Allow registering decomps for HigherOrderOp; add decomp for out_dtype (#108080)
We allow registering decomps for HigherOrderOp via the existing decomp
mechanisms:
- I refactored those APIs to accept torch._ops.OperatorBase, which is the base
class for torch.ops.HigherOrderOperator and torch.ops.OpOverload
- HigherOrderOps must directly call maybe_handle_decomp in their
ProxyTorchDispatchMode handling in order to resolve decompositions. We
can change this in the future so that they do not need to do this.
Next, we add an inductor decomp for out_dtype. This decomp shouldn't be
generally available because we want to preserve out_dtype to the backend
for other use cases (i.e. executorch).
Test Plan:
- new tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/108080
Approved by: https://github.com/HDCharles
