Re: [avr-gcc-list] Compiler error creating ISR prologue?

[darkschine]

I stand corrected.
It's not often that you need to check for Z result after a clr.
I always thought it was a way of clearing a register while preserving SREG
(since the programmer will know what the result will be anyway)
I guess you would use [ldi 0x00] for that


mrtangent wrote:
> 
> Yes, CLR affects SREG (S, V, N, Z).
> 
> See <http://www.atmel.com/dyn/resources/prod_documents/doc0856.pdf>
>       page 11 (Instruction Set Summary)
>       page 54 (CLR – Clear Register)
> 
> CLR is just a convenient shorthand for EOR, where the two operands happen
> to be the same register.
> 
> Cheers,
> 
> --Dave
> 
> On Aug 14, 2010, at 1:39 AM, darkschine wrote:
> 
>> 
>> Are you sure that "clr" has an impact on SREG? I think you should double
>> check...
>> 
>> 
>> Johannes Bauer wrote:
>>> 
>>> On 12.08.2010 18:13, Johannes Bauer wrote:
>>> 
>>>> This appears to be strange to me. The "clr r1" instruction should IMO
>>>> be
>>>> placed after the first "push r0" instruction.
>>> 
>>> You are wrong, Johannes. It appears to you that the "clr r1" instruction 
>>> should be placed after the SREG has been pushed (obviously, as clr also 
>>> clears the SREG flags).
>>> 
>>> But otherwise, I still think there's a bug :-)
>>> 
>>> Regards,
>>> Johannes
>>> 
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>>> 
>> 
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