pytorch

5b3c0ae5 - Use a FutureFactoryRegistry to allow libtorch_cpu files to create CUDAFuture (#56984)

Use a FutureFactoryRegistry to allow libtorch_cpu files to create CUDAFuture (#56984) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56984 This is a preparation PR before we can create CUDAFuture in rref_impl.cpp. The solution is adding a `FutureFactoryRegistry` in `rpc/utils.*`. The TensorPipe RPC agent is responsible for registering `CUDAFuture` factory and `ivalue::Future` factory. The reason that we need this change instead of directly using `USE_CUDA` macro in RRef files is as follows. There are three build targets: `torch_cpu`, `torch_cuda`, and `torch_python`. `torch_python` is built on top of the other two. `torch_cpu` is CPU-only, which contains no CUDA-related code, and hence no `USE_CUDA` macro. `tensorpipe_*` files are in `torch_python` which does have access to CUDA. However RRef source files are in `torch_cpu`, which cannot contain CUDA code. The recommended solution is to allow dynamic dispatching. Therefore, we had this PR. Test Plan: Imported from OSS Reviewed By: lw Differential Revision: D28020917 Pulled By: mrshenli fbshipit-source-id: e67c76a273074aebb61877185cc5e6bc0a1a5448