On 26.03.2011 21:52, Denis Steckelmacher wrote: > Hello, > > After some messages on this list, I reconsidered my GSoC proposal and decided > to give a try at an OpenCL state tracker. I will base my work on the Clover > branch of Mesa. > > I read its code, which is very well-done and clean, but I saw one big > difficulty : I don't know how to translate LLVM IR to TGSI. The big problem > is > that TGSI is made mostly with OpenGL in mind. We can use it to decode video > frames using vertex and fragment shader stages, but using it to run on the > GPU > the complex output given by LLVM, and without using any part of the OpenGL > pipeline (OpenCL can be used to do mathematics, and that doesn't draw > anything > on the screen), is tricky. > > The problem is how OpenCL can upload data on the GPU and then download the > computed results. One solution may be to create one or more textures > containing the input data (maybe one texture by input data type), and then > use Gallium has pipe_resource. You'd create them for device memory allocations and hand them (or their addresses) to the compute program (not a shader) which would write to / load from a global memory location lying within such a resource (or you might say write to the resource). Then you just map it to read stuff out if you need to.
> a fragment shader to compute the resulting values and to put them in a render > buffer that will never be drawn on screen but instead downloaded from the GPU > and sent back to the application. > > I don't know if it would be possible to do things like that, especially > considering that precise results across all graphics cards may be difficult > to > get with OpenGL. An other problem of this LLVM to TGSI conversion is that the > TGSI instruction set is not completely implemented on all the pipe drivers, > and that unimplemented instructions may be needed by a specific LLVM IR > instruction. > > I'm open to any suggestion regarding this OpenCL state tracker. If you say it > will be very difficult to do that during the summer, I think I will apply to > work on the OpenGL 3+ support in Mesa (without doing a new state tracker) and > the GLSL compiler. > > Best regards, > Denis Steckelmacher. > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
