[PATCH 1/2] OpenMP/Fortran: Combined directives with map/firstprivate of same symbol

[Julian Brown <julian@codesourcery.com>]

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On Wed, 26 Oct 2022 12:39:39 +0200
Tobias Burnus <tobias@codesourcery.com> wrote:

> The ICE seems to be because gcc/fortran/trans-openmp.cc's
> gfc_split_omp_clauses mishandles this as the dump shows the following:
> 
>    #pragma omp target firstprivate(a) map(tofrom:a)
>          #pragma omp parallel firstprivate(a)
> 
>   * * *
> 
> In contrast, for the C testcase:
> 
> void foo(int x) {
> #pragma omp target parallel for simd map(x) firstprivate(x)
> for (int k = 0; k < 1; ++k)
>    x = 1;
> }
> 
> the dump is as follows, which seems to be sensible:
> 
>    #pragma omp target map(tofrom:x)
>          #pragma omp parallel firstprivate(x)
>                #pragma omp for nowait
>                      #pragma omp simd

First, here's a patch to address this bit...

This patch fixes a case where a combined directive (e.g. "!$omp target
parallel ...") contains both a map and a firstprivate clause for the
same variable.  When the combined directive is split into two nested
directives, the outer "target" gets the "map" clause, and the inner
"parallel" gets the "firstprivate" clause, like so:
  
  !$omp target parallel map(x) firstprivate(x)
  
  -->
  
  !$omp target map(x)
    !$omp parallel firstprivate(x)
      ...

When there is no map of the same variable, the firstprivate is distributed
to both directives, e.g. for 'y' in:
  
  !$omp target parallel map(x) firstprivate(y)
  
  -->
  
  !$omp target map(x) firstprivate(y)
    !$omp parallel firstprivate(y)
      ...

This is not a recent regression, but appears to fix a long-standing ICE.
(The included testcase is based on one by Tobias.)

Tested with offloading to NVPTX, alongside previously-posted patches
(in review or approved but waiting for other patches), i.e.:
  
  OpenMP/OpenACC: Rework clause expansion and nested struct handling
  OpenMP/OpenACC: Refine condition for when map clause expansion happens
  OpenMP: Pointers and member mappings

and the patch following.  OK?

2022-12-06  Julian Brown  <julian@codesourcery.com>

gcc/fortran/
        * trans-openmp.cc (gfc_add_firstprivate_if_unmapped): New function.
        (gfc_split_omp_clauses): Call above.

libgomp/
        * testsuite/libgomp.fortran/combined-directive-splitting-1.f90: New
        test.

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From c66db363066913ae4939f2aa706427338b109d71 Mon Sep 17 00:00:00 2001
Message-Id: <c66db363066913ae4939f2aa706427338b109d71.1670438768.git.julian@codesourcery.com>
From: Julian Brown <julian@codesourcery.com>
Date: Tue, 6 Dec 2022 12:18:33 +0000
Subject: [PATCH 1/2] OpenMP/Fortran: Combined directives with map/firstprivate
 of same symbol

This patch fixes a case where a combined directive (e.g. "!$omp target
parallel ...") contains both a map and a firstprivate clause for the
same variable.  When the combined directive is split into two nested
directives, the outer "target" gets the "map" clause, and the inner
"parallel" gets the "firstprivate" clause, like so:

  !$omp target parallel map(x) firstprivate(x)

  -->

  !$omp target map(x)
    !$omp parallel firstprivate(x)
      ...

When there is no map of the same variable, the firstprivate is distributed
to both directives, e.g. for 'y' in:

  !$omp target parallel map(x) firstprivate(y)

  -->

  !$omp target map(x) firstprivate(y)
    !$omp parallel firstprivate(y)
      ...

This is not a recent regression, but appears to fix a long-standing ICE.
(The included testcase is based on one by Tobias.)

Tested with offloading to NVPTX, alongside previously-posted patches
(in review or approved but waiting for other patches), i.e.:

  OpenMP/OpenACC: Rework clause expansion and nested struct handling
  OpenMP/OpenACC: Refine condition for when map clause expansion happens
  OpenMP: Pointers and member mappings

and the patch following.  OK?

2022-12-06  Julian Brown  <julian@codesourcery.com>

gcc/fortran/
	* trans-openmp.cc (gfc_add_firstprivate_if_unmapped): New function.
	(gfc_split_omp_clauses): Call above.

libgomp/
	* testsuite/libgomp.fortran/combined-directive-splitting-1.f90: New
	test.
---
 gcc/fortran/trans-openmp.cc                   | 37 ++++++++++++++++-
 .../combined-directive-splitting-1.f90        | 41 +++++++++++++++++++
 2 files changed, 76 insertions(+), 2 deletions(-)
 create mode 100644 libgomp/testsuite/libgomp.fortran/combined-directive-splitting-1.f90

diff --git a/gcc/fortran/trans-openmp.cc b/gcc/fortran/trans-openmp.cc
index e39f7b1cb273..c61cd1bf55de 100644
--- a/gcc/fortran/trans-openmp.cc
+++ b/gcc/fortran/trans-openmp.cc
@@ -6121,6 +6121,39 @@ gfc_add_clause_implicitly (gfc_omp_clauses *clauses_out,
     }
 }
 
+/* Kind of opposite to above, add firstprivate to CLAUSES_OUT if it is mapped
+   in CLAUSES_IN's FIRSTPRIVATE list but not its MAP list.  */
+
+static void
+gfc_add_firstprivate_if_unmapped (gfc_omp_clauses *clauses_out,
+				  gfc_omp_clauses *clauses_in)
+{
+  gfc_omp_namelist *n = clauses_in->lists[OMP_LIST_FIRSTPRIVATE];
+  gfc_omp_namelist **tail = NULL;
+
+  for (; n != NULL; n = n->next)
+    {
+      gfc_omp_namelist *n2 = clauses_out->lists[OMP_LIST_MAP];
+      for (; n2 != NULL; n2 = n2->next)
+	if (n->sym == n2->sym)
+	  break;
+      if (n2 == NULL)
+	{
+	  gfc_omp_namelist *dup = gfc_get_omp_namelist ();
+	  *dup = *n;
+	  dup->next = NULL;
+	  if (!tail)
+	    {
+	      tail = &clauses_out->lists[OMP_LIST_FIRSTPRIVATE];
+	      while (*tail && (*tail)->next)
+		tail = &(*tail)->next;
+	    }
+	  *tail = dup;
+	  tail = &(*tail)->next;
+	}
+    }
+}
+
 static void
 gfc_free_split_omp_clauses (gfc_code *code, gfc_omp_clauses *clausesa)
 {
@@ -6504,8 +6537,8 @@ gfc_split_omp_clauses (gfc_code *code,
 	 simd and masked/master.  Put it on the outermost of those and duplicate
 	 on parallel and teams.  */
       if (mask & GFC_OMP_MASK_TARGET)
-	clausesa[GFC_OMP_SPLIT_TARGET].lists[OMP_LIST_FIRSTPRIVATE]
-	  = code->ext.omp_clauses->lists[OMP_LIST_FIRSTPRIVATE];
+	gfc_add_firstprivate_if_unmapped (&clausesa[GFC_OMP_SPLIT_TARGET],
+					  code->ext.omp_clauses);
       if (mask & GFC_OMP_MASK_TEAMS)
 	clausesa[GFC_OMP_SPLIT_TEAMS].lists[OMP_LIST_FIRSTPRIVATE]
 	  = code->ext.omp_clauses->lists[OMP_LIST_FIRSTPRIVATE];
diff --git a/libgomp/testsuite/libgomp.fortran/combined-directive-splitting-1.f90 b/libgomp/testsuite/libgomp.fortran/combined-directive-splitting-1.f90
new file mode 100644
index 000000000000..e662a2bd3b20
--- /dev/null
+++ b/libgomp/testsuite/libgomp.fortran/combined-directive-splitting-1.f90
@@ -0,0 +1,41 @@
+module m
+  integer :: a = 1
+  !$omp declare target enter(a)
+end module m
+
+module m2
+contains
+subroutine bar()
+  use m
+  implicit none
+  !$omp declare target
+  a = a + 5
+end subroutine bar
+end module m2
+
+program p
+  use m
+  use m2
+  implicit none
+  integer :: b, i
+
+  !$omp target parallel do map(always, tofrom: a) firstprivate(a)
+    do i = 1, 1
+      a = 7
+      call bar()
+      if (a /= 7) error stop 1
+      a = a + 8
+    end do
+  if (a /= 6) error stop 2
+
+  b = 3
+  !$omp target parallel do map(always, tofrom: a) firstprivate(b)
+    do i = 1, 1
+      a = 3
+      call bar ()
+      if (a /= 8) error stop 3
+      a = a + b
+    end do
+  if (a /= 11) error stop 4
+end program p
+
-- 
2.29.2