Re: [Patch] OpenMP/Fortran: Fix defaultmap(none) issue with dummy procedures [PR114283]

[Tobias Burnus <tburnus@baylibre.com>]

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Jakub Jelinek wrote:

> So firstprivate clause handling remaps them then if declare target indirect
> is used? If so, the patch looks reasonable to me.

[I have now updated the patch to turn the testcase to ensure
that is also keeps works at runtime.]

OpenMP leaves it a bit open when the remapping has to happen,
but one can construct cases – in particular with unified-shared memory –
where it is not possible to do this upon entry to a target region.

Thus, it has to be done when the function is invoked, e.g.

i = (*g) ();

is turned (in the target region but only on the device side) into

i = (*GOMP_target_map_indirect_ptr (g)) ();

Thus, as long as the host pointer value is transferred to the device,
it works – as the lookup is done on the device side. Directly using a
device address (remap when mapping to the target) will also not shorten
the lookup, i.e. there is no need for it.

Does it still look reasonable to you?

Tobias

PS: The current OpenMP specification, it is listed mainly described via
the glossary (newest change is the addition of dummy procedure):

"indirect device invocation – An indirect call to the _device_ version of 
a _procedure_ on a _device_ other than the _host-device_, through a 
function pointer (C/C++), a pointer to a member function (C++), a dummy 
procedure (Fortran), or a procedure pointer (Fortran) that refers to the 
host version of the _procedure_."

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OpenMP/Fortran: Fix defaultmap(none) issue with dummy procedures [PR114283]

Dummy procedures look similar to variables but aren't - neither in Fortran
nor in OpenMP. As the middle end sees PARM_DECLs, mark them as predetermined
firstprivate for mapping (as already done in gfc_omp_predetermined_sharing).

This does not address the isses related to procedure pointers, which are
still discussed on spec level [see PR].

	PR fortran/114283

gcc/fortran/ChangeLog:

	* trans-openmp.cc (gfc_omp_predetermined_mapping): Map dummy
	procedures as firstprivate.

libgomp/ChangeLog:

	* testsuite/libgomp.fortran/declare-target-indirect-4.f90: New test.

 gcc/fortran/trans-openmp.cc                        |  9 +++++
 .../libgomp.fortran/declare-target-indirect-4.f90  | 43 ++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/gcc/fortran/trans-openmp.cc b/gcc/fortran/trans-openmp.cc
index a2bf15665b3..1dba47126ed 100644
--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -343,6 +343,15 @@ gfc_omp_predetermined_mapping (tree decl)
 	    && GFC_DECL_SAVED_DESCRIPTOR (decl)))
     return OMP_CLAUSE_DEFAULTMAP_TO;
 
+  /* Dummy procedures aren't considered variables by OpenMP, thus are
+     disallowed in OpenMP clauses.  They are represented as PARM_DECLs
+     in the middle-end, so return OMP_CLAUSE_DEFAULTMAP_FIRSTPRIVATE here
+     to avoid complaining about their uses with defaultmap(none).  */
+  if (TREE_CODE (decl) == PARM_DECL
+      && TREE_CODE (TREE_TYPE (decl)) == POINTER_TYPE
+      && TREE_CODE (TREE_TYPE (TREE_TYPE (decl))) == FUNCTION_TYPE)
+    return OMP_CLAUSE_DEFAULTMAP_FIRSTPRIVATE;
+
   /* These are either array or derived parameters, or vtables.  */
   if (VAR_P (decl) && TREE_READONLY (decl)
       && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)))
diff --git a/libgomp/testsuite/libgomp.fortran/declare-target-indirect-4.f90 b/libgomp/testsuite/libgomp.fortran/declare-target-indirect-4.f90
new file mode 100644
index 00000000000..43f4295494c
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/declare-target-indirect-4.f90
@@ -0,0 +1,43 @@
+! { dg-additional-options "-fdump-tree-gimple" }
+
+! PR fortran/114283
+
+! { dg-final { scan-tree-dump "#pragma omp parallel shared\\(i\\) if\\(0\\) default\\(none\\) firstprivate\\(g\\)" "gimple" } }
+! { dg-final { scan-tree-dump "#pragma omp target num_teams\\(-2\\) thread_limit\\(0\\) firstprivate\\(h\\) map\\(from:j \\\[len: 4\\\]\\) defaultmap\\(none\\)" "gimple" } }
+
+
+module m
+  implicit none (type, external)
+  !$omp declare target indirect enter(f1, f2)
+contains
+  integer function f1 ()
+    f1 = 99
+  end
+  integer function f2 ()
+    f2 = 89
+  end
+end module m
+
+use m
+implicit none (type, external)
+call sub1(f1)
+call sub2(f2)
+contains
+  subroutine sub1(g)
+    procedure(integer) :: g
+    integer :: i
+    !$omp parallel default(none) if(.false.) shared(i)
+      i = g ()
+    !$omp end parallel
+    if (i /= 99) stop 1
+  end
+
+  subroutine sub2(h)
+    procedure(integer) :: h
+    integer :: j
+    !$omp target defaultmap(none) map(from:j)
+      j = h ()
+    !$omp end target
+    if (j /= 89) stop 1
+  end
+end