title: What does the bracket mean in XLA HLO's tensor shape?
body: <p>I am confused with the number in <code>{}</code>. For example, the below code is sample XLA HLO, and I am having trouble understanding what <code>%bitcast.26</code> does.</p>
  <pre><code>%gather.347 = f16[8192,768]{1,0} gather(f16[30522,768]{1,0} %convert.339, s32[8192]{0} %bitcast.25), offset_dims={1}, collapsed_slice_dims={0}, start_index_map={0}, index_vector_dim=1, slice_sizes={1,768}
  %bitcast.26 = f16[16,512,768]{2,1,0} bitcast(f16[8192,768]{1,0} %gather.347)
  </code></pre>
  <p>Of course, I can see that the dimension changed from <code>f16[8192,768]{1,0}</code> to <code>f16[16,512,768]{2,1,0}</code>, but I do not get what <code>{1,0}</code> and <code>{2,1,0}</code> represents.</p>