[PATCH] Handle empty infinite loops in OpenACC for PR84955

[Tom de Vries]

On 04/16/2018 08:13 PM, Tom de Vries wrote:
> On 04/12/2018 08:58 PM, Jakub Jelinek wrote:
>> On Thu, Apr 12, 2018 at 11:39:43AM -0700, Cesar Philippidis wrote:
>>> Strange. I didn't observe any regressions when I tested it. But, then
>>> again, I was testing against revision
>>>
>>> r259092 | jason | 2018-04-04 09:42:55 -0700 (Wed, 04 Apr 2018) | 4 lines
>>>
>>> which is over a week old. I'll revert that patch for now, and revisit
>>> this issue in stage1.
>>
>> You should have kept the omp-expand.c chunk, that is correct and 
>> shouldn't
>> cause issues.
> 
> Committed as attached (with correct changelog entry, the previously 
> committed patch had an incorrect one).
> 

Backported to gcc-7-branch as attached.

Thanks,
- Tom

> diff --git a/gcc/omp-expand.c b/gcc/omp-expand.c
> index bb20490..c7d30ea 100644
> --- a/gcc/omp-expand.c
> +++ b/gcc/omp-expand.c
> @@ -5439,6 +5439,14 @@ expand_oacc_for (struct omp_region *region, struct omp_for_data *fd)
>   
>   	  split->flags ^= EDGE_FALLTHRU | EDGE_TRUE_VALUE;
>   
> +	  /* Add a dummy exit for the tiled block when cont_bb is missing.  */
> +	  if (cont_bb == NULL)
> +	    {
> +	      edge e = make_edge (body_bb, exit_bb, EDGE_FALSE_VALUE);
> +	      e->probability = profile_probability::even ();
> +	      split->probability = profile_probability::even ();
> +	    }
> +
>   	  /* Initialize the user's loop vars.  */
>   	  gsi = gsi_start_bb (elem_body_bb);
>   	  expand_oacc_collapse_vars (fd, true, &gsi, counts, e_offset);

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