42
END DO
end

* And do concurrent also supports masks:

logical :: my_mask(3)
integer :: i, b(3)
b(i) = [5, 5, 2]
my_mask = [.true., .false., .true.]
do concurrent (i=1:3, b(i) == 5 .and. my_mask(i))
  b(i) = -42
end do
end

Tobias