[PyTorch] Add ExclusivelyOwned (#59419)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59419
This introduces ExclusivelyOwned, which allows isolated
pieces of code that can make ownership guarantees to opt out of
reference counting operations on `intrusive_ptr` and `Tensor`
entirely. To elaborate, if you know you are the exclusive owner of an
`intrusive_ptr` or `Tensor`, moving it into an `ExclusivelyOwned` will
avoid performing atomic reference counting operations at destruction
time. The documentation comment should provide sufficient explanation; please request changes if not.
ghstack-source-id: 131376658
Test Plan:
Added `ExclusivelyOwned_test.cpp`. It passes. When I ran it
under valgrind, valgrind reported no leaks.
Inspected assembly from `inspect` functions in
`ExclusivelyOwned_test.cpp` in an optimized (opt-clang) build. As
expected, `ExclusivelyOwned` calls `release_resources()` and the
`TensorImpl` virtual destructor without including any atomic reference
counting operations.
Reviewed By: ezyang
Differential Revision: D28885314
fbshipit-source-id: 20bf6c82b0966aaa635ab0233974781ed15f93c1
