For cases where both clip and cull are used, and a shader has both
inputs and outputs that can contain them, we need metadata to tell
us where the clip array ends and the cull array begins, since they
get combined into CLIP location registers. For outputs, this is in
the nir info, but for input we pass it in a sideband channel.
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20346>
Jesse Natalie
e4e0ab2207