On Thu, Dec 6, 2012 at 1:27 PM, Alex Deucher <alexdeuc...@gmail.com> wrote: > On Thu, Dec 6, 2012 at 1:21 PM, Vincent Lejeune <v...@ovi.com> wrote: >> Sorry for the inconvenience. >> I think the r600g backend work because of this patch, which switch MUL and >> MUL_IEEE definition : >> http://lists.freedesktop.org/archives/mesa-dev/2012-November/030748.html >> >> The rationale behind the patch is use the fmul instead of a custom intrinsic >> for OpenGL path. >> Glsl-to-llvm generates as "vanilla" instructions as possible and uses fmul, >> this consolidates behaviour >> between tgsi-to-llvm and glsl-to-llvm. >> IMHO emitting MUL and MUL_IEEE should be decided with the presence of some >> "fast-math" arg to the backend, >> or some context variable telling if we have a glsl or an opencl shader. > > MUL and MUL_IEEE are not related to performance, rather to behavior: > > MUL Floating-point multiply. 0*anything = 0. > MUL_IEEE IEEE Floating-point multiply. Uses IEEE rules for 0*anything.
IIRC, we want the MUL behavior in GL. In the pre-LLVM days we used MUL_IEEE and switching to MUL fixed a bunch of piglit tests. Alex _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
