aco/ngg: Export a zero-area triangle when primitive count is 0.

This is a workaround for a bug in Navi 1x NGG HW.

Very rarely, the Navi 1x PA can hang when an NGG workgroup exports
0 total primitives. According to AMD, we always need this workaround
when it is possible that the number of primitives is 0.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7232>
1 file changed