[65/77] Add a SCALAR_TYPE_MODE macro

This patch adds a SCALAR_TYPE_MODE macro, along the same lines as
SCALAR_INT_TYPE_MODE and SCALAR_FLOAT_TYPE_MODE.  It also adds
two instances of as_a <scalar_mode> to c_common_type, when converting
an unsigned fixed-point SCALAR_TYPE_MODE to the equivalent signed mode.

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

gcc/
	* tree.h (SCALAR_TYPE_MODE): New macro.
	* expr.c (expand_expr_addr_expr_1): Use it.
	(expand_expr_real_2): Likewise.
	* fold-const.c (fold_convert_const_fixed_from_fixed): Likeise.
	(fold_convert_const_fixed_from_int): Likewise.
	(fold_convert_const_fixed_from_real): Likewise.
	(native_encode_fixed): Likewise
	(native_encode_complex): Likewise
	(native_encode_vector): Likewise.
	(native_interpret_fixed): Likewise.
	(native_interpret_real): Likewise.
	(native_interpret_complex): Likewise.
	(native_interpret_vector): Likewise.
	* omp-simd-clone.c (simd_clone_adjust_return_type): Likewise.
	(simd_clone_adjust_argument_types): Likewise.
	(simd_clone_init_simd_arrays): Likewise.
	(simd_clone_adjust): Likewise.
	* stor-layout.c (layout_type): Likewise.
	* tree.c (build_minus_one_cst): Likewise.
	* tree-cfg.c (verify_gimple_assign_ternary): Likewise.
	* tree-inline.c (estimate_move_cost): Likewise.
	* tree-ssa-math-opts.c (convert_plusminus_to_widen): Likewise.
	* tree-vect-loop.c (vect_create_epilog_for_reduction): Likewise.
	(vectorizable_reduction): Likewise.
	* tree-vect-patterns.c (vect_recog_widen_mult_pattern): Likewise.
	(vect_recog_mixed_size_cond_pattern): Likewise.
	(check_bool_pattern): Likewise.
	(adjust_bool_pattern): Likewise.
	(search_type_for_mask_1): Likewise.
	* tree-vect-slp.c (vect_schedule_slp_instance): Likewise.
	* tree-vect-stmts.c (vectorizable_conversion): Likewise.
	(vectorizable_load): Likewise.
	(vectorizable_store): Likewise.
	* ubsan.c (ubsan_encode_value): Likewise.
	* varasm.c (output_constant): Likewise.

gcc/c-family/
	* c-lex.c (interpret_fixed): Use SCALAR_TYPE_MODE.
	* c-common.c (c_build_vec_perm_expr): Likewise.

gcc/c/
	* c-typeck.c (build_binary_op): Use SCALAR_TYPE_MODE.
	(c_common_type): Likewise.  Use as_a <scalar_mode> when setting
	m1 and m2 to the signed equivalent of a fixed-point
	SCALAR_TYPE_MODE.

gcc/cp/
	* typeck.c (cp_build_binary_op): Use SCALAR_TYPE_MODE.

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

From-SVN: r251516