In Gen11+, when emitting a fence for both L3 and SLM, the generated
code would look like
SEND, MOV (for stall), SEND, MOV (for stall)
This commit change that so two SENDs are emitted before the MOVs for
stall. This is similar to the approach used in Ivy Bridge for the
render fence.
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3278>