OpenMP: C++ "declare mapper" support

This patch adds support for OpenMP 5.0 "declare mapper" functionality
for C++.  I've merged it to og13 based on the last version
posted upstream, with some minor changes due to the newly-added
'present' map modifier support.  There's also a fix to splay-tree
traversal in gimplify.cc:omp_instantiate_implicit_mappers, and this patch
omits the rearrangement of gimplify.cc:gimplify_{scan,adjust}_omp_clauses
that I separated out into its own patch and applied (to og13) already.

2023-06-30  Julian Brown  <julian@codesourcery.com>

gcc/c-family/
	* c-common.h (omp_mapper_list): Add forward declaration.
	(c_omp_find_nested_mappers, c_omp_instantiate_mappers): Add prototypes.
	* c-omp.cc (c_omp_find_nested_mappers): New function.
	(remap_mapper_decl_info): New struct.
	(remap_mapper_decl_1, omp_instantiate_mapper,
	c_omp_instantiate_mappers): New functions.

gcc/cp/
	* constexpr.cc (reduced_constant_expression_p): Add OMP_DECLARE_MAPPER
	case.
	(cxx_eval_constant_expression, potential_constant_expression_1):
	Likewise.
	* cp-gimplify.cc (cxx_omp_finish_mapper_clauses): New function.
	* cp-objcp-common.h (LANG_HOOKS_OMP_FINISH_MAPPER_CLAUSES,
	LANG_HOOKS_OMP_MAPPER_LOOKUP, LANG_HOOKS_OMP_EXTRACT_MAPPER_DIRECTIVE,
	LANG_HOOKS_OMP_MAP_ARRAY_SECTION): Define langhooks.
	* cp-tree.h (lang_decl_base): Add omp_declare_mapper_p field.  Recount
	spare bits comment.
	(DECL_OMP_DECLARE_MAPPER_P): New macro.
	(omp_mapper_id, cp_check_omp_declare_mapper, omp_instantiate_mappers,
	cxx_omp_finish_mapper_clauses, cxx_omp_mapper_lookup,
	cxx_omp_extract_mapper_directive, cxx_omp_map_array_section: Add
	prototypes.
	* decl.cc (check_initializer): Add OpenMP declare mapper support.
	(cp_finish_decl): Set DECL_INITIAL for OpenMP declare mapper var decls
	as appropriate.
	* decl2.cc (mark_used): Instantiate OpenMP "declare mapper" magic var
	decls.
	* error.cc (dump_omp_declare_mapper): New function.
	(dump_simple_decl): Use above.
	* parser.cc (cp_parser_omp_clause_map): Add KIND parameter.  Support
	"mapper" modifier.
	(cp_parser_omp_all_clauses): Add KIND argument to
	cp_parser_omp_clause_map call.
	(cp_parser_omp_target): Call omp_instantiate_mappers before
	finish_omp_clauses.
	(cp_parser_omp_declare_mapper): New function.
	(cp_parser_omp_declare): Add "declare mapper" support.
	* pt.cc (tsubst_decl): Adjust name of "declare mapper" magic var decls
	once we know their type.
	(tsubst_omp_clauses): Call omp_instantiate_mappers before
	finish_omp_clauses, for target regions.
	(tsubst_expr): Support OMP_DECLARE_MAPPER nodes.
	(instantiate_decl): Instantiate initialiser (i.e definition) for OpenMP
	declare mappers.
	* semantics.cc (gimplify.h): Include.
	(omp_mapper_id, omp_mapper_lookup, omp_extract_mapper_directive,
	cxx_omp_map_array_section, cp_check_omp_declare_mapper): New functions.
	(finish_omp_clauses): Delete GOMP_MAP_PUSH_MAPPER_NAME and
	GOMP_MAP_POP_MAPPER_NAME artificial clauses.
	(omp_target_walk_data): Add MAPPERS field.
	(finish_omp_target_clauses_r): Scan for uses of struct/union/class type
	variables.
	(finish_omp_target_clauses): Create artificial mapper binding clauses
	for used structs/unions/classes in offload region.

gcc/fortran/
	* parse.cc (tree.h, fold-const.h, tree-hash-traits.h): Add includes
	(for additions to omp-general.h).

gcc/
	* gimplify.cc (gimplify_omp_ctx): Add IMPLICIT_MAPPERS field.
	(new_omp_context): Initialise IMPLICIT_MAPPERS hash map.
	(delete_omp_context): Delete IMPLICIT_MAPPERS hash map.
	(instantiate_mapper_info): New structs.
	(remap_mapper_decl_1, omp_mapper_copy_decl, omp_instantiate_mapper,
	omp_instantiate_implicit_mappers): New functions.
	(gimplify_scan_omp_clauses): Handle MAPPER_BINDING clauses.
	(gimplify_adjust_omp_clauses): Instantiate implicit declared mappers.
	(gimplify_omp_declare_mapper): New function.
	(gimplify_expr): Call above function.
	* langhooks-def.h (lhd_omp_finish_mapper_clauses,
	lhd_omp_mapper_lookup, lhd_omp_extract_mapper_directive,
	lhd_omp_map_array_section): Add prototypes.
	(LANG_HOOKS_OMP_FINISH_MAPPER_CLAUSES,
	LANG_HOOKS_OMP_MAPPER_LOOKUP, LANG_HOOKS_OMP_EXTRACT_MAPPER_DIRECTIVE,
	LANG_HOOKS_OMP_MAP_ARRAY_SECTION): Define macros.
	(LANG_HOOK_DECLS): Add above macros.
	* langhooks.cc (lhd_omp_finish_mapper_clauses,
	lhd_omp_mapper_lookup, lhd_omp_extract_mapper_directive,
	lhd_omp_map_array_section): New dummy functions.
	* langhooks.h (lang_hooks_for_decls): Add OMP_FINISH_MAPPER_CLAUSES,
	OMP_MAPPER_LOOKUP, OMP_EXTRACT_MAPPER_DIRECTIVE, OMP_MAP_ARRAY_SECTION
	hooks.
	* omp-general.h (omp_name_type<T>): Add templatized struct, hash type
	traits (for omp_name_type<tree> specialization).
	(omp_mapper_list<T>): Add struct.
	* tree-core.h (omp_clause_code): Add OMP_CLAUSE__MAPPER_BINDING_.
	* tree-pretty-print.cc (dump_omp_clause): Support GOMP_MAP_UNSET,
	GOMP_MAP_PUSH_MAPPER_NAME, GOMP_MAP_POP_MAPPER_NAME artificial mapping
	clauses.  Support OMP_CLAUSE__MAPPER_BINDING_ and OMP_DECLARE_MAPPER.
	* tree.cc (omp_clause_num_ops, omp_clause_code_name): Add
	OMP_CLAUSE__MAPPER_BINDING_.
	* tree.def (OMP_DECLARE_MAPPER): New tree code.
	* tree.h (OMP_DECLARE_MAPPER_ID, OMP_DECLARE_MAPPER_DECL,
	OMP_DECLARE_MAPPER_CLAUSES): New defines.
	(OMP_CLAUSE__MAPPER_BINDING__ID, OMP_CLAUSE__MAPPER_BINDING__DECL,
	OMP_CLAUSE__MAPPER_BINDING__MAPPER): New defines.

include/
	* gomp-constants.h (gomp_map_kind): Add GOMP_MAP_UNSET,
	GOMP_MAP_PUSH_MAPPER_NAME, GOMP_MAP_POP_MAPPER_NAME artificial mapping
	clause types.

gcc/testsuite/
	* c-c++-common/gomp/map-6.c: Update error scan output.
	* c-c++-common/gomp/declare-mapper-3.c: New test (only enabled for C++
	for now).
	* c-c++-common/gomp/declare-mapper-4.c: Likewise.
	* c-c++-common/gomp/declare-mapper-5.c: Likewise.
	* c-c++-common/gomp/declare-mapper-6.c: Likewise.
	* c-c++-common/gomp/declare-mapper-7.c: Likewise.
	* c-c++-common/gomp/declare-mapper-8.c: Likewise.
	* c-c++-common/gomp/declare-mapper-9.c: Likewise.
	* c-c++-common/gomp/declare-mapper-12.c: Likewise.
	* g++.dg/gomp/declare-mapper-1.C: New test.
	* g++.dg/gomp/declare-mapper-2.C: New test.

libgomp/
	* testsuite/libgomp.c++/declare-mapper-1.C: New test.
	* testsuite/libgomp.c++/declare-mapper-2.C: New test.
	* testsuite/libgomp.c++/declare-mapper-3.C: New test.
	* testsuite/libgomp.c++/declare-mapper-4.C: New test.
	* testsuite/libgomp.c++/declare-mapper-5.C: New test.
	* testsuite/libgomp.c++/declare-mapper-6.C: New test.
	* testsuite/libgomp.c++/declare-mapper-7.C: New test.
	* testsuite/libgomp.c++/declare-mapper-8.C: New test.
	* testsuite/libgomp.c-c++-common/declare-mapper-9.c: New test (only
	enabled for C++ for now).
	* testsuite/libgomp.c-c++-common/declare-mapper-10.c: Likewise.
	* testsuite/libgomp.c-c++-common/declare-mapper-11.c: Likewise.
	* testsuite/libgomp.c-c++-common/declare-mapper-12.c: Likewise.
	* testsuite/libgomp.c-c++-common/declare-mapper-13.c: Likewise.
	* testsuite/libgomp.c-c++-common/declare-mapper-14.c: Likewise.

3 files changed, 312 insertions, 0 deletions

diff --git a/gcc/c-family/ChangeLog.omp b/gcc/c-family/ChangeLog.omp
index 92c305aa85d..73abb6a7bc9 100644
--- a/gcc/c-family/ChangeLog.omp
+++ b/gcc/c-family/ChangeLog.omp
@@ -1,5 +1,14 @@
 2023-06-30  Julian Brown  <julian@codesourcery.com>
 
+	* c-common.h (omp_mapper_list): Add forward declaration.
+	(c_omp_find_nested_mappers, c_omp_instantiate_mappers): Add prototypes.
+	* c-omp.cc (c_omp_find_nested_mappers): New function.
+	(remap_mapper_decl_info): New struct.
+	(remap_mapper_decl_1, omp_instantiate_mapper,
+	c_omp_instantiate_mappers): New functions.
+
+2023-06-30  Julian Brown  <julian@codesourcery.com>
+
 	* c-common.h (c_omp_address_inspector): Remove static from get_origin
 	and maybe_unconvert_ref methods.
 	* c-omp.cc (c_omp_split_clauses): Support OMP_ARRAY_SECTION.
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 6d7cda89aa4..acd0c861a55 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1308,6 +1308,9 @@ extern tree c_omp_check_context_selector (location_t, tree);
 extern void c_omp_mark_declare_variant (location_t, tree, tree);
 extern void c_oacc_annotate_loops_in_kernels_regions (tree, tree (*) (tree));
 extern void c_omp_adjust_map_clauses (tree, bool);
+template<typename T> struct omp_mapper_list;
+extern void c_omp_find_nested_mappers (struct omp_mapper_list<tree> *, tree);
+extern tree c_omp_instantiate_mappers (tree);
 
 namespace omp_addr_tokenizer { struct omp_addr_token; }
 typedef omp_addr_tokenizer::omp_addr_token omp_addr_token;
diff --git a/gcc/c-family/c-omp.cc b/gcc/c-family/c-omp.cc
index da0fd3ebe3c..16b620fcb3d 100644
--- a/gcc/c-family/c-omp.cc
+++ b/gcc/c-family/c-omp.cc
@@ -4740,6 +4740,306 @@ c_omp_address_inspector::expand_map_clause (tree c, tree expr,
   return error_mark_node;
 }
 
+/* Given a mapper function MAPPER_FN, recursively scan through the map clauses
+   for that mapper, and if any of those should use a (named or unnamed) mapper
+   themselves, add it to MLIST.  */
+
+void
+c_omp_find_nested_mappers (omp_mapper_list<tree> *mlist, tree mapper_fn)
+{
+  tree mapper = lang_hooks.decls.omp_extract_mapper_directive (mapper_fn);
+  tree mapper_name = NULL_TREE;
+
+  if (mapper == error_mark_node)
+    return;
+
+  gcc_assert (TREE_CODE (mapper) == OMP_DECLARE_MAPPER);
+
+  for (tree clause = OMP_DECLARE_MAPPER_CLAUSES (mapper);
+       clause;
+       clause = OMP_CLAUSE_CHAIN (clause))
+    {
+      tree expr = OMP_CLAUSE_DECL (clause);
+      enum gomp_map_kind clause_kind = OMP_CLAUSE_MAP_KIND (clause);
+      tree elem_type;
+
+      if (clause_kind == GOMP_MAP_PUSH_MAPPER_NAME)
+	{
+	  mapper_name = expr;
+	  continue;
+	}
+      else if (clause_kind == GOMP_MAP_POP_MAPPER_NAME)
+	{
+	  mapper_name = NULL_TREE;
+	  continue;
+	}
+
+      gcc_assert (TREE_CODE (expr) != TREE_LIST);
+      if (TREE_CODE (expr) == OMP_ARRAY_SECTION)
+	{
+	  while (TREE_CODE (expr) == OMP_ARRAY_SECTION)
+	    expr = TREE_OPERAND (expr, 0);
+
+	  elem_type = TREE_TYPE (expr);
+	}
+      else
+	elem_type = TREE_TYPE (expr);
+
+      /* This might be too much... or not enough?  */
+      while (TREE_CODE (elem_type) == ARRAY_TYPE
+	     || TREE_CODE (elem_type) == POINTER_TYPE
+	     || TREE_CODE (elem_type) == REFERENCE_TYPE)
+	elem_type = TREE_TYPE (elem_type);
+
+      elem_type = TYPE_MAIN_VARIANT (elem_type);
+
+      if (AGGREGATE_TYPE_P (elem_type)
+	  && !mlist->contains (mapper_name, elem_type))
+	{
+	  tree nested_mapper_fn
+	    = lang_hooks.decls.omp_mapper_lookup (mapper_name, elem_type);
+
+	  if (nested_mapper_fn)
+	    {
+	      mlist->add_mapper (mapper_name, elem_type, nested_mapper_fn);
+	      c_omp_find_nested_mappers (mlist, nested_mapper_fn);
+	    }
+	  else if (mapper_name)
+	    {
+	      error ("mapper %qE not found for type %qT", mapper_name,
+		     elem_type);
+	      continue;
+	    }
+	}
+    }
+}
+
+struct remap_mapper_decl_info
+{
+  tree dummy_var;
+  tree expr;
+};
+
+/* Helper for rewriting DUMMY_VAR into EXPR in a map clause decl.  */
+
+static tree
+remap_mapper_decl_1 (tree *tp, int *walk_subtrees, void *data)
+{
+  remap_mapper_decl_info *map_info = (remap_mapper_decl_info *) data;
+
+  if (operand_equal_p (*tp, map_info->dummy_var))
+    {
+      *tp = map_info->expr;
+      *walk_subtrees = 0;
+    }
+
+  return NULL_TREE;
+}
+
+/* Instantiate a mapper MAPPER for expression EXPR, adding new clauses to
+   OUTLIST.  OUTER_KIND is the mapping kind to use if not already specified in
+   the mapper declaration.  */
+
+static tree *
+omp_instantiate_mapper (tree *outlist, tree mapper, tree expr,
+			enum gomp_map_kind outer_kind)
+{
+  tree clauses = OMP_DECLARE_MAPPER_CLAUSES (mapper);
+  tree dummy_var = OMP_DECLARE_MAPPER_DECL (mapper);
+  tree mapper_name = NULL_TREE;
+
+  remap_mapper_decl_info map_info;
+  map_info.dummy_var = dummy_var;
+  map_info.expr = expr;
+
+  for (tree c = clauses; c; c = OMP_CLAUSE_CHAIN (c))
+    {
+      tree unshared = unshare_expr (c);
+      enum gomp_map_kind clause_kind = OMP_CLAUSE_MAP_KIND (c);
+      tree t = OMP_CLAUSE_DECL (unshared);
+      tree type = NULL_TREE;
+      bool nonunit_array_with_mapper = false;
+
+      if (clause_kind == GOMP_MAP_PUSH_MAPPER_NAME)
+	{
+	  mapper_name = t;
+	  continue;
+	}
+      else if (clause_kind == GOMP_MAP_POP_MAPPER_NAME)
+	{
+	  mapper_name = NULL_TREE;
+	  continue;
+	}
+
+      if (TREE_CODE (t) == OMP_ARRAY_SECTION)
+	{
+	  location_t loc = OMP_CLAUSE_LOCATION (c);
+	  tree t2 = lang_hooks.decls.omp_map_array_section (loc, t);
+
+	  if (t2 == t)
+	    {
+	      nonunit_array_with_mapper = true;
+	      /* We'd want use the mapper for the element type if this worked:
+		 look that one up.  */
+	      type = TREE_TYPE (TREE_TYPE (t));
+	    }
+	  else
+	    {
+	      t = t2;
+	      type = TREE_TYPE (t);
+	    }
+	}
+      else
+	type = TREE_TYPE (t);
+
+      gcc_assert (type);
+
+      if (type == error_mark_node)
+	continue;
+
+      walk_tree (&unshared, remap_mapper_decl_1, &map_info, NULL);
+
+      if (OMP_CLAUSE_MAP_KIND (unshared) == GOMP_MAP_UNSET)
+	OMP_CLAUSE_SET_MAP_KIND (unshared, outer_kind);
+
+      type = TYPE_MAIN_VARIANT (type);
+
+      tree mapper_fn = lang_hooks.decls.omp_mapper_lookup (mapper_name, type);
+
+      if (mapper_fn && nonunit_array_with_mapper)
+	{
+	  sorry ("user-defined mapper with non-unit length array section");
+	  continue;
+	}
+      else if (mapper_fn)
+	{
+	  tree nested_mapper
+	    = lang_hooks.decls.omp_extract_mapper_directive (mapper_fn);
+	  if (nested_mapper != mapper)
+	    {
+	      if (clause_kind == GOMP_MAP_UNSET)
+		clause_kind = outer_kind;
+
+	      outlist = omp_instantiate_mapper (outlist, nested_mapper,
+						t, clause_kind);
+	      continue;
+	    }
+	}
+      else if (mapper_name)
+	{
+	  error ("mapper %qE not found for type %qT", mapper_name, type);
+	  continue;
+	}
+
+      *outlist = unshared;
+      outlist = &OMP_CLAUSE_CHAIN (unshared);
+    }
+
+  return outlist;
+}
+
+/* Given a list of CLAUSES, scan each clause and invoke a user-defined mapper
+   appropriate to the type of the data in that clause, if such a mapper is
+   visible in the current parsing context.  */
+
+tree
+c_omp_instantiate_mappers (tree clauses)
+{
+  tree c, *pc, mapper_name = NULL_TREE;
+
+  for (pc = &clauses, c = clauses; c; c = *pc)
+    {
+      bool using_mapper = false;
+
+      switch (OMP_CLAUSE_CODE (c))
+	{
+	case OMP_CLAUSE_MAP:
+	  {
+	    tree t = OMP_CLAUSE_DECL (c);
+	    tree type = NULL_TREE;
+	    bool nonunit_array_with_mapper = false;
+
+	    if (OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_PUSH_MAPPER_NAME
+		|| OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_POP_MAPPER_NAME)
+	      {
+		if (OMP_CLAUSE_MAP_KIND (c) == GOMP_MAP_PUSH_MAPPER_NAME)
+		  mapper_name = OMP_CLAUSE_DECL (c);
+		else
+		  mapper_name = NULL_TREE;
+		pc = &OMP_CLAUSE_CHAIN (c);
+		continue;
+	      }
+
+	    if (TREE_CODE (t) == OMP_ARRAY_SECTION)
+	      {
+		location_t loc = OMP_CLAUSE_LOCATION (c);
+		tree t2 = lang_hooks.decls.omp_map_array_section (loc, t);
+
+		if (t2 == t)
+		  {
+		    /* !!! Array sections of size >1 with mappers for elements
+		       are hard to support.  Do something here.  */
+		    nonunit_array_with_mapper = true;
+		    type = TREE_TYPE (TREE_TYPE (t));
+		  }
+		else
+		  {
+		    t = t2;
+		    type = TREE_TYPE (t);
+		  }
+	      }
+	    else
+	      type = TREE_TYPE (t);
+
+	    if (type == NULL_TREE || type == error_mark_node)
+	      {
+		pc = &OMP_CLAUSE_CHAIN (c);
+		continue;
+	      }
+
+	    enum gomp_map_kind kind = OMP_CLAUSE_MAP_KIND (c);
+	    if (kind == GOMP_MAP_UNSET)
+	      kind = GOMP_MAP_TOFROM;
+
+	    type = TYPE_MAIN_VARIANT (type);
+
+	    tree mapper_fn
+	      = lang_hooks.decls.omp_mapper_lookup (mapper_name, type);
+
+	    if (mapper_fn && nonunit_array_with_mapper)
+	      {
+		sorry ("user-defined mapper with non-unit length "
+		       "array section");
+		using_mapper = true;
+	      }
+	    else if (mapper_fn)
+	      {
+		tree mapper
+		  = lang_hooks.decls.omp_extract_mapper_directive (mapper_fn);
+		pc = omp_instantiate_mapper (pc, mapper, t, kind);
+		using_mapper = true;
+	      }
+	    else if (mapper_name)
+	      {
+		error ("mapper %qE not found for type %qT", mapper_name, type);
+		using_mapper = true;
+	      }
+	  }
+	  break;
+
+	default:
+	  ;
+	}
+
+      if (using_mapper)
+	*pc = OMP_CLAUSE_CHAIN (c);
+      else
+	pc = &OMP_CLAUSE_CHAIN (c);
+    }
+
+  return clauses;
+}
+
 const struct c_omp_directive c_omp_directives[] = {
   /* Keep this alphabetically sorted by the first word.  Non-null second/third
      if any should precede null ones.  */