https://bugs.freedesktop.org/show_bug.cgi?id=84977
--- Comment #7 from Tom Stellard tstellar@gmail.com --- (In reply to David Heidelberger (okias) from comment #6)
in function r300FPTranslateRGBSwizzle is return value of sd == 0 (for sure)
So it sounds like this might be a bug somewhere in rc_reg_class_variable_get_class()
At the very bottom of this function, there is a call to find_class(), it would be good to put a printf to check the value of can_change_writemask and also class_index.