argument-list

    One or more of the arguments listed in the following table. For
    each argument, you can specify one or more registers:

    Option       Description

    aligned=<>   Declares one or more registers to be aligned on
                 longword boundaries.
    unaligned=<> Declares one or more registers to be unaligned.
                 Because this is an explicit declaration, this
                 unaligned condition will not produce a fault at
                 run time.
    read=<>      Declares one or more registers, which otherwise the
                 compiler could not detect as input registers, to be
                 read.
    written=<>   Declares one or more registers, which otherwise the
                 compiler could not detect as output registers, to be
                 written to.