i965: Improve conditional rendering in fallback paths.

We need to fall back in a couple of cases:
- Sandybridge (it just doesn't do this in hardware)
- Occlusion queries on Gen7-7.5 with command parser version < 2
- Transform feedback overflow queries on Gen7, or on Gen7.5 with
  command parser version < 7

In these cases, we printed a perf_debug message and fell back to
_mesa_check_conditional_render(), which stalls until the full
query result is available.  Additionally, the code to handle this
was a bit of a mess.

We can do better by using our normal conditional rendering code,
and setting a new state, BRW_PREDICATE_STATE_STALL_FOR_QUERY, when
we would have set BRW_PREDICATE_STATE_USE_BIT.  Only if that state
is set do we perf_debug and potentially stall.  This means we avoid
stalls when we have a partial query result (i.e. we know it's > 0,
but don't have the full value).  The perf_debug should trigger less
often as well.

Still, this is primarily intended as a cleanup.

Reviewed-by: Jason Ekstrand <[email protected]>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index b1374092bac..36a1ec6c9d1 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -576,7 +576,11 @@ enum brw_predicate_state {
    /* In this case whether to draw or not depends on the result of an
     * MI_PREDICATE command so the predicate enable bit needs to be checked.
     */
-   BRW_PREDICATE_STATE_USE_BIT
+   BRW_PREDICATE_STATE_USE_BIT,
+   /* In this case, either MI_PREDICATE doesn't exist or we lack the
+    * necessary kernel features to use it.  Stall for the query result.
+    */
+   BRW_PREDICATE_STATE_STALL_FOR_QUERY,
 };
 
 struct shader_times;