Register DefaultBackend implementations for functional/inplace structured operators (#53037)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53037
As remarked in #52277 it is easy to give an (inefficient, due to extra
redispatches) DefaultBackend implementation of foo and foo_ in terms of
foo_out. This patch enables code generation for DefaultBackend in these
cases by default for all structured kernels. You can see the payoff
in MSNPU extension: it only has to register a kernel for add.out, and it
gets add and add_ kernels automatically.
The actual code changes are very modest:
- When DefaultBackend, call the dispatched (not direct native::)
functions to allocate tensors, change device guard, etc
- Don't call impl() for DefaultBackend (as it doesn't exist); instead,
directly generate a call to at::foo_out to do the actual work.
- Do NOT generate DefaultBackend implementation for foo_out. Actually,
there is a case to be made for this being a good idea with more infra;
see comments inside.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Reviewed By: bdhirsh
Differential Revision: D26731225
Pulled By: ezyang
fbshipit-source-id: 939da7cb69f694722ec293e5e42e74a755dd0985
