[PATCH] D105648: [OpenMP] Support OpenMP 5.1 attributes

[Erich Keane via Phabricator via cfe-commits]

erichkeane added inline comments.


================
Comment at: clang/lib/Parse/ParseDeclCXX.cpp:4285
+    // created for us by the caller.
+    return true;
+  }
----------------
aaron.ballman wrote:
> aaron.ballman wrote:
> > erichkeane wrote:
> > > ABataev wrote:
> > > > erichkeane wrote:
> > > > > aaron.ballman wrote:
> > > > > > erichkeane wrote:
> > > > > > > Another place to make the same comment :D  I wonder if giving a diagnostic on attempting to use omp::directive in a previous version should have either an extension warning or more explicit warning would be a good idea?
> > > > > > Ah, now I see what you're after. We could do that, but I think deciding whether to expose this in older modes is more of an open question. I went with the conservative approach first, but we could relax this later.
> > > > > Well, I was going for 1 of two things:
> > > > > 
> > > > > 1- allow in older modes, then do a warning that you're using it in the wrong version.
> > > > > 
> > > > > 2- Customize the error from "unknown attribute directive" to something like, "attribute omp::directive is only available in OMP5.1 mode".
> > > > I think we can enable it for the previous versions, at least as an extension. Thoughts?
> > > It'll mean a larger test-surface I'd think, but there _IS_ precedent both ways.  
> > > IMO, we are probably better off doing #2 above (a better 'unknown attribute' diagnostic), then doing it as an extension if GCC makes that choice, or there is a compelling reaosn.
> > I think it makes sense to improve the diagnostic here, but I think we should hold off on enabling it as an extension in older OpenMP modes until we have some usage experience with the feature. Once we have confidence that the feature works well in 5.1, then it's easy enough for us to support it in older modes.
> Actually, I'm rethinking whether that makes sense. In order to have the new diagnostic, we'd have to perform this check *before* the `hasAttribute()` check above because the attributes aren't known. That adds a bit more checking back into the patch that was just removed (not the end of the world) and it makes out-of-spec OpenMP attributes behave differently than  other out-of-spec kinds of attributes (which is strange). I think my preference is to leave this with the generic "unknown attribute" diagnostic. If we decide to enable it as an extension, then `hasAttribute()` will know about them and we can more easily add the forward/backward compat warnings at that point. WDYT?
I guess my main motivation is that OMP version is a little bit more of a subtle difference, so I'd think the hint would be appreciated. That said, it DOES look like it is going to be enough of a hassle that we could perhaps do it as a future patch.

There is perhaps an improvement todiagnostics in general here (for the Attribute owner, not the author of this patch :-P) to differentiate, "this attribute name is nonsense" vs "this attribute name is only available in higher language settings".


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  https://reviews.llvm.org/D105648/new/

https://reviews.llvm.org/D105648