* loop.h (precondition_loop_p): Added new mode argument.
	* unroll.c (precondition_loop_p): Likewise.
	(approx_final_value): Function deleted and subsumed
 	into loop_iterations.
	(loop_find_equiv_value): New function.
	(loop_iterations): Use loop_find_equiv_value to find increments
	too large to be immediate constants.  Also use it to find terms
	common to initial and final iteration values that can be removed.

From-SVN: r23885