xla

137415b7 - Add send/recv support for https://github.com/pytorch/xla/issues/3138 (#3494)

Add send/recv support for https://github.com/pytorch/xla/issues/3138 (#3494) * Add send/recv support. * fix build break. * fix build break. * fix typo in test. * make sent tensor depend on send token. * fix build break. * fix build break. * Address Jack's comments.