gcse.c (modify_pair): Define.

	* gcse.c (modify_pair): Define.  Define a VEC of it.
	(canon_modify_mem_list): Convert to an array of VECs.
	(free_insn_expr_list_list): Delete.
	(clear_modify_mem_tables): Call VEC_free instead.
	(record_last_mem_set_info): Don't modify canon_modify_mem_list.
	(alloc_gcse_mem): Adjust for canon_modify_mem_list change.
	(canon_list_insert, compute_transp): Likewise.

From-SVN: r171980