Enable LTC Input/Output Mapping (#75828)
Summary:
This PR enables Input/Output aliasing for Lazy Tensor Core. `SetUpAlias` is a virtual function that can be overridden in a vendor's custom `LoweringContext` implementation.
The return type of `LoweringContext::GetResultShape` has also been updated to return a `c10::optional` value, since `GetResultShape` isn't currently implemented for the TorchScript backend.
The changes here mirror the interface used by `torch_xla`: https://github.com/pytorch/xla/blob/master/torch_xla/csrc/tensor.cpp#L1548-L1549
cc: antoniojkim ke1337 wconstab silvasean
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75828
Reviewed By: Krovatkin
Differential Revision: D35952593
Pulled By: wconstab
fbshipit-source-id: e20b11e44e0e1beda1b1c47aa3a8b611afd97b7f
(cherry picked from commit bcbc9ef01ef8eb84667e5c42edc10d38d5d78395)
