[PATCH] D124382: [Clang] Recognize target address space in superset calculation

[Jakub Chlanda via Phabricator via cfe-commits]

jchlanda added a comment.

In D124382#3480600 <https://reviews.llvm.org/D124382#3480600>, @Anastasia wrote:

> 



> And I think we could add this feature in a very light way for example by reserving the numbers from the clang `LangAS` enum to be used with the language address spaces in the prototypes of builtins.

I'm not sure I understand how that would look, could you please elaborate?

> Just to understand further - do you need the builtins to have a specific address space prototype? And do you need this to improve error handling in libclc code base?

With the wrappers suggested we could declare all the pointers to be in generic AS and that would get us around the target vs language AS problem. I don't think that would improve the situation, as from llvm perspective/use case all those builtins would be incorrect and there would be no way for users to tell that there is a specific AS requirement on them, nor would the compiler be able to warn/error. Then the only thing making it work would be those wrappers, embedded deeply in the source of libclc, which at the moment is not even shipped with upstream llvm.
The builtins in question are not exclusively OpenCL/SYCL related, say `TARGET_BUILTIN(__nvvm_cp_async_ca_shared_global_16, "vv*3vC*1", "", AND(SM_80,PTX70))` would need to take both pointer in a generic address space here. It feels like explicitly providing AS in the prototype is needed.

> this for example won’t work for builtins that are shared between targets.

While I agree in principle, I'm not sure if there are any target agnostic and AS specific builtins, sounds like a dangerous thing to introduce. And in any case, it's the target that provides the AS map.


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