Skip Slice if it's no op (#19155)
Summary:
If it's identity op, just skip the slice and return the input.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19155
Reviewed By: zrphercule
Differential Revision: D14890238
Pulled By: houseroad
fbshipit-source-id: f87b93df2cca0cb0e8ae2a1d95ba148044eafd4a
