Jason Ekstrand <ja...@jlekstrand.net> writes: > On May 25, 2018 15:19:25 Matt Turner <matts...@gmail.com> wrote: > >> On Thu, May 24, 2018 at 2:56 PM, Jason Ekstrand <ja...@jlekstrand.net> wrote: >>> From: Francisco Jerez <curroje...@riseup.net> >>> >>> The hardware's control flow logic is 16-wide so we're out of luck >>> here. We could, in theory, support SIMD32 if we know the control-flow >>> is uniform but we don't have that information at this point. >> >> This is what the "fork" instruction is for on Gen6 :) > > Yeah, Curro pointed that out too... > >
The main problem about the fork instruction is that it prevents the compiler from interleaving code from the low and high channel groups within control flow, which largely defeats the purpose of SIMD32 of amortizing instruction latency costs. The other problem is that it would involve substantial effort and it is... well... SNB-specific, earlier platforms still won't get support for non-uniform control flow in SIMD32, and newer platforms don't need it. Probably not worth the effort... > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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