How to define different base register classes?

[Irit Mano]

Hi,

I'm writing a GCC based compiler for the CompactRISC CR16C architecture.
This architecture supports (among others) the following addressing modes:
1. base register + optional displacement
2. index register + base register + optional displacement
The definition "base register" in cases 1 and 2 is different (2 is a subset of 1).

Is there a way to tell GCC (using target macros other other method) about these
2 different classes?

Thanks for your help,

Irit Mano
CompactRISC compiler team
National Semiconductor