When poly_line smoothing is enabled then this lowering pass will
modify the alpha component of every write to fragment output
using sample coverage mask.
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16245>
Arvind Yadav