Nnapi Delegation: Quick improvements (#63489)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63489
A few quick improvements to the Android NNAPI Delegate, some of which were discussed here https://github.com/pytorch/pytorch/pull/62272:
1) `throw std::exception` replaced with `TORCH_CHECK` to reduce runtime
size (nnapi_backend_lib.cpp)
2) weights processing moved from compile to preprocess step, since it can
be done AOT (nnapi_backend_lib.cpp & nnapi_backend_preprocess.cpp)
3) `ser_model_` and `shape_compute_module_` member variables removed, since they are never used after
`init()`, so they are not needed (nnapi_backend_lib.cpp)
Test Plan:
Unit tests: `python test/test_jit.py TestNnapiBackend`
Run SparkAR segmentation with delegated NNAPI as done here D30259033 (can use `jf download GAekdAwsyGKXhggFALN4LnSBTzcubsIXAAAz --file "v303-nnd-mod.ptl"` to get a preprocessed model from these changes)
Imported from OSS
Reviewed By: raziel, iseeyuan
Differential Revision: D30398880
fbshipit-source-id: b6872e1e9ccd583622b80659da00c83fdd82580e
