HIP vector types do not link properly with a combination of gcc and hcc

[jglaser]

With the development version of HIP (3a7eb69), I get linker errors in a project which mixes gcc-compiled objects with hipcc-compiled device methods. The reason is a change in hcc_detail/hip_vector_types.h, which defines e.g. double4 differently with gcc and clang. The linker doesn't recognize they're the same anymore. Reverting back to roc 2.9.

[jglaser]

The changes introduced in 4a635ad are really problematic. For instance, the definition of the Scalar_accessor functions as members of the vector types introduces problems with template argument deduction, in particular when e.g. double4 members are passed to atomicMax functions or other templates (like in serialization libraries). These functions expect e.g. the double4 member .x to be of data type double, but now it is of data type hip_impl::Scalar_accessor. Moreover, some operators like bitwise shift which are not present in CUDA are introduced here and can cause compilation errors. Could these changes be reverted?