re PR tree-optimization/50912 (gimple assertion failure at gimple.h:1940 with -msse2)

	PR tree-optimization/50912
	* tree-vectorizer.h (slp_void_p): New.
	(struct _slp_tree): Replace left and right with children.  Update
	documentation.
	(struct _slp_oprnd_info): New.
	(vect_get_vec_defs): Declare.
	(vect_get_slp_defs): Update arguments.
	* tree-vect-loop.c (vect_create_epilog_for_reduction): Call
	vect_get_vec_defs instead of vect_get_slp_defs.
	(vectorizable_reduction): Likewise.
	* tree-vect-stmts.c (vect_get_vec_defs): Remove static, add argument.
	Update call to vect_get_slp_defs.
	(vectorizable_conversion): Update call to vect_get_vec_defs.
	(vectorizable_assignment, vectorizable_shift,
	vectorizable_operation): Likewise.
	(vectorizable_type_demotion): Call vect_get_vec_defs instead of
	vect_get_slp_defs.
	(vectorizable_type_promotion, vectorizable_store): Likewise.
	(vect_analyze_stmt): Fix typo.
	* tree-vect-slp.c (vect_free_slp_tree): Update SLP tree traversal.
	(vect_print_slp_tree, vect_mark_slp_stmts,
	vect_mark_slp_stmts_relevant, vect_slp_rearrange_stmts,
	vect_detect_hybrid_slp_stmts, vect_slp_analyze_node_operations,
	vect_schedule_slp_instance): Likewise.
	(vect_create_new_slp_node): New.
	(vect_create_oprnd_info, vect_free_oprnd_info): Likewise.
	(vect_get_and_check_slp_defs): Pass information about defs using
	oprnds_info, allow any number of operands.
	(vect_build_slp_tree): Likewise.  Update calls to
	vect_get_and_check_slp_defs.  Fix comments.
	(vect_analyze_slp_instance): Move node creation to
	vect_create_new_slp_node.
	(vect_get_slp_defs): Allow any number of operands.

From-SVN: r180819