There are several places that should have supported the various sized
versions of bcsel and the various nir_op_[fi]csel_* opcodes. Rather
than enumerate the whole list, add a property.
v2: Make the comment for NIR_OP_IS_SELECTION more descriptive.
Suggested by Jason.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17048>