Do not use `std::labs` (#69704)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69704
Instead, compute size diff inside the if statement
Test Plan: Imported from OSS
Reviewed By: zou3519, seemethere
Differential Revision: D32997004
Pulled By: malfet
fbshipit-source-id: a23819240bfe8278a11ebc6bae1e856de162f082
