This patch adds a wrapper around mode_for_size for cases in which
the mode class is MODE_INT (the commonest case).  The return type
can then be an opt_scalar_int_mode instead of a machine_mode.

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* machmode.h (int_mode_for_size): New function.
	* builtins.c (set_builtin_user_assembler_name): Use int_mode_for_size
	instead of mode_for_size.
	* calls.c (save_fixed_argument_area): Likewise.  Make use of BLKmode
	explicit.
	* combine.c (expand_field_assignment): Use int_mode_for_size
	instead of mode_for_size.
	(make_extraction): Likewise.
	(simplify_shift_const_1): Likewise.
	(simplify_comparison): Likewise.
	* dojump.c (do_jump): Likewise.
	* dwarf2out.c (mem_loc_descriptor): Likewise.
	* emit-rtl.c (init_derived_machine_modes): Likewise.
	* expmed.c (flip_storage_order): Likewise.
	(convert_extracted_bit_field): Likewise.
	* expr.c (copy_blkmode_from_reg): Likewise.
	* graphite-isl-ast-to-gimple.c (max_mode_int_precision): Likewise.
	* internal-fn.c (expand_mul_overflow): Likewise.
	* lower-subreg.c (simple_move): Likewise.
	* optabs-libfuncs.c (init_optabs): Likewise.
	* simplify-rtx.c (simplify_unary_operation_1): Likewise.
	* tree.c (vector_type_mode): Likewise.
	* tree-ssa-strlen.c (handle_builtin_memcmp): Likewise.
	* tree-vect-data-refs.c (vect_lanes_optab_supported_p): Likewise.
	* tree-vect-generic.c (expand_vector_parallel): Likewise.
	* tree-vect-stmts.c (vectorizable_load): Likewise.
	(vectorizable_store): Likewise.

gcc/ada/
	* gcc-interface/decl.c (gnat_to_gnu_entity): Use int_mode_for_size
	instead of mode_for_size.
	(gnat_to_gnu_subprog_type): Likewise.
	* gcc-interface/utils.c (make_type_from_size): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251469