Here is a C++ (C++ is required because C front-end does not yet support ?: for
vectors) testcase you should add:
```
#define vector __attribute__((vector_size(4*sizeof(int))))
void f(vector int *a)
{
vector int cst = (vector int){1,2,3,4};
vector int t = (*a == cst);
*a = (t ? *a : cst);
}
```-- https://forge.sourceware.org/gcc/gcc/pulls/193#issuecomment-6750
