bfloat16: vectorized unary ops (#35092)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/35092
Test Plan: Imported from OSS
Differential Revision: D20721147
Pulled By: ngimel
fbshipit-source-id: 5d40eed36fd5c8b2d0d08bfb1b416fb608a5eaef
