user: Converte this assembly snippet into its equivalent C code:

```asm
<helper_double_3_recursive>:
  endbr64
  cmp    $0x3,%esi
  je     L4
L9:
  ret
L4:
  lea    0x10(%rdi),%rax
  lea    0x20(%rdi),%rdx
  lea    0x30(%rdi),%rcx
  movupd (%rdi),%xmm0
  movupd (%rax),%xmm1
  movupd (%rdx),%xmm2
  movupd (%rcx),%xmm3
  movapd %xmm0,%xmm8
  haddpd %xmm8,%xmm8
  movapd %xmm0,%xmm9
  hsubpd %xmm9,%xmm9
  blendpd $0x1,%xmm8,%xmm9
  movapd %xmm9,%xmm0
  movapd %xmm1,%xmm8
  haddpd %xmm8,%xmm8
  movapd %xmm1,%xmm9
  hsubpd %xmm9,%xmm9
  blendpd $0x1,%xmm8,%xmm9
  movapd %xmm9,%xmm1
  movapd %xmm2,%xmm8
  haddpd %xmm8,%xmm8
  movapd %xmm2,%xmm9
  hsubpd %xmm9,%xmm9
  blendpd $0x1,%xmm8,%xmm9
  movapd %xmm9,%xmm2
  movapd %xmm3,%xmm8
  haddpd %xmm8,%xmm8
  movapd %xmm3,%xmm9
  hsubpd %xmm9,%xmm9
  blendpd $0x1,%xmm8,%xmm9
  movapd %xmm9,%xmm3
  movapd %xmm0,%xmm8
  movapd %xmm0,%xmm9
  addpd  %xmm1,%xmm8
  subpd  %xmm1,%xmm9
  movapd %xmm2,%xmm10
  movapd %xmm2,%xmm11
  addpd  %xmm3,%xmm10
  subpd  %xmm3,%xmm11
  movapd %xmm8,%xmm0
  movapd %xmm8,%xmm2
  addpd  %xmm10,%xmm0
  subpd  %xmm10,%xmm2
  movapd %xmm9,%xmm1
  movapd %xmm9,%xmm3
  addpd  %xmm11,%xmm1
  subpd  %xmm11,%xmm3
  movupd %xmm0,(%rdi)
  movupd %xmm1,(%rax)
  movupd %xmm2,(%rdx)
  movupd %xmm3,(%rcx)
  jmp    L9
```

assistant: ```c
void helper_double_3_recursive(double *buf, int depth) {
  if (depth == 3) {
    for (int j = 0; j < 8; j += 8) {
      for (int k = 0; k < 2; k += 2) {
        __asm__ volatile("movupd (%0), %%xmm0\n"
                         "movupd (%1), %%xmm1\n"
                         "movupd (%2), %%xmm2\n"
                         "movupd (%3), %%xmm3\n"
                         "movapd %%xmm0, %%xmm8\n"
                         "haddpd %%xmm8, %%xmm8\n"
                         "movapd %%xmm0, %%xmm9\n"
                         "hsubpd %%xmm9, %%xmm9\n"
                         "blendpd $1, %%xmm8, %%xmm9\n"
                         "movapd %%xmm9, %%xmm0\n"
                         "movapd %%xmm1, %%xmm8\n"
                         "haddpd %%xmm8, %%xmm8\n"
                         "movapd %%xmm1, %%xmm9\n"
                         "hsubpd %%xmm9, %%xmm9\n"
                         "blendpd $1, %%xmm8, %%xmm9\n"
                         "movapd %%xmm9, %%xmm1\n"
                         "movapd %%xmm2, %%xmm8\n"
                         "haddpd %%xmm8, %%xmm8\n"
                         "movapd %%xmm2, %%xmm9\n"
                         "hsubpd %%xmm9, %%xmm9\n"
                         "blendpd $1, %%xmm8, %%xmm9\n"
                         "movapd %%xmm9, %%xmm2\n"
                         "movapd %%xmm3, %%xmm8\n"
                         "haddpd %%xmm8, %%xmm8\n"
                         "movapd %%xmm3, %%xmm9\n"
                         "hsubpd %%xmm9, %%xmm9\n"
                         "blendpd $1, %%xmm8, %%xmm9\n"
                         "movapd %%xmm9, %%xmm3\n"
                         "movapd %%xmm0, %%xmm8\n"
                         "movapd %%xmm0, %%xmm9\n"
                         "addpd %%xmm1, %%xmm8\n"
                         "subpd %%xmm1, %%xmm9\n"
                         "movapd %%xmm2, %%xmm10\n"
                         "movapd %%xmm2, %%xmm11\n"
                         "addpd %%xmm3, %%xmm10\n"
                         "subpd %%xmm3, %%xmm11\n"
                         "movapd %%xmm8, %%xmm0\n"
                         "movapd %%xmm8, %%xmm2\n"
                         "addpd %%xmm10, %%xmm0\n"
                         "subpd %%xmm10, %%xmm2\n"
                         "movapd %%xmm9, %%xmm1\n"
                         "movapd %%xmm9, %%xmm3\n"
                         "addpd %%xmm11, %%xmm1\n"
                         "subpd %%xmm11, %%xmm3\n"
                         "movupd %%xmm0, (%0)\n"
                         "movupd %%xmm1, (%1)\n"
                         "movupd %%xmm2, (%2)\n"
                         "movupd %%xmm3, (%3)\n" ::"r"(buf + j + k + 0),
                         "r"(buf + j + k + 2), "r"(buf + j + k + 4), "r"(buf + j + k + 6)
                         : "%xmm0", "%xmm1", "%xmm2", "%xmm3", "%xmm4", "%xmm5", "%xmm6", "%xmm7", "%xmm8", "%xmm9", "%xmm10", "%xmm11", "%xmm12", "%xmm13", "%xmm14", "%xmm15", "memory");
      }
    }
    return;
  }
}
```