do not use constexpr with CUDA >= 9.2 compiler on Windows. (#18986)
Summary:
Define `AT_CPP14_CONSTEXPR` from `constexpr` to empty on Windows with CUDA >= 9.2 as workaround.
Discussed in #18425.
When using CUDA 10.1 on Windows, I faced following errors:
~~~
D:/data/source/pytorch\c10/util/ArrayRef.h(144): error: variable in constexpr function does not have automatic storage duration
detected during instantiation of "const T &c10::ArrayRef<T>::front() const [with T=at::Tensor]"
D:/data/source/pytorch/aten/src\ATen/DeviceGuard.h(30): here
~~~
From documentation of CUDA Toolkit v10.1.105, compiler supports `constexpr` and relaxing requirements (in C++14), but compilation failed.
I suppose this could be compiler bug and require this workaround.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18986
Differential Revision: D14821836
Pulled By: ezyang
fbshipit-source-id: 9800da2fe7291e7c09e8e5e882adebab08d83ae3
