Remove SLP_INSTANCE_GROUP_SIZE

Remove SLP_INSTANCE_GROUP_SIZE

This removes the SLP_INSTANCE_GROUP_SIZE member since the number of
lanes throughout a SLP subgraph is not necessarily constant.

2020-05-13  Richard Biener  <rguenther@suse.de>

	* tree-vectorizer.h (SLP_INSTANCE_GROUP_SIZE): Remove.
	(_slp_instance::group_size): Likewise.
	* tree-vect-loop.c (vectorizable_reduction): The group size
	is the number of lanes in the node.
	* tree-vect-slp.c (vect_attempt_slp_rearrange_stmts): Likewise.
	(vect_analyze_slp_instance): Do not set SLP_INSTANCE_GROUP_SIZE,
	verify it matches the instance trees number of lanes.
	(vect_slp_analyze_node_operations_1): Use the numer of lanes
	in the node as group size.
	(vect_bb_vectorization_profitable_p): Use the instance root
	number of lanes for the size of life.
	(vect_schedule_slp_instance): Use the number of lanes as
	group_size.
	* tree-vect-stmts.c (vectorizable_load): Remove SLP instance
	parameter.  Use the number of lanes of the load for the group
	size in the gap adjustment code.
	(vect_analyze_stmt): Adjust.
	(vect_transform_stmt): Likewise.