Re: [avr-gcc-list] Optimization?

[MWP]

I wouldnt be supprised if it has somthing to do with incr k, but then not
using it. I cant answer why it works with O3 tho... weird.

try using asm("nop") instead of incr k;

MWp

On Mon, 12 Nov 2001, Patrick Lanphier wrote:

> Well the below code works fine, flashing that is, when using the -O3
> optimization but does not work with -O1 optimization, I don't understand.
> 
> 
> /**************************************************************************
> 
> avr-gcc -O0 -mmcu=at90s2313 -c demo2.c -o main.o
> avr-gcc -o main.elf main.o
> avr-objcopy -O ihex main.elf main.hex
> 
> ***************************************************************************/
> 
> #include <io.h>
> #include <interrupt.h>
> #include <sig-avr.h>
> 
> int main(void)
> {
>   uint8_t f,i, j, k;
> 
>   outp(255, DDRB);           /* port B all outputs */
>   outp(0, PORTB);          /* turn all leds off  */
> 
>   while(1){
>     outp(0, PORTB);        // turn led on
>     for(f=0; f<255; f++)      // delay
>       for(i=0; i<255; i++)
>         for(j=0; j<255; j++)
>           k=k+1;
>     outp(255, PORTB);          // turn led off
>     for(f=0; f<255; f++)        // delay
>       for(i=0; i<255; i++)
>         for(j=0; j<255; j++)
>           k=k+1;
>   }
> }
> 
> Patrick Lanphier
> The Artemis Group
> http://www.artemisgroup.com
> phone: 814-235-0444
>   fax: 800-582-9710
> 
> 
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