[PATCH 07/14] OpenMP: implicitly map base pointer for array-section pointer components

[Julian Brown <julian@codesourcery.com>]

Following from discussion in:

  https://gcc.gnu.org/pipermail/gcc-patches/2021-May/570075.html

and:

  https://gcc.gnu.org/pipermail/gcc-patches/2022-December/608100.html

and also upstream OpenMP issue 342, this patch changes mapping for array
sections of pointer components on compute regions like this:

  #pragma omp target map(s.ptr[0:10])
  {
    ...use of 's'...
  }

so the base pointer 's.ptr' is implicitly mapped, and thus pointer
attachment happens.  This is subtly different in the "enter data"
case, e.g:

  #pragma omp target enter data map(s.ptr[0:10])

if 's.ptr' (or the whole of 's') is not present on the target before
the directive is executed, the array section is copied to the target
but pointer attachment does *not* take place, since 's' (or 's.ptr')
is not mapped implicitly for "enter data".

To get a pointer attachment with "enter data", you can do, e.g:

  #pragma omp target enter data map(s.ptr, s.ptr[0:10])

  #pragma omp target
  {
    ...implicit use of 's'...
  }

That is, once the attachment has happened, implicit mapping of 's'
and uses of 's.ptr[...]' work correctly in the target region.

ChangeLog

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

gcc/
	* gimplify.cc (omp_accumulate_sibling_list): Don't require
	explicitly-mapped base pointer for compute regions.

gcc/testsuite/
	* c-c++-comon/gomp/target-implicit-map-2.c: Update expected scan output.

libgomp/
	* testsuite/libgomp.c-c++-common/target-implicit-map-2.c: Fix missing
	"free".
	* testsuite/libgomp.c-c++-common/target-implicit-map-3.c: New test.
	* testsuite/libgomp.c-c++-common/target-map-zlas-1.c: New test.
	* testsuite/libgomp.c/target-22.c: Remove explicit base pointer
	mappings.
---
 gcc/gimplify.cc                               |  9 ++--
 .../c-c++-common/gomp/target-implicit-map-2.c |  3 +-
 .../target-implicit-map-2.c                   |  2 +
 .../target-implicit-map-5.c                   | 50 +++++++++++++++++++
 .../libgomp.c-c++-common/target-map-zlas-1.c  | 36 +++++++++++++
 libgomp/testsuite/libgomp.c/target-22.c       |  3 +-
 6 files changed, 97 insertions(+), 6 deletions(-)
 create mode 100644 libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-5.c
 create mode 100644 libgomp/testsuite/libgomp.c-c++-common/target-map-zlas-1.c

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 9be5d9c5328..6a43c792450 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -10696,6 +10696,7 @@ omp_accumulate_sibling_list (enum omp_region_type region_type,
   poly_int64 cbitpos;
   tree ocd = OMP_CLAUSE_DECL (grp_end);
   bool openmp = !(region_type & ORT_ACC);
+  bool target = (region_type & ORT_TARGET) != 0;
   tree *continue_at = NULL;
 
   while (TREE_CODE (ocd) == ARRAY_REF)
@@ -10800,9 +10801,9 @@ omp_accumulate_sibling_list (enum omp_region_type region_type,
 	    }
 
 	  /* For OpenMP semantics, we don't want to implicitly allocate
-	     space for the pointer here.  A FRAGILE_P node is only being
-	     created so that omp-low.cc is able to rewrite the struct
-	     properly.
+	     space for the pointer here for non-compute regions (e.g. "enter
+	     data").  A FRAGILE_P node is only being created so that
+	     omp-low.cc is able to rewrite the struct properly.
 	     For references (to pointers), we want to actually allocate the
 	     space for the reference itself in the sorted list following the
 	     struct node.
@@ -10810,6 +10811,7 @@ omp_accumulate_sibling_list (enum omp_region_type region_type,
 	     mapping of the attachment point, but not otherwise.  */
 	  if (*fragile_p
 	      || (openmp
+		  && !target
 		  && attach_detach
 		  && TREE_CODE (TREE_TYPE (ocd)) == POINTER_TYPE
 		  && !OMP_CLAUSE_ATTACHMENT_MAPPING_ERASED (grp_end)))
@@ -11122,6 +11124,7 @@ omp_accumulate_sibling_list (enum omp_region_type region_type,
 
 	  if (*fragile_p
 	      || (openmp
+		  && !target
 		  && attach_detach
 		  && TREE_CODE (TREE_TYPE (ocd)) == POINTER_TYPE
 		  && !OMP_CLAUSE_ATTACHMENT_MAPPING_ERASED (grp_end)))
diff --git a/gcc/testsuite/c-c++-common/gomp/target-implicit-map-2.c b/gcc/testsuite/c-c++-common/gomp/target-implicit-map-2.c
index 5ba1d7efe08..222272df5b1 100644
--- a/gcc/testsuite/c-c++-common/gomp/target-implicit-map-2.c
+++ b/gcc/testsuite/c-c++-common/gomp/target-implicit-map-2.c
@@ -49,4 +49,5 @@ main (void)
 
 /* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(tofrom:a \[len: [0-9]+\]\[implicit\]\)} "gimple" } } */
 
-/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(struct:a \[len: 1\]\) map\(alloc:a\.ptr \[len: 0\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(attach:a\.ptr \[bias: 0\]\)} "gimple" } } */
+/* { dg-final { scan-tree-dump {#pragma omp target num_teams.* map\(struct:a \[len: 1\]\) map\(alloc:a\.ptr \[len: [0-9]+\]\) map\(tofrom:\*_[0-9]+ \[len: [0-9]+\]\) map\(attach:a\.ptr \[bias: 0\]\)} "gimple" } } */
+/* { dg-final { scan-tree-dump-not {map\(struct:a \[len: 1\]\) map\(alloc:a\.ptr \[len: 0\]\)} "gimple" } } */
diff --git a/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-2.c b/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-2.c
index 974a9786c3f..4c49cd091c3 100644
--- a/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-2.c
+++ b/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-2.c
@@ -42,5 +42,7 @@ main (void)
 
   #pragma omp target exit data map(from:a.ptr, a.ptr[:N])
 
+  free (a.ptr);
+
   return 0;
 }
diff --git a/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-5.c b/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-5.c
new file mode 100644
index 00000000000..81a7752685c
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/target-implicit-map-5.c
@@ -0,0 +1,50 @@
+#include <stdlib.h>
+
+#define N 10
+
+struct S
+{
+  int a, b;
+  int *ptr;
+  int c, d;
+};
+
+int
+main (void)
+{
+  struct S a;
+  a.ptr = (int *) malloc (sizeof (int) * N);
+
+  for (int i = 0; i < N; i++)
+    a.ptr[i] = 0;
+
+  #pragma omp target enter data map(to: a.ptr)
+  #pragma omp target enter data map(to: a.ptr[:N])
+
+  #pragma omp target
+  for (int i = 0; i < N; i++)
+    a.ptr[i] += 1;
+
+  #pragma omp target update from(a.ptr[:N])
+
+  for (int i = 0; i < N; i++)
+    if (a.ptr[i] != 1)
+      abort ();
+
+  #pragma omp target map(a.ptr[:N])
+  for (int i = 0; i < N; i++)
+    a.ptr[i] += 1;
+
+  #pragma omp target update from(a.ptr[:N])
+
+  for (int i = 0; i < N; i++)
+    if (a.ptr[i] != 2)
+      abort ();
+
+  #pragma omp target exit data map(release: a.ptr[:N])
+  #pragma omp target exit data map(release: a.ptr)
+
+  free (a.ptr);
+
+  return 0;
+}
diff --git a/libgomp/testsuite/libgomp.c-c++-common/target-map-zlas-1.c b/libgomp/testsuite/libgomp.c-c++-common/target-map-zlas-1.c
new file mode 100644
index 00000000000..1ec0c9a0d5f
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/target-map-zlas-1.c
@@ -0,0 +1,36 @@
+#include <stdlib.h>
+
+#define N 10
+
+struct S
+{
+  int a, b;
+  int *ptr;
+  int c, d;
+};
+
+int
+main (void)
+{
+  struct S a;
+  a.ptr = (int *) malloc (sizeof (int) * N);
+
+  for (int i = 0; i < N; i++)
+    a.ptr[i] = 0;
+
+  #pragma omp target enter data map(to: a.ptr[:N])
+
+  #pragma omp target map(a, a.ptr[:0])
+  for (int i = 0; i < N; i++)
+    a.ptr[i] += 1;
+
+  #pragma omp target exit data map(from: a.ptr[:N])
+
+  for (int i = 0; i < N; i++)
+    if (a.ptr[i] != 1)
+      abort ();
+
+  free (a.ptr);
+
+  return 0;
+}
diff --git a/libgomp/testsuite/libgomp.c/target-22.c b/libgomp/testsuite/libgomp.c/target-22.c
index 492744ad0ef..aad8a0a09df 100644
--- a/libgomp/testsuite/libgomp.c/target-22.c
+++ b/libgomp/testsuite/libgomp.c/target-22.c
@@ -21,8 +21,7 @@ main ()
   s.v.b = a + 16;
   s.w = c + 3;
   int err = 0;
-  #pragma omp target map (to: s.w, s.v.b, s.u, s.s) \
-		     map (to:s.v.b[0:z + 7], s.u[z + 1:z + 4]) \
+  #pragma omp target map (to:s.v.b[0:z + 7], s.u[z + 1:z + 4]) \
 		     map (tofrom:s.s[3:3]) \
 		     map (from: s.w[z:4], err) private (i)
   {
-- 
2.31.1