Make more use of HWI_COMPUTABLE_MODE_P

Make more use of HWI_COMPUTABLE_MODE_P

This patch uses HWI_COMPUTABLE_MODE_P (X) instead of
GET_MODE_PRECISION (X) <= HOST_BITS_PER_WIDE_INT in cases
where X also needs to be a scalar integer.

2017-10-22  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* combine.c (simplify_comparison): Use HWI_COMPUTABLE_MODE_P.
	(record_promoted_value): Likewise.
	* expr.c (expand_expr_real_2): Likewise.
	* ree.c (update_reg_equal_equiv_notes): Likewise.
	(combine_set_extension): Likewise.
	* rtlanal.c (low_bitmask_len): Likewise.
	* simplify-rtx.c (neg_const_int): Likewise.
	(simplify_binary_operation_1): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r253990