[PATCH vkd3d v2 3/4] vkd3d-shader/spirv: Support runtime descriptor array offsets using push constants.

[Henri Verbeet]

On Wed, 10 Nov 2021 at 08:04, Conor McCarthy <cmccarthy at codeweavers.com> wrote:
> +struct vkd3d_shader_descriptor_offset
> +{
> +    unsigned int static_offset;
> +    unsigned int dynamic_offset_index;
> +};
> +
>  /**
>   * A chained structure containing descriptor offsets.
>   *
> @@ -477,10 +483,28 @@ struct vkd3d_shader_descriptor_offset_info
>      const void *next;
>
>      /**
> -     * Pointer to an array of offsets into the descriptor arrays referenced by
> -     * the 'bindings' array in struct vkd3d_shader_interface_info. This allows
> -     * mapping multiple shader resource arrays to a single binding point in
> -     * the target environment.
> +     * Byte offset within the push constants of an array of 32-bit
> +     * descriptor array offsets. See the description of 'binding_offsets'
> +     * below.
> +     */
> +    unsigned int descriptor_table_offset;
> +    /** Size, in elements, of the descriptor table push constant array. */
> +    unsigned int descriptor_table_count;
> +
> +    /**
> +     * Pointer to an array of struct vkd3d_shader_descriptor_offset objects.
> +     * The 'static_offset' field contains an offset into the descriptor arrays
> +     * referenced by the 'bindings' array in struct vkd3d_shader_interface_info.
> +     * This allows mapping multiple shader resource arrays to a single binding
> +     * point in the target environment.
> +     *
> +     * 'dynamic_offset_index' in struct vkd3d_shader_descriptor_offset allows
> +     * offsets to be set at runtime. The 32-bit descriptor table push constant
> +     * at this index will be added to 'static_offset' to calculate the final
> +     * binding offset.
> +     *
> +     * If runtime offsets are not required, set all 'dynamic_offset_index'
> +     * values to \c ~0u and 'descriptor_table_count' to zero.
>       *
>       * For example, to map Direct3D constant buffer registers 'cb0[0:3]' and
>       * 'cb1[6:7]' to descriptors 8-12 and 4-5 in the Vulkan descriptor array in
> @@ -508,7 +532,7 @@ struct vkd3d_shader_descriptor_offset_info
>       * This field may be NULL, in which case the corresponding offsets are
>       * specified to be 0.
>       */
> -    const unsigned int *binding_offsets;
> +    const struct vkd3d_shader_descriptor_offset *binding_offsets;
>
>      /**
>       * Pointer to an array of offsets into the descriptor arrays referenced by
> @@ -517,7 +541,7 @@ struct vkd3d_shader_descriptor_offset_info
>       * not supported in this version of vkd3d-shader, and therefore this field
>       * must either be NULL or specify 0 offsets.
>       */
> -    const unsigned int *uav_counter_offsets;
> +    const struct vkd3d_shader_descriptor_offset *uav_counter_offsets;
>  };
>
Conceptually, this is starting to look a fair bit like the existing
vkd3d_shader_parameter mechanism. What would it take to extend that
mechanism to work for descriptor offsets?