Unhandled node; perhaps the node should have been lowered, or the backend should have specified an IRGen case for this node to a backend-specific Instr.

Hey @jfix ! Thanks for the reply. so I tried compiling with g++ instead of clang, then I hit the above assertion instead of a segfault. 
I was using a mock backend, and tried to add the padNode in “transformpostlowering” looks like the node should be lowered. Thanks for the Help.