Mesa (master): gallium/util: optimize pipe_vertex_buffer_reference binding the same buffer

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Module: Mesa
Branch: master
Commit: 104a41bd0743596f7eccadcef3a70a3d40c370d7
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=104a41bd0743596f7eccadcef3a70a3d40c370d7

Author: Marek Olšák <marek.olsak at amd.com>
Date:   Sat Jan  2 16:35:15 2021 -0500

gallium/util: optimize pipe_vertex_buffer_reference binding the same buffer

This eliminates atomic ops when the buffer doesn't change.

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8298>

---

 src/gallium/auxiliary/util/u_inlines.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/gallium/auxiliary/util/u_inlines.h b/src/gallium/auxiliary/util/u_inlines.h
index d751f1cce28..f3a74d7fb0a 100644
--- a/src/gallium/auxiliary/util/u_inlines.h
+++ b/src/gallium/auxiliary/util/u_inlines.h
@@ -223,6 +223,14 @@ static inline void
 pipe_vertex_buffer_reference(struct pipe_vertex_buffer *dst,
                              const struct pipe_vertex_buffer *src)
 {
+   if (dst->buffer.resource == src->buffer.resource) {
+      /* Just copy the fields, don't touch reference counts. */
+      dst->stride = src->stride;
+      dst->is_user_buffer = src->is_user_buffer;
+      dst->buffer_offset = src->buffer_offset;
+      return;
+   }
+
    pipe_vertex_buffer_unreference(dst);
    if (!src->is_user_buffer)
       pipe_resource_reference(&dst->buffer.resource, src->buffer.resource);