I as remember, volatile loops were discussed a while ago.
Check the code below.
cheers
~d
P.S. this is a bad programin' technique... i suppose...
volatile short *pbuf, *plast;
int main(void)
{
short buf[10];
pbuf = buf;
plast = buf + 10;
while(pbuf < plast)
__asm__ __volatile__
("; nop %0,%1"
:
"+m" (pbuf),
"+m" (plast) : );
return 0;
}
On Tuesday 06 April 2004 21:43, Matthias Weingart wrote:
> On Tue, Apr 06, 2004 at 11:33:28AM -0500, Sergei Sharonov wrote:
> > volatile short *pbuf, *plast;
> >
> > pbuf = buf;
> > plast = buf + 10;
> > while(pbuf < plast);
>
> This compiles to
>
> 1494: 82 41 26 02 mov r1, &0x0226 ;
> 1498: 0e 41 mov r1, r14 ;
> 149a: 3e 50 14 00 add #20, r14 ;#0x0014
> 149e: 82 4e 28 02 mov r14, &0x0228 ;
> 14a2: 0f 41 mov r1, r15 ;
> 14a4: 0f 9e cmp r14, r15 ;
> 14a6: fe 2b jnc $-2 ;abs 0x14a4
>
> It does update pbuf and plast, but then use the values hold in the
> registers to do the while loop - what is obviously wrong. When you change
> plast in a int.routine the while loop will never get any notice of this.
> Sergei was right. A little bit to much optimisation. ;-)
>
> Matthias
>
>
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