openmp: Add support for the 'present' modifier

This implements support for the OpenMP 5.1 'present' modifier, which can be
used in map clauses in the 'target', 'target data', 'target data enter' and
'target data exit' constructs, and in the 'to' and 'from' clauses of the
'target update' construct.  It is also supported in defaultmap.

The modifier triggers a fatal runtime error if the data specified by the
clause is not already present on the target device.  It can also be combined
with 'always' in map clauses.

2023-06-06  Kwok Cheung Yeung  <kcy@codesourcery.com>
	    Tobias Burnus  <tobias@codesourcery.com>

gcc/c/
	* c-parser.cc (c_parser_omp_clause_defaultmap,
	c_parser_omp_clause_map): Parse 'present'.
	(c_parser_omp_clause_to, c_parser_omp_clause_from): Remove.
	(c_parser_omp_clause_from_to): New; parse to/from clauses with
	optional present modifer.
	(c_parser_omp_all_clauses): Update call.
	(c_parser_omp_target_data, c_parser_omp_target_enter_data,
	c_parser_omp_target_exit_data): Handle new map enum values
	for 'present' mapping.

gcc/cp/
	* parser.cc (cp_parser_omp_clause_defaultmap,
	cp_parser_omp_clause_map): Parse 'present'.
	(cp_parser_omp_clause_from_to): New; parse to/from
	clauses with optional 'present' modifier.
	(cp_parser_omp_all_clauses): Update call.
	(cp_parser_omp_target_data, cp_parser_omp_target_enter_data,
	cp_parser_omp_target_exit_data): Handle new enum value for
	'present' mapping.
	* semantics.cc (finish_omp_target): Likewise.

gcc/fortran/
	* dump-parse-tree.cc (show_omp_namelist): Display 'present' map
	modifier.
	(show_omp_clauses): Display 'present' motion modifier for 'to'
	and 'from' clauses.

	* gfortran.h (enum gfc_omp_map_op): Add entries with 'present'
	modifiers.
	(struct gfc_omp_namelist): Add 'present_modifer'.
	* openmp.cc (gfc_match_motion_var_list): New, handles optional
	'present' modifier for to/from clauses.
	(gfc_match_omp_clauses): Call it for to/from clauses; parse 'present'
	in defaultmap and map clauses.
	(resolve_omp_clauses): Allow 'present' modifiers on 'target',
	'target data', 'target enter' and 'target exit'	directives.
	* trans-openmp.cc (gfc_trans_omp_clauses): Apply 'present' modifiers
	to tree node for 'map', 'to' and 'from'	clauses.  Apply 'present' for
	defaultmap.

gcc/
	* gimplify.cc (omp_notice_variable): Apply GOVD_MAP_ALLOC_ONLY flag
	and defaultmap flags if the defaultmap has GOVD_MAP_FORCE_PRESENT flag
	set.
	(omp_get_attachment): Handle map clauses with 'present' modifier.
	(omp_group_base): Likewise.
	(gimplify_scan_omp_clauses): Reorder present maps to come first.
	Set GOVD flags for present defaultmaps.
	(gimplify_adjust_omp_clauses_1): Set map kind for present defaultmaps.
	* omp-low.cc (scan_sharing_clauses): Handle 'always, present' map
	clauses.
	(lower_omp_target): Handle map clauses with 'present' modifier.
	Handle 'to' and 'from' clauses with 'present'.
	* tree-core.h (enum omp_clause_defaultmap_kind): Add
	OMP_CLAUSE_DEFAULTMAP_PRESENT defaultmap kind.
	* tree-pretty-print.cc (dump_omp_clause): Handle 'map', 'to' and
	'from' clauses with 'present' modifier.  Handle present defaultmap.
	* tree.h (OMP_CLAUSE_MOTION_PRESENT): New #define.

include/
	* gomp-constants.h (GOMP_MAP_FLAG_SPECIAL_5): New.
	(GOMP_MAP_FLAG_FORCE): Redefine.
	(GOMP_MAP_FLAG_PRESENT, GOMP_MAP_FLAG_ALWAYS_PRESENT): New.
	(enum gomp_map_kind): Add map kinds with 'present' modifiers.
	(GOMP_MAP_COPY_TO_P, GOMP_MAP_COPY_FROM_P): Evaluate to true for
	map variants with 'present'
	(GOMP_MAP_ALWAYS_TO_P, GOMP_MAP_ALWAYS_FROM_P): Evaluate to true
	for map variants with 'always, present' modifiers.
	(GOMP_MAP_ALWAYS): Redefine.
	(GOMP_MAP_FORCE_P, GOMP_MAP_PRESENT_P): New.

libgomp/
	* libgomp.texi (OpenMP 5.1 Impl. status): Set 'present' support for
	defaultmap to 'Y', add 'Y' entry for 'present' on to/from/map clauses.
	* target.c (gomp_to_device_kind_p): Add map kinds with 'present'
	modifier.
	(gomp_map_vars_existing): Use new GOMP_MAP_FORCE_P macro.
	(gomp_map_vars_internal, gomp_update, gomp_target_rev):
	Emit runtime error if memory region not present.
	* testsuite/libgomp.c-c++-common/target-present-1.c: New test.
	* testsuite/libgomp.c-c++-common/target-present-2.c: New test.
	* testsuite/libgomp.c-c++-common/target-present-3.c: New test.
	* testsuite/libgomp.fortran/target-present-1.f90: New test.
	* testsuite/libgomp.fortran/target-present-2.f90: New test.
	* testsuite/libgomp.fortran/target-present-3.f90: New test.

gcc/testsuite/

	* c-c++-common/gomp/map-6.c: Update dg-error, extend to test for
	duplicated 'present' and extend scan-dump tests for 'present'.
	* gfortran.dg/gomp/defaultmap-1.f90: Update dg-error.
	* gfortran.dg/gomp/map-7.f90: Extend parse and dump test for
	'present'.
	* gfortran.dg/gomp/map-8.f90: Extend for duplicate 'present'
	modifier checking.
	* c-c++-common/gomp/defaultmap-4.c: New test.
	* c-c++-common/gomp/map-9.c: New test.
	* c-c++-common/gomp/target-update-1.c: New test.
	* gfortran.dg/gomp/defaultmap-8.f90: New test.
	* gfortran.dg/gomp/map-11.f90: New test.
	* gfortran.dg/gomp/map-12.f90: New test.
	* gfortran.dg/gomp/target-update-1.f90: New test.