[PATCH] D28321: [CUDA] Add __declspec spellings for CUDA attributes.

[Justin Lebar via Phabricator via cfe-commits]

jlebar added inline comments.


================
Comment at: clang/include/clang/Basic/Attr.td:604
 
+// CUDA attributes are spelled __attribute__((attr)) or __declspec(__attr__).
+
----------------
aaron.ballman wrote:
> jlebar wrote:
> > aaron.ballman wrote:
> > > For my own edification, do you have a link to some documentation of what CUDA attributes are spelled with `__declspec`?
> > I do not believe such documentation exists.  It is an implementation detail in the CUDA headers -- users never write `__attribute__((device))` or `__declspec(__device__)`.  Instead, they write `__device__`.
> Then why are we introducing `__declspec(__device__)` rather than a keyword attribute `__device__`?
> 
> My biggest concern is: I would like to verify that these actually should be supported as a `__declspec` attribute. From my simple testing in MSVC, it does not appear to support `__declspec(__device__)`, but perhaps I am doing it wrong (I'm mostly unfamiliar with CUDA). If this isn't something MSVC supports, then it is the first attribute we're supporting with a __declspec spelling that is not actually a Microsoft attribute, which is something worth discussing.
> Then why are we introducing __declspec(__device__) rather than a keyword attribute __device__?

`__device__` is a macro defined in the CUDA headers, which must include and we are not able to modify.


================
Comment at: clang/include/clang/Basic/Attr.td:610
   let LangOpts = [CUDA];
   let Documentation = [Undocumented];
 }
----------------
aaron.ballman wrote:
> jlebar wrote:
> > aaron.ballman wrote:
> > > Now would be a good time to add the documentation for these attributes, otherwise there's a lot less chance users will know what ways they can spell the attributes (or what the attribute do).
> > See above, these are an implementation detail.
> We can still document that we support the attributes under their macro names, or do users not typically think of these macros as being attributes? I am mostly concerned about discoverability of the attributes -- how is a user to know what Clang does or does not support?
> how is a user to know what Clang does or does not support?

These macros are fundamental to CUDA support.  The statement "you can compile CUDA code with clang" will immediately imply to every CUDA developer in existence the statement "you can use `__device__` in your code".


https://reviews.llvm.org/D28321