* alias.c (canon_true_dependence): Special case (mem:blk (scratch)).

        * gcse.c (free_insn_expr_list_list): New.
        (clear_modify_mem_tables): Use it.  Fix bit set usage.
        (canon_list_insert): Use EXPR_LISTs for expressions.
        (record_last_mem_set_info): Factor BLOCK_NUM (insn).

From-SVN: r52624