> Hi,
>
> thanks for all the input!
> Leon, this really is a cool function. It will go to my collection ;-).
>
> Though I used your version, Steve. Worked out of the box!
> Why does it say "+r" ?
I think the "+r" means that it is both an input and an output, allowing it
to be initialised at the C level ("unsigned char tmp = 0"). Of course, this
initialisation is not actually needed, since all 8 bits of the original tmp
get shifted out, so an instruction could be saved by using plain "unsigned
char tmp;", and changing to "=r".
David
> And, perhaps you could add the "gcc manual hint" to the 1.ยง in chapter 6
(didn't
> even had the idea to look there, too).
>
> Greetz and thanks,
>
> Georg
>
>
> Steve Underwood wrote:
> > Hi Georg,
> >
> > I haven't tested this, but to embed the assembly language you need
> > something like the following. If you look in the mspgcc documentation
> > you will find some information about this. If you look in the GNU GCC
> > documentation you will find some more. However, this area is not as well
> > documented as it might be, with clear examples, etc. Figuring out
> > exactly how to use those dependency fields is not easy.
> >
> > Regards,
> > Steve
> >
> > unsigned char reverse(unsigned char b)
> > {
> > unsigned char tmp = 0;
> >
> > for( i=0; i<8; i++ )
> > {
> > __asm__ (
> > " rrc.b %[b] \n"
> > " rrl.b %[tmp] \n"
> > : [tmp] "+r"(tmp)
> > : [b] "r"(b));
> > }
> > return tmp;
> > }
> >
> > Georg Ritter wrote:
> >
> >> Good morning!
> >>
> >> I'm looking for a proper implementation of a bitwisereverse function
> >> of a byte (1010 0001 becomes: 1000 0101). I want to replace an ugly
> >> and clumpsy function I used in testing.
> >>
> >> I would like to write smth like:
> >>
> >> unsigned char reverse(unsigned char b)
> >> {
> >> unsigned char tmp=0;
> >> for( i=0; i<8; i++ )
> >> {
> >> // RRC.B of b
> >> // RRL.B into tmp
> >> }
> >> return tmp;
> >> }
> >>
> >> There's no real "C" way of doing it, isn't it? So what could the
> >> inline asmbly line for that look like. I never used it before, and
> >> it's tricky and documents didn't enlighten my too much. So my versions
> >> either didn't compile or didn't work.
> >>
> >> Or is there a smaller (in terms of code size) way of doing the
> >> reversion (hacker contest ;-) )?
> >..
>
>
>
>
> -------------------------------------------------------
> The SF.Net email is sponsored by EclipseCon 2004
> Premiere Conference on Open Tools Development and Integration
> See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
> http://www.eclipsecon.org/osdn
> _______________________________________________
> Mspgcc-users mailing list
> Mspgcc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/mspgcc-users
>
>
>
