loop.c (prescan_loop): Don't check unknown_address_altered when deciding if insert_loop_mem is safe.

	* loop.c (prescan_loop): Don't check unknown_address_altered
	when deciding if insert_loop_mem is safe.  Add BLKmode MEMs
	to loop_store_mems as necessary.
	(loop_invariant_p): Don't check unknown_address_altered
	or unknown_constant_address_altered.

From-SVN: r36045