tree-ssa-loop-ivopts.c (aff_combination_convert, [...]): New functions.

	* tree-ssa-loop-ivopts.c (aff_combination_convert,
	determine_common_wider_type): New functions.
	(get_computation_aff): Use them to simplify arithmetic between
	UBASE and CBASE if they are shortened from the same type.

Co-Authored-By: Adam Nemet <anemet@caviumnetworks.com>

From-SVN: r117182