Re: [f-cpu] calling conventions

[Ben Franchuk <bfranchuk@jetnet.ab.ca>]

Michael Riepe wrote:

> With respect to the memory load/store capabilities (or inabilities) of the
> F-CPU, I think that passing arguments in registers is the best choice.
> The other simple alternative - putting all arguments on the stack -
> will be much slower (and also produce longer code).

Mind you other than FORTH and dumb little functions like 
strlen() or strcat() most functions take a long time to 
execute compared to entry and exit times. I suspect that a lot
of slow routines are more do to poor Instruction set architecture
than coding style. Take a compare operation like A = C > F; for a
typical 8 bit CPU. 

ld   hl,C
push hl
ld   hl,F
call compare
st   F,hl

Stack or register parameter passing will not make up for a poor
instruction
set if you have a rather high number of subroutines that perform dumb
simple tasks that a better architecture could handle. It is not the time
a instruction executes, but rather the unknown latency of the entire
system that is critical. 
 
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html
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