https://bugs.freedesktop.org/show_bug.cgi?id=29439
--- Comment #3 from Ian Romanick idr@freedesktop.org 2010-08-07 12:19:01 PDT --- i915 is going to have the same problem when we enable GLSL there. Our plan is to emit a warning in the shader log and have DDX and DDY always return 0. We've also discussed having a driconf option to enable / disable the behavior. That might be worth trying for r300 as well.