https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97212
--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> ---
The testcase has:
#pragma omp target map(tofrom: a, sum) depend(out: a) nowait
#pragma omp task depend(in: a) shared(a)
and calls:
__builtin_GOMP_target_ext
__builtin_GOMP_task
The libgomp code has for "GOMP_task":
if (!if_clause || team == NULL
|| (thr->task && thr->task->final_task)
|| team->task_count > 64 * team->nthreads)
...
if ((flags & GOMP_TASK_FLAG_DEPEND)
&& thr->task && thr->task->depend_hash)
gomp_task_maybe_wait_for_dependencies (depend);
...
else
...
if (depend_size)
{
gomp_task_handle_depend (task, parent, depend);
if (task->num_dependees)
{
/* Tasks that depend on other tasks are not put into the
various waiting queues, so we are done for now. Said
tasks are instead put into the queues via
gomp_task_run_post_handle_dependers() after their
dependencies have been satisfied. After which, they
can be picked up by the various scheduling
points. */
gomp_mutex_unlock (&team->task_lock);
return;
}
}
For the attached code, we run into the else branch, i.e. the dependency is
analyzed – a dependency is detected but then the code just returns.
There is no call to gomp_task_run_post_handle_dependers (which is only called
by gomp_task_run_post_handle_depend which in turn is only called by
(gomp_barrier_handle_tasks and GOMP_taskwait).
The latter are "task synchronization point = A taskwait, taskgroup, or a
barrier construct." (OpenMP glossary)
Thus, the question is whether
* either the if branch should be called instead of the else branch
* or whether some task synchronization should be done after the task.
