This patch adds a wrapper around smallest_mode_for_size
for cases in which the mode class is MODE_INT.  Unlike
(int_)mode_for_size, smallest_mode_for_size always returns
a mode of the specified class, asserting if no such mode exists.
smallest_int_mode_for_size therefore returns a scalar_int_mode
rather than an opt_scalar_int_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 (smallest_mode_for_size): Fix formatting.
	(smallest_int_mode_for_size): New function.
	* cfgexpand.c (expand_debug_expr): Use smallest_int_mode_for_size
	instead of smallest_mode_for_size.
	* combine.c (make_extraction): Likewise.
	* config/arc/arc.c (arc_expand_movmem): Likewise.
	* config/arm/arm.c (arm_expand_divmod_libfunc): Likewise.
	* config/i386/i386.c (ix86_get_mask_mode): Likewise.
	* config/s390/s390.c (s390_expand_insv): Likewise.
	* config/sparc/sparc.c (assign_int_registers): Likewise.
	* config/spu/spu.c (spu_function_value): Likewise.
	(spu_function_arg): Likewise.
	* coverage.c (get_gcov_type): Likewise.
	(get_gcov_unsigned_t): Likewise.
	* dse.c (find_shift_sequence): Likewise.
	* expmed.c (store_bit_field_1): Likewise.
	* expr.c (convert_move): Likewise.
	(store_field): Likewise.
	* internal-fn.c (expand_arith_overflow): Likewise.
	* optabs-query.c (get_best_extraction_insn): Likewise.
	* optabs.c (expand_twoval_binop_libfunc): Likewise.
	* stor-layout.c (layout_type): Likewise.
	(initialize_sizetypes): Likewise.
	* targhooks.c (default_get_mask_mode): Likewise.
	* tree-ssa-loop-manip.c (canonicalize_loop_ivs): Likewise.

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

From-SVN: r251471