[Patch][v2] OpenMP/Fortran: Partially fix non-rect loop nests [PR107424]

[Tobias Burnus]

Hi Jakub, hi all,

updated patch included, i.e. avoiding 'count' for 'j' when a 'j.0' would
do (i.e. only local var without the different step calculation). I also
now reject if there is a non-unit step on the loop using an outer var.

Eventually still to be done: replace the 'sorry' by working code, i.e.
implement the suggestions to handle some/all non-unit iteration steps as
proposed in this thread.

On 20.01.23 18:39, Jakub Jelinek wrote:
> I think instead of non-unity etc. it is better to talk about constant
> step 1 or -1.

I concur.


> The actual problem with non-simple loops for non-rectangular loops is
> both in case it is an inner loop which uses some outer loop's iterator,
> or if it is outer loop whose iterator is used, both of those cases
> will not be handled properly.

I have now added a check for the other case as well.

Just to confirm, the following is fine, isn't it?

!$omp simd collapse(4)
do i = 1, 10, 2
   do outer_var = 1, 10  ! step = + 1
     do j = 1, 10, 2
       do inner_var = 1, outer_var  ! step = 1

i.e. both the inner_var and outer_var have 'step = 1',
even if other loops in the 'collapse' have step != 1.
I think it should be fine.

OK mainline?

Tobias
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