[PATCH] Fix oacc kernels default mapping for scalars

[Tom de Vries <Tom_deVries at mentor dot com>]

Hi,

The OpenACC 2.0a standard says this about the default mapping for 
variables used in a kernels region:
...
An array or variable of aggregate data type referenced in the kernels 
construct that does not appear in a data clause for the construct or
any enclosing data construct will be treated as if it appeared in a 
present_or_copy clause for the kernels construct.

A scalar variable referenced in the kernels construct that does not 
appear in a data clause for the construct or any enclosing data 
construct will be treated as if it appeared in a copy clause.
...

But atm, all variables including the scalar ones have 'present_or_copy' 
defaults.

This patch makes sure scalar variables get the 'copy' default.

Bootstrapped and reg-tested on x86_64. OK for stage3 trunk?

Thanks,
- Tom

Fix oacc kernels default mapping for scalars

2015-11-27  Tom de Vries  <tom@codesourcery.com>

	* gimplify.c (enum gimplify_omp_var_data): Add enum value
	GOVD_MAP_FORCE.
	(oacc_default_clause): Fix default for scalars in oacc kernels.
	(gimplify_adjust_omp_clauses_1): Handle GOVD_MAP_FORCE.

	* c-c++-common/goacc/kernels-default-2.c: New test.
	* c-c++-common/goacc/kernels-default.c: New test.

---
 gcc/gimplify.c                                       | 19 ++++++++++++++-----
 gcc/testsuite/c-c++-common/goacc/kernels-default-2.c | 17 +++++++++++++++++
 gcc/testsuite/c-c++-common/goacc/kernels-default.c   | 14 ++++++++++++++
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index fcac745..68d90bf 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -87,6 +87,9 @@ enum gimplify_omp_var_data
   /* Flag for GOVD_MAP, if it is always, to or always, tofrom mapping.  */
   GOVD_MAP_ALWAYS_TO = 65536,
 
+  /* Flag for GOVD_MAP, if it is a forced mapping.  */
+  GOVD_MAP_FORCE = 131072,
+
   GOVD_DATA_SHARE_CLASS = (GOVD_SHARED | GOVD_PRIVATE | GOVD_FIRSTPRIVATE
 			   | GOVD_LASTPRIVATE | GOVD_REDUCTION | GOVD_LINEAR
 			   | GOVD_LOCAL)
@@ -5976,8 +5979,12 @@ oacc_default_clause (struct gimplify_omp_ctx *ctx, tree decl, unsigned flags)
       gcc_unreachable ();
 
     case ORT_ACC_KERNELS:
-      /* Everything under kernels are default 'present_or_copy'.  */
+      /* Scalars are default 'copy' under kernels, non-scalars are default
+	 'present_or_copy'.  */
       flags |= GOVD_MAP;
+      if (!AGGREGATE_TYPE_P (TREE_TYPE (decl)))
+	flags |= GOVD_MAP_FORCE;
+
       rkind = "kernels";
       break;
 
@@ -7489,10 +7496,12 @@ gimplify_adjust_omp_clauses_1 (splay_tree_node n, void *data)
     }
   else if (code == OMP_CLAUSE_MAP)
     {
-      OMP_CLAUSE_SET_MAP_KIND (clause,
-			       flags & GOVD_MAP_TO_ONLY
-			       ? GOMP_MAP_TO
-			       : GOMP_MAP_TOFROM);
+      int kind = (flags & GOVD_MAP_TO_ONLY
+		  ? GOMP_MAP_TO
+		  : GOMP_MAP_TOFROM);
+      if (flags & GOVD_MAP_FORCE)
+	kind |= GOMP_MAP_FLAG_FORCE;
+      OMP_CLAUSE_SET_MAP_KIND (clause, kind);
       if (DECL_SIZE (decl)
 	  && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
 	{
diff --git a/gcc/testsuite/c-c++-common/goacc/kernels-default-2.c b/gcc/testsuite/c-c++-common/goacc/kernels-default-2.c
new file mode 100644
index 0000000..232b123
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/goacc/kernels-default-2.c
@@ -0,0 +1,17 @@
+/* { dg-additional-options "-O2" } */
+/* { dg-additional-options "-fdump-tree-gimple" } */
+
+#define N 2
+
+void
+foo (void)
+{
+  unsigned int a[N];
+
+#pragma acc kernels
+  {
+    a[0]++;
+  }
+}
+
+/* { dg-final { scan-tree-dump-times "map\\(tofrom" 1 "gimple" } } */
diff --git a/gcc/testsuite/c-c++-common/goacc/kernels-default.c b/gcc/testsuite/c-c++-common/goacc/kernels-default.c
new file mode 100644
index 0000000..58cd5e1
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/goacc/kernels-default.c
@@ -0,0 +1,14 @@
+/* { dg-additional-options "-O2" } */
+/* { dg-additional-options "-fdump-tree-gimple" } */
+
+void
+foo (void)
+{
+  unsigned int i;
+#pragma acc kernels
+  {
+    i++;
+  }
+}
+
+/* { dg-final { scan-tree-dump-times "map\\(force_tofrom" 1 "gimple" } } */