Re: [PATCH] [og10] libgomp, Fortran: Fix OpenACC "gang reduction on an orphan loop" error message

[Frederik Harwath <frederik@codesourcery.com>]

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Thomas Schwinge <thomas@codesourcery.com> writes:

Hi Thomas,

>> Can I include the patch in OG10?
>
> Unless Julian/Kwok speak up soon: OK, thanks.

This has been delayed a bit by my vacation, but I have now committed
the patch.

> May want to remove "libgomp" from the first line of the commit log --
> this commit doesn't relate to libgomp specifically.
>
> (Ideally, we'd also test 'serial' construct in addition to 'kernels',
> 'parallel', but we can add that later.  I anyway have a WIP patch
> waiting, adding more 'serial' construct testing, for a different reason,
> so I'll include it there.)

I forgot to remove "libgomp" from the commit message, sorry, but
I have included the test cases for the "serial construct".

Best regards,
Frederik

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From 7c10ae450b95495dda362cb66770bb78b546592e Mon Sep 17 00:00:00 2001
From: Frederik Harwath <frederik@codesourcery.com>
Date: Mon, 20 Jul 2020 11:24:21 +0200
Subject: [PATCH] libgomp, Fortran: Fix OpenACC "gang reduction on an orphan
 loop" error message

According to the OpenACC standard version 2.5 and later, reductions on
orphaned gang loops are explicitly disallowed (cf.  section "Changes
from Version 2.0 to 2.5").  A loop is "orphaned" if it is not
lexically contained in a compute construct (cf. section "Loop
construct" of the OpenACC standard), i.e. in either a "parallel", a
"serial", or a "kernels" construct.

This commit fixes the check for reductions on orphaned gang loops in
the Fortran frontend which (in contrast to the C, C++ frontends)
erroneously rejects reductions on gang loops that are contained in
"kernels" constructs.

2020-07-20  Frederik Harwath  <frederik@codesourcery.com>

gcc/fortran/

	* openmp.c (oacc_is_parallel_or_serial): Removed function.
	(oacc_is_kernels): New function.
	(oacc_is_compute_construct): New function.
	(resolve_oacc_loop_blocks): Use "oacc_is_compute_construct"
	instead of "oacc_is_parallel_or_serial" for checking that a
	loop is not orphaned.

gcc/testsuite/

	* gfortran.dg/goacc/orphan-reductions-2.f90: New test
	verifying that the "gang reduction on an orphan loop" error message
	is not emitted for non-orphaned loops.

	* c-c++-common/goacc/orphan-reductions-2.c: Likewise for C and C++.
---
 gcc/fortran/ChangeLog                         |   9 ++
 gcc/fortran/openmp.c                          |  13 ++-
 gcc/testsuite/ChangeLog                       |   7 ++
 .../c-c++-common/goacc/orphan-reductions-2.c  | 103 ++++++++++++++++++
 .../gfortran.dg/goacc/orphan-reductions-2.f90 |  87 +++++++++++++++
 5 files changed, 216 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/goacc/orphan-reductions-2.c
 create mode 100644 gcc/testsuite/gfortran.dg/goacc/orphan-reductions-2.f90

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index e86279cb647..5a1f81c286e 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,12 @@
+2020-07-20  Frederik Harwath  <frederik@codesourcery.com>
+
+	* openmp.c (oacc_is_parallel_or_serial): Removed function.
+	(oacc_is_kernels): New function.
+	(oacc_is_compute_construct): New function.
+	(resolve_oacc_loop_blocks): Use "oacc_is_compute_construct"
+	instead of "oacc_is_parallel_or_serial" for checking that a
+	loop is not orphaned.
+
 2020-07-08  Harald Anlauf  <anlauf@gmx.de>
 
 	Backported from master:
diff --git a/gcc/fortran/openmp.c b/gcc/fortran/openmp.c
index ab68e9f2173..706933c869a 100644
--- a/gcc/fortran/openmp.c
+++ b/gcc/fortran/openmp.c
@@ -5927,9 +5927,16 @@ oacc_is_serial (gfc_code *code)
 }
 
 static bool
-oacc_is_parallel_or_serial (gfc_code *code)
+oacc_is_kernels (gfc_code *code)
 {
-  return oacc_is_parallel (code) || oacc_is_serial (code);
+  return code->op == EXEC_OACC_KERNELS || code->op == EXEC_OACC_KERNELS_LOOP;
+}
+
+static bool
+oacc_is_compute_construct (gfc_code *code)
+{
+  return oacc_is_parallel (code) || oacc_is_serial (code)
+    || oacc_is_kernels (code);
 }
 
 static gfc_statement
@@ -6223,7 +6230,7 @@ resolve_oacc_loop_blocks (gfc_code *code)
       for (c = omp_current_ctx; c; c = c->previous)
 	if (!oacc_is_loop (c->code))
 	  break;
-      if (c == NULL || !oacc_is_parallel_or_serial (c->code))
+      if (c == NULL || !oacc_is_compute_construct (c->code))
 	gfc_error ("gang reduction on an orphan loop at %L", &code->loc);
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 59e6c93b07a..fa1937a4ea2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2020-07-20  Frederik Harwath  <frederik@codesourcery.com>
+
+	* gfortran.dg/goacc/orphan-reductions-2.f90: New test
+	verifying that the "gang reduction on an orphan loop" error message
+	is not emitted for non-orphaned loops.
+	* c-c++-common/goacc/orphan-reductions-2.c: Likewise for C and C++.
+
 2020-07-12  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from master:
diff --git a/gcc/testsuite/c-c++-common/goacc/orphan-reductions-2.c b/gcc/testsuite/c-c++-common/goacc/orphan-reductions-2.c
new file mode 100644
index 00000000000..d30321710dd
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/goacc/orphan-reductions-2.c
@@ -0,0 +1,103 @@
+/* Verify that the error message for gang reduction on orphaned OpenACC loops
+   is not reported for non-orphaned loops. */
+
+#include <assert.h>
+
+int
+kernels (int n)
+{
+  int i, s1 = 0, s2 = 0;
+#pragma acc kernels
+  {
+#pragma acc loop gang reduction(+:s1) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s1 = s1 + 2;
+
+#pragma acc loop gang reduction(+:s2) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s2 = s2 + 2;
+  }
+  return s1 + s2;
+}
+
+int
+parallel (int n)
+{
+  int i, s1 = 0, s2 = 0;
+#pragma acc parallel
+  {
+#pragma acc loop gang reduction(+:s1) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s1 = s1 + 2;
+
+#pragma acc loop gang reduction(+:s2) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s2 = s2 + 2;
+  }
+  return s1 + s2;
+}
+
+int
+serial (int n)
+{
+  int i, s1 = 0, s2 = 0;
+#pragma acc serial /* { dg-warning "region contains gang partitioned code but is not gang partitioned" } */
+  {
+#pragma acc loop gang reduction(+:s1) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s1 = s1 + 2;
+
+#pragma acc loop gang reduction(+:s2) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s2 = s2 + 2;
+  }
+  return s1 + s2;
+}
+
+int
+serial_combined (int n)
+{
+  int i, s1 = 0, s2 = 0;
+#pragma acc serial loop gang reduction(+:s1) /* { dg-bogus "gang reduction on an orphan loop" } */
+  /* { dg-warning "region contains gang partitioned code but is not gang partitioned" "" { target *-*-* } .-1 } */
+  for (i = 0; i < n; i++)
+    s1 = s1 + 2;
+
+#pragma acc serial loop gang reduction(+:s2) /* { dg-bogus "gang reduction on an orphan loop" } */
+  /* { dg-warning "region contains gang partitioned code but is not gang partitioned" "" { target *-*-* } .-1 } */
+  for (i = 0; i < n; i++)
+    s2 = s2 + 2;
+
+  return s1 + s2;
+}
+
+int
+parallel_combined (int n)
+{
+  int i, s1 = 0, s2 = 0;
+#pragma acc parallel loop gang reduction(+:s1) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s1 = s1 + 2;
+
+#pragma acc parallel loop gang reduction(+:s2) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s2 = s2 + 2;
+
+  return s1 + s2;
+}
+
+int
+kernels_combined (int n)
+{
+  int i, s1 = 0, s2 = 0;
+#pragma acc kernels loop gang reduction(+:s1) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s1 = s1 + 2;
+
+#pragma acc kernels loop gang reduction(+:s2) /* { dg-bogus "gang reduction on an orphan loop" } */
+  for (i = 0; i < n; i++)
+    s2 = s2 + 2;
+
+  return s1 + s2;
+}
+
diff --git a/gcc/testsuite/gfortran.dg/goacc/orphan-reductions-2.f90 b/gcc/testsuite/gfortran.dg/goacc/orphan-reductions-2.f90
new file mode 100644
index 00000000000..6ad38039696
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/goacc/orphan-reductions-2.f90
@@ -0,0 +1,87 @@
+! Verify that the error message for gang reductions on orphaned OpenACC loops
+! is not reported for non-orphaned loops.
+
+subroutine kernels
+  implicit none
+
+  integer, parameter :: n = 100
+  integer :: i, sum
+  sum = 0
+
+  !$acc kernels
+  !$acc loop gang reduction(+:sum) ! { dg-bogus "gang reduction on an orphan loop" }
+  do i = 1, n
+     sum = sum + 1
+  end do
+  !$acc end kernels
+end subroutine kernels
+
+subroutine parallel
+  implicit none
+
+  integer, parameter :: n = 100
+  integer :: i, sum
+  sum = 0
+
+  !$acc parallel
+  !$acc loop gang reduction(+:sum) ! { dg-bogus "gang reduction on an orphan loop" }
+  do i = 1, n
+     sum = sum + 1
+  end do
+  !$acc end parallel
+end subroutine parallel
+
+subroutine serial
+  implicit none
+
+  integer, parameter :: n = 100
+  integer :: i, sum
+  sum = 0
+
+  !$acc serial ! { dg-warning "region contains gang partitioned code but is not gang partitioned" }
+  !$acc loop gang reduction(+:sum) ! { dg-bogus "gang reduction on an orphan loop" }
+  do i = 1, n
+     sum = sum + 1
+  end do
+  !$acc end serial
+end subroutine serial
+
+subroutine kernels_combined
+  implicit none
+
+  integer, parameter :: n = 100
+  integer :: i, sum
+  sum = 0
+
+  !$acc kernels loop gang reduction(+:sum) ! { dg-bogus "gang reduction on an orphan loop" }
+  do i = 1, n
+     sum = sum + 1
+  end do
+end subroutine kernels_combined
+
+subroutine parallel_combined
+  implicit none
+
+  integer, parameter :: n = 100
+  integer :: i, sum
+  sum = 0
+
+  !$acc parallel loop gang reduction(+:sum) ! { dg-bogus "gang reduction on an orphan loop" }
+  do i = 1, n
+     sum = sum + 1
+  end do
+end subroutine parallel_combined
+
+subroutine serial_combined
+  implicit none
+
+  integer, parameter :: n = 100
+  integer :: i, sum
+  sum = 0
+
+  !$acc serial loop gang reduction(+:sum) ! { dg-bogus "gang reduction on an orphan loop" }
+  ! { dg-warning "region contains gang partitioned code but is not gang partitioned" "" { target *-*-* } .-1 }
+  do i = 1, n
+     sum = sum + 1
+  end do
+end subroutine serial_combined
-- 
2.17.1