[Bug tree-optimization/123897] [16 Regression] during GIMPLE pass: widening_mul ICE: verify_gimple failed: non-trivial conversion in unary operation

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123897

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced testcase:
```
typedef __attribute__((__vector_size__(sizeof(int)*8))) signed int v8i;
typedef __attribute__((__vector_size__(sizeof(int)*8))) unsigned int v8u;
void f(v8i *a,v8i *b,v8u *c)
{
  *c = (v8u)(*a * *b) - *c;
}
```