[[block]] struct DrawIndirectArgs {
  vertexCount : atomic<u32>;
};
[[group(0), binding(5)]] var<storage, read_write> drawOut : DrawIndirectArgs;

var<private> cubeVerts : u32 = 0u;

[[stage(compute)]]
fn computeMain([[builtin(global_invocation_id)]] global_id : vec3<u32>) {
  // Increment cubeVerts based on some criteria...

  // This fails SPIR-V validation
  let firstVertex : u32 = atomicAdd(&drawOut.vertexCount, cubeVerts);
}