Passing function arguments in registers

["Michael P. Hayes" <michaelh at ongaonga dot chch dot cri dot nz>]

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.