Move IValues from stack into kernels (#19783)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19783
Previously, the IValues were copied into the kernel arguments, which caused a refcount bump if Tensor was taken by value.
Now, a kernel can take Tensor by value without any refcount bump because it is moved in.
Reviewed By: dzhulgakov
Differential Revision: D15091973
fbshipit-source-id: 4c5ff2e3ee86f5934cc84191697f7dbc9c3ee345
