On Wednesday 31 July 2002 01:09 pm, Aaron wrote:

> People think assemblers are hard?  I always imagined that it'd be a
> lot easier to write an assembler than a compiler.  I'm a biologist,
> not a computer scientist or elec engineer, but I always thought
> that you don't do more than superficial optimization within an
> assembler, but simply translate human-readable opcodes, like
> translating "returnTop" in SqVM assembly to the byte 7C.

It can be more complicated than just translating opcodes.

For instance, you could do register/RAM allocation (overlaying 
function temps, for instance); on the PIC you have to deal with a 
banked program space as well as a banked RAM/register space. So you 
have to be able to stretch instructions for the extra bytes needed 
for extended jumps/calls or RAM references. Which may cause other 
jumps to have to become extended jumps.

A clever assembler could try to arrange all the RAM used by a 
particular function to be on the same RAM page, and all the functions 
called to be in the same ROM page.

-- 
Ned Konz
http://bike-nomad.com
GPG key ID: BEEA7EFE