functorch.jvp support for autograd.Function (#90077)
This PR adds functorch.jvp support for autograd.Function. It does so by
adding a jvp rule for custom_function_call.
For a regular PyTorch operation (like at::sin), the VariableType kernel:
- re-dispatches to at::sin
- calls the jvp rule for at::sin
The jvp rule for custom_function_call does just that. It constructs a
new autograd.Function (because the above logic already exists). Inside
the forward, it re-dispatches to custom_function_call. In the jvp rule,
it just calls whatever the jvp rule is supposed to be.
Since this logic is really close to the custom_function_call_grad, I
just put them together.
Test Plan:
- added jvp rules to the autograd.Function in autograd_function_db
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90077
Approved by: https://github.com/albanD, https://github.com/soulitzer
