user: Please show me the C implementation that matches the assembly code listed below:

```asm
<vp9_sub_pixel_variance16x2_sse2>:
  endbr64
  push   %r14
  mov    %r8,%r14
  push   %r13
  push   %rbp
  mov    %ecx,%ebp
  mov    %r9d,%ecx
  push   %rbx
  mov    %edx,%ebx
  sub    $0x38,%rsp
  mov    %fs:0x28,%rax
  mov    %rax,0x28(%rsp)
  xor    %eax,%eax
  cmp    $0x8,%edx
  mov    0x60(%rsp),%r13
  sete   %al
  test   %ebp,%ebp
  jne    L26
  test   %al,%al
  jne    L93
L26:
  cmp    $0x8,%ebp
  sete   %dl
  test   %ebx,%ebx
  jne    L90
  test   %dl,%dl
  je     L90
  sub    $0x8,%rsp
  mov    $0x2,%r8d
  mov    %r14,%rdx
  lea    0x28(%rsp),%rax
  push   %rax
  lea    0x28(%rsp),%r9
  call   <vp9_half_vert_variance16x_h_sse2@plt>
  mov    0x30(%rsp),%eax
  mov    0x28(%rsp),%edx
  pop    %rdi
  pop    %r8
L23:
  imul   %edx,%edx
  mov    %eax,0x0(%r13)
  shr    $0x5,%edx
  sub    %edx,%eax
  mov    0x28(%rsp),%rdx
  sub    %fs:0x28,%rdx
  jne    L56
  add    $0x38,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r13
  pop    %r14
  ret
  nopl   0x0(%rax)
L93:
  sub    $0x8,%rsp
  mov    %r14,%rdx
  mov    $0x2,%r8d
  lea    0x28(%rsp),%rax
  push   %rax
  lea    0x28(%rsp),%r9
  call   <vp9_half_horiz_variance16x_h_sse2@plt>
  mov    0x30(%rsp),%eax
  mov    0x28(%rsp),%edx
  pop    %r9
  pop    %r10
  jmp    L23
  nopl   0x0(%rax,%rax,1)
L90:
  test   %al,%al
  je     L17
  test   %dl,%dl
  je     L17
  sub    $0x8,%rsp
  mov    %r14,%rdx
  mov    $0x2,%r8d
  lea    0x28(%rsp),%rax
  push   %rax
  lea    0x28(%rsp),%r9
  call   <vp9_half_horiz_vert_variance16x_h_sse2@plt>
  mov    0x30(%rsp),%eax
  mov    0x28(%rsp),%edx
  pop    %rcx
  pop    %rsi
  jmp    L23
  nopl   0x0(%rax)
L17:
  sub    $0x8,%rsp
  mov    %ebx,%r9d
  mov    $0x2,%r8d
  mov    %r14,%rdx
  lea    0x28(%rsp),%rax
  push   %rax
  lea    0x28(%rsp),%rax
  push   %rax
  push   %rbp
  mov    %ecx,0x2c(%rsp)
  mov    %esi,0x28(%rsp)
  mov    %rdi,0x20(%rsp)
  call   <vp9_filter_block2d_bil_var_sse2@plt>
  add    $0x18,%rsp
  lea    0x8(%r14),%rdx
  mov    %ebx,%r9d
  lea    0x2c(%rsp),%rax
  mov    0x8(%rsp),%rdi
  mov    $0x2,%r8d
  push   %rax
  add    $0x8,%rdi
  lea    0x2c(%rsp),%rax
  push   %rax
  push   %rbp
  mov    0x2c(%rsp),%ecx
  mov    0x28(%rsp),%esi
  call   <vp9_filter_block2d_bil_var_sse2@plt>
  mov    0x3c(%rsp),%edx
  mov    0x44(%rsp),%eax
  add    0x38(%rsp),%edx
  add    0x40(%rsp),%eax
  add    $0x20,%rsp
  jmp    L23
L56:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
unsigned int vp9_sub_pixel_variance16x2_sse2(const unsigned char *src_ptr, int src_pixels_per_line, int xoffset, int yoffset, const unsigned char *dst_ptr, int dst_pixels_per_line, unsigned int *sse) {
  int xsum0, xsum1;
  unsigned int xxsum0, xxsum1;
  if (xoffset == 8 && yoffset == 0) {
    vp9_half_horiz_variance16x_h_sse2(src_ptr, src_pixels_per_line, dst_ptr, dst_pixels_per_line, 2, &xsum0, &xxsum0);
  } else if (xoffset == 0 && yoffset == 8) {
    vp9_half_vert_variance16x_h_sse2(src_ptr, src_pixels_per_line, dst_ptr, dst_pixels_per_line, 2, &xsum0, &xxsum0);
  } else if (xoffset == 8 && yoffset == 8) {
    vp9_half_horiz_vert_variance16x_h_sse2(src_ptr, src_pixels_per_line, dst_ptr, dst_pixels_per_line, 2, &xsum0, &xxsum0);
  } else {
    vp9_filter_block2d_bil_var_sse2(src_ptr, src_pixels_per_line, dst_ptr, dst_pixels_per_line, 2, xoffset, yoffset, &xsum0, &xxsum0);
    vp9_filter_block2d_bil_var_sse2(src_ptr + 8, src_pixels_per_line, dst_ptr + 8, dst_pixels_per_line, 2, xoffset, yoffset, &xsum1, &xxsum1);
    xsum0 += xsum1;
    xxsum0 += xxsum1;
  }
  *sse = xxsum0;
  return (xxsum0 - (((unsigned int)xsum0 * xsum0) >> 5));
}
```