Mesa (master): vc4: Don' t flush on read-only access of buffers read by the CL.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 21a9ed620764bde2021aa7592cf2695dad8f3f74
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=21a9ed620764bde2021aa7592cf2695dad8f3f74

Author: Eric Anholt <eric at anholt.net>
Date:   Fri Apr 15 14:27:34 2016 -0700

vc4: Don't flush on read-only access of buffers read by the CL.

Fixes piglit mixed-immediate-and-vbo, and may significantly improve
performance of applications that store a 4-byte IB in the same VBO as
vertex data.

---

 src/gallium/drivers/vc4/vc4_context.c  | 13 ++++++++-----
 src/gallium/drivers/vc4/vc4_context.h  |  3 ++-
 src/gallium/drivers/vc4/vc4_resource.c |  7 ++++++-
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/gallium/drivers/vc4/vc4_context.c b/src/gallium/drivers/vc4/vc4_context.c
index a0888f2..eeadea0 100644
--- a/src/gallium/drivers/vc4/vc4_context.c
+++ b/src/gallium/drivers/vc4/vc4_context.c
@@ -133,7 +133,8 @@ vc4_pipe_flush(struct pipe_context *pctx, struct pipe_fence_handle **fence,
  * This helps avoid flushing the command buffers when unnecessary.
  */
 bool
-vc4_cl_references_bo(struct pipe_context *pctx, struct vc4_bo *bo)
+vc4_cl_references_bo(struct pipe_context *pctx, struct vc4_bo *bo,
+                     bool include_reads)
 {
         struct vc4_context *vc4 = vc4_context(pctx);
 
@@ -143,10 +144,12 @@ vc4_cl_references_bo(struct pipe_context *pctx, struct vc4_bo *bo)
         /* Walk all the referenced BOs in the drawing command list to see if
          * they match.
          */
-        struct vc4_bo **referenced_bos = vc4->bo_pointers.base;
-        for (int i = 0; i < cl_offset(&vc4->bo_handles) / 4; i++) {
-                if (referenced_bos[i] == bo) {
-                        return true;
+        if (include_reads) {
+                struct vc4_bo **referenced_bos = vc4->bo_pointers.base;
+                for (int i = 0; i < cl_offset(&vc4->bo_handles) / 4; i++) {
+                        if (referenced_bos[i] == bo) {
+                                return true;
+                        }
                 }
         }
 
diff --git a/src/gallium/drivers/vc4/vc4_context.h b/src/gallium/drivers/vc4/vc4_context.h
index aa973bd..2457e67 100644
--- a/src/gallium/drivers/vc4/vc4_context.h
+++ b/src/gallium/drivers/vc4/vc4_context.h
@@ -397,7 +397,8 @@ void vc4_flush(struct pipe_context *pctx);
 void vc4_job_init(struct vc4_context *vc4);
 void vc4_job_submit(struct vc4_context *vc4);
 void vc4_job_reset(struct vc4_context *vc4);
-bool vc4_cl_references_bo(struct pipe_context *pctx, struct vc4_bo *bo);
+bool vc4_cl_references_bo(struct pipe_context *pctx, struct vc4_bo *bo,
+                          bool include_reads);
 void vc4_emit_state(struct pipe_context *pctx);
 void vc4_generate_code(struct vc4_context *vc4, struct vc4_compile *c);
 struct qpu_reg *vc4_register_allocate(struct vc4_context *vc4, struct vc4_compile *c);
diff --git a/src/gallium/drivers/vc4/vc4_resource.c b/src/gallium/drivers/vc4/vc4_resource.c
index 2f89da5..050941c 100644
--- a/src/gallium/drivers/vc4/vc4_resource.c
+++ b/src/gallium/drivers/vc4/vc4_resource.c
@@ -171,7 +171,12 @@ vc4_resource_transfer_map(struct pipe_context *pctx,
                         vc4_flush(pctx);
                 }
         } else if (!(usage & PIPE_TRANSFER_UNSYNCHRONIZED)) {
-                if (vc4_cl_references_bo(pctx, rsc->bo)) {
+                /* If we're writing and the buffer is being used by the CL, we
+                 * have to flush the CL first.  If we're only reading, we need
+                 * to flush if the CL has written our buffer.
+                 */
+                if (vc4_cl_references_bo(pctx, rsc->bo,
+                                         usage & PIPE_TRANSFER_WRITE)) {
                         if ((usage & PIPE_TRANSFER_DISCARD_RANGE) &&
                             prsc->last_level == 0 &&
                             prsc->width0 == box->width &&