Summary:
This is used in the GPU portion of the build, but really shouldn't be.
Most of these helpers were only used by the GPU portion, which has much
nicer builtins available in new clang. Using these in the main offload
build is broken on Windows and not available on older compilers, so we
split. Also means one less header we share.
The alignment helpers are trivially replaced by an LLVM utility, the
only thing that remains are the pointer arithmetic functions. There's no
conveient place to put these so I just let them stay.
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