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
two cases:
o If you are using the VAXREGS (OpenVMS Alpha only) optimization
option. This optimization allows the compiler to use as
temporary registers any of the VAX registers which are not
explicitly being used by the VAX MACRO code.
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. If you are not using the VAXREGS
optimization switch or any of the Alpha registers, the input mask
is used only to document your routine.
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
two cases:
o If you are using the VAXREGS (OpenVMS Alpha only) optimization
switch. This optimization allows the compiler to use as
temporary registers any of the VAX registers which are not
explicitly being used by the VAX MACRO code.
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.
This also pertains to the compiler's temporary register usage.
On OpenVMS Alpha systems, the compiler may use registers R13 and
above as temporary registers if they are unused in the routine
source code. Because R13 through R15 must be preserved, if
modified, on OpenVMS Alpha systems, the compiler preserves those
registers if it uses them.
However, if they appear in the scratch register set declaration,
the compiler will not preserve them if it uses them as temporary
registers. As a result, these registers may be scratched at
routine exit, even if they were not used in the routine source
but are in the scratch set. If the VAXREGS (OpenVMS Alpha only)
optimization is used, this applies to registers R2 through R12,
as well.
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 or OpenVMS I64, if the OpenVMS VAX version
needs to reference the entry with a .MASK directive, and if the
OpenVMS Alpha or OpenVMS I64 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.