Fortran: Implement the F2018 reduce intrinsic [PR85836]

Fortran:  Implement the F2018 reduce intrinsic [PR85836]

2025-03-21  Paul Thomas  <pault@gcc.gnu.org>

gcc/fortran
	PR fortran/85836
	* check.cc (get_ul_from_cst_cl): New function used in
	check_operation.
	(check_operation): New function used in check_reduce and
	check_co_reduce.
	(gfc_check_co_reduce): Use it.
	(gfc_check_reduce): New function.
	(gfc_check_rename): Add prototype for intrinsic with 6 arguments.
	* gfortran.h : Add isym id for reduce and prototype for f6.
	* intrinsic.cc (do_check): Add another argument expression and use
	it in the call to the six argument specific check.
	(add_sym_6): New function.
	(add_functions): Add the discription of the reduce intrinsic and
	add it to the intrinsic list.
	* intrinsic.h : Add prototypes for gfc_check_reduce and
	gfc_resolve_reduce.
	* iresolve.cc (generate_reduce_op_wrapper): Generate a wrapper
	subroutine for the 'operation' function to enable the library
	implementation to be type agnostic and use pointer arithmetic
	throughout.
	(gfc_resolve_reduce): New function.
	* trans-expr.cc (gfc_conv_procedure_call): Add flag for scalar
	reduce. Generate a return variable 'sr' for scalar reduce, pass its
	address to the library function and return it as the scalar result.
	* trans-intrinsic.cc (gfc_conv_intrinsic_function): Array valued
	reduce is called in same way as reshape. Fall through for call to
	the scalar version.

gcc/testsuite/
	PR fortran/85836
	* gfortran.dg/reduce_1.f90: New test
	* gfortran.dg/reduce_2.f90: New test

libgfortran/
	PR libfortran/85836
	* Makefile.am : Add reduce.c
	* Makefile.in : Regenerated
	* gfortran.map : Add _gfortran_reduce, _gfortran_reduce_scalar,
	_gfortran_reduce_c and _gfortran_reduce_scalar_c to the list.
	* intrinsics/reduce.c (reduce, reduce_scalar, reduce_c,
	reduce_scalar_c): New functions and prototypes