mesa/st: Implement GL_TIME_ELAPSED w/ PIPE_QUERY_TIMESTAMP.

ARB/EXT_timer_query's definition of GL_TIME_ELAPSED match precisely the
subtraction of two GL_TIMESTAMP queries.

And for a lot of drivers, that's precisely how they have to implement
internally -- by emitting two hardware timestamp queries.

So, to simplify driver implementation, simply allow doing so in the state
tracker.

Eventually if no driver implements PIPE_QUERY_TIME_ELAPSED then we could
retire it.

Reviewed-by: Dave Airlie <[email protected]>
Reviewed-by: Marek Olšák <[email protected]>
Reviewed-by: Brian Paul <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/mesa/state_tracker/st_cb_queryobj.h b/src/mesa/state_tracker/st_cb_queryobj.h
index 03487b15317..d5b10753245 100644
--- a/src/mesa/state_tracker/st_cb_queryobj.h
+++ b/src/mesa/state_tracker/st_cb_queryobj.h
@@ -39,6 +39,10 @@ struct st_query_object
 {
    struct gl_query_object base;
    struct pipe_query *pq;
+
+   /* Begin TIMESTAMP query for GL_TIME_ELAPSED_EXT queries */
+   struct pipe_query *pq_begin;
+
    unsigned type;  /**< PIPE_QUERY_x */
 };