Hi Richard,

New version v5 is attached.

v5 main changes against v4:
  1) use _stmt instead of _cnt to avoid confusion
  2) factor out function vect_rgroup_iv_might_wrap_p
  3) use generic scalar_stmt for min/max stmt

Does this look better?  Thanks in advance!

BR,
Kewen
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gcc/ChangeLog:

	* config/rs6000/rs6000.c (rs6000_adjust_vect_cost_per_loop): New
	function.
	(rs6000_finish_cost): Call rs6000_adjust_vect_cost_per_loop.
	* tree-vect-loop.c (vect_estimate_min_profitable_iters): Add cost
	modeling for vector with length.
	(vect_rgroup_iv_might_wrap_p): New function, factored out from...
	* tree-vect-loop-manip.c (vect_set_loop_controls_directly): ...this.
	Update function comment.
	* tree-vect-stmts.c (vect_gen_len): Update function comment.
	* tree-vectorizer.h (vect_rgroup_iv_might_wrap_p): New declare.