short-circuit pow for complex 1 and 0 exponents (#39117)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/39117
Test Plan: Imported from OSS
Differential Revision: D21764704
Pulled By: nairbv
fbshipit-source-id: 7f501b429aa63d121f4841fbb0ef3378b911afcd
