RE: [avr-gcc-list] dev and mod may not be optimized

[Weddington, Eric]

> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
> org] On Behalf Of Dmitry K.
> Sent: Tuesday, December 11, 2007 3:44 PM
> To: address@hidden
> Cc: Nathan Moore
> Subject: Re: [avr-gcc-list] dev and mod may not be optimized
> 
> 
> Alas, the usage of div() function is more space and more time
> expansive. The reason is that div() uses an another function:
> __divmodhi4(), i.e. 16-bits.
> 
> Compare two programs:
>   prog1:  150 bytes, 238 clocks
>   prog2:  212 bytes, 316 clocks
> 
> Regards,
> Dmitry.
> 
> -------------------------------------------------------------
> volatile unsigned char a, b, v = 123;
> int main ()
> {
>     unsigned char c = v;
>     a = c / 10;
>     b = c % 10;
>     return 0;
> }
> -------------------------------------------------------------
> #include <stdlib.h>
> volatile unsigned char a, b, v = 123;
> int main ()
> {
>     div_t d;
>     d = div (v, 10);
>     a = d.quot;
>     b = d.rem;
>     return 0;
> }
> --------------------------------------------------------------

Should we implement 2 (or 3) div functions then in avr-libc? 8, 16, and
32 bit?

Eric