Re: [avr-libc-dev] OPTIMIZE_SPEED for avr5?

[Ned Konz]

Joerg Wunsch wrote:
> As David Brown wrote:
>
>   
> > Size is the main priority when you are low on flash space -
> > otherwise, it is irrelevant.  If your chosen AVR has 16k flash, then
> > it does not matter if the program code takes 2k or 15.9k of that
> > flash.  In particular, for smaller devices, program space will be at
> > a premium, while for the larger devices, much of the flash will
> > often be things like tables or other data that is of fixed size.
> >     
>
> The issue here is, to the best of my knowledge, we don't have access
> to the -O level when linking, so we cannot operate depending on the
> user's wishes.  We thus have to decide for *one* implementation that
> goes into the library.
>
>   
if we could get to the -O level when compiling, we could create a 
reference to (or definition of?) an external symbol whose name and/or 
value is dependent on the -O flags used for the compilation. This could 
be used to pull in the appropriate library:

|#ifdef __OPTIMIZE__|
|#ifdef __OPTIMIZE_SIZE__|
   extern void __optimized_for_size(void);

#else
   extern void __optimized_for_speed(void);
#endif
#endif

> Perhaps we could offer different sets of libraries containing these
> functions in their speed-optimized version, in the same sense as we
> are already offering different sets of printf and scanf libraries.
> That way, the users can decide to use a different implementation if
> they prefer (say, -lc is equivalent to -lc_size while there's a
> different -lc_fast available).
>
>