[Mesa-dev] [PATCH] i965/gen7: Use WE_all mode when enabling channel masks for URB write.
eric at anholt.net
Mon Mar 25 08:50:11 PDT 2013
Paul Berry <stereotype441 at gmail.com> writes:
> Gen7 adds mask bits to the message header for a URB write which allow
> the write to apply only to certain channels. We don't use this
> functionality, so to ensure that the entire write always occurs, we
> emit an OR instruction to set the mask bits.
> With the advent of geometry shaders, URB writes won't just happen at
> the end of a thread; they will happen in mid-thread too. Thus, we can
> no longer rely on channel 0 being enabled, so we need to emit the OR
> instruction in WE_all mode to ensure that it is executed.
Reviewed-by: Eric Anholt <eric at anholt.net>
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