Re: [Sdcc-user] pic16 without stack

[Theblond <the...@fr...>]

Hello,

for this reason, I try to avoid parameters in function calls.

The think I do not understand, the allocation of temporary storage.
Sometimes there is absolutely no need for the, but are allocated anyway.

Theblond

Sébastien Lorquet írta:
> hello,
> 
> I have a question about something I didn't find in the manual.
> 
> With the pic16, we automatically have a stack. The resulting code is huge.
> 
> char foo(char c, char d) {
> return c+d;
> }
> 
> generates:
> ; ; Starting pCode block
> S_main__foo    code
> _foo:
> ;    .line    81; main.c    char foo(char c, char d) {
>     MOVFF    FSR2L, POSTDEC1
>     MOVFF    FSR1L, FSR2L
>     MOVFF    r0x00, POSTDEC1
>     MOVFF    r0x01, POSTDEC1
>     MOVLW    0x02
>     MOVFF    PLUSW2, r0x00
>     MOVLW    0x03
>     MOVFF    PLUSW2, r0x01
> ;    .line    82; main.c    return c+d;
>     MOVF    r0x01, W
>     ADDWF    r0x00, F
>     MOVF    r0x00, W
>     MOVFF    PREINC1, r0x01
>     MOVFF    PREINC1, r0x00
>     MOVFF    PREINC1, FSR2L
>     RETURN
> 
> This is a very big overhead. and every movff counts for 2 instructions.
> 
> But on the contrary, the 8051 port maps its local variables and
> parameters in normal ram, managing the overlaps.
> 
> Why can't we use such a data model for the pic port?
> 
> this would make a much more compact code.
> 
> Regards
> Sebastien
> 
> 
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