fold-const.c (build_range_check): Make sure to use a valid type to apply the "(c...

fold-const.c (build_range_check): Make sure to use a valid type to apply the "(c>=low) && (c<=high) into...

	* fold-const.c (build_range_check): Make sure to use a valid type to
	apply the "(c>=low) && (c<=high) into (c-low>=0) && (c-low<=high-low)"
	transformation.

	(range_predecessor): New static function.
	(range_successor): Likewise.
	(merge_ranges): Use them to compute predecessors and successors of
	range bounds.

From-SVN: r111866