Allow both Variables and Tensors in c10 kernel interface (#20816)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20816
Previously, the c10 dispatcher expected ops to be called with Variables and unwrapped them to Tensors before calling into the kernel.
The kernel was expected to return Tensors that were re-wrapped into Variables before passing them on into the system.
However, that doesn't work with kernels that call other operators. One recent example was a kernel that returned the result of `torch::ones()` as output.
Now, with this diff, the c10 dispatcher still passes Tensors to the kernel and Variables back into the system, but it accepts ops to be called with both Tensors or Variables
and kernels are also allowed to return either.
After https://github.com/pytorch/pytorch/pull/17072 , we should be able to get rid of the whole wrapping/unwrapping logic.
Reviewed By: hl475
Differential Revision: D15453963
fbshipit-source-id: 7602b7f2bc43e8ceb8a8c0e97aafcc53d4c47b6c
