Split python_ir.h in a more sensible way (#19081)
Summary:
Files included in libtorch do depend on torch/csrc/utils/object_ptr.h, e.g. ir.cpp: https://github.com/pytorch/pytorch/blob/master/torch/csrc/jit/ir.h#L10 (including usage in std::vector that requires destructor for THPPointer)
However, object_ptr.h depends on python stub: https://github.com/pytorch/pytorch/blob/master/torch/csrc/utils/object_ptr.h#L3
Whereas object_ptr.cpp depends full on on python: https://github.com/pytorch/pytorch/blob/master/torch/csrc/utils/object_ptr.cpp#L8
`torch/csrc/utils/object_ptr.cpp` is included only in Python extension target: https://github.com/pytorch/pytorch/blob/master/torch/CMakeLists.txt#L541
The only reason it was working on master is that compiler was aggressive enough in pruning unused inline functions. With a bit of changes in flags, it started breaking (like in kostmo's PR).
This PR splits out python-dependent bits more explicitly by forward declaring THPPointer for real.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/19081
Reviewed By: ezyang
Differential Revision: D14860091
Pulled By: dzhulgakov
fbshipit-source-id: 4e86cb8e2ac57aedb3cd00c15270d65bb376206c
