Chaipi Wijnbergen wrote:
>
> Dear PIC experts,
>
> I am using CCS PCM C compiler. I looked at the assembly that it generated
> and did not understand something, maybe you can help me with it.
>
> When I wrote :
>
>     i++;
>
> It compiled it into :
>
>     movf i, W
>     incf i, F
>
> And when I wrote:
>
>     i--;
>
> It compiled it into :
>
>     movf i, W
>     decf i, F
>
> All instructions movf/decf/incf modify only the Z flag, so it can be used
> the same way later as a test for branching, there is no extra information
> on the status register supplied by the movf instructions, only W register
> now holds the previus data of i, which was not used at all.
>
> Any idea why is the MOVF infront of incf/decf ?
>
> Thanks Chaipi
>                                \\\|///

Perhaps, because you're doing "post-increment". So the compiler preserves
the old value of the variable, in case you say :

        a = i++;

in this case, the old value of "i" is stored in "a".

Try, what happens, if you say "++i", i.e. "pre-increment" ?
Does it generate a different sequence? It should!

Wolfram


+-----------------------------------------------+
! Wolfram Liebchen, liebchen@ipserv.ffo.fgan.de !
!      Forschungsinstitut fuer Optik            !
!      Schloss Kressbach                        !
!      D-72072 Tuebingen                        !
!      Tel: +49 (0)7071 / 709-158               !
!      Fax: +49 (0)7071 / 709-270   (G3 / G4)   !
+-----------------------------------------------+