[Mesa-dev] [PATCH] i965: skip varyings without slot

[Timothy Arceri]

On 16/06/17 18:12, Juan A. Suarez Romero wrote:

> Commit 00620782c9 (i965: use nir_shader_gather_info() over
> do_set_program_inouts()) changed how we compute the outputs written.
>
> In the previous version it was using the IR declared outputs, while in
> the new one it uses NIR to parse the instructions that write outputs.
>
> Thus, if the shader has declared some output that is not written later
> in the code, like this:
>
> ~~~
> struct S {
>      vec4 a;
>      vec4 b;
>      vec4 c;
> };
>
> layout (xfb_offset = sizeof_type) out S s;
>
> void main()
> {
>
>      s.a = vec4(1.0, 0.0, 0.0, 1.0);
>      s.c = vec4(0.0, 1.0, 0.0, 1.0);
> }
> ~~~
>
> The former version computing 3 outputs written (s.a, s.b and s.c), while
> the new version only counts 2 (s.a and s.c).
>
> This means that with the new version, then could be varyings in the VUE
> map that do not have an slot assigned (s.b), that must be skipped.
>
> This fixes KHR-GL45.enhanced_layouts.xfb_capture_struct.
> ---
>   src/mesa/drivers/dri/i965/genX_state_upload.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c b/src/mesa/drivers/dri/i965/genX_state_upload.c
> index a5ad2ca..573f0e3 100644
> --- a/src/mesa/drivers/dri/i965/genX_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/genX_state_upload.c
> @@ -3102,9 +3102,10 @@ genX(upload_3dstate_so_decl_list)(struct brw_context *brw,
>         const unsigned stream_id = output->StreamId;
>         assert(stream_id < MAX_VERTEX_STREAMS);
>   
> -      buffer_mask[stream_id] |= 1 << buffer;
> +      if (vue_map->varying_to_slot[varying] == -1)
> +	      continue;
>   
> -      assert(vue_map->varying_to_slot[varying] >= 0);
> +      buffer_mask[stream_id] |= 1 << buffer;
>   
My feeling is we should try to avoid adding it to the VUE map in the 
first place rather than trying to work around it.

Is it not possible to do that instead?


>         /* Mesa doesn't store entries for gl_SkipComponents in the Outputs[]
>          * array.  Instead, it simply increments DstOffset for the following