openmp: Relax handling of implicit map vs. existing device mappings

This patch implements relaxing the requirements when a map with the implicit
attribute encounters an overlapping existing map. As the OpenMP 5.0 spec
describes on page 320, lines 18-27 (and 5.1 spec, page 352, lines 13-22):

"If a single contiguous part of the original storage of a list item with an
 implicit data-mapping attribute has corresponding storage in the device data
 environment prior to a task encountering the construct that is associated with
 the map clause, only that part of the original storage will have corresponding
 storage in the device data environment as a result of the map clause."

2021-11-12  Chung-Lin Tang  <cltang@codesourcery.com>

include/ChangeLog:

	* gomp-constants.h (GOMP_MAP_FLAG_SPECIAL_3): Define special bit macro.
	(GOMP_MAP_IMPLICIT): New special map kind bits value.
	(GOMP_MAP_FLAG_SPECIAL_BITS): Define helper mask for whole set of
	special map kind bits.
	(GOMP_MAP_IMPLICIT_P): New predicate macro for implicit map kinds.

gcc/ChangeLog:

	* tree.h (OMP_CLAUSE_MAP_RUNTIME_IMPLICIT_P): New access macro for
	'implicit' bit, using 'base.deprecated_flag' field of tree_node.
	* tree-pretty-print.c (dump_omp_clause): Add support for printing
	implicit attribute in tree dumping.
	* gimplify.c (gimplify_adjust_omp_clauses_1):
	Set OMP_CLAUSE_MAP_RUNTIME_IMPLICIT_P to 1 if map clause is implicitly
	created.
	(gimplify_adjust_omp_clauses): Adjust place of adding implicitly created
	clauses, from simple append, to starting of list, after non-map clauses.
	* omp-low.c (lower_omp_target): Add GOMP_MAP_IMPLICIT bits into kind
	values passed to libgomp for implicit maps.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/target-implicit-map-1.c: New test.
	* c-c++-common/goacc/combined-reduction.c: Adjust scan test pattern.
	* c-c++-common/goacc/firstprivate-mappings-1.c: Likewise.
	* c-c++-common/goacc/mdc-1.c: Likewise.
	* g++.dg/goacc/firstprivate-mappings-1.C: Likewise.

libgomp/ChangeLog:

	* target.c (gomp_map_vars_existing): Add 'bool implicit' parameter, add
	implicit map handling to allow a "superset" existing map as valid case.
	(get_kind): Adjust to filter out GOMP_MAP_IMPLICIT bits in return value.
	(get_implicit): New function to extract implicit status.
	(gomp_map_fields_existing): Adjust arguments in calls to
	gomp_map_vars_existing, and add uses of get_implicit.
	(gomp_map_vars_internal): Likewise.
	* testsuite/libgomp.c-c++-common/target-implicit-map-1.c: New test.

1 files changed, 12 insertions, 2 deletions

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index e5877c83..4e022d8 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -10889,6 +10889,10 @@ gimplify_adjust_omp_clauses_1 (splay_tree_node n, void *data)
 	  gcc_unreachable ();
 	}
       OMP_CLAUSE_SET_MAP_KIND (clause, kind);
+      /* Setting of the implicit flag for the runtime is currently disabled for
+	 OpenACC.  */
+      if ((gimplify_omp_ctxp->region_type & ORT_ACC) == 0)
+	OMP_CLAUSE_MAP_RUNTIME_IMPLICIT_P (clause) = 1;
       if (DECL_SIZE (decl)
 	  && TREE_CODE (DECL_SIZE (decl)) != INTEGER_CST)
 	{
@@ -11504,9 +11508,15 @@ gimplify_adjust_omp_clauses (gimple_seq *pre_p, gimple_seq body, tree *list_p,
 	list_p = &OMP_CLAUSE_CHAIN (c);
     }
 
-  /* Add in any implicit data sharing.  */
+  /* Add in any implicit data sharing.  Implicit clauses are added at the start
+     of the clause list, but after any non-map clauses.  */
   struct gimplify_adjust_omp_clauses_data data;
-  data.list_p = list_p;
+  tree *implicit_add_list_p = orig_list_p;
+  while (*implicit_add_list_p
+	 && OMP_CLAUSE_CODE (*implicit_add_list_p) != OMP_CLAUSE_MAP)
+    implicit_add_list_p = &OMP_CLAUSE_CHAIN (*implicit_add_list_p);
+
+  data.list_p = implicit_add_list_p;
   data.pre_p = pre_p;
   splay_tree_foreach (ctx->variables, gimplify_adjust_omp_clauses_1, &data);