On Sat, Mar 27, 2010 at 02:11:54AM +0100, Marek Olšák wrote: > > From the driver point of view, we don't have to work on the GLSL compiler > itself. The Mesa state tracker compiles GLSL to an assembler-like language > called TGSI which is then translated ([1]) to the R300 compiler ([2]) shader > representation. The more TGSI we handle, the more GLSL support we get. > > So now the status. r300g GLSL is missing the following features: > > 1) Branching and looping > > This is the most important one and there are 3 things which need to be done. > * Unrolling loops and converting conditionals to multiplications. This is > crucial for R3xx-R4xx GLSL support. I don't say it will work in all cases > but should be fine for the most common ones. This is kind of a standard in > all proprietary drivers supporting shaders 2.0. It would be nice have it > work with pure TGSI shaders so that drivers like nvfx can reuse it too and I > personally prefer to have this feature first before going on. > * Teaching the R300 compiler loops and conditionals for R500 fragment > shaders. Note that R500 supports the jump instruction so besides adding new > opcodes, the compiler optimization passes should be updated too (I think > they haven't been designed with loops in mind). > * The same but for R500 vertex shaders. The difference is conditionals must > be implemented using predication opcodes and predication writes (stuff gets > masked out). I think this only affects the conversion to machine code at the > end of the pipeline. > > 2) Derivatives instructions fix > > It's implemented but broken. From docs: "If src0 is computed in the previous > instruction, then a NOP needs to be inserted between the two instructions. > Do this by setting the NOP flag in the previous instruction. This is not > required if the previous instruction is a texture lookup." .. and that > should be the fix. > > 3) Perspective, flat, and centroid varying modifiers, gl_FrontFacing > > I think this is specific to the rasterizer (RS) block in hw ([3]). > > [1] src/gallium/drivers/r300/r300_tgsi_to_rc.c > [2] src/mesa/drivers/dri/r300/compiler/ > [3] src/gallium/drivers/r300/r300_state_derived.c >
Thanks. This is really helpful. I am in the process of looking through the code and some of the documentation. I'll respond with some questions when I start writing my proposal. -Tom ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
