Passing function arguments in registers

[Michael P. Hayes]

Jeffrey A Law writes:
 > What exactly are the calling conventions for this target?

The register allocation order is  AR2, R2, R3, RC, RS, RE (then stack).

However, the first and second floating point values are always in R2
and R3 (and all other floats are on the stack).  Structs are always
passed on the stack.