Indexed address problem

[saajan dot chana at cambridgeconsultants dot com]

Hello,

We are trying to write a new backend for GCC.  The target machine is
16-bit, with 24-bit pointers.  However, the indexed addressing mode has a
24-bit base and a 16-bit index, so we want to generate RTXs such as

(mem:QI (plus:SI (reg:HI <index>)
                 (reg:SI <base>)))

(mem:HI (plus:SI (mult:SI (reg:HI <index>)
                          (const_int 2))
                 (reg:SI <base>)))

etc.

But I've not managed to get this to work reliably.  Can this be done
relatively painlessly?  Also, we are currently working on a gcc 3.4 branch;
are there any changes in gcc 4.x which would make this easier?

Thanks for your help,

Saajan.



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