[Mesa-dev] [PATCH] gallium/u_vbuf: drop min/max-scanning for empty indirect draws

[Marek Olšák]

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Thu, Jun 28, 2018 at 9:22 AM, Erik Faye-Lund
<erik.faye-lund at collabora.com> wrote:
> When building with asserts enabled, we'll end up triggering an assert
> in pipe_buffer_map_range down this code-path, due to trying to map
> an empty range. Even if we avoid that, we'll trigger another assert
> a bit later, because u_vbuf_get_minmax_index returns a min-index of
> -1 here, which gets promoted to an unsigned value, and gives us an
> out-of-bounds buffer-mapping offset.
>
> Since we can't really have a well-defined min/max range here when
> the range is empty anyway, we should just drop this dance in the
> first place. After all, no rendering is going to be produced.
>
> This fixes a crash in dEQP-GLES31.functional.draw_indirect.random.0
> on VirGL for me.
>
> Signed-off-by: Erik Faye-Lund <erik.faye-lund at collabora.com>
> ---
> I noticed this while debugging something else, so I thought I'd send
> a patch upstream, as the problem doesn't seem unique to my usecase.
>
>  src/gallium/auxiliary/util/u_vbuf.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/src/gallium/auxiliary/util/u_vbuf.c b/src/gallium/auxiliary/util/u_vbuf.c
> index 42f37c7574..76a1d143d9 100644
> --- a/src/gallium/auxiliary/util/u_vbuf.c
> +++ b/src/gallium/auxiliary/util/u_vbuf.c
> @@ -1183,6 +1183,9 @@ void u_vbuf_draw_vbo(struct u_vbuf *mgr, const struct pipe_draw_info *info)
>        new_info.start = data[2];
>        pipe_buffer_unmap(pipe, transfer);
>        new_info.indirect = NULL;
> +
> +      if (!new_info.count)
> +         return;
>     }
>
>     if (new_info.index_size) {
> --
> 2.18.0.rc2
>
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