I found an issue when I tried to add gluoncv SSD support for relay. In this tutorial: https://github.com/kevinthesun/tvm/blob/RefactorSSDOperator/tutorials/nnvm/deploy_ssd.py, if I set frontend to be relay, sometimes it compiles well, while sometimes it failed with segmentation fault in op fusing pass when visiting TupleNode.
Can it be that relay multi-threading compilation has some issues?