https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89581
--- Comment #1 from Yichao Yu ---
The problem is still there when compiled with -O2
```
f:
pushq %rbp
vmovq (%r8), %xmm1
movq%rcx, %rax
vmovq 8(%r8), %xmm0
vaddsd (%rdx), %xmm1, %xmm1
vaddsd 8(%rdx), %xmm0, %xmm0
movq%rsp, %rbp
andq$-16, %rsp
vmovsd %xmm1, (%rcx)
vmovsd %xmm0, 8(%rcx)
leave
ret
```
but is not there under `-O2` when the arguments and results are passed
explicitly by reference.
```
void f2(vdouble *res, const vdouble *x, const vdouble *y)
{
*res = (vdouble){x->x1 + y->x1, x->x2 + y->x2};
}
```
```
f2:
vmovsd 8(%rdx), %xmm0
vmovsd (%rdx), %xmm1
vaddsd 8(%r8), %xmm0, %xmm0
vaddsd (%r8), %xmm1, %xmm1
vmovsd %xmm0, 8(%rcx)
vmovsd %xmm1, (%rcx)
```
The problem comes back, however, with the explicit pass by reference version
when compiled under -O3
```
f2:
pushq %rbp
vmovapd (%rdx), %xmm0
vaddpd (%r8), %xmm0, %xmm0
movq%rsp, %rbp
andq$-16, %rsp
vmovaps %xmm0, (%rcx)
leave
ret
```
