flow.c (last_mem_set): Delete variable.

flow.c (last_mem_set): Delete variable.

        * flow.c (last_mem_set): Delete variable.  References removed.
        (mem_set_list): New variable.
        (life_analysis): Initialize and finalize alias analysis.
        (propagate_block); Initialize mem_set_list.  Clear for CALL_INSNs.
        (insn_dead_p): For a store to memory, search the entire mem_set_list
        for a match.
        (mark_set_1): Kill entries on the mem_set_list for aliased writes or
        changes to their addresses.  Add new entries to the mem_set_list for
        memory writes writes.
        (mark_used_regs): Kill entries on the mem_set_list which may be
        referenced by a load operation.

Co-Authored-By: Jeffrey A Law <law@cygnus.com>
From-SVN: r24734