question about AltiVec builtins

[Paolo Bonzini]

I wrote back in February:

>     "The same is for gcc.dg/simd-1.c and gcc.dg/20020531-1.c, where
>     one was checking for incompatibility between vector types with
>     different signedness but the same mode, and the other was happily
>     passing an unsigned V8QI to __builtin_ia32_paddusb which expects a
>     signed V8QI.
And when I cited this to Aldy, he said:

> I agree that, for simd-1.c, the test should not expect an error on
> sign difference.
Paolo