pytorch

a1584555 - Negate halves on GPU using __hneg() when possible, instead of using float conversion.

Negate halves on GPU using __hneg() when possible, instead of using float conversion. Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/23626 Test Plan: Imported from OSS Differential Revision: D16656730 Pulled By: ezyang fbshipit-source-id: 7e1f4e334f484a3ed4392949ff7679cefd67a74e