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petrm

While Loop Eficiency.....

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Hi, example (C2C+ 5.5.1):

     while (pir1 & 100000b);

compiler makes:

label_0070
btfss _pir1, 5
goto label_0071
goto label_0070
label_0071

This is absolutely OK.

 

But if I want this:

     while (~pir1 & 100000b);  (or while ((pir1 & 100000b))!=1; )

compiler makes:

label_0058
comf _pir1, W
andlw D'32'
sublw 0
btfsc STATUS, Z
goto label_0059
goto label_0058

instead of: (it's enough simply :)

label_58
btfsc _pir1,5   
goto label_59   
goto label_58
label_59

 

Is there some way, how to "learn :)" compiler to make this better code ?

 

Of course, this is only some instr. more than in asm, but sometimes is this important.

Regards PetrM.

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