Passing function arguments in registers

[Jeffrey A Law]

  In message < 199710100357.QAA01814@ongaonga.chch.cri.nz >you write:
  > Michael Meissner writes:
  >  > Michael P. Hayes writes:
  >  > | 
  >  > | The c4x port I have been working on requires a weird function argument
  >  > | passing model to be compatible with the vendor's compiler.  The order
  >  > | that registers are allocated depends on the number of floating point
  >  > | arguments passed.  To date, I have hacked calls.c and function.c to
  >  > | include a macro FUNCTION_ARG_PRESCAN, which is used during a first
  >  > | pass scan to allow the backend to determine the types of arguments to
  >  > | expect.  Can someone suggest a better strategy or have I missed
  >  > | something obvious?
  >  > 
  >  > You don't need it.  You can do it via INIT_CUMULATIVE_ARGS and
  >  > INIT_CUMULATIVE_INCOMING_ARGS.  See rs6000/rs6000.{h,c} for something
  >  > similar, where we need to know whether it is call a prototyped
  >  > function or not.
  > 
  > I had considered this approach but the problem is if there is no
  > prototype, the argument types are unknown in advance, without using a
  > pre-scan pass.
What exactly are the calling conventions for this target?

jeff