On Mon, 12 Sep 2011 12:58:52 +0200 francesco.gring...@ing.unibs.it wrote: > On Sep 12, 2011, at 12:35 PM, Michael Büsch wrote: > > > On Mon, 12 Sep 2011 12:09:01 +0200 > > francesco.gring...@ing.unibs.it wrote: > > > >> but trying on a = 0x8000 and b = 0x7fff helped me understanding. a - b = > >> 0x8000 + 2'(0x7fff) = 0x0001 > 0. While 0x8000 < 0x7fff. > > > > I don't get it. > > Can you write simple pseudocode for your instruction? > Will try for jdn. > > > For example, for jls, we have this pseudocode: > > > > if (xxx < yyy) > > pc := jjj > > (where xxx and yyy are two's complement) > > > > ** jump if difference is negative > > 0d6 xxx yyy jjj > > if ( xxx - yyy < 0 ) > pc := jjj > > C-pseudocode for jdn > > short c = xxx - yyy; > if ( c < 0 ) > goto jjj;
Ok. So the existing signed-compare jumps look at the carry of the subtraction operation, but the new jdX instructions look at bit 0x8000 of the subtraction result. (if set -> negative, otherwise positive). jdX ignores the carry. Did I get it now? -- Greetings, Michael. _______________________________________________ b43-dev mailing list b43-dev@lists.infradead.org http://lists.infradead.org/mailman/listinfo/b43-dev
