Re: [avr-gcc-list] More observations: array of pointers to functions

[Paulo Marques]

David McNab wrote:
> On Mon, 2007-02-26 at 13:22 -0700, Eric Weddington wrote:
> > The line that you have above does some pretty needles math. You should be
> > able to just simply do:
> >
> >     fptr = (FuncPtr)pgm_read_word(&funcs_table[i]);
> >
> > Does that make any difference in the size of your code? It would be
> > interesting to know one way or the other...
>
> The above option generates a whole lot more code.
>
> I posted my code earlier because I found that while it's not the most
> elegant C, it does generate the smallest code with gcc-avr at -O3

It might not make a difference here, but you keep saying things like 
"but caused severe code bloat, even at -O3."

-O3 is supposed to be _fast_, not _small_. For small code you should use 
-Os.

For a good size / speed compromise, just use -O2. With -O3 the compiler 
is allowed to do whatever it needs to do to increase performance, 
including loop unswitching, more agressive inlining, etc., even if it 
costs a lot of code size.

As for your particular problem, check the simple code from Joerg Wunsch 
as it seems to give the most optimal assembly possible for your problem.

--
Paulo Marques
Software Development Department - Grupo PIE, S.A.
Phone: +351 252 290600, Fax: +351 252 290601
Web: www.grupopie.com

"The face of a child can say it all, especially the
mouth part of the face."