[gcc/devel/omp/gcc-12] OpenMP/Fortran: Use firstprivat not alloc for ptr attach for arrays

[gcc/devel/omp/gcc-12] OpenMP/Fortran: Use firstprivat not alloc for ptr attach for arrays

[Tobias Burnus]

https://gcc.gnu.org/g:438b4cec449984c98c576c2ea7270394a783c72d

commit 438b4cec449984c98c576c2ea7270394a783c72d
Author: Tobias Burnus <tobias@codesourcery.com>
Date:   Fri May 13 20:00:34 2022 +0200

    OpenMP/Fortran: Use firstprivat not alloc for ptr attach for arrays
    
    For a non-descriptor array,  map(A(n:m)) was mapped as
      map(tofrom:A[n-1] [len: ...]) map(alloc:A [pointer assign, bias: ...])
    with this patch, it is changed to
      map(tofrom:A[n-1] [len: ...]) map(firstprivate:A [pointer assign, bias: ...])
    
    The latter avoids an alloc - and also avoids the race condition with
    nowait in the enclosed testcase. (Note: predantically, the testcase is
    invalid since OpenMP 5.1, violating the map clause restriction at [354:10-13].
    
    gcc/fortran/ChangeLog:
    
            * trans-openmp.cc (gfc_trans_omp_clauses): When mapping nondescriptor
            array sections, use GOMP_MAP_FIRSTPRIVATE_POINTER instead of
            GOMP_MAP_POINTER for the pointer attachment.
    
    libgomp/ChangeLog:
    
            * testsuite/libgomp.fortran/target-nowait-array-section.f90: New test.
    
    (cherry picked from commit a46d6268371c446566f656858aada8775a0c988e)

Diff:
---
 gcc/fortran/ChangeLog.omp                          |  9 ++++
 gcc/fortran/trans-openmp.cc                        | 12 +++--
 libgomp/ChangeLog.omp                              |  7 +++
 .../target-nowait-array-section.f90                | 56 ++++++++++++++++++++++
 4 files changed, 81 insertions(+), 3 deletions(-)

diff --git a/gcc/fortran/ChangeLog.omp b/gcc/fortran/ChangeLog.omp
index 63eba462c43..21592517cb0 100644
--- a/gcc/fortran/ChangeLog.omp
+++ b/gcc/fortran/ChangeLog.omp
@@ -1,3 +1,12 @@
+2022-07-04  Tobias Burnus  <tobias@codesourcery.com>
+
+	Backport from mainline:
+	2022-05-13  Tobias Burnus  <tobias@codesourcery.com>
+
+	* trans-openmp.cc (gfc_trans_omp_clauses): When mapping nondescriptor
+	array sections, use GOMP_MAP_FIRSTPRIVATE_POINTER instead of
+	GOMP_MAP_POINTER for the pointer attachment.
+
 2022-06-30  Kwok Cheung Yeung  <kcy@codesourcery.com>
 
 	* openmp.cc (gfc_resolve_omp_allocate): Initialize tail to NULL.
diff --git a/gcc/fortran/trans-openmp.cc b/gcc/fortran/trans-openmp.cc
index 3e756a02d01..b047b869d43 100644
--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -4774,9 +4774,15 @@ gfc_trans_omp_clauses (stmtblock_t *block, gfc_omp_clauses *clauses,
 		  /* An array element or array section which is not part of a
 		     derived type, etc.  */
 		  bool element = n->expr->ref->u.ar.type == AR_ELEMENT;
-		  gfc_trans_omp_array_section (block, n, decl, element,
-					       GOMP_MAP_POINTER, node, node2,
-					       node3, node4);
+		  tree type = TREE_TYPE (decl);
+		  gomp_map_kind k = GOMP_MAP_POINTER;
+		  if (!openacc
+		      && !GFC_DESCRIPTOR_TYPE_P (type)
+		      && !(POINTER_TYPE_P (type)
+			   && GFC_DESCRIPTOR_TYPE_P (TREE_TYPE (type))))
+		    k = GOMP_MAP_FIRSTPRIVATE_POINTER;
+		  gfc_trans_omp_array_section (block, n, decl, element, k,
+					       node, node2, node3, node4);
 		}
 	      else if (n->expr
 		       && n->expr->expr_type == EXPR_VARIABLE
diff --git a/libgomp/ChangeLog.omp b/libgomp/ChangeLog.omp
index 6d3c4772e86..134387d47c4 100644
--- a/libgomp/ChangeLog.omp
+++ b/libgomp/ChangeLog.omp
@@ -1,3 +1,10 @@
+2022-07-04  Tobias Burnus  <tobias@codesourcery.com>
+
+	Backport from mainline:
+	2022-05-13  Tobias Burnus  <tobias@codesourcery.com>
+
+	* testsuite/libgomp.fortran/target-nowait-array-section.f90: New test.
+
 2022-06-20  Andrew Stubbs  <ams@codesourcery.com>
 
 	* plugin/plugin-gcn.c (struct usm_splay_tree_key_s): New.
diff --git a/libgomp/testsuite/libgomp.fortran/target-nowait-array-section.f90 b/libgomp/testsuite/libgomp.fortran/target-nowait-array-section.f90
new file mode 100644
index 00000000000..7560cff746b
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/target-nowait-array-section.f90
@@ -0,0 +1,56 @@
+! Runs the the target region asynchrolously and checks for it
+!
+! Note that  map(alloc: work(:, i)) + nowait  should be save
+! given that a nondescriptor array is used. However, it still
+! violates a map clause restriction, added in OpenMP 5.1 [354:10-13].
+
+PROGRAM test_target_teams_distribute_nowait
+  USE ISO_Fortran_env, only: INT64
+  implicit none
+    INTEGER, parameter :: N = 1024, N_TASKS = 16
+    INTEGER :: i, j, k, my_ticket
+    INTEGER :: order(n_tasks)
+    INTEGER(INT64) :: work(n, n_tasks)
+    INTEGER :: ticket
+    logical :: async
+
+    ticket = 0
+
+    !$omp target enter data map(to: ticket, order)
+
+    !$omp parallel do num_threads(n_tasks)
+    DO i = 1, n_tasks
+       !$omp target map(alloc: work(:, i), ticket) private(my_ticket) nowait
+       !!$omp target teams distribute map(alloc: work(:, i), ticket) private(my_ticket) nowait
+       DO j = 1, n
+          ! Waste cyles
+!          work(j, i) = 0
+!          DO k = 1, n*(n_tasks - i)
+!             work(j, i) = work(j, i) + i*j*k
+!          END DO
+          my_ticket = 0
+          !$omp atomic capture
+          ticket = ticket + 1
+          my_ticket = ticket
+          !$omp end atomic
+          !$omp atomic write
+          order(i) = my_ticket
+       END DO
+       !$omp end target !teams distribute
+    END DO
+    !$omp end parallel do
+
+    !$omp target exit data map(from:ticket, order)
+
+    IF (ticket .ne. n_tasks*n) stop 1
+    if (maxval(order) /= n_tasks*n) stop 2
+    ! order(i) == n*i if synchronous and between n and n*n_tasks if run concurrently
+    do i = 1, n_tasks
+      if (order(i) < n .or. order(i) > n*n_tasks) stop 3
+    end do
+    async = .false.
+    do i = 1, n_tasks
+      if (order(i) /= n*i) async = .true.
+    end do
+    if (.not. async) stop 4 ! Did not run asynchronously
+end