[Bug 65416] r300g does not eliminate unread varyings

https://bugs.freedesktop.org/show_bug.cgi?id=65416

--- Comment #5 from Marek Olšák maraeo@gmail.com --- I have implemented it, but there is a problem. If I enable the optimization, EXT_separate_shader_objects must be disabled. Is it okay with you?

This is a valid sequence with EXT_sso: glUseProgram(prog_with_vs_and_fs); glUseShaderProgramEXT(prog_with_fs);

prog_with_vs_and_fs cannot be optimized, because the program object can be bound partially (in this case only the vertex shader from the program object is bound).

ARB_separate_shader_objects doesn't have this issue.