openmp, fortran: Add support for map iterators in OpenMP target construct (Fortran)

openmp, fortran: Add support for map iterators in OpenMP target construct (Fortran)

This adds support for iterators in map clauses within OpenMP
'target' constructs in Fortran.

Some special handling for struct field maps has been added to libgomp in
order to handle arrays of derived types.

gcc/fortran/

	* dump-parse-tree.cc (show_omp_namelist): Add iterator support for
	OMP_LIST_MAP.
	* match.cc (gfc_free_namelist): Free namespace for OMP_LIST_MAP.
	* openmp.cc (gfc_free_omp_clauses): Free namespace in namelist for
	OMP_LIST_MAP.
	(gfc_match_omp_clauses): Parse 'iterator' modifier for 'map' clause.
	(resolve_omp_clauses): Resolve iterators for OMP_LIST_MAP.
	* trans-openmp.cc: Include tree-ssa-loop-niter.h.
	(gfc_trans_omp_array_section): Add iterator argument.  Replace
	instances of iterator variables with the initial value when
	computing biases.
	* trans-openmp.cc (gfc_trans_omp_clauses): Handle iterators in
	OMP_LIST_MAP clauses.  Add expressions to iter_block rather than
	block.  Do not apply iterators to firstprivate maps.  Pass iterator
	to gfc_trans_omp_array_section.

gcc/

	* gimplify.cc (compute_omp_iterator_count): Account for difference
	in loop boundaries in Fortran.
	(build_omp_iterator_loop): Change upper boundary condition for
	Fortran.  Insert block statements into innermost loop.
	(remove_unused_omp_iterator_vars): Copy block subblocks of old
	iterator to new iterator and remove original.
	(contains_vars_1): New.
	(contains_vars): New.
	(extract_base_bit_offset): Add iterator argument.  Remove iterator
	variables from base.  Do not set variable_offset if the offset
	does not contain any remaining variables.
	(omp_accumulate_sibling_list): Add iterator argument to
	extract_base_bit_offset.
	* tree-pretty-print.cc (dump_block_node): Ignore BLOCK_SUBBLOCKS
	containing iterator block statements.

gcc/testsuite/

	* gfortran.dg/gomp/target-map-iterators-1.f90: New.
	* gfortran.dg/gomp/target-map-iterators-2.f90: New.
	* gfortran.dg/gomp/target-map-iterators-3.f90: New.
	* gfortran.dg/gomp/target-map-iterators-4.f90: New.

libgomp/

	* target.c (kind_to_name): Handle GOMP_MAP_STRUCT and
	GOMP_MAP_STRUCT_UNORD.
	(gomp_add_map): New.
	(gomp_merge_iterator_maps): Expand fields of a struct mapping
	breadth-first.
	* testsuite/libgomp.fortran/target-map-iterators-1.f90: New.
	* testsuite/libgomp.fortran/target-map-iterators-2.f90: New.
	* testsuite/libgomp.fortran/target-map-iterators-3.f90: New.

Co-authored-by: Andrew Stubbs <ams@baylibre.com>