max_args=number

    Maximum number of arguments the called procedure expects. The
    compiler uses this value as the number of longwords it allocates
    in the fixed temporary region of the stack frame, if the argument
    list must be homed. If homing is not necessary, the max_args
    count is not required. The compiler flags procedure entry
    points, where max_args has not been specified, that require homed
    argument lists.

    Note that, for .CALL_ENTRY routines in which max_args exceeds
    14, the compiler uses the received argument count, or max_args,
    whichever is smaller, when homing the argument list.

 home_args=TRUE|FALSE

    Indication to the compiler that the called procedure's argument
    list should or should not be homed. The home_args argument
    overrides the compiler's default logic for determining the
    circumstances under which an argument list must be homed.

 quad_args=TRUE|FALSE

    Indication to the compiler that the called procedure's argument
    list will have quadword references.

 input=<>

    Register set that indicates those registers from which the
    routine receives input values.

    This register set informs the compiler that the registers
    specified have meaningful values at routine entry and are
    unavailable for use as temporary registers even before the first
    compiler-detected use of the registers. Specifying registers in
    this register set affects compiler temporary register usage in
    this case:

    o  If you are explicitly using any of the Alpha or Itanium
       registers (R13 and above).

    In either of these cases, if you do not specify a register that
    is being used as input in the input argument, the compiler may
    use the register as a temporary register, corrupting the input
    value.

    This register set has no effect on the compiler's default
    register preservation behavior.

 output=<>

    Register set that indicates those registers to which the routine
    assigns values that are returned to the routine's caller.
    Registers included in this register set are not saved and
    restored by the compiler, even if they are modified by the
    routine.

    This register set also informs the compiler that the registers
    specified have meaningful values at routine exit and are
    unavailable for use as temporary registers even after the last
    compiler-detected use of the registers. Specifying registers in
    this register set affects compiler temporary register usage in
    this case:

    o  If you are explicitly using any of the Alpha or Itanium
       registers (R13 and above).

    In either of these cases, if you do not specify a register that
    is being used as output in the output argument, the compiler may
    use the register as a temporary register, corrupting the output
    value.

 scratch=<>

    Register set that indicates registers that are used within the
    routine but which should not be saved and restored at routine
    entry and exit. The caller of the routine does not expect to
    receive output values nor does it expect the registers to be
    preserved. Registers included in this register set are not saved
    and restored by the compiler, even if they are modified by the
    routine.

    On OpenVMS I64 systems, the compiler will not use these registers
    as temporary registers.  On OpenVMS x86-64, the compiler will never
    use the Alpha registers as temporary registers.

 preserve=<>

    Register set that indicates those registers that should be
    preserved over the routine call. This should include only those
    registers that are modified and whose full 64-bit contents should
    be saved and restored.

    This register set causes registers to be preserved whether or
    not they would have been preserved automatically by the compiler.
    Note that because R0 and R1 are scratch registers, by calling
    standard definition, the compiler never saves and restores them
    unless you specify them in this register set. Registers R16 and
    above are not allowed.

    This register set overrides the output and scratch register sets.
    If you specify a register both in the preserve register set and
    in the output or scratch register sets, the compiler will report
    the warning:

    %AMAC-W-REGDECCON, register declaration conflict in routine A

 label=name

    Optionally specify a label as in a VAX MACRO .ENTRY directive. This
    can be used if a module is to be common between OpenVMS VAX and
    OpenVMS Alpha; OpenVMS I64; or OpenVMS x86-64, if the OpenVMS VAX
    version needs to reference the entry with a .MASK directive, and if
    the OpenVMS Alpha; OpenVMS I64; or OpenVMS x86-64 version needs to
    use one or more of the special .CALL_ENTRY parameters. When the
    label parameter is specified and the symbol VAX is defined, an
    .ENTRY directive is used. If the symbol VAX is not defined, it
    creates the label and does a normal .CALL_ENTRY. Note that label is
    not the first parameter. Therefore, you cannot simply replace
    .ENTRY with .CALL_ENTRY. You must use the label parameter
    declaration.