On Don, 2012-12-06 at 10:52 -0800, Tom Stellard wrote: > On Thu, Dec 06, 2012 at 07:25:55PM +0100, Michel Dänzer wrote: > > On Don, 2012-12-06 at 09:05 -0800, Tom Stellard wrote: > > > On Thu, Dec 06, 2012 at 05:08:07PM +0100, Michel Dänzer wrote: > > > > On Mit, 2012-12-05 at 09:32 -0800, Vincent Lejeune wrote: > > > > > > > > I suspect the problem is a (non-)IEEE semantics mismatch between TGSI > > > > and LLVM introduced by this change. > > > > > > What are the semantics of TGSI opcodes? For MUL and MAD, tgsi_exec uses > > > IEEE > > > operations, but it seems like the glsl frontend thinks they are non-IEEE. > > > > Not sure... FWIW, the tests pass on llvmpipe. > > I just looked at the TGSI->LLVM code, which is shared by r600g, > radeonsi, and llvmpipe. For TGSI_OPCODE_MUL, it actually uses both > the IEEE and non-IEEE definitions depending on what the arguments are. > If one of the arguments to MUL is the compile time constant zero then it > uses the non-IEEE definition (0 * anything) = 0, otherwise it produces > a fmul instruction which has IEEE semantics. This probably deserves > it's own thread, because I think newer versions of GLSL require IEEE, > but older versions and also ARB have different semantics.
Right, also, the code you described doesn't cover cases where a non-constant value is 0. > > > Should we revert this and the associated LLVM changes? > > > > I guess it depends on the answer to the above question about the > > expected semantics. > > > > Given that these tests seem to use indirect addressing, could it be that > > they just happened to pass by accident before? > > Yeah, those tests must have been passing by accident. Are there any other > failing tests? No, those are the only two tests that regressed for me. So I guess this can be ignored for now. It would be interesting to know which tests Alex was referring to though, which were fixed by switching from MUL_IEEE to MUL. Maybe those are covered by the code you described above though. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Debian, X and DRI developer _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
