[PATCH vkd3d 1/8] vkd3d-shader: Read the resource index from idx[1] instead of idx[0] when looking up SM5.1 bindings.

[Henri Verbeet]

On Sat, 23 May 2020 at 00:56, Zebediah Figura <zfigura at codeweavers.com> wrote:
> We still use the first index to uniquely identify the register in vkd3d_symbol,
> only changing which field is used to declare it.
>
> One alternative to the "resource_idx" field of struct vkd3d_shader_register
> could be to store that long with "register_space", and pass it as an extra
> parameter to vkd3d_dxbc_compiler_get_descriptor_binding().
>
The way I understand shader model 5.1 resource/sampler declarations,
they essentially assign an unique ID to a slice of a register space.
In that sense, the most appropriate place for this would indeed be in
the "declaration" part of struct vkd3d_shader_instruction, like the
register space. I think the fact that "resource_idx" is unused outside
of declaration instructions is consistent with that.

> More generally, there may be something to be said for exposing fields with
> specific meaning from vkd3d_shader_register, instead of a flat array idx[3], so
> as to hide the differences between SM5 and SM5.1 from spirv.c. If an SM1-3
> frontend is added as well, this may be an even greater help (mostly considering
> constant buffers.) In that case, resource_idx could become one such field.
>
In general, maybe. For this specific case, see above; I think it makes
more sense to think of "resource_idx" as part of the declaration than
as part of the register. The fact that SM 5.1 bytecode stores it as
part of a register token seems like it should largely just be an
interesting detail.

>  static struct vkd3d_shader_descriptor_binding vkd3d_dxbc_compiler_get_descriptor_binding(
>          struct vkd3d_dxbc_compiler *compiler, const struct vkd3d_shader_register *reg,
> -        enum vkd3d_shader_resource_type resource_type, bool is_uav_counter)
> +        unsigned int register_space, enum vkd3d_shader_resource_type resource_type, bool is_uav_counter)
That looks like it should be in 5/8.