Updating all call-sites of the legacy dispatcher registration API in fbcode to the new API. (#48178)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48178
I migrated all call sites that used the legacy dispatcher registration API (RegisterOperators()) to use the new API (TORCH_LIBRARY...). I found all call-sites by running `fbgs RegisterOperators()`. This includes several places, including other OSS code (nestedtensor, torchtext, torchvision). A few things to call out:
For simple ops that only had one registered kernel without a dispatch key, I replaced them with:
```
TORCH_LIBRARY_FRAGMENT(ns, m) {
m.def("opName", fn_name);
}
```
For ops that registered to a specific dispatch key / had multiple kernels registered, I registered the common kernel (math/cpu) directly inside a `TORCH_LIBRARY_FRAGMENT` block, and registered any additional kernels from other files (e.g. cuda) in a separate `TORCH_LIBRARY_IMPL` block.
```
// cpu file
TORCH_LIBRARY_FRAGMENT(ns, m) {
m.def("opName(schema_inputs) -> schema_outputs");
m.impl("opName", torch::dispatch(c10::DispatchKey::CPU, TORCH_FN(cpu_kernel)));
}
// cuda file
TORCH_LIBRARY_IMPL(ns, CUDA, m) {
m.impl("opName", torch::dispatch(c10::DispatchKey::CUDA, TORCH_FN(cuda_kernel)));
}
```
Special cases:
I found a few ops that used a (legacy) `CPUTensorId`/`CUDATensorId` dispatch key. Updated those to use CPU/CUDA- this seems safe because the keys are aliased to one another in `DispatchKey.h`
There were a handful of ops that registered a functor (function class) to the legacy API. As far as I could tell we don't allow this case in the new API, mainly because you can accomplish the same thing more cleanly with lambdas. Rather than delete the class I wrote a wrapper function on top of the class, which I passed to the new API.
There were a handful of ops that were registered only to a CUDA dispatch key. I put them inside a TORCH_LIBRARY_FRAGMENT block, and used a `def()` and `impl()` call like in case two above.
Test Plan: Imported from OSS
Reviewed By: ezyang
Differential Revision: D25056090
Pulled By: bdhirsh
fbshipit-source-id: 8f868b45f545e5da2f21924046e786850eba70d9
