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

[Dmitry K.]

On Saturday 03 March 2007 07:57, Eric Weddington wrote:
> > Today, there is a bit of functions (memset, memcpy and
> > memcpy_P), which are in 2 variants: compact and speed.
> > This acceleration is very effective: a few of progmem
> > words give 10..30% speed increase. I plan to expand this
> > function list slightly.
> >
> > Avr-libc compiles a speed variant for avr3 family only.
> > What about to add avr5? Is there any objections?
>
> Hi Dmitry,
>
> This brings up the overall issue of what should the goal be for avr-libc?
> Speed, or size?
>
> I still lean towards *size* as the number 1 priority for all code, for all
> architectures and devices. When AVR compilers are compared, they are always
> compared on code size, not code speed.

OK, I shall not change any compilation options.
Though a discrepancy remains between avr3 and avr5.

Nevertheless, I shall a little expand the list of functions
where this option is present. Certainly, it can affect a code
only in case of compulsory inclusion of this option. I shall
repeat, that it is a question only of small quantity of functions
which it is often enough used and where such optimization is
effective enough. For example (not commited now):
   memset:          3.5 vs 6 clock/byte, cost= 4 words
   memcpy,memmove:  5.5 vs 8 clock/byte, cost= 5 words
   memcmp:          7.5 vs 10 clock/byte, cost= 6 words
   strlen:          4 vs 5 clock/byte, cost= 2 words

I would not be so categorical in an estimation of a priority
of the size. Eventually, speed is important from the very
beginning of the project, and the size starts to interest only
after overflow of memory.

Dmitry.