remove RTTI check for TensorImpl shadow copy (#22773)
Summary:
We introduced RTTI in recent change: https://github.com/pytorch/pytorch/pull/21613
For internal mobile build we don't enable '-frtti' yet. This diff is trying to replace
RTTI with alternative approach.
According to dzhulgakov we could compare two tensors' type_id directly in most cases -
which is more strict than comparing TensorImpl subclass type as TensorImpl -> type_id
mapping is 1-to-n but it's more proper for this use case.
The only two cases where we can relax direct type comparison (for legacy reason) are:
1. CPUTensor <-> CUDATensor;
2. SparseCPUTensor <-> SparseCUDATensor;
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22773
Differential Revision: D16277696
Pulled By: ljk53
fbshipit-source-id: 043e264fbacc37b7a11af2046983c70ddb62a599
