pan/bi: Add discard ops

These run on the ADD unit and evidently need to be their own clause
(probably treated as a high-latency instruction). Like csel, they can
either do a float comparison directly or ingest a 0/1 value.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4025>
1 file changed