This will make it easier for back-ends to share code between geometry shader and vertex shader compilation. Also, it is renamed to "UsesClipDistanceOut" to clarify that (a) in geometry shaders, it refers to the gl_ClipDistance output rather than the gl_ClipDistance input, and (b) it is irrelevant in fragment shaders. Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> Reviewed-by: Matt Turner <mattst88@gmail.com>