OpenMP 5.0: Remove array section base-pointer mapping semantics and other front-end adjustments

This patch implements three pieces of functionality:

(1) Adjust array section mapping to have standards conforming behavior,
mapping array sections should *NOT* also map the base-pointer:

struct S { int *ptr; ... };
struct S s;

Instead of generating this during gimplify:
                              map(to:*_1 [len: 400]) map(attach:s.ptr [bias: 0])

Now, adjust to:

(i.e. do not map the base-pointer together. The attach operation is still
generated, and if s.ptr is already mapped prior, attachment will happen)

The correct way of achieving the base-pointer-also-mapped behavior would be to
use:

(A small Fortran front-end patch to trans-openmp.c:gfc_trans_omp_array_section
 is also included, which removes generation of a GOMP_MAP_ALWAYS_POINTER for
 array types, which appears incorrect and causes a regression in
 libgomp.fortranlibgomp.fortran/struct-elem-map-1.f90)

(2) Related to the first item above, are fixes in libgomp/target.c to not
overwrite attached pointers when handling device<->host copies, mainly for the
"always" case.

(3) The third is a set of changes to the C/C++ front-ends to extend the allowed
component access syntax in map clauses. These changes are enabled for both
OpenACC and OpenMP.

gcc/c/ChangeLog:

	* c-parser.c (struct omp_dim): New struct type for use inside
	c_parser_omp_variable_list.
	(c_parser_omp_variable_list): Allow multiple levels of array and
	component accesses in array section base-pointer expression.
	(c_parser_omp_clause_to): Set 'allow_deref' to true in call to
	c_parser_omp_var_list_parens.
	(c_parser_omp_clause_from): Likewise.
	* c-typeck.c (handle_omp_array_sections_1): Extend allowed range
	of base-pointer expressions involving INDIRECT/MEM/ARRAY_REF and
	POINTER_PLUS_EXPR.
	(c_finish_omp_clauses): Extend allowed ranged of expressions
	involving INDIRECT/MEM/ARRAY_REF and POINTER_PLUS_EXPR.

gcc/cp/ChangeLog:

	* parser.c (struct omp_dim): New struct type for use inside
	cp_parser_omp_var_list_no_open.
	(cp_parser_omp_var_list_no_open): Allow multiple levels of array and
	component accesses in array section base-pointer expression.
	(cp_parser_omp_all_clauses): Set 'allow_deref' to true in call to
	cp_parser_omp_var_list for to/from clauses.
	* semantics.c (handle_omp_array_sections_1): Extend allowed range
	of base-pointer expressions involving INDIRECT/MEM/ARRAY_REF and
	POINTER_PLUS_EXPR.
	(handle_omp_array_sections): Adjust pointer map generation of
	references.
	(finish_omp_clauses): Extend allowed ranged of expressions
	involving INDIRECT/MEM/ARRAY_REF and POINTER_PLUS_EXPR.

gcc/fortran/ChangeLog:

	* trans-openmp.c (gfc_trans_omp_array_section): Do not generate
	GOMP_MAP_ALWAYS_POINTER map for main array maps of ARRAY_TYPE type.

gcc/ChangeLog:

	* gimplify.c (extract_base_bit_offset): Add 'tree *offsetp' parameter,
	accomodate case where 'offset' return of get_inner_reference is
	non-NULL.
	(is_or_contains_p): Further robustify conditions.
	(omp_target_reorder_clauses): In alloc/to/from sorting phase, also
	move following GOMP_MAP_ALWAYS_POINTER maps along.  Add new sorting
	phase where we make sure pointers with an attach/detach map are ordered
	correctly.
	(gimplify_scan_omp_clauses): Add modifications to avoid creating
	GOMP_MAP_STRUCT and associated alloc map for attach/detach maps.

gcc/testsuite/ChangeLog:

	* c-c++-common/goacc/deep-copy-arrayofstruct.c: Adjust testcase.
	* c-c++-common/gomp/target-enter-data-1.c: New testcase.
	* c-c++-common/gomp/target-implicit-map-2.c: New testcase.

libgomp/ChangeLog:

	* target.c (gomp_map_vars_existing): Make sure attached pointer is
	not overwritten during cross-host/device copying.
	(gomp_update): Likewise.
	(gomp_exit_data): Likewise.
	* testsuite/libgomp.c++/target-11.C: Adjust testcase.
	* testsuite/libgomp.c++/target-12.C: Likewise.
	* testsuite/libgomp.c++/target-15.C: Likewise.
	* testsuite/libgomp.c++/target-16.C: Likewise.
	* testsuite/libgomp.c++/target-17.C: Likewise.
	* testsuite/libgomp.c++/target-21.C: Likewise.
	* testsuite/libgomp.c++/target-23.C: Likewise.
	* testsuite/libgomp.c/target-23.c: Likewise.
	* testsuite/libgomp.c/target-29.c: Likewise.
	* testsuite/libgomp.c-c++-common/target-implicit-map-2.c: New testcase.

1 files changed, 50 insertions, 4 deletions

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index ed36709..6f273bf 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -36406,11 +36406,22 @@ check_no_duplicate_clause (tree clauses, enum omp_clause_code code,
    The optional ALLOW_DEREF argument is true if list items can use the deref
    (->) operator.  */
 
+struct omp_dim
+{
+  tree low_bound, length;
+  location_t loc;
+  bool no_colon;
+  omp_dim (tree lb, tree len, location_t lo, bool nc)
+    : low_bound (lb), length (len), loc (lo), no_colon (nc) {}
+};
+
 static tree
 cp_parser_omp_var_list_no_open (cp_parser *parser, enum omp_clause_code kind,
 				tree list, bool *colon,
 				bool allow_deref = false)
 {
+  auto_vec<omp_dim> dims;
+  bool array_section_p;
   cp_token *token;
   bool saved_colon_corrects_to_scope_p = parser->colon_corrects_to_scope_p;
   if (colon)
@@ -36491,6 +36502,7 @@ cp_parser_omp_var_list_no_open (cp_parser *parser, enum omp_clause_code kind,
 	    case OMP_CLAUSE_MAP:
 	    case OMP_CLAUSE_FROM:
 	    case OMP_CLAUSE_TO:
+	    start_component_ref:
 	      while (cp_lexer_next_token_is (parser->lexer, CPP_DOT)
 		     || (allow_deref
 			 && cp_lexer_next_token_is (parser->lexer, CPP_DEREF)))
@@ -36514,14 +36526,19 @@ cp_parser_omp_var_list_no_open (cp_parser *parser, enum omp_clause_code kind,
 	    case OMP_CLAUSE_REDUCTION:
 	    case OMP_CLAUSE_IN_REDUCTION:
 	    case OMP_CLAUSE_TASK_REDUCTION:
+	      array_section_p = false;
+	      dims.truncate (0);
 	      while (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_SQUARE))
 		{
+		  location_t loc = UNKNOWN_LOCATION;
 		  tree low_bound = NULL_TREE, length = NULL_TREE;
+		  bool no_colon = false;
 
 		  parser->colon_corrects_to_scope_p = false;
 		  cp_lexer_consume_token (parser->lexer);
 		  if (!cp_lexer_next_token_is (parser->lexer, CPP_COLON))
 		    {
+		      loc = cp_lexer_peek_token (parser->lexer)->location;
 		      low_bound = cp_parser_expression (parser);
 		      /* Later handling is not prepared to see through these.  */
 		      gcc_checking_assert (!location_wrapper_p (low_bound));
@@ -36530,7 +36547,10 @@ cp_parser_omp_var_list_no_open (cp_parser *parser, enum omp_clause_code kind,
 		    parser->colon_corrects_to_scope_p
 		      = saved_colon_corrects_to_scope_p;
 		  if (cp_lexer_next_token_is (parser->lexer, CPP_CLOSE_SQUARE))
-		    length = integer_one_node;
+		    {
+		      length = integer_one_node;
+		      no_colon = true;
+		    }
 		  else
 		    {
 		      /* Look for `:'.  */
@@ -36543,6 +36563,8 @@ cp_parser_omp_var_list_no_open (cp_parser *parser, enum omp_clause_code kind,
 			}
 		      if (kind == OMP_CLAUSE_DEPEND || kind == OMP_CLAUSE_AFFINITY)
 			cp_parser_commit_to_tentative_parse (parser);
+		      else
+			array_section_p = true;
 		      if (!cp_lexer_next_token_is (parser->lexer,
 						   CPP_CLOSE_SQUARE))
 			{
@@ -36561,8 +36583,30 @@ cp_parser_omp_var_list_no_open (cp_parser *parser, enum omp_clause_code kind,
 		      goto skip_comma;
 		    }
 
-		  decl = tree_cons (low_bound, length, decl);
+		  dims.safe_push (omp_dim (low_bound, length, loc, no_colon));
 		}
+
+	      if ((kind == OMP_CLAUSE_MAP
+		   || kind == OMP_CLAUSE_FROM
+		   || kind == OMP_CLAUSE_TO)
+		  && !array_section_p
+		  && (cp_lexer_next_token_is (parser->lexer, CPP_DOT)
+		      || (allow_deref
+			  && cp_lexer_next_token_is (parser->lexer,
+						     CPP_DEREF))))
+		{
+		  for (unsigned i = 0; i < dims.length (); i++)
+		    {
+		      gcc_assert (dims[i].length == integer_one_node);
+		      decl = build_array_ref (dims[i].loc,
+					      decl, dims[i].low_bound);
+		    }
+		  goto start_component_ref;
+		}
+	      else
+		for (unsigned i = 0; i < dims.length (); i++)
+		  decl = tree_cons (dims[i].low_bound, dims[i].length, decl);
+
 	      break;
 	    default:
 	      break;
@@ -40064,11 +40108,13 @@ cp_parser_omp_all_clauses (cp_parser *parser, omp_clause_mask mask,
 	    clauses = cp_parser_omp_var_list (parser, OMP_CLAUSE_TO_DECLARE,
 					      clauses);
 	  else
-	    clauses = cp_parser_omp_var_list (parser, OMP_CLAUSE_TO, clauses);
+	    clauses = cp_parser_omp_var_list (parser, OMP_CLAUSE_TO, clauses,
+					      true);
 	  c_name = "to";
 	  break;
 	case PRAGMA_OMP_CLAUSE_FROM:
-	  clauses = cp_parser_omp_var_list (parser, OMP_CLAUSE_FROM, clauses);
+	  clauses = cp_parser_omp_var_list (parser, OMP_CLAUSE_FROM, clauses,
+					    true);
 	  c_name = "from";
 	  break;
 	case PRAGMA_OMP_CLAUSE_UNIFORM: