validate_draw.wgsl

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override supports_indirect_first_instance: bool;

struct MetadataEntry {

    // bits 0..30 are an offset into `src`

    // bit 31 signifies that we are validating an indexed draw

    src_offset: u32,

    // bits 0..30 are an offset into `dst`

    // bit 30 is the most significant bit of `vertex_or_index_limit`

    // bit 31 is the most significant bit of `instance_limit`

    dst_offset: u32,

    vertex_or_index_limit: u32,

    instance_limit: u32,

struct MetadataRange {

    start: u32,

    count: u32,

var<push_constant> metadata_range: MetadataRange;

@group(0) @binding(0)

var<storage, read> metadata: array<MetadataEntry>;

@group(1) @binding(0)

var<storage, read> src: array<u32>;

@group(2) @binding(0)

var<storage, read_write> dst: array<u32>;

fn is_bit_set(data: u32, index: u32) -> bool {

    return ((data >> index) & 1u) == 1u;

@compute @workgroup_size(64)

fn main(@builtin(global_invocation_id) global_invocation_id: vec3u) {

    if global_invocation_id.x >= metadata_range.count { return; }

    let metadata = metadata[metadata_range.start + global_invocation_id.x];

    var failed = false;

    let is_indexed = is_bit_set(metadata.src_offset, 31);

    let src_base_offset = ((metadata.src_offset << 2) >> 2);

    let dst_base_offset = ((metadata.dst_offset << 2) >> 2);

    let first_vertex_or_index = src[src_base_offset + 2];

    let vertex_or_index_count = src[src_base_offset + 0];

        let can_overflow = is_bit_set(metadata.dst_offset, 30);

        let sub_overflows = metadata.vertex_or_index_limit < first_vertex_or_index;

        failed |= sub_overflows && !can_overflow;

        let vertex_or_index_limit = metadata.vertex_or_index_limit - first_vertex_or_index;

        failed |= vertex_or_index_limit < vertex_or_index_count;

    let first_instance = src[src_base_offset + 3 + u32(is_indexed)];

    let instance_count = src[src_base_offset + 1];

        let can_overflow = is_bit_set(metadata.dst_offset, 31);

        let sub_overflows = metadata.instance_limit < first_instance;

        failed |= sub_overflows && !can_overflow;

        let instance_limit = metadata.instance_limit - first_instance;

        failed |= instance_limit < instance_count;

    if !supports_indirect_first_instance {

        failed |= first_instance != 0u;

    if failed {

        dst[dst_base_offset + 0] = 0u;

        dst[dst_base_offset + 1] = 0u;

        dst[dst_base_offset + 2] = 0u;

        dst[dst_base_offset + 3] = 0u;

        if (is_indexed) {

            dst[dst_base_offset + 4] = 0u;

    } else {

        dst[dst_base_offset + 0] = src[src_base_offset + 0];

        dst[dst_base_offset + 1] = src[src_base_offset + 1];

        dst[dst_base_offset + 2] = src[src_base_offset + 2];

        dst[dst_base_offset + 3] = src[src_base_offset + 3];

        if (is_indexed) {

            dst[dst_base_offset + 4] = src[src_base_offset + 4];