Re: [avr-libc-dev] volatile in pgmspace.h ?

[E. Weddington]

> >  > __LPM_enhanced__ should use "lpm %0,Z" (not Z+).
> >
> >This was added because of a request to add other macros 
to
> >allow further contiguous reads of flash without having to
> >provide the address. I knew that this was only going to 
be
> >available for the enhanced cores. I wrote an RFC to this
> >list, with little response:
> ><http://mail.nongnu.org/archive/html/avr-libc-dev/2003-
> >06/msg00002.html>
> >However, I haven't implmented this yet. If you feel that
> >they shouldn't be implmented, let me know. I am not
> >attached to it either way.
> 
>  From my opinion, the most used case is the reading of 
several bytes, 
> not only one.
> Then the Z+ would be useful for the optimizer.
> If the Z-pointer is not changed, it stays at the same 
adress. I can 
> hardly imagine a case, where this is useful.
> The Z+ does cost the same time as without increment.
> 
> Are there any other reasons, for a decision?

True. But as Marek pointed out, it cannot be guaranteed 
that GCC will *not* change the contents of Z between calls 
to inline assembly, even if it seems unlikely. If this 
cannot be guaranteed, then any advantage of having those 
extra _next macros would be moot. This is the main reason 
for not including them in avr-libc.

Eric