[sdcc-devel] Having __far pointers that are wider than generic pointers?

[Philipp K. K. <pk...@sp...>]

For the Rabbit ports, I'm considering introducing memory models where
__far pointers are wider than generic pointers. I.e. the __far address
space would be a superset of the generic address space.
AFAIK, no other port currently does this. Will this cause problems?

Reasons:

The Rabbits have efficient access to a 16-bit address space. But
acessing a wider access space needs to be done using special
instructions. So we might want a memory model where we have efficient
memory access by default, and only use the special instructions when
accessing something in __far space. This is also how Dynamic C, the
compiler provided by the Rabbit vendor, does it.

The alternative would be a mcs51-like approach, where we have __near
pointers for access to the 16-bit address space, and any unqualified
pointer points to __far by default. Like for mcs51, this would make
using generic pointers less efficient.

Philipp