On Mon, Jun 12, 2017 at 7:57 PM, Roland Scheidegger <[email protected]> wrote: > FWIW surely on nv50 you could keep a single mad instruction for umad > (sad maybe too?). (I'm actually wondering if the hw really can't do > unfused float multiply+add as a single instruction but I know next to > nothing about nvidia hw...)
The compiler should reassociate a mul + add into a mad where possible. In actuality, IMAD is actually super-slow... allegedly slower than IMUL + IADD. Not sure why. Maxwell added a XMAD operation which is faster but we haven't figured out how to operate it yet. I'm not aware of a muladd version of fma on fermi and newer (GL 4.0). The tesla series does have a floating point mul+add (but no fma). _______________________________________________ Nouveau mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/nouveau
