[Mesa-dev] [RFC PATCH 3/3] gallium: remove pipe_index_buffer and set_index_buffer

[Roland Scheidegger]

As mentioned before, I'm not exactly thrilled by this (as I just happen
to like the old interface), but could live with it for GL's performance
sake, if others like that. I suppose though you'd have quite some code
to adapt...
Are those performance numbers with just this patch or all 3?

Roland


Am 11.04.2017 um 22:15 schrieb Marek Olšák:
> From: Marek Olšák <marek.olsak at amd.com>
> 
> pipe_draw_info::indexed is replaced with index_size. index_size == 0 means
> non-indexed.
> 
> Instead of pipe_index_buffer::offset, pipe_draw_info::start is used.
> For indexed indirect draws, pipe_draw_info::start is added to the indirect
> start. This is the only case when "start" affects indirect draws.
> 
> pipe_draw_info::index is a union. Use either index::buffer or
> index::user_buffer depending on the value of pipe_draw_info
> ::has_user_indices.
> 
> Performance numbers with the drawoverhead microbenchmark.
> 
> Before::
>    DrawElements only: 4.5 million draws/second
>    DrawElements w/ nop state change: 4.4 million draws/sec (overhead: 0.000007 ms/draw)
>    DrawElements w/ state change: 1.9 million draws/sec (overhead: 0.000293 ms/draw)
> 
> After:
>    DrawElements only: 5.0 million draws/second
>    DrawElements w/ nop state change: 4.9 million draws/sec (overhead: 0.000007 ms/draw)
>    DrawElements w/ state change: 2.2 million draws/sec (overhead: 0.000254 ms/draw)
> 
> The improvement will be much smaller with real apps.
> ---
>  src/gallium/include/pipe/p_context.h |  4 ----
>  src/gallium/include/pipe/p_state.h   | 35 ++++++++++++++++++-----------------
>  2 files changed, 18 insertions(+), 21 deletions(-)
> 
> diff --git a/src/gallium/include/pipe/p_context.h b/src/gallium/include/pipe/p_context.h
> index 4d5535b..4b75386 100644
> --- a/src/gallium/include/pipe/p_context.h
> +++ b/src/gallium/include/pipe/p_context.h
> @@ -53,7 +53,6 @@ struct pipe_grid_info;
>  struct pipe_fence_handle;
>  struct pipe_framebuffer_state;
>  struct pipe_image_view;
> -struct pipe_index_buffer;
>  struct pipe_query;
>  struct pipe_poly_stipple;
>  struct pipe_rasterizer_state;
> @@ -354,9 +353,6 @@ struct pipe_context {
>                                 unsigned num_buffers,
>                                 const struct pipe_vertex_buffer * );
>  
> -   void (*set_index_buffer)( struct pipe_context *pipe,
> -                             const struct pipe_index_buffer * );
> -
>     /*@}*/
>  
>     /**
> diff --git a/src/gallium/include/pipe/p_state.h b/src/gallium/include/pipe/p_state.h
> index 69d2378..7f482d4 100644
> --- a/src/gallium/include/pipe/p_state.h
> +++ b/src/gallium/include/pipe/p_state.h
> @@ -630,19 +630,6 @@ struct pipe_vertex_element
>  };
>  
>  
> -/**
> - * An index buffer.  When an index buffer is bound, all indices to vertices
> - * will be looked up in the buffer.
> - */
> -struct pipe_index_buffer
> -{
> -   unsigned index_size;  /**< size of an index, in bytes */
> -   unsigned offset;  /**< offset to start of data in buffer, in bytes */
> -   struct pipe_resource *buffer; /**< the actual buffer */
> -   const void *user_buffer;  /**< pointer to a user buffer if buffer == NULL */
> -};
> -
> -
>  struct pipe_draw_indirect_info
>  {
>     unsigned offset; /**< must be 4 byte aligned */
> @@ -652,7 +639,7 @@ struct pipe_draw_indirect_info
>  
>     /* Indirect draw parameters resource is laid out as follows:
>      *
> -    * if indexed is TRUE:
> +    * if using indexed drawing:
>      *  struct {
>      *     uint32_t count;
>      *     uint32_t instance_count;
> @@ -682,12 +669,18 @@ struct pipe_draw_indirect_info
>   */
>  struct pipe_draw_info
>  {
> -   boolean indexed;  /**< use index buffer */
> +   ubyte index_size;  /**< if 0, the draw is not indexed. */
>     enum pipe_prim_type mode:8;  /**< the mode of the primitive */
> -   boolean primitive_restart;
> +   unsigned primitive_restart:1;
> +   unsigned has_user_indices:1; /**< if true, use index.user_buffer */
>     ubyte vertices_per_patch; /**< the number of vertices per patch */
>  
> -   unsigned start;  /**< the index of the first vertex */
> +   /**
> +    * Direct draws: start is the index of the first vertex
> +    * Non-indexed indirect draws: not used
> +    * Indexed indirect draws: start is added to the indirect start.
> +    */
> +   unsigned start;
>     unsigned count;  /**< number of vertices */
>  
>     unsigned start_instance; /**< first instance id */
> @@ -709,6 +702,14 @@ struct pipe_draw_info
>  
>     /* Pointers must be at the end for an optimal structure layout on 64-bit. */
>  
> +   /**
> +    * An index buffer.  When an index buffer is bound, all indices to vertices
> +    * will be looked up from the buffer.
> +    *
> +    * If has_user_indices, use index.user_buffer, else use index.buffer.
> +    */
> +   union pipe_buffer_binding index;
> +
>     struct pipe_draw_indirect_info *indirect; /**< Indirect draw. */
>  
>     /**
>