pytorch

a9ad2e2f - fix batch norm for empty inputs (#30035)

fix batch norm for empty inputs (#30035) Summary: Fix for https://github.com/pytorch/pytorch/issues/29578 Shape check is moved up as much as possible, because backends by and large don't correctly handle empty inputs, so check needs to be done before backend selection. That also automatically takes care of backward, because forward for empty input is automatically differentiable, so no backend-specific backward routines are ever called. Pull Request resolved: https://github.com/pytorch/pytorch/pull/30035 Test Plan: tests for empty inputs are added. Differential Revision: D18584427 Pulled By: ngimel fbshipit-source-id: a42918f50eb1f6995921aafa92879cd42dd5e9e1