// Fails with "D3D compile failed with value cannot be NaN, isnan() may not be necessary.  /Gis may force isnan() to be performed"
fn Bad(index: u32, rd: vec3<f32>) -> vec3<f32> {
  var normal: vec3<f32> = vec3<f32>(0.0);
  normal[index] = -sign(rd[index]);
  return normalize(normal);
}

 struct S { v : vec3<f32>; i : u32; };
[[binding(0), group(0)]] var<storage, read_write> io : S;
[[stage(compute), workgroup_size(1)]]
fn main([[builtin(local_invocation_index)]] idx : u32) {
    io.v = Bad(io.i, io.v);
}