GPU instruction set did not need to be as compact as a cpu instruction set. Shader code are small.
So you can add few fields present on all instruction, like itanium does. You could target 64 bits instructions, instead of 32 bits. Beside that, some people did not like conditionnal instruction at all (it was a Linus Torvalds post), because branch prediction is easy to do quite right, but data prediction is need for conditionnal code and it's much harder. http://ondioline.org/mail/cmov-a-bad-idea-on-out-of-order-cpus Out of order cpu looks like an horrible big mess, but if you keep it raisonnable, you can save a lot of cpu cycle without too much hardware (branch prediction, few register renaming) Nicolas 2012/6/25 Timothy Normand Miller <[email protected]>: > On Mon, Jun 25, 2012 at 10:49 AM, Nicolas Boulay <[email protected]> wrote: > >> >> You want conditionnal "Load" and "store" ? >> > > Interesting question. Conditional store, certainly. Conditional > load? Maybe, but we'd have to match the requests with the fetches > exactly. > > It may be that we end up with some meaningless instruction > combinations. The worst that can happen is that if someone programs > the GPU in assembly, they can lock it up. We wouldn't let a compiler > do stupid things. > > -- > Timothy Normand Miller > http://www.cse.ohio-state.edu/~millerti > Open Graphics Project _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
