[cfe-dev] __builtin_shufflevector question

[Eli Friedman]

On Sun, Jul 28, 2013 at 4:06 PM, Craig Topper <craig.topper at gmail.com> wrote:
> I've started looking at cleaning this up a bit more.
>
> I'm leaning towards removing form 2 support from CGExprScalar.cpp since it
> doesn't work in Sema and therefore could never have been used/tested. I'm
> not even 100% sure what the semantics are supposed to be as far as widths of
> the individual arguments relative to each other. Thoughts?

That's fine.

> Additionally, he error messages in SemaChecking here are a bit misleading
> given the overloaded nature of this instruction. For instance, we have a
> message that says
>
> "first two arguments to __builtin_shufflevector must have the same type"
>
> This error gets used for form 3 and when form 1 has a mask of non-integer
> integer type or a mismatch in the number of elements. Clearly form 1 needs
> clearer error messages for those cases. But then you end up needing to
> specify which form of __builtin_shufflevector in all of the error messages
> to avoid statements like "first two arguments must be..." which is only true
> for one of the forms. Or should we just have separate __builtin names for
> the constant index form and the mask form?

Separate builtin names sounds like a good idea to me.

-Eli