[Mesa-dev] [PATCH 3/3] gallium/u_vbuf: handle indirect multidraws correctly and efficiently

[Eric Anholt]

Marek Olšák <maraeo at gmail.com> writes:

> From: Marek Olšák <marek.olsak at amd.com>
>
> ---
>  src/gallium/auxiliary/util/u_vbuf.c | 189 ++++++++++++++++++++++++----
>  1 file changed, 165 insertions(+), 24 deletions(-)
>
> diff --git a/src/gallium/auxiliary/util/u_vbuf.c b/src/gallium/auxiliary/util/u_vbuf.c
> index 87b159ec1bf..b0b92f7e966 100644
> --- a/src/gallium/auxiliary/util/u_vbuf.c
> +++ b/src/gallium/auxiliary/util/u_vbuf.c
> @@ -1132,20 +1132,45 @@ static void u_vbuf_set_driver_vertex_buffers(struct u_vbuf *mgr)
>     unsigned start_slot, count;
>  
>     start_slot = ffs(mgr->dirty_real_vb_mask) - 1;
>     count = util_last_bit(mgr->dirty_real_vb_mask >> start_slot);
>  
>     pipe->set_vertex_buffers(pipe, start_slot, count,
>                              mgr->real_vertex_buffer + start_slot);
>     mgr->dirty_real_vb_mask = 0;
>  }
>  
> +static void
> +u_vbuf_split_indexed_multidraw(struct u_vbuf *mgr, struct pipe_draw_info *info,
> +                               unsigned *indirect_data, unsigned stride,
> +                               unsigned draw_count)
> +{
> +   assert(info->index_size);
> +   info->indirect = NULL;
> +
> +   for (unsigned i = 0; i < draw_count; i++) {
> +      unsigned offset = i * stride / 4;
> +
> +      info->count = indirect_data[offset + 0];
> +      info->instance_count = indirect_data[offset + 1];
> +
> +      if (!info->count || !info->instance_count)
> +         continue;
> +
> +      info->start = indirect_data[offset + 2];
> +      info->index_bias = indirect_data[offset + 3];
> +      info->start_instance = indirect_data[offset + 4];
> +
> +      u_vbuf_draw_vbo(mgr, info);
> +   }
> +}
> +
>  void u_vbuf_draw_vbo(struct u_vbuf *mgr, const struct pipe_draw_info *info)
>  {
>     struct pipe_context *pipe = mgr->pipe;
>     int start_vertex, min_index;
>     unsigned num_vertices;
>     boolean unroll_indices = FALSE;
>     const uint32_t used_vb_mask = mgr->ve->used_vb_mask;
>     uint32_t user_vb_mask = mgr->user_vb_mask & used_vb_mask;
>     const uint32_t incompatible_vb_mask =
>        mgr->incompatible_vb_mask & used_vb_mask;
> @@ -1160,47 +1185,162 @@ void u_vbuf_draw_vbo(struct u_vbuf *mgr, const struct pipe_draw_info *info)
>        if (mgr->dirty_real_vb_mask & used_vb_mask) {
>           u_vbuf_set_driver_vertex_buffers(mgr);
>        }
>  
>        pipe->draw_vbo(pipe, info);
>        return;
>     }
>  
>     new_info = *info;
>  
> -   /* Fallback. We need to know all the parameters. */
> +   /* Handle indirect (multi)draws. */
>     if (new_info.indirect) {
> -      struct pipe_transfer *transfer = NULL;
> -      int *data;
> -
> -      if (new_info.index_size) {
> -         data = pipe_buffer_map_range(pipe, new_info.indirect->buffer,
> -                                      new_info.indirect->offset, 20,
> -                                      PIPE_TRANSFER_READ, &transfer);
> -         new_info.index_bias = data[3];
> -         new_info.start_instance = data[4];
> -      }
> -      else {
> -         data = pipe_buffer_map_range(pipe, new_info.indirect->buffer,
> -                                      new_info.indirect->offset, 16,
> -                                      PIPE_TRANSFER_READ, &transfer);
> -         new_info.start_instance = data[3];
> +      const struct pipe_draw_indirect_info *indirect = new_info.indirect;
> +      unsigned draw_count = 0;
> +
> +      /* Get the number of draws. */
> +      if (indirect->indirect_draw_count) {
> +         pipe_buffer_read(pipe, indirect->indirect_draw_count,
> +                          indirect->indirect_draw_count_offset,
> +                          4, &draw_count);
> +      } else {
> +         draw_count = indirect->draw_count;
>        }
>  
> -      new_info.count = data[0];
> -      new_info.instance_count = data[1];
> -      new_info.start = data[2];
> -      pipe_buffer_unmap(pipe, transfer);
> -      new_info.indirect = NULL;
> -
> -      if (!new_info.count)
> +      if (!draw_count)
>           return;
> +
> +      unsigned data_size = (draw_count - 1) * indirect->stride +
> +                           (new_info.index_size ? 20 : 16);
> +      unsigned *data = alloca(data_size);

draw_count can be potentially huge, right?  This should be a malloc, I
think.

Other than that, wow.  I don't think I would have gone to this effort
and would have just done the split path instead.  Still, with the alloca
change:

Reviewed-by: Eric Anholt <eric at anholt.net>

Thanks for the "The driver will not look at these values because
indirect != NULL" comments -- the code would be really surprising
without that!
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