re PR tree-optimization/57705 (Non-constant step induction vars not vectorized)

re PR tree-optimization/57705 (Non-constant step induction vars not vectorized)

	PR tree-optimization/57705
	* tree-vect-loop.c (vect_is_simple_iv_evolution): Allow
	SSA_NAME step, provided that it is not defined inside the loop.
	(vect_analyze_scalar_cycles_1): Disallow SSA_NAME step in nested
	loop.
	(get_initial_def_for_induction): Handle SSA_NAME IV step.

	* gcc.dg/vect/pr57705.c: New test.
	* gcc.dg/vect/vect-iv-7.c: Add noclone attribute, remove xfail.

From-SVN: r200394