From 63cf7fad13fc9cfdd2ae7b031426f79107000300 Mon Sep 17 00:00:00 2001 From: Paul Berry Date: Fri, 9 Dec 2011 16:40:32 -0800 Subject: [PATCH] i965: Flush pipeline on EndTransformFeedback. A common use case for transform feedback is to perform one draw operation that writes transform feedback output to a buffer, followed by a second draw operation that consumes that buffer as vertex input. Since vertex input is consumed at an earlier pipeline stage than writing transform feedback output, we need to flush the pipeline to ensure that the transform feedback output is completely written before the data is consumed. In an ideal world, we would do some dependency tracking, so that we would only flush the pipeline if the next draw call was about to consume data generated by a previous draw call in the same batch. However, since we don't have that sort of dependency tracking infrastructure right now, we just unconditionally flush the buffer every time glEndTransformFeedback() is called. This will cause a performance hit compared to the ideal case (since we will sometimes flush the pipeline unnecessarily), but fortunately the performance hit will be confined to circumstances where transform feedback is in use. Reviewed-by: Kenneth Graunke Reviewed-by: Eric Anholt --- src/mesa/drivers/dri/i965/brw_context.c | 1 + src/mesa/drivers/dri/i965/brw_context.h | 5 +++++ src/mesa/drivers/dri/i965/gen6_sol.c | 16 ++++++++++++++++ 3 files changed, 22 insertions(+) diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c index d8cad54667a..2096be9f86c 100644 --- a/src/mesa/drivers/dri/i965/brw_context.c +++ b/src/mesa/drivers/dri/i965/brw_context.c @@ -117,6 +117,7 @@ static void brwInitDriverFunctions( struct dd_function_table *functions ) brw_init_queryobj_functions(functions); functions->PrepareExecBegin = brwPrepareExecBegin; + functions->EndTransformFeedback = brw_end_transform_feedback; } bool diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h index febd4fe4365..6fa71a3c14e 100644 --- a/src/mesa/drivers/dri/i965/brw_context.h +++ b/src/mesa/drivers/dri/i965/brw_context.h @@ -1076,6 +1076,11 @@ brw_update_sol_surface(struct brw_context *brw, bool brw_fprog_uses_noperspective(const struct gl_fragment_program *fprog); +/* gen6_sol.c */ +void +brw_end_transform_feedback(struct gl_context *ctx, + struct gl_transform_feedback_object *obj); + /*====================================================================== diff --git a/src/mesa/drivers/dri/i965/gen6_sol.c b/src/mesa/drivers/dri/i965/gen6_sol.c index 491b39cce12..38aedcc4297 100644 --- a/src/mesa/drivers/dri/i965/gen6_sol.c +++ b/src/mesa/drivers/dri/i965/gen6_sol.c @@ -27,6 +27,7 @@ */ #include "brw_context.h" +#include "intel_batchbuffer.h" #include "brw_defines.h" static void @@ -69,3 +70,18 @@ const struct brw_tracked_state gen6_sol_surface = { }, .emit = gen6_update_sol_surfaces, }; + +void +brw_end_transform_feedback(struct gl_context *ctx, + struct gl_transform_feedback_object *obj) +{ + /* After EndTransformFeedback, it's likely that the client program will try + * to draw using the contents of the transform feedback buffer as vertex + * input. In order for this to work, we need to flush the data through at + * least the GS stage of the pipeline, and flush out the render cache. For + * simplicity, just do a full flush. + */ + struct brw_context *brw = brw_context(ctx); + struct intel_context *intel = &brw->intel; + intel_batchbuffer_emit_mi_flush(intel); +} -- 2.30.2