Re: [avr-gcc-list] GCC 3.0.2 unsigned int bug?

[Dmitry]

The compiler does the right thing on the loop unrolling pass.
It does 32 iterations where it can reach the value of 1024.

try to recompile this file with d less than 1024 and d=1024+something.

have fun,
D.


On Mon, 17 Dec 2001 14:06:09 -0600
Chris Elmquist <address@hidden> wrote:

> 
> I'm new here... just playing around with avr-gcc 3.0.2 on
> Linux.
> 
> I'm having trouble understanding this:
> 
> void delay(void)
> {
>         unsigned int d;
> 
>         d = 0x1000;
>         while (d) d--;
> }
> 
> generates this code (using avr-objdump --disassemble):
> 
> 0000004a <delay>:
>   4a:   80 e0           ldi     r24, 0x00       ; 0
>   4c:   90 e1           ldi     r25, 0x10       ; 16
>   4e:   80 50           subi    r24, 0x00       ; 0
>   50:   94 40           sbci    r25, 0x04       ; 4
>   52:   e9 f7           brne    .-6             ; 0x4e
>   54:   08 95           ret
> 
> I can clearly see that the MSB goes in r25 and the LSB in r24
> but then why does it subtract 0x04 from the MSB each iteration?
> 
> Suspecting maybe a disassembler problem, the '94 40' opcode
> indeed would subtract 0x40 from the MSB wouldn't it?
> 
> Am I missing something obvious here or is this a bug?
> 
> Chris
> -- 
> Chris Elmquist      mailto:address@hidden     http://www.pobox.com/~chrise
> 
> _______________________________________________
> avr-gcc-list mailing list
> address@hidden
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> 


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