PR tree-optimization/82604

	PR tree-optimization/82604
	* tree-loop-distribution.c (enum partition_kind): New enum item
	PKIND_PARTIAL_MEMSET.
	(partition_builtin_p): Support above new enum item.
	(generate_code_for_partition): Ditto.
	(compute_access_range): Differentiate cases that equality can be
	proven at all loops, the innermost loops or no loops.
	(classify_builtin_st, classify_builtin_ldst): Adjust call to above
	function.  Set PKIND_PARTIAL_MEMSET for partition appropriately.
	(finalize_partitions, distribute_loop): Don't fuse partition of
	PKIND_PARTIAL_MEMSET kind when distributing 3-level loop nest.
	(prepare_perfect_loop_nest): Distribute 3-level loop nest only if
	parloop is enabled.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@256990 138bc75d-0d04-0410-961f-82ee72b054a4