Terry Harris escreveu:
> On Fri, 03 Jul 2009 20:14:13 -0300, you wrote:
>
>   =

>> OK, explain this under this theory:
>>
>> Look how they do 'Var =3D 0;' :
>>
>> bcf    STATUS,C
>> *movlw*   0
>> btfsc   STATUS,C
>> *movlw*   1
>> movwf   Var
>>     =

>
> Evaluate the right hand expression and put the result in something just b=
ig
> enough (in this case the carry flag). Copy the result to the lvalue.
>   =


Makes absolutely no sense. It is testing something itself set hard
coded. And there are two movlw, the expression doesn't have any
conditionals.


>> 'Var =3D 1;'
>>
>> clrf   Var
>> bsf   STATUS,C
>> rlf   Var,f
>>     =

>
> Same again although I don't know why it chose a different method to copy.

Just to grow the code, perhaps?

>> 'Var =3D 2;'
>>
>> clrw
>> iorlw   2
>> movwf   Temp
>> movf   Temp,w
>> movwf   Var
>>     =

>
> Same again but the expression needs a file to hold the result. =

>
> It seems the compiler is being smart recognising constant expressions of 0
> and 1 will fit in a bit and treating them differently. The generated code
> looks dumb but I presume provides more scope of optimisation by the bit of
> the compiler you didn't buy. =

>   =


The temporary location seems reasonable in unoptimized code, but why
load w in a such awkward way?

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