re PR tree-optimization/37027 (SLP loop vectorization missing support for reductions)

	PR tree-optimization/37027
	* tree-vectorizer.h (struct _loop_vec_info): Add new field reductions 
	and macro to access it.
	(vectorizable_reduction): Add argument.
	(vect_get_slp_defs): Likewise.
	* tree-vect-loop.c (vect_analyze_scalar_cycles_1): Collect reduction
	statements for possible use in SLP.
	(new_loop_vec_info): Initialize LOOP_VINFO_REDUCTIONS.
	(destroy_loop_vec_info): Free LOOP_VINFO_REDUCTIONS.
	(vect_create_epilog_for_reduction): Handle SLP. Modify documentation,
	add new argument.
	(vectorizable_reduction): Likewise.
	* tree-vect-stmts.c (vect_get_vec_defs): Update call to 
	vect_get_slp_defs.
	(vectorizable_type_demotion, vectorizable_type_promotion,
	vectorizable_store): Likewise.
	(vect_analyze_stmt): Update call to vectorizable_reduction.
	(vect_transform_stmt): Likewise.
	* tree-vect-slp.c (vect_get_and_check_slp_defs): Handle reduction.
	(vect_build_slp_tree): Fix indentation. Check that there are no loads
	from different interleaving chains in same node.
	(vect_slp_rearrange_stmts): New function.
	(vect_supported_load_permutation_p): Allow load permutations for 
	reductions. Call vect_slp_rearrange_stmts() to rearrange statements
	inside SLP nodes if necessary.
	(vect_analyze_slp_instance): Handle reductions.
	(vect_analyze_slp): Try to build SLP instances originating from groups
	of reductions.
	(vect_detect_hybrid_slp_stmts): Skip reduction statements.
	(vect_get_constant_vectors): Create initial vectors for reductions
	according to reduction code. Add new argument.
	(vect_get_slp_defs): Add new argument, pass it to 
	vect_get_constant_vectors.
	(vect_schedule_slp_instance): Remove SLP tree root statements.

From-SVN: r158506