[PATCH] D85009: [Sema][BFloat] Forbid arithmetic on vectors of bfloat.

[JF Bastien via Phabricator via cfe-commits]

jfb added a comment.

In D85009#2187603 <https://reviews.llvm.org/D85009#2187603>, @simon_tatham wrote:

> In D85009#2187549 <https://reviews.llvm.org/D85009#2187549>, @jfb wrote:
>
>> Is that true of all vector bfloat implementations? It seems like arithmetic on these types is something implementations would likely support.
>
> As I understand it, Arm currently has the only implementation in clang so far. But if other targets disagree, we can make this conditional on `getVectorKind()`, so that `VectorType::NeonVector` gets this restriction and other vector types get whatever they need.

You mean: only aarch64 backend supports lowering bfloat16 vectors at the moment? Because the clang support isn't "ARM bfloat", it's just bfloat. The tests are ARM bfloat and I think that's fine (i.e. Sema should be able to check ISA-specific problems), but in general this property your checking for seems like a target property.

If I write C or C++ code using bfloat, I'd like to know what that type actually means and what I can do with it. As a developer, it'll be super frustrating once other targets support bfloat... should those target have their own bfloat (because it won't be compatible with ARM's), or should bfloat work differently on different targets?

I actually don't know what the intended approach is here, which is why I'm asking :)


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