message: No longer has a post-cast exchange in reduce
  Summary: Poplar no longer generates this step in the set of operations
  Test Plan: test passing
  Reviewers: georgep
diff: @@ -216,12 +216,7 @@ class IpuXlaConvTest(test_util.TensorFlowTestCase):
  # Note that intermidiates are still floats, so there is a final cast
  ok = ['Execution',
  '/ExchangePre',
  - 'Execution',
  - 'Execution',
  - '/ExchangePre',
  - 'Execution',
  - 'Sum/reduce.*.clone_f16/final_stage/Cast/Cast',
  - 'Sum/reduce.*.clone_f16/final_stage/Cast/Cast/PostExchangeArrange']
  + 'Sum/reduce.*.clone_f16/final_stage/Cast/Cast']
  self.assertTrue(tu.check_all_compute_sets_in_list(cs_list, ok))
  if __name__ == "__main__":
  