pytorch

47ad6628 - add optional refining (#69776)

add optional refining (#69776) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/69776 If we have an node output which is an optional type, but both if blocks produce a non-optional value, we can try to refine the if output type, which can open up further optimization opportunities. Test Plan: Imported from OSS Reviewed By: jbschlosser Differential Revision: D33515235 Pulled By: eellison fbshipit-source-id: 34f6ab94ac4238498f9db36a1b673c5d165e832e