On Thu, Jan 19, 2017 at 12:40 PM, Nicolai Hähnle <nicolai.haeh...@amd.com> wrote: > On 19.01.2017 17:50, Ilia Mirkin wrote: >> >> NVIDIA can't do division either (double or otherwise - but double is >> even worse since the rcp is only half there). It has some fancy >> functions which get things like division, sqrt, etc. > > > What does that mean, precisely? It might make sense to have a cap-bit after > all, and then if somebody can be bothered to do it, have the front-end > generate TGSI for the kind of Newton-Raphson code that LLVM implements for > GCN.
Well, there are 2 64-bit "special" (i.e. beyond add/mul/fma/conversion) operations available - "rcp64h" and "rsq64h". These operations consume a double, and produce the high 32 bits of the result. Everything else has to be done by hand. For rcp/rsq, that means newton-raphson steps, for sqrt and div, that can mean a lot more, depending on how accurate you want it. IMHO this is something that should be left up to the drivers. Cheers, -ilia _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
