Make it easier to add more backends (#1059)
Summary:
This PR makes it easier to add more backends.
To add a new backend:
1. create a file, say `jit.py`, in https://github.com/pytorch/benchmark/tree/main/torchbenchmark/util/backends.
2. In the file, create a function, say `def torchsript(model, backend_args)`, to transform the model using your backend, or add run contexts to it.
3. In https://github.com/pytorch/benchmark/blob/5a857e97721019eb0aa622976a8ac378cd4f2fbb/torchbenchmark/util/backends/__init__.py#L35, register your backend with import, e.g., `from .jit import torchscript`.
You can now try your own backend with your own backend:
`python run.py <model-name> --backend <backend-name> <backend-options`, for example:
```
$ python run.py resnet50 --backend torchscript
CPU Total Wall Time: 667.329 milliseconds
Correctness: True
$ python run.py resnet50 --backend torchscript --no-ofi
CPU Total Wall Time: 1633.694 milliseconds
Correctness: True
```
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1059
Reviewed By: erichan1
Differential Revision: D38139725
Pulled By: xuzhao9
fbshipit-source-id: 4d578c4ddb94276755b7ae3ae80b794e3b1e6920
