As a further example that just came to mind, nv40 (GeForce 6-7 and PS3 RSX) supports control flow in fragment shaders, but does not apparently support the "continue" keyword (since NV_fragment_program2, which maps almost directly to the hardware, does not have it either).
I implemented TGSI control flow in a private branch, but did not implement the "continue" keyword. Implementing "continue" requires to transform the code to generate and carry around "should continue" flags, or perform even less trivial transformations including code duplication. Unfortunately, doing requires non-local modifications, and thus would require to do something beyond just scanning the TGSI source code as the nv30/nv40 driver currently does. If there was a TGSI->LLVM->TGSI module, the LLVM->TGSI control flow reconstruction would already handle this, and it would be enough to tell it to not make use of the "continue" instruction: it would then automatically generate the proper if/endif structure, duplicating code and/or introducing flags as needed in a generic way. As things stand now, I'm faced with either just hoping the GLSL programs don't use "continue", implementing an hack in the nv40 shader backend (where such an high-level optimization does not belong at all and can't be done cleanly), or writing the LLVM module myself before tackling this. With an LLVM-based infrastructure, there would be a clear and straightforward way to solve this, will all the supporting infrastructure already available and the ability to create an optimization pass reusable by other drivers that may face the same issue. This is just an example, by the way: others can be found. ------------------------------------------------------------------------------ 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
