On Mon, May 11, 2015 at 3:29 PM, Roland Scheidegger <srol...@vmware.com> wrote: > Reviewed-by: Roland Scheidegger <srol...@vmware.com> > > As for b2i I'm not really convinced using INEG is preferable there. > Generally I'd favor logic ops over arithmetic any day. > I suppose backend probably need to try to recognize such patterns anyway > for best performance (so that for instance things like b2i->i2b should > be no-ops), and I just don't see that INEG using AND instead would help > much there in general. But I don't really know...
Well, there are a number of instructions that can take "neg" modifiers (like add, mul, mad). None that can take "& 1" modifiers (although and/etc can take "not" modifiers). By the time things get to gallium, the bool-ness of variables is lost, so it can be tricky to figure if & 1 really means "b2i" or if it really means "random value & 1". I guess bool's are always produced by comparisons, so you could just key it off of whether the random value is produced by a set or not. [I'm already planning a similar hack for "& 1.0", where the set instruction can actually produce the 1.0 value directly if told so.] I'm curious why you prefer bit manipulation over arithmetic? I have the opposite preference... -ilia _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
