[Mesa-dev] [PATCH] radeonsi: Fix off-by-one for maximum vertex element index in some cases

[Alex Deucher]

On Tue, Mar 12, 2013 at 7:57 AM, Michel Dänzer <michel at daenzer.net> wrote:
> From: Michel Dänzer <michel.daenzer at amd.com>
>
> In cases where the vertex element size is smaller than the vertex buffer
> stride, the previous calculation could end up 1 too low. This would result
> in the GPU using index 0 instead of the maximum index for those elements,
> which would be visible as intermittent distorted triangles.
>
> NOTE: This is a candidate for the 9.1 branch.
>
> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  src/gallium/drivers/radeonsi/si_state_draw.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/src/gallium/drivers/radeonsi/si_state_draw.c b/src/gallium/drivers/radeonsi/si_state_draw.c
> index f8460b0..1049d2b 100644
> --- a/src/gallium/drivers/radeonsi/si_state_draw.c
> +++ b/src/gallium/drivers/radeonsi/si_state_draw.c
> @@ -448,8 +448,14 @@ static void si_vertex_buffer_update(struct r600_context *rctx)
>                 si_pm4_sh_data_add(pm4, va & 0xFFFFFFFF);
>                 si_pm4_sh_data_add(pm4, (S_008F04_BASE_ADDRESS_HI(va >> 32) |
>                                          S_008F04_STRIDE(vb->stride)));
> -               si_pm4_sh_data_add(pm4, (vb->buffer->width0 - vb->buffer_offset) /
> -                                        MAX2(vb->stride, 1));
> +               if (vb->stride)
> +                       /* Round up by rounding down and adding 1 */
> +                       si_pm4_sh_data_add(pm4,
> +                                          (vb->buffer->width0 - offset -
> +                                           util_format_get_blocksize(ve->src_format)) /
> +                                          vb->stride + 1);
> +               else
> +                       si_pm4_sh_data_add(pm4, vb->buffer->width0 - offset);
>                 si_pm4_sh_data_add(pm4, rctx->vertex_elements->rsrc_word3[i]);
>
>                 if (!bound[ve->vertex_buffer_index]) {
> --
> 1.8.2.rc3
>
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