cleanups to alias analysis (#21221)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21221
ghimport-source-id: 778e7317bbe874d35a903d89af5e0bc9721c8680
Reviewed By: jamesr66a
Differential Revision: D15592313
Pulled By: suo
fbshipit-source-id: d6f6d2be8cd80b40dd26d0bb3be30f074e356105
