[PyTorch] Optimize c10::optional<ArrayRef<T>> for size (#59333)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59333
Code comment should explain this in sufficient detail. In brief, making it 16 bytes should get it to be passed in registers.
ghstack-source-id: 130631329
Test Plan: Updated optional_test and added static_assert in Optional.cpp.
Reviewed By: ezyang
Differential Revision: D28843027
fbshipit-source-id: 3029f05e03a9f04ca7337962e7770cdeb9a608d9
