Ok the reason is that identical workload appends a unique suffix to func_name like fused_nn_conv2d_add_16, while previously func_name is the same in identical workloads. So currently the lookup at tvm/relay_integration.py at 9c66587218dff190b384418d1d0e53d79dc8d288 · apache/tvm · GitHub always fails and all tasks end up having weight 1.
Apparently this only happens when VM compiler is used for task extraction.