LGTM

Added comment for the front end support part.

Change make sense to me (same rational as CUDA or OpenCL).

In D80932#2072064, @Anastasia wrote:

In D80932#2071321, @bader wrote:

In D80932#2068863, @Anastasia wrote:

Why? Can you explain what you are trying to achieve with this?

I think @asavonic can provide more detailed answer, but IIRC we spent a lot time trying to marry template meta-programming with OpenCL address space deductions, but even simplest template functions from C++ standard library breaks compilation. It's important to note one important difference in design goals for SYCL and C++ for OpenCL. SYCL aims to enable compilation of regular C++ as much as possible where as one of the C++ for OpenCL goals is to keep compatibility with OpenCL C. These two goals might lead to different design decisions.

I don't see a contradiction in those goals. We plan to support C++ libraries with C++ for OpenCL of course with functionality that is accepted by conformant OpenCL implementations. For example, libraries that use virtual functions leading to function pointers are not going to work portably in OpenCL devices. If SYCL aims to compile to conformant OpenCL devices then it should not be very different I imagine?

(Edited a bit)

Side note: might be good to also involve @Anastasia, as some of the future patches will overlap with OpenCL.