The MSVC STL includes specializations of `_Is_memfunptr` for every
function pointer type, including every calling convention.
The problem is the AMDGPU target doesn't support the x86 `vectorcall`
calling convention so clang sets it to the default CC. This ends up
clashing with the already-existing overload for the default CC, so we
get a duplicate definition error when including `type_traits` (which we
heavily use in the SYCL STL) and compiling for AMDGPU on Windows.
This doesn't happen for pure AMDGPU non-SYCL because it doesn't include
the C++ STL, and it doesn't happen for CUDA/HIP because a similar
workaround was done
[here](fa49c3a888).
I am not an expert in Sema, so I did a kinda of hardcoded fix, please
let me know if there is a better way to fix this.
As far as I can tell we can't do exactly the same fix that was done for
CUDA because we can't differentiate between device and host code so
easily.
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Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>
257b727584