Re: Re[2]: [avr-gcc-list] Re: GCC-AVR Update (20082003)

[Theodore A. Roth]

On Mon, 25 Aug 2003, Keith Gudger wrote:

> Here are some recent numbers:
>
> ON my application, a USB HID device implemented in the AT43USB355, in IAR
> it takes 12K, in avr-gcc, it takes 16K.
>
> The difference is that IAR has "cross-call optimization".  What this does
> is look for common code snippets.  If they're longer than 2-3 words (I'm
> guessing) they substitute a rcall.  It really helps in my code.  It only
> seems to work inside of each source file, so your source files need to be
> larger than you might think is optimum.  Part of why it works for me is
> that a lot of the USB functionality is packed in just a couple of files,
> giving fodder to this optimizer.

Just out of curiousity, what kind of performance hit do you take
because of this? Every rcall/ret is going to cost you 7 clock cycles
with 4k of code doing this, it seems like it would add up fairly
quick. Can you disable this optimization is speed critical code
sections?

Ted Roth