897c47aa1c
These implement gl_ClipDistance in hardware, avoiding the fragment shader lowering. Unfortunately, they can't be disabled on a per-plane basis and they can't be interpolated, so using them for OpenGL would still require a bunch of extra lowering steps. Still, we should document the hardware and the caveats. Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21097>