openmp, fortran: Add Fortran support for parsing metadirectives

openmp, fortran: Add Fortran support for parsing metadirectives

This adds support for parsing OpenMP metadirectives in the Fortran front end.

2022-01-25  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* omp-general.c (omp_check_context_selector): Revert string length
	check.
	(omp_context_name_list_prop): Likewise.

	gcc/fortran/
	* decl.c (gfc_match_end): Handle COMP_OMP_METADIRECTIVE and
	COMP_OMP_BEGIN_METADIRECTIVE.
	* dump-parse-tree.c (show_omp_node): Handle EXEC_OMP_METADIRECTIVE.
	(show_code_node): Handle EXEC_OMP_METADIRECTIVE.
	* gfortran.h (enum gfc_statement): Add ST_OMP_METADIRECTIVE,
	ST_OMP_BEGIN_METADIRECTIVE and ST_OMP_END_METADIRECTIVE.
	(struct gfc_omp_metadirective_clause): New structure.
	(gfc_get_omp_metadirective_clause): New macro.
	(struct gfc_st_label): Add omp_region field.
	(enum gfc_exec_op): Add EXEC_OMP_METADIRECTIVE.
	(struct gfc_code): Add omp_metadirective_clauses field.
	(gfc_free_omp_metadirective_clauses): New prototype.
	(match_omp_directive): New prototype.
	* io.c (format_asterisk): Initialize omp_region field.
	* match.h (gfc_match_omp_begin_metadirective): New prototype.
	(gfc_match_omp_metadirective): New prototype.
	* openmp.c (gfc_match_omp_eos): Match ')' in context selectors.
	(gfc_free_omp_metadirective_clauses): New.
	(gfc_match_omp_clauses): Remove context_selector argument.  Rely on
	gfc_match_omp_eos to match end of clauses.
	(match_omp): Remove extra argument to gfc_match_omp_clauses.
	(gfc_match_omp_context_selector): Remove extra argument to
	gfc_match_omp_clauses.  Set gfc_matching_omp_context_selector
	before call to gfc_match_omp_clauses and reset after.
	(gfc_match_omp_context_selector_specification): Modify to take a
	gfc_omp_set_selector** argument.
	(gfc_match_omp_declare_variant): Pass set_selectors to
	gfc_match_omp_context_selector_specification.
	(match_omp_metadirective): New.
	(gfc_match_omp_begin_metadirective): New.
	(gfc_match_omp_metadirective): New.
	(resolve_omp_metadirective): New.
	(gfc_resolve_omp_directive): Handle EXEC_OMP_METADIRECTIVE.
	* parse.c (gfc_matching_omp_context_selector): New variable.
	(gfc_in_metadirective_body): New variable.
	(gfc_omp_region_count): New variable.
	(decode_omp_directive): Match 'begin metadirective',
	'end metadirective' and 'metadirective'.
	(match_omp_directive): New.
	(case_omp_structured_block): New.
	(case_omp_do): New.
	(gfc_ascii_statement): Handle metadirective statements.
	(gfc_omp_end_stmt): New.
	(parse_omp_do): Delegate to gfc_omp_end_stmt.
	(parse_omp_structured_block): Delegate to gfc_omp_end_stmt. Handle
	ST_OMP_END_METADIRECTIVE.
	(parse_omp_metadirective_body): New.
	(parse_executable): Delegate to case_omp_structured_block and
	case_omp_do.  Return after one statement if compiling regular
	metadirective.  Handle metadirective statements.
	(gfc_parse_file): Reset gfc_omp_region_count,
	gfc_in_metadirective_body and gfc_matching_omp_context_selector.
	* parse.h (enum gfc_compile_state): Add COMP_OMP_METADIRECTIVE and
	COMP_OMP_BEGIN_METADIRECTIVE.
	(gfc_omp_end_stmt): New prototype.
	(gfc_matching_omp_context_selector): New declaration.
	(gfc_in_metadirective_body): New declaration.
	(gfc_omp_region_count): New declaration.
	* resolve.c (gfc_resolve_code): Handle EXEC_OMP_METADIRECTIVE.
	* st.c (gfc_free_statement): Handle EXEC_OMP_METADIRECTIVE.
	* symbol.c (compare_st_labels): Take omp_region into account.
	(gfc_get_st_labels): Incorporate omp_region into label.
	* trans-decl.c (gfc_get_label_decl): Add omp_region into translated
	label name.
	* trans-openmp.c (gfc_trans_omp_directive): Handle
	EXEC_OMP_METADIRECTIVE.
	(gfc_trans_omp_set_selector): Hoist code from...
	(gfc_trans_omp_declare_variant): ...here.
	(gfc_trans_omp_metadirective): New.
	* trans-stmt.h (gfc_trans_omp_metadirective): New prototype.
	* trans.c (trans_code): Handle EXEC_OMP_METADIRECTIVE.