Function calls for fallback paths (#43274)
Summary:
This PR adds API to package unoptimized/fallback blocks as function calls. It's mainly meant to be used by TensorExpressionsFuser and SpecializeAutogradZero passes as both specialize the original graph but would also like to provide a fallback path in case the assumptions under which the graph was specialized do not hold for some inputs.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43274
Reviewed By: malfet
Differential Revision: D23406961
Pulled By: Krovatkin
fbshipit-source-id: ef21fc9ad886953461b09418d02c75c58375490c
