Take:
```
void f(short *a, float *b)
{
        a[0] = b[0];
        a[1] = b[1];
        a[2] = b[2];
        a[3] = b[3];
}

void f1(float *a, short *b)
{
        a[0] = b[0];
        a[1] = b[1];
        a[2] = b[2];
        a[3] = b[3];
}
```
GCC can SLP f1 (which does V4SF->V4HI) but not f1.
LLVM can though:
```
f:
        ldr     q0, [x1]
        fcvtzs  v0.4s, v0.4s
        xtn     v0.4h, v0.4s
        str     d0, [x0]
        ret
```