Change memory format promotion rules of point wise operators. (#37968)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37968
Modify memory format promotion rules to avoid promoting when one of the input is ambiguous. New rules are:
Ambiguous + Contiguous = Contiguous
Ambiguous + Channels Last = Channels Last
Contiguous + Ambiguous ( NC11 ) = Contiguous
Contiguous + Channels Last = Contiguous ( + Warning ) Before this PR: Channels Last
Channels Last + Contiguous = Channels Last ( + Warning )
Channels Last + Ambiguous = Channels Last
Bias + Channels Last = Channels Last
Channels Last + Bias = Channels Last
Test Plan: Imported from OSS
Differential Revision: D21819573
Pulled By: VitalyFedyunin
fbshipit-source-id: 7381aad11720b2419fb37a6da6ff4f54009c6532
