Re: [avr-gcc-list] How to reserve registers

[Paulo Marques]

Georg-Johann Lay wrote:
> Paulo Marques wrote:
> 
>> push    r0
>> in      r0, SREG
>> push    r1
>> eor  r1, r1
>> push    r2
>>
>> sec
>   ^^^
> Superfluous
> 
>> in   r2, GPIOR0
>> adc  r2, r1
> 
> Why using ADC? AVR has INC (increment by 1) instruction that works with any
> register.

INC doesn't set the carry bit...

>> out     GPIOR0, r2
>> in   r2, GPIOR1
>> adc  r2, r1
> 
> ditto

This is propagating the carry from the previous add, doing a multibyte
increment.

>> out     GPIOR1, r2
>> in   r2, GPIOR2
>> adc  r2, r1
> 
> ditto

ditto :)

>> out     GPIOR2, r2
>> lds  r2, high_counter_byte
>> adc  r2, r1
> 
> ditto

ditto :)

>> sts     high_counter_byte, r2
>>
>> pop  r2
>> pop  r1
>> out  SREG, r0
>> pop  r0
>> reti

-- 
Paulo Marques
Software Development Department - Grupo PIE, S.A.
Phone: +351 252 290600, Fax: +351 252 290601
Web: www.grupopie.com

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